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Unmanned Spaceflight.com _ Jupiter _ OPAG Reports

Posted by: JRehling Nov 9 2007, 08:28 PM

http://www.lpi.usra.edu/opag/announcements.html

That's one little URL with a lifetime's worth of reading material.

Three detailed studies are available in PDF format. The missing body is Titan, which will be the subject of a forthcoming report.

The three focus missions are:
Europa Explorer: Fairly detailed description of a mission that is pretty much what Europa Orbiter would have been.

Jupiter System Observer: Basically, Galileo 2 (without the antenna mishap!). The craft would start with a 3-year tour of all the Galileans, then spend 1 year in an elliptical Ganymede orbit, then the rest of the mission in a tight, polar Ganymede orbit (like MGS at Mars). That would map the heck out of Ganymede, but also be close enough to the rest of the system to make long-range observations for years. Note that Ganymede would thereby provide a lot of radiation shielding.

Enceladus: where three profiles are examined in depth: Enceladus Orbiter only; Enceladus Orbiter with soft lander; Saturn orbiter with Enceladus soft lander.

There's more to chew on here than I have had (or may ever have) time for, but I'll throw in my two cents' worth:

Seems like a Europa-only mission would only benefit from coming after a JSO. EE would explore Europa much better than JSO would; why even have JSO observations at Europa if EE came first? In many ways, these two missions are competitive. EE would have the big payoff, but JSO seems like basic recon that would prime EE, especially giving specs on radar performance. But if we waited til JSO was 4 years into its mission before completing design of EE, then put EE sometime mid-century.

If an Enceladus mission included a Saturn orbiter, then maybe the same orbiter could provide data relay for separate Titan elements. However, a lot of the Enceladus science goals would require an Enceladus orbiter, so I don't think a Saturn orbiter for Enceladus/Titan will win out.

Note that Enceladus orbital velocity is low enough that the craft could manage to take lots of hits from ice pellets and survive. Put a bulletproof vest on the craft and let it soar through the plumes endlessly.

Posted by: Mariner9 Nov 12 2007, 08:19 PM

Drats. Everytime I try to download the Europa report I only seem to get four pages. I wonder if my Adobe Reader needs to be upgraded. The other reports come down fine.

As I recall the whole idea for a JSO / Ganymede orbiter mission came along a couple years back. The proposal was made to fly a very high resolution imaging package and eventually park it in orbit around Ganymede. The idea was to keep it alive a lot longer by keeping it out of the heavier radiation it would encounter in Europa orbit.

My impression was that it was beleived that it would be cheaper to develope the JSO because it wouldn't need all the radiation hardening you would have on a Europa orbiter. I scanned through the JSO report, and saw budgetary numbers in the 3 billion range.

If NASA headquarters was hoping that these studies would provide them with a cheaper alternative then one of two possibilities comes to mind. Either (a) those hopes were in vain and you just can't save that much by this route, or (cool.gif someone didn't get the memo and the JSO engineers decided to go whole hog with a full fledged (and radiation hardened) Flagship study and go for the gold. Gold in this case being 'plated'.

A third more cynical possibility would be that people really want the Europa orbiter and so purposely made the JSO come out just as expensive and therefore no more appealing from a budget standpoint.

Please note that I'm NOT advocating that third option... just saving someone else from suggesting it. I'm leaning more towards option (a) as an explanation.

Posted by: JRehling Nov 12 2007, 08:42 PM

QUOTE (Mariner9 @ Nov 12 2007, 12:19 PM) *
Drats. Everytime I try to download the Europa report I only seem to get four pages.
[...]
As I recall the whole idea for a JSO / Ganymede orbiter mission came along a couple years back. The proposal was made to fly a very high resolution imaging package and eventually park it in orbit around Ganymede. The idea was to keep it alive a lot longer by keeping it out of the heavier radiation it would encounter in Europa orbit. [...] I scanned through the JSO report, and saw budgetary numbers in the 3 billion range.


I think the Europa report is only four pages. That's all I see.

JSO would certainly average lower radiation per day than EE (dose at Ganymede about 5% the dose at Europa), the plan is for a very much longer mission, so it will take a high lifetime dose. A short JSO mission would take very little radiation dose, but also have not much point.

JSO sounds like a good mission to me, on the Galileo/Cassini level. But its competition with EE puts it in strange turf. I don't see it taking root.

Posted by: vjkane Nov 12 2007, 08:57 PM

QUOTE (Mariner9 @ Nov 12 2007, 08:19 PM) *
Drats. Everytime I try to download the Europa report I only seem to get four pages. ...

My impression was that it was beleived that it would be cheaper to develope the JSO because it wouldn't need all the radiation hardening you would have on a Europa orbiter. I scanned through the JSO report, and saw budgetary numbers in the 3 billion range.


It's not your Acrobat reader -- I get just four pages, too.

As for JSO, I spent some time going through the budget figures. There's really two missions described. One uses up all the potential flagship budget (~$3B) and the other reduces the amount of Ganymede science through some instrument descope and an elliptical rather than circular orbit. The descoped mission appears to be about 2/3 the cost of the proposed mission (there are more expensive versions, for example with an atmospheric probe). See figure 3-4 on page 3-5. The report also says that no attempt was made to define a minimal acceptable mission, although some descope options are presented that suggest ideas.

My take is that once you get to this class of mission, you are in $2-3B range, and the choice of moons doesn't matter that much.

It is a shame the Europa report isn't up. I'd like to compare the science packages. From the JSO report, it appears that two instruments weighing about 100 kg are needed to enable long distance observations (a combined camera/NIR spectrometer and and an IR spectrometer). I think it would be criminal to return to Jupiter with a 3-axis stabilized craft and not include these instruments plus along with flybys of Io and a long orbital tour to observe satellites not to be orbited plus Jupiter.

Posted by: vjkane Nov 13 2007, 05:14 PM

Some more details comparing the Europa explorer and JSO options.

There's a very good detailed description of Europa Explorer's strawman instruments and the way they would be used -- as of last May -- at http://www.lpi.usra.edu/opag/may_07_meeting/presentations/europa_flagship_study.pdf . You'll notice that they are very similar to those in the JSO Flagship final report, with the following differences:

(1) The final version of JSO calls for a half-meter aperture telescope with the Narrow-Angle Camera and Vis-NIR Spectrometer hooked up to it, for a resolution of 0.4 meters/pixel from 200 km range for the Camera. (This is actully a change from the design of JSO's strawman payload last May, which called for separate optics for the camer and spectrometer -- the result being that they both had considerably lower resolution while weighing only 5 kg less total than the new setup.) Europa Explorer as of last may called, by contrast, for a Narrow-Angle Camera with a resolution 5 times poorer, but weighing only 15 kg -- plus a separate Vis-NIR spectrometer weighing 30 kg. I rather expect to see a similar combined-optics system now adopted for Europa Explorer (whether it features a comparably big telescope or not).

(2) JSO contains a big hulking Thermal-IR Spectrometer weighing fully 43 kg -- whose separate IR optics, in fact, are as huge (0.5 meters) as those for JSO's NAC-VNIS combination! (This is also a new change; last May, the TIR Spectrometer was to weigh only 20 kg but was to be accompanied by a separate 15-kg Thermal Imager.) Clearly good high-res thermal-IR spectra are considered very important on this mission, in order to study Jupiter's atmosphere and Io. Europa Explorer, as of my latest info, carried only an 8-kg Thermal Imager. So presumably a full-fledged Thermal-IR spectrometer is the most likely instrument to be listed for JSO but rejected from Europa Explorer -- since the latter is supposed to focus more on Europa, with general Jupiter-system science being a lower priority than it is for JSO.

(3) The Medium-Res Stereo Camera on JSO, again, has a resolution 5 times better than the stereo camera on Europa Explorer (plus a pixel swath twice as wide) -- but weighs twice as much. (Europa Explorer would also carry a 3-kg Wide-Angle Camera.)

(4) The Plasma and Energetic Particle Spectrometer on JSO weighs twice as much as the 12-kg one on the Europa Explorer (although it uses only a little more power) -- but Europa Explorer would also carry a separate 15-kg Ion & Neutral Mass Spectrometer, which is not on JSO, to analyze substance sputtered off Europa's surface by Jupiter's radiation. (This is the lowest-priority instrument on Europa Explorer.) I don't know what to make of this difference -- since the Europa Explorer plasma instrument, unless it's descoped, would also have ability to make time-of-flight analyses of the composition of plasma. Presumably the JSO version is more sophisticated in its sensitivity or resolution.

So, really, the instrument payloads for the two missions are strikingly similar. The main differences seem to be higher optical resolution for the cameras and near-IR spectrometer on JSO, and the absence of a thermal-IR spectrometer on Europa Explorer. All of which is to some extent changeable; the final version of Euripa explorer might easily end up carrying a thermal-IR spectrometer and combined optics for its cameras and spectrometers, although I imagine these would all be lighter-weight and lower-capability than their equivalents on JSO.

One more important note: it was stated at the Icy Moons Workshop that JSO would carry just as much radiation shielding as Europa Explorer, in order both to allow those Io flybys (reduced from four to three in JSO's latest version) and to prolong its lifetime in the Jupiter system for as long as possible. The overall features of the final version of the JSO spacecraft and that of May's version of Europa Explorer are very similar:
Europa Explorer: 7225 kg total mass, 2608 m/sec delta-V
JSO: 7262 kg; 2705 m/sec

The main differences are that JSO would carry a lot more total instrument mass (310 versus 212 kg), an 8th MMRTG to power the craft, and of course more area of radiation shielding to cover the extra instruments (although, since JSO would only be designed to endure 1.8 Mrad versus Europa Explorer's 2.3 Mrad, the shielding would be thinner and so its total mass would be virtually identical -- 165 versus 162 kg). The buses for the May version of Europa Explorer and that of the current JSO -- minus their science instruments and radiation shielding -- have almost the same mass: 1889 kg versus 1934. But the new JSO has not only more science instrument mass (310 vs. 212 kg), but considerably more radiation shielding (243 kg vs. 165) -- so that its total dry mass is 220 kg higher than that of Europa Explorer.

Also, JSO carries more propellant for the additional 97 meters/sec of delta-V it required for its mission. All this is apparently possible because the 2017 launch opportunity listed for JSO is a good deal better than the 2015 window listed for Europa Explorer: 7810 kg capability versus 7225 (using a Delta IV-heavy and a VEEGA trajectory in both cases). So: delay Europa Explorer by a couple of years, and you could put a lot more on it, too.

One other difference: JSO's final version allows mission data rates of fully 600-1600 kbps, whereas the May version of Europa Explorer provided only 200-300 kbps -- but this seems due to the fact that JSO would have a 50-watt Ka-band transmitter with a low-powered X-band backup, whereas the May version of Explorer used a 50-watt X-band transmitter and only a 3.5-watt Ka-band one. The power requirement of JSO's version is only modestly higher, and its mass is actually slightly less than for Explorer's version -- so I imagine the final version of Explorer will be changed to the JSO setup.

We seem to be looking at only minor differences between Europa Explorer and JSO: the latter would trade off somewhat thinner radiation shielding to allow more instruments an 8th MMRTG, and maybe a somewhat higher com rate. And, even then, the only significant instrument differences are (as mentioned above) just smaller optics for the cameras and VNIR spectrometer (which Europa Explorer would partially compensate for by lowering itself into a 100-kg attitude Europa orbit, versus JSO's 200-km Ganymede orbit), and the lack of a full-fledged thermal-IR spectrometer.

Posted by: PhilCo126 Nov 13 2007, 06:08 PM

Again this points out we live in exciting times, with upcoming missions near Mercury (Messenger 2011), cometary & asteroid flyby (Rosetta 2011 + 2014) and the flyby of the best-known KBO Pluto (New Horizons 2015). Exciting times indeed!

Posted by: JRehling Nov 13 2007, 07:39 PM

QUOTE (vjkane @ Nov 13 2007, 09:14 AM) *
Some more details comparing the Europa explorer and JSO options.
[...]
We seem to be looking at only minor differences between Europa Explorer and JSO: the latter would trade off somewhat thinner radiation shielding to allow more instruments
[...]
And, even then, the only significant instrument differences are (as mentioned above) just smaller optics for the cameras and VNIR spectrometer (which Europa Explorer would partially compensate for by lowering itself into a 100-kg attitude Europa orbit, versus JSO's 200-km Ganymede orbit), and the lack of a full-fledged thermal-IR spectrometer.


Thanks for breaking it down.

Another aspect to the better optics for JSO is that the studies of Io and Jupiter from long range will benefit directly from the improvement in spatial resolution. Ganymede itself doesn't warrant such a commitment in hardware, and it basically "lucks out", becoming one of the best-mapped bodies in the solar system because this mission architecture doesn't really sacrifice anything by providing that capability.

Added note on the JSO report: Its discussion of radiation exposure assumes no shielding from Ganymede, even though it is expected that close proximity to Ganymede will provide net shielding. A priori, I would have guessed that it would block almost 50% of the charged particle flux. I know that Ganymede's own magnetic field makes that somewhat unpredictable, but I still figure that about half the time, Ganymede would stand in between JSO and the "radiant" of charged particle flux from Jupiter's field.

I guess the way this will end up shaking out is that EE will fly soon-ish, and JSO will fly way later. It would be nice to tailor their durations so that more or less continuous coverage of Io and Jupiter's temporally-varying phenomena could be provided, or even to have both of them operating initially simultaneously to provide excellent studies of the particles and fields sorts of things, but that would entail a lot of billions being spent at Jupiter while Saturn's retinue waits for a follow-up.

So I think EE will be the next Outer SS flagship mission and the following slot will probably go to Titan. JSO may be able to outshine Enceladus for the next spot, and then perhaps tailor its tour to provide more unique closeups of Io and Callisto while ignoring Europa and Ganymede which will be otherwise covered thoroughly.

Other Outer SS priorities worth considering include Neptune orbiter and yet other Europa/Titan follow-ons. It's not a question of whether or not something interesting will be ignored, but how many interesting things will be ignored (for the next 40-60 years or so).

Posted by: JRehling Nov 13 2007, 10:38 PM

The full Europa Explorer report is now up. More reading (282 pp) material for your bedside stand.

Baseline mission is a jovian system tour of about 2 years followed by a 92-day primary mission in Europa orbit, with high expectations that the craft would survive considerably longer. Presumably, other targets in the jovian system would get minimal attention once Europa orbit was achieved, since more Europa coverage will always be desirable. (Eg, stereo/laser topographical map will get denser and denser with more observations.)

14 Ganymede flybys and 4 Callisto flybys before Europa orbit. Ganymede is highly useful for gravity assists, but the scientific value of Ganymede flybys would be severely lessened if a JSO mission were ever to fly.

JSO thus becomes a mission where Io is a major consideration, although Ganymede would be better observed. Deep in the radiation belts, Io doesn't fare well as a flyby target according to the real estate rule of Location, location, location.

Posted by: volcanopele Nov 14 2007, 07:38 PM

Sweet! Obviously, the two that I favor are JSO and the Titan Explorer. Of the two, I am pulling for JSO, but I wish both could be selected. JSO seems to be the best mission WRT science/dollar. Yes, it seems a lot like Galileo 2, but I don't think that should be considered a bad thing. We don't stop sending orbiters or landers to Mars, for example, simply because it was done before. With each mission, we understand what questions to ask and what instruments best answer our new questions. JSO will end up doing quite a bit of Europa science that will answer the most pressing question about that world (that an orbiter can answer): what is the thickness of the ice shell? My only problem with this mission is that it could make it more difficult to justify a dedicated Io New Frontiers mission, but barring an opening up of the mission selection process for NF, JSO maybe the Iophiles best hope for the next couple of decades.

The Titan Explorer is probably a close second for me, mostly because it is a mission dedicated to only one object, so I think the science/dollar is a bit lower, but considering the diverse geology and atmospheric science that could be obtained from this mission, it would still be a spectacular mission. Still want to see what the baseline mission looks like. An arrival date in the mid-2020s would be ideal to hit around equinox.

The Europa Explorer and the Enceladus mission, I think, are tied for third. I think a choice between those two missions would have to wait till the end of the Cassini mission. By then, hopefully the question of the source of the plume will be resolved. If the source is in fact a liquid water reservoir, as Porco et al. suggest, I think this mission just way ahead of Europa, given that samples from such a reservoir could be much more easily obtained, in a single mission, than Europa. If the source is much more mundane, as Kieffer et al. suggest, then a mission to Enceladus becomes a much lower priority. For Europa, while the orbiter mission is quite interesting, its focus on Europa pre-EOI and the fact that it will not answer the most pressing question about Europa (the presence of life), I think makes its science/dollar much lower than JSO.

Posted by: vjkane Nov 14 2007, 08:01 PM

QUOTE (volcanopele @ Nov 14 2007, 07:38 PM) *
I am pulling for JSO, but I wish both could be selected. JSO seems to be the best mission WRT science/dollar.


would you vote the same way if the JSO long distance remote sensing instruments (big camera/NIR spectrometer and IR spectrometer) were on the Europa orbiter? Assume that the two missions (JSO and Europa Explorer) were combined, both did Io flybys, both flew by which ever moon wasn't orbited a lot of times, and the only difference was which moon was orbited at the end of the mission.

Posted by: volcanopele Nov 14 2007, 08:07 PM

Yes, if the only difference were which moon was orbited, then yes, I would change my vote to the Europa Explorer. However, keep in mind that another thing that makes JSO interesting is that it can orbit Ganymede for a much longer period than EE could due to the greater radiation exposure at Europa. This provides a much longer opportunity to observe Io and Jupiter which maybe more important than the resolution gained by being at Europa (plus, with a much shorter mission at Europa, more than likely there were would be few if any observations of the rest of the system while in Europa orbit).

Posted by: vjkane Nov 16 2007, 12:39 AM

I've taken a look through the JSO and Europa Explorer proposals. My take on the choice for the next Flagship mission is that there are two classes of missions being proposed. The first class is to a single moon: Europa, Titan, or Enceladus. (While the Europa Explorer will do some Jovian system science, it's instruments are not optimized for that purpose.) The JSO mission would be a true Jovian system mission with a Ganymede mission in addition. It appears to this arm chair engineer that JSO could be flown to either Europa or Ganymede with fairly few changes.

In my opinion, if the next mission is a focused moon mission, Titan is the most interesting of these three options, and the proposed Titan mission with an orbiter, lander(s), and possibly a balloon (I read somewhere that this may be dropped from the proposal, but am not sure) seems very capable. However, if given a choice between a Jovian system mission that ends orbiting either Europa or Ganymede, I think this is the most science for the buck.

Posted by: JRehling Nov 18 2007, 10:14 PM

QUOTE (vjkane @ Nov 15 2007, 04:39 PM) *
I've taken a look through the JSO and Europa Explorer proposals. My take on the choice for the next Flagship mission is that there are two classes of missions being proposed. The first class is to a single moon: Europa, Titan, or Enceladus. (While the Europa Explorer will do some Jovian system science, it's instruments are not optimized for that purpose.) The JSO mission would be a true Jovian system mission with a Ganymede mission in addition. It appears to this arm chair engineer that JSO could be flown to either Europa or Ganymede with fairly few changes.


As described, here are the difference in outcomes:

Jupiter: Long-range reconnaisance more frequently and for a much longer time with JSO.
Io: Long-range reconnaisance more frequently and for a much longer time with JSO. About four well-distributed close flybys with JSO. No close flybys with EE (several nontargeted flybys about 400K km in distance all with similar geometry).
Europa: "Total" mapping with EE. About 7 close flybys with JSO.
Ganymede: "Total" mapping with JSO. About 14 close flybys with EE.
Callisto: Roughly the same outcome in either mission. (Slightly better with JSO.)

Here's my question: How much of the Io long-term observations CAN'T be done from Earth for a ton less money? AFAIK, Io sports about ten major eruptions at any given time, and those are observable from Earth with adaptive optics. For a fraction the cost of JSO, build about 5 tropical observatories dedicated to Io, such that two or three of them can view Io at any time. And, hey, observe Jupiter, Uranus, Neptune, etc., every few hours as well.

If you run a program like that, then JSO looks like a distant poor stepchild to EE in science value. Sure, it would provide some nice close-ups of Io, but Galileo didn't totally skimp on those. And the value of those would be more than made up for by the fact that EE would provide "total" mapping of a world of primary interest (Europa) instead of a world of secondary interest (Ganymede).

The key with Europa is that a survey with selected, partial coverage at top resolution might miss a landing site of unique value, eg, over a hot spot where the ice shell is thinner/softer. None of the other moons have any potential payoff of that kind, and JSO would only provide a chance at finding such a place if it exists.

I'd say that EE is the better mission by far if we do what we should and track Io (and all the gas giants) consistently from here a few AU away. I'd add that I see a lot more value to a few Io flybys than the 14 Ganymede flybys if the EE plan could be tweaked like that. Plan JSO for the distant future, and EE could plan on skipping all Ganymede science except where programmatically convenient (gravity assists).

My lone-wolf conjecture on Europa vs. Enceladus is that Europa's ocean is likely more interesting than Enceladus's because it's "dirty". Even if water is key to life, we can also say that 100% pure water is inherently incompatible with life. From what we've seen so far, Enceladus's water is not quite 100% pure, but doesn't feature many complex compounds. I could see it being a reservoir of window-washing fluid of no astrobiological potential. Meanwhile, we can *see* that Europa's innards have some interesting goop in them; otherwise, the triple bands would be white, not tan.

Titan deserves a heck of a mission, too, but I think it'll merit waiting for Cassini finishing its reconnaisance before completing that design. Europa had its last close-up about a decade ago; it's due.

Posted by: rlorenz Nov 19 2007, 01:37 AM

QUOTE (JRehling @ Nov 18 2007, 05:14 PM) *
>Here's my question: How much of the Io long-term observations CAN'T be done from Earth for a ton less money? AFAIK, Io sports about ten major eruptions at any given time, and those are observable from Earth with adaptive optics. For a fraction the cost of JSO, build about 5 tropical observatories dedicated to Io, such that two or three of them can view Io at any time. And, hey, observe Jupiter, Uranus, Neptune, etc., every few hours as well.
.....


Interesting question. I think there is a lot of great science to be had from planetary monitoring
(20 mins per target per night would do fine in most cases) of io's eruptions and clouds on
Titan, Uranus and Neptune, plus Venus nightside, and Jupiter/Saturn by an observatory system
like you suggest . But to do a good job these need to be 10m-class facilities with AO...not cheap
and NASA is in the business of building spacecraft rather than infrastructure.

A lot of that science could be had by more creative scheduling of existing facilities (e.g. allowing 1/20
of a night allocations for months on end..)

(A retort question - how much more science would you get by beefing up (or even restoring to
higher reliability) the DSN - allowing you to downlink more (and/or lose less) data from existing missions.
I bet in terms of science/$ it is a good expenditure, but infrastructure is never a sexy item to
sell)

As for Io - you can see eruptions are there from the Earth, identifying the location, measuring the total
heat flux in a number of bands (allowing area/temperature estimates) but that doesnt give you any
of the geomorphology, plume dynamics etc that a JSO would give you.

Posted by: tedstryk Nov 19 2007, 11:37 AM

I tend to favor JSO due to the better Io coverage, not to mention the Ganymede coverage. However, while I find Europa interesting, I have never been on the Europa bandwagon. To put it another way, I find it one member of the Callisto-Ganymede-Europa-Io series, and to understand these worlds, obsessively focusing on just one of them (at this point, at least) seems a poor choice.

Posted by: ngunn Nov 19 2007, 01:23 PM

I tend to agree. Whereas EE is really a fixed-term suicide mission due to the Europan radiation environment, JSO could potentially survive into a very long extended mission in Ganymede orbit, continuing to monitor changes in every part of the Jovian system - conceivably including active processes on Europa. Another thing: I'm significantly more uneasy about dropping litter on Europa than on Ganymede.

On the other hand EE is at a more advanced stage of planning and is also an enormously exciting proposal. I'd hate to have the responsibility of deciding.

Posted by: nprev Nov 19 2007, 01:48 PM

Although I'm not really a Europaphile myself, I'd have to vote for EE as the pick of this litter. Not only would we get nice new coverage for the other Galilean moons (and remote monitoring of Io), but remember that Europa's been declared a high-priority objective in close alignment with one of NASA's top-level science goals. Therefore, EE would probably be easier to sell to senior management then the other missions.

(My emphasis here is on getting an outer-planet mission in the pipeline ASAP; we're looking at quite a gap already after Cassini & NH).

Nigel, you're right; I don't envy the task of whomever has to choose amongst these proposals, I want to fly them all. Is this Alan's new job?

Posted by: tedstryk Nov 19 2007, 06:05 PM

QUOTE (nprev @ Nov 19 2007, 01:48 PM) *
Although I'm not really a Europaphile myself, I'd have to vote for EE as the pick of this litter. Not only would we get nice new coverage for the other Galilean moons (and remote monitoring of Io), but remember that Europa's been declared a high-priority objective in close alignment with one of NASA's top-level science goals. Therefore, EE would probably be easier to sell to senior management then the other missions.

Depends. Both would do Europa science. However, it is my understanding that JSO is significantly cheaper because of not having to stay as far inside the Jovian magnetosphere for an extended period of time. It also would, for the same reasons, not require as much new technology. And frankly, I think it would help us better select instruments and priorities for future missions. Galileo's coverage was so spotty that you can't convince me that there aren't new major areas of interest we are missing. I mean, look at all we have found on Mars with imagers since the Mariners and Vikings? Galileo and Voyager coverage of the Galileans doesn't even begin to compare. For instance, JSO might discover plumes eminating from Europa a la Enceladus (which would be much smaller because of Europa's greater gravitational pull). If so, it would be desireable to have appropriate instruments for in situ studies (sort of a below-the-ice freebie, although it wouldn't exactly be pristine material after being propelled into space). Galileo did a plume search, but it was never likely to suceed, given the extremely limited number of images it was able to take. JSO could even continue such a search from Ganymede if it was deemed desireable. My point is that Europa could still be used as a selling point.

Posted by: JRehling Nov 19 2007, 06:06 PM

QUOTE (rlorenz @ Nov 18 2007, 05:37 PM) *
Interesting question. I think there is a lot of great science to be had from planetary monitoring
[...]
But ... NASA is in the business of building spacecraft rather than infrastructure.

As for Io - you can see eruptions are there from the Earth, identifying the location, measuring the total
heat flux in a number of bands (allowing area/temperature estimates) but that doesnt give you any
of the geomorphology, plume dynamics etc that a JSO would give you.


True, identifying the funding party is an outstanding concern; some of that work is taking place now, from the ground as well as HST; basically, NASA won't make this solution happen, but it may end up happening anyway, which would have the same effect on shifting the comparative values of various spacecraft options.

True also that JSO would provide far greater resolution than an Earth-based campaign, but some of that would be compensated for with EE observations of Io. No doubt, JSO does a better job than Earth-based + EE; I am just trying to whittle down the difference to the point where it doesn't outweigh EE's far better reconnaisance of Europa. (Minus JSO's far better, bordering on excessive, reconnaisance of mid-level priority Ganymede.)

QUOTE (rlorenz @ Nov 18 2007, 05:37 PM) *
(A retort question - how much more science would you get by beefing up (or even restoring to
higher reliability) the DSN - allowing you to downlink more (and/or lose less) data from existing missions.
I bet in terms of science/$ it is a good expenditure, but infrastructure is never a sexy item to
sell)


Even a few losses in data return, amortized over mission costs, probably would pay for a lot more in the way of DSN sites. That ratio will probably increase as faster onboard electronics with greater storage capacity lead to outer-planet missions that have enough data to spend the whole apoapsis portion of the orbit transmitting data without running out of things to say. (Eg, a Kayuga-style HDTV system on a Galileo/Cassini kind of mission.)

What would make infrastructure sexy would be if it made for good pork barrel spending. Stations in Spain and Australia can't do that, but stations in Hawaii and North Carolina could.

Posted by: nprev Nov 19 2007, 06:21 PM

QUOTE (tedstryk @ Nov 19 2007, 10:05 AM) *
Galileo's coverage was so spotty that you can't convince me that there aren't new major areas of interest we are missing. I mean, look at all we have found on Mars with imagers since the Mariners and Vikings? Galileo and Voyager coverage of the Galileans doesn't even begin to compare.


Hmm. That's a very persuasive point, Ted; we haven't really completed a Cassini-quality survey of the Jovian system yet. Might change my mind here, gotta think about it.

Posted by: tedstryk Nov 19 2007, 06:44 PM

Two things that I would really like to see are long term monitoring of Jupiter by remote sensing instruments, with high resolution movies of clouds and lightning (on both the day and night side), which was the science goal most damaged by Galileo's antenna problems, as well as high resolution multispectral mapping of the moons. Galileo's color coverage was awful (except for Io, but this was low resolution). Most color images that were returned are low resolution color images overlayed on a high resolution image, which can be deceiving. Often the images were made by taking a full pixel resolution green image (often with lossy compression) and then taking the other colors with more compression plus 2x2 binning. The 2x2-binned color data would be overlayed on the green image. Not only does that make the color boundaries seem less distinct, but it means that the grayscale is based on only one filter, which wrecks havoc on colorful worlds. Ganymede is full of tectonic features, but also appears to have many largescale color variations. It may prove quite interesting to map these with more filters and at high resolution. We may discover something completely unexpected.

Building on this, I fear that a mission like JSO may never fly if EE flies first. And again, I disagree with the Europa fettish (at least at this point). The sequence reminds me of Rhea-Tethys-Dione-Enceladus (and several others, such as Mimas and Iapetus may or may not fit in there somewhere). They are worlds that formed out of the same stuff that have had very different amounts of activity. Trying to understand one of the moons with only spotty coverage of the others would be a mistake (Granted, for the Enceladus mission, this wouldn't be a factor, since Cassini is providing excellent coverage).

Posted by: ugordan Nov 19 2007, 06:45 PM

QUOTE (tedstryk @ Nov 19 2007, 07:05 PM) *
Galileo's coverage was so spotty that you can't convince me that there aren't new major areas of interest we are missing.

True. However, even if there's some important area of interest waiting for us there, there's one that was clearly already identified - Europa. Should we dismiss it some more just so we can go chasing other (possibly) interesting stuff in the Jovian system or concentrate on scrutinizing Europa right now? I'm in favor of the second option. The other areas will pop up eventually anyway. Studying Europa potentially has much bigger implications biologically and even philosophically than, say, mapping locations of Ionian volcanoes (I probably alienated quite a few folks now).

JSO (from what I understand) would provide us with a very rounded-up investigation of the Jovian system, but it probably wouldn't amount to a "quantum leap" in knowledge about any particular object. Winding up in Ganymede's orbit, it would give us awesome coverage of the moon. That's great, but is Ganymede really that worthy of a target? Compare this to EE which wouldn't give as a nice round-up like that, but it sure would provide for that "quantum leap" and for an object that is identified as a high priority, likely solving questions that were raised since Voyagers flew through the system.

I get a feeling (maybe unrightfully so) that JSO would be a sort of Galileo on steroids. Voyager flybys gave us that "wow, the Jovian system is very interesting, we should go into orbit there". Then came Galileo and we basically went "wow, Europa is really intriguing, we should go into orbit there". That's why EE, not JSO seems like the next logical step to me.

I'm a sucker for cool imagery as much as the next guy and would like to see great coverage of all the moons out there, but there's more to it than mapping surfaces. As much as I like images of colorful Io, Ganymede and Callisto, I want to find out what's beneath that frigid ice crust of Europa even more. If there is anything except more ice. Even if that means having to look at more greyish-bland imagery than at other Galileans. I wouldn't call it a fetish or some trendy thing to want to understand Europa, the moon's under the microscope for a good reason IMO.

Posted by: JRehling Nov 19 2007, 06:56 PM

QUOTE (tedstryk @ Nov 19 2007, 10:05 AM) *
Galileo's coverage was so spotty that you can't convince me that there aren't new major areas of interest we are missing. I mean, look at all we have found on Mars with imagers since the Mariners and Vikings? Galileo and Voyager coverage of the Galileans doesn't even begin to compare.


There oughta be a metric of diversity. Deimos seems to have a lot fewer terrain types than Earth. Some worlds, you haven't seen it all til you've seen it all. Others, any sampling of the surface will do.

In terms of the Galileans, Callisto is most likely to be homogenous. The difference between a dedicated orbiter and two good flybys might be how much of the same stuff you see. Ganymede is much more interesting, but it would be hard to prove that the same isn't true there: maybe one close up of the grooves plus km-scale global mapping shows you the full set of variety.

Io, in any of these plans, gets a compromise approach: You can't observe Io up close for a very long time, even though you'd like to. So you have to observe it up close in glimpses, then for a long time from afar. JSO obviously does this better than EE; I think reading between the lines, you see JSO as mainly an Io mission that happens to spend all of its time in bed with Io's sister.

JSO would also be very useful for good plume search surveys of Europa, but that's a particular kind of investigation that may be a wild goose chase. Europa is one of the very few outer SS worlds that will eventually merit a multi-mission sequence, so we want to play Twenty Questions very carefully when the questions cost a couple of billion dollars.

Ultimately, I think Europa's likely diversity is what makes it the key target of interest. I keep thinking about (but not mentioning) Conamara Chaos. This is where we saw the sliding ice blocks that said so much about the crust and its dynamics. Conamara is tiny -- only 100 km or so. There are other areas of Europa we still never have seen with decent resolution, and they may contain a half-dozen more Conamaras -- or sites much more (recently) active than that. With this in mind, I want to see us absolutely nail Europa before we spend a billion dollars anywhere else in the jovian system. JSO would improve our Europa coverage, but it would mean we'd STILL need to launch another EE-style mission before the next Europa mission.

Given that, I'd argue for EE now and then after that contemplating a mission architecture where a JSO-like mission could serve as the comsat for a Europa lander.

I'm not normally part of the astrobiology mafia, but Europa has a surface about as old as Philadelphia whereas the other icy Galileans have surfaces as old as the Moon. Io obviously is a seriously competing interest (fraught, unfortunately, with perils), but Ganymede and Callisto aren't even in the same league as Europa in terms of follow-on interest.

I'd consider adding Io flyby(s) to EE -- later launch dates could improve mass margins so that more shielding could be added. But if EE doesn't fly next, then we're postponing an endgame which is potentially the most interesting in the solar system -- there could be dead bacteria in that dirty ice, waiting for a microscope to see!

Posted by: volcanopele Nov 19 2007, 07:10 PM

QUOTE (ugordan @ Nov 19 2007, 11:45 AM) *
I get a feeling (maybe unrightfully so) that JSO would be a sort of Galileo on steroids. Voyager flybys gave us that "wow, the Jovian system is very interesting, we should go into orbit there". Then came Galileo and we basically went "wow, Europa is really intriguing, we should go into orbit there". That's why EE, not JSO seems like the next logical step to me.

But what makes it so much better than Io or Ganymede? So much more interesting that it seems like a logical next step? Trust me, it isn't those cool fractures... It is the ocean and the possibility of life. JSO has a long-wavelength radio antenna so it can sample the thickness of the ice. Sure it can't map variations like EE could, but it would be enough to answer the question of how thick that ice crust is. As far as the life question goes, let's say it all together now: Europa Explorer IS NOT(!!!) an Astrobiology mission. It will not find life. It will not search for organics. Those will require a follow-up mission: a lander (now that is your logical next step, and one that makes sense). Err, I am starting to sound like He who shalt not be named...

QUOTE
I'm a sucker for cool imagery as much as the next guy and would like to see great coverage of all the moons out there, but there's more to it than mapping surfaces. As much as I like images of colorful Io, Ganymede and Callisto, I want to find out what's beneath that frigid ice crust of Europa even more. If there is anything except more ice. Even if that means having to look at more greyish-bland imagery than at other Galileans. I wouldn't call it a fetish or a trendy thing to want to understand Europa, the moon's under the microscope for a good reason IMO.

What do you think you will get from EE for the most part: a lot of images of fractures (not saying that is necessarily a bad thing, but let's call a duck a duck).

I am not saying that EE is bad mission, just that the amount of science it will accomplish per dollar spent is less than JSO, IMHO. Most of the important questions at Europa that can be answered from orbit will likely be answerable with JSO as currently baselined. All the "cool" questions will require a lander.

Posted by: ugordan Nov 19 2007, 07:19 PM

QUOTE (volcanopele @ Nov 19 2007, 08:10 PM) *
As far as the life question goes, let's say it all together now: Europa Explorer IS NOT(!!!) an Astrobiology mission. It will not find life. It will not search for organics.

I never once said it's going to be a search for life. I don't expect it to go diving into the ocean. It WILL be able to characterize the ocean (if any) much, much better than a flyby mission would. What makes you think an ocean would have a uniform crust depth everywhere? Several radio measurements with flybys would give you samples, not a global distribution. EE would be able to perform global high-res imaging JRehling talked about (Conamara Chaos etc.) - identifying potentially good candidate sites for future landers and it would provide much better high-res imaging of the actual surface topography at those sites. I'm aware the imagery would be basically cracks and more cracks - as I said, I'm ready to live with that.
As for a lander being the next logical step, you really wouldn't want to send anything down before mapping the surface topography pretty well, and Europa obviously is very rough at small scales. Once again, something that wouldn't be done adequately via flybys - too sparse a coverage.

Posted by: nprev Nov 19 2007, 08:42 PM

Hmm again...keeping up with all these great arguments is challenging, but most enjoyable! smile.gif

Maybe a compromise is feasible. It really seems as if we're talking about two missions with largely similar capabilities in terms of payload. The question then becomes "which moon should *** orbit during the terminal phase of the nominal mission?" I think a merger of requirements is quite possible, and I have to side with Gordan on Europa being the most desirable moon to orbit given our present state of knowledge about the Jovian system.

Of course, this may change based on the findings of the mission itself. IIRC, Ganymede has an OH- torus, which might indicate outgassing. The key would be to design a mission that has the option of orbiting either moon, and therefore building in the radiation hardening regardless.

Posted by: vjkane Nov 19 2007, 08:46 PM

I think that the discussion of which moon is more interesting combines personal interest with scientific importance. For me, Io is *personally* the most interesting of the moons. Each of us probably have our favorite moon based on some emotional reaction.

As for which moon is scientifically most interesting for mission that will orbit one, here is how I look at this:

Io would tell us a lot about early stages of being a silicate planet, but you can never orbit it because of the radiation

Callisto is too homogeneous and doesn't exhibit a wide range of icy moon/planet forming stages

Ganymede is heterogeneous and exhibits a wide range of formation stages. Studying it reveals a lot about large icy moons (including, I suspect, Titan and Triton)

Europa is a special case without other analogues in the solar system. If we plan to explore it on/under the surface in the lifetime of my 18 year old son, then it should be the target of the next orbital mission.

Whatever moon is chosen to orbit, I think the craft needs capable instruments for long range studies of Jupiter, Io, and better coverage of other moons from flybys. The current EE instruments seem lightweight for this, IMO.

Posted by: tedstryk Nov 19 2007, 09:46 PM

I still fail to see what makes Europa so much more interesting. An outside chance at microbes that EE won't detect but might lead us to is interesting, but from my perspective, understanding the overall evolution of the Jovian system and the solar system as a whole is more interesting. Also, with a high transmission rate, combined with a camera a lot of pixels and a fast integration time, could provide excellent coverage - Galileo gives us a distorted perspective. Also, I support JSO for the same reason I like DAWN. I knew we would pick a Vesta mission one of these days, but I wasn't sure if we would go to Ceres in my lifetime. I am sure we will go to Europa sooner or later, but I am not so sure about a mission to Ganymede unless JSO flies.

Posted by: nprev Nov 19 2007, 10:13 PM

QUOTE (tedstryk @ Nov 19 2007, 01:46 PM) *
I still fail to see what makes Europa so much more interesting. An outside chance at microbes that EE won't detect but might lead us to is interesting, but from my perspective, understanding the overall evolution of the Jovian system and the solar system as a whole is more interesting.


The thing is, Europa has captured not only public imagination via popularization but also the interest of very influential groups such as the AAAS; that's a pretty tough current to swim against with respect to pitching mission proposals. (We gotta talk realpolitik, unfortunately, when discussing issues like this; I don't like it either, but it is what it is).

However, gonna restate what I said earlier: A good compromise would be an orbiter that could be targeted at the end of an extensive Galilean tour to orbit either Europa or Ganymede, with target selection largely based on mission findings up to the decision point. I completely and utterly agree with you that it is entirely possible that many more surprises await discovery in the Galileans, and therefore that a Europa bias may be premature; allowing some versatility in EOM scenario selection is the best option to maximize science return. (Unusual result in current times: the EOM phase is likely to be the most interesting of the entire mission!)

Posted by: tedstryk Nov 19 2007, 10:25 PM

QUOTE (nprev @ Nov 19 2007, 10:13 PM) *
The thing is, Europa has captured not only public imagination via popularization but also the interest of very influential groups such as the AAAS; that's a pretty tough current to swim against with respect to pitching mission proposals. (We gotta talk realpolitik, unfortunately, when discussing issues like this; I don't like it either, but it is what it is).

However, gonna restate what I said earlier: A good compromise would be an orbiter that could be targeted at the end of an extensive Galilean tour to orbit either Europa or Ganymede, with target selection largely based on mission findings up to the decision point. I completely and utterly agree with you that it is entirely possible that many more surprises await discovery in the Galileans, and therefore that a Europa bias may be premature; allowing some versatility in EOM scenario selection is the best option to maximize science return. (Unusual result in current times: the EOM phase is likely to be the most interesting of the entire mission!)

I am not sure the public even knows what Europa is. I really think it would be a shame if astrobiology and hype guides mission selection. The thing is, Europa's radiation shielding requirements are much greater. I wonder how much a "Galileo-II" style mission that examines the moons and then finishes off with trying to fly through the inner Jovian system as many times as possible like the original Galileo did would cost.

Posted by: ngunn Nov 19 2007, 10:28 PM

QUOTE (ugordan @ Nov 19 2007, 06:45 PM) *
but is Ganymede really that worthy of a target?


Wow, this debate has really taken off!

Without denigrating EE I would just like to address the question above. My answer is yes. If we make the pessimistic assumtion that the Europan ocean is not full of jellyfish then a geophysical study of Ganymede and the dynamical history of the whole Jovian system become the main research targets. Topography old AND new, the whole history is there. Magnetic dynamo - how does it work and what protection does it provide? Long term vantage point: perfect.

Posted by: nprev Nov 19 2007, 10:34 PM

Ted, when I said "public", should've said "aware public"; they're out there, mostly Discovery Channel watchers here in the US....and they vote, and they write letters, and they're usually affluent. Not a large consituency, but often quite vocal.

Fact of the matter is that there have been numerous TV programs about Europa, so the buzz is there. Question really boils down to how to design a mission that maximizes science return while simultaneously garnering enough funding & support to actually materialize? Not an easy problem to solve.

Posted by: ugordan Nov 19 2007, 10:43 PM

QUOTE (ngunn @ Nov 19 2007, 11:28 PM) *
If we make the pessimistic assumtion that the Europan ocean is not full of jellyfish then a geophysical study of Ganymede and the dynamical history of the whole Jovian system become the main research targets.

With all due respect, should we really be making such assumptions? With foreknowledge, 20/20 hindsight and whatever, then yes, a Ganymede orbiter would make more sense. We just don't know what's out there, that's why we want to send missions there in the first place.

Isn't that kind of like saying "if we assume Titan and its surface is not that worthy of closer scrutiny (i.e. dull and dead, despite evidence to contrary), we can concentrate on investigating other wonderful moons in the Saturnian system"?

Posted by: nprev Nov 19 2007, 10:55 PM

Man, this thread is on fire...great stuff, though.

Gordan made a great point about assumptions. It's arguably true that right now, after Cassini's efforts to date, we know more about the Saturnian system than we do about the Jovian. Given the fact that the state of the art has advanced, it makes sense to do a similarly-scaled survey of Jupiter & its environs, with the icing on the cake being a detailed survey of either Europa or Ganymede at the end of the mission.

This is the versatility that I and others have wished for Cassini, but it can't happen. However, a blending of objectives & concepts for JSO & EE might achieve this.

Posted by: volcanopele Nov 19 2007, 11:00 PM

Again, the problem is that the EE has nothing to with any possible jellyfish in Europa's ocean. EE is caught in a catch-22 where the whole push to go to Europa is to look for life, but EE won't have anything to do with that question, but we may need the orbiter to look for good places to land to answer that question. I think it might be useful, as vjkane has suggested, merge JSO and EE to get the best of both worlds: get the added science that the pre-EOI (or pre-GOI) orbital mission would provide at Io, Jupiter, and the other moons, then get the orbital mission at Europa. This would add to the cost of EE, but it might be worth it.

The only problem right now with the Europa "vision" at NASA are the timescales involved. The Mars people are complaining about a possible gap in Mars mission in the next decade to pay for MSR; at Europa, we would have EE in the 2017-2027 time frame, and the lander in the decade after that...

Posted by: ugordan Nov 19 2007, 11:10 PM

QUOTE (volcanopele @ Nov 20 2007, 12:00 AM) *
The only problem right now with the Europa "vision" at NASA are the timescales involved. The Mars people are complaining about a possible gap in Mars mission in the next decade to pay for MSR; at Europa, we would have EE in the 2017-2027 time frame, and the lander in the decade after that...

That's assuming the orbiter would find anything interesting enough to merit a landing... I see your point about funding and prioritizing, though.

We'd all like to have JIMO back so everyone'd be happy, but this is not an ideal world. To be frank I'll be happy to see the day any flagship Jupiter-bound mission gets off the ground. If it turns out to be focussing on Europa, all the better. smile.gif

Posted by: vjkane Nov 19 2007, 11:32 PM

Just to add more fun to this debate, a long time ago when a Europa orbiter was a new idea I read an AIAA paper on possible implementation architectures. The majority of the paper talked about implementing an orbiter. However, as a backup option, an arbitrarily large number (I think this paper discussed a dozen or two) flybys of Europa could be done. Using gravity assist, the encounter point with Europa in its orbit could be changed. In this way, you can have the closest flyby occur at any number of longitudes at Europa. Apparently it was harder to vary latitudes.

Fast forward to the $1B Enceladus flyby study. It had a number of flybys of that moon that walked around latitudes and then modified the Saturn orbit to approach Enceladus from the other side. This way, both hemispheres would be observed.

Now look ahead to a Jovian orbiter. It's mission could be tweaked to make a large number of flybys of one moon and then orbit another. The primary costs would be mission operations, fuel, and radiation exposure (especially if the moon with lots of flybys is Europa).

So get on your wishing caps. You almost can have two intensive moon studies (plus remote studies of Jupiter and Io and maybe some Io flybys). Imagine what the JSO instrument set could do with 24 flybys of Ganymede or Europa spaced 15 degrees around the equator. If the flybys are close enough, you can get snippets of coverage with the radar system.

Posted by: Juramike Nov 19 2007, 11:36 PM

Here's my rundown (pretty much mentioned by vjkane - I apologize if I repeat/paraphrase too much):

Pros (what we think we'd learn going into the program)/ Cons (mission lifetime issues)

Io - volcanic and tidal flexing of silicate bodies/ high radiation environment
Europa - relatively boring ice geology, potential for future astrobiology missions / radiation environment
Ganymede - big planet diverse geology, will teach us about geology on large ice moons/extrasolar planets / easier radiation environment
Callisto - relatively boring geology / easiest radiation environment

The lessons from Ganymede formation and geology can be extended to large differentiated ice planets such as Titan, Triton, (and Pluto - which will only get a flyby), as well as new icy planets in extrasolar systems. IMHO, a Jupiter explorer that ends up with a majority of coverage at Ganymede will pluck the scientific low-hanging fruit and get us the most bang for our buck. That should be the first mission back to the Jovian system. We will develop knowledge about a whole class of planets.

Europa is astrobiologically interesting. We need to go there. But there is lots of technical work that needs to be put in place to survive a lengthy stay in that environment and thoroughly examine possible landing sites from orbit. This would be a good next step in the Jovian system.

Follow-on Jovian missions should then target landing and drilling into Europa. These missions would be very complicated and the technologies to do this would need to be developed to assure mission success.

The first science we can easily do from orbit is geology, not astrobiology:

Ganymede will teach lessons about the geology of whole class of large ice worlds.

Europa will teach geoloby lessons only applicable to Europa and Enceladas, and maybe to tidally preturbed small moons in other systems (which we won't be able to detect for a very long time).

I vote Ganymede (JSO), then Europa for the next Jovian mission.

-Mike

Posted by: Mariner9 Nov 20 2007, 12:07 AM

I'm surprised that almost the entire debate seems based on the idea that the only thing interesting about Europa is that there might be life below the ice.

Have any of you looked at the pictures? Or read the articles? There is lot going on down on Europa. Cycloidal cracks. Chaos terrain. Possible periodic geysers spewing up through the cracks, staining the surrounding terrain with various salts and compounds.

Even if you throw the whole "life" thing out, here we have a planet sized moon, a huge ice pack covering a global subsurface ocean, with a large diversity of geologic activity. And pretty darn unique. One of the things that makes it so fascinating is that no other object in the solar system looks anything at all like it.

Now, as to what can you learn with orbital vs. flyby?

There are at least two things you can't do with flybys. A laser altimiter in orbit can measure the flexing of the surface due to tidal forces as Europa moves through it's orbit. That flexure is the most reliable way to determine how thick the ice shell is, the radar system is really unlikely to penetrate the shell if it is more than a couple kilometers thick.

The second item is a magnetometer which can measure the induced magnetic field in the European ocean. In all of Galileo's flybys they only detected a change in that induced field on one encounter. That was because you get point samples of the magnetic field, and by unhappy luck all of their flybys occured when the field would have rougly the same alignment. If you put a probe in orbit, you can really milk that information as the moon moves through the Jovian magnetosphere.

All the other investigations can be done, if not as well, using multiple flybys. But those two investigations might prove to provide some of the most important revelations.

JSO would undoubtably add considerably to our knowledge of the whole Jovian system. But that might be all it did: be a super-Galileo. Might not be a lot of paradigm shifts.

EE would at least be an enhanced-Galileo with it's Callisto and Ganymede encounters. But in the case of Europa it has the likely potential to uncover very fundamental disocveries that would completely revolutionize our knowledge of Europa.

So in my mind, if you're going to spend roughly the same ammount of money for JSO vs. EE, I'd go for EE.

Posted by: djellison Nov 20 2007, 12:10 AM

You could make those same arguments regarding the uniqueness of Europa with just about any other body in the solar system. You can make it about Io, Enceladus and Titan in this context without any exaggeration.

Doug

Posted by: tedstryk Nov 20 2007, 12:13 AM

I think that the additional time observing the Jovian system is a big selling point, particularly if it has a good long range camera. Another factor is that JSO, which will not have to deal with the Jovian radiation at Europa for extended periods of time, may not be as technically difficult, which might mean that it may be less likely to be delayed. Another factor is that once it is in Ganymede orbit, it can be used to the last drop, because it doesn't pose nearly the planetary protection issue a Europa orbiter would. I do think the informed public does like Europa. Still, I think they could be sold on the frozen tectonics of Ganymede (which could be related to the early earth - a stretch, but so are Europan brine shrimp) and the volcanoes of Io, not to mention Jupiter.

Speaking of that, we do have one more mission on deck already, Juno. Granted, it won't be much for image hounds and moon-lovers. Still, having an outer planets mission in queue is a good thing, because it keeps the bean counters used to having one in development. Continuity is an important thing.

Posted by: NMRguy Nov 20 2007, 12:42 AM

QUOTE (vjkane @ Nov 19 2007, 12:36 AM) *
Whatever moon is chosen to orbit, I think the craft needs capable instruments for long range studies of Jupiter, Io, and better coverage of other moons from flybys. The current EE instruments seem lightweight for this, IMO.

This is really the problem that I am having with the EE. When you compare the general features of the tours for EE and JSO (especially before moon insertion), EE comes up short. Because of the more intense radiation, EE's shielding must be better such that its science payload is significantly reduced--JSO can carry 40% more instrumentation than EE. All the instruments on JSO seem much more capable.

JSO's tour is much more balanced as well. We get to enjoy a full three years during the Jovian phase for JSO, while the current tour for EE is only two years. As also mentioned, Io, Europa, Ganymede, and Callisto all see close flybys before GOI (currently 4, 6, 7 and 11). Moon orbit insertion should certainly be within our technological limits, but if something were to go wrong, at least we would have good science for the entire system. This reduces some of the risk. EE is much less varied and skips Io altogether (currently 0, 4, 13, 4). If there were a critical failure during EOI, then EE would actually return very little Europan science. (Would it then be known as GE?).

I tend to agree with Ted that the longer observation time with JSO, including a significantly longer life after GOI, is very appealing.

QUOTE (Juramike @ Nov 20 2007, 12:36 AM) *
relatively boring ice geology

I would have to strongly disagree with this statement. Sure, from a Fe-rich or silica-rich magmatic point of view, the Europan surface has little to offer. Differentiation occurred long ago, sending all of the heavier minerals into the core. But there aren’t many craters on Europa—its surface is probably younger than much of Earth’s surface. From a tectonics point of view (which is very much in the realm of geologic interest), this is a very interesting problem that should be investigated.

For me, it’s this surface activity (and not the astrobiology) that catches my interest. Sure, Io would be more desirable, but it isn’t feasible. In the end, I have to prefer parking the probe around Europa, but I can’t support the current pre-EOI tour. How firm are these EE tour plans? Some sort of hybrid must be possible.

Posted by: Mariner9 Nov 20 2007, 01:08 AM

QUOTE (djellison @ Nov 19 2007, 04:10 PM) *
You could make those same arguments regarding the uniqueness of Europa with just about any other body in the solar system. You can make it about Io, Enceladus and Titan in this context without any exaggeration.

Doug



Sorry if I was unclear on the choice I was making. I was comparing JSO vs. EE.

Many (but not all) of the arguments on this thread were boiling down to having Europa vs. Ganymede as the final destination of the probe. In my mind if your choice is between orbiting Europa, or Ganymede, then Europa wins.

I was not even considering or discussing Io, Enceladus or Titan.

Posted by: vjkane Nov 20 2007, 01:29 AM

The swing argument in favor of making the next Flagship mission the Europa Explorer may be preparation for follow on missions. We won't be able to answer any biological questions about Europa with EE -- but we have to find the safest and most scientifically promising landing site on Europa for that mission, which is in fact the central justification for Europa Explorer. Europa landers -- like Mars sample returns -- will be very few and far between, and we have to take great care to maximize both the chances that they'll survive and the chances that they'll find something really interesting. Without that need, Europa Explorer's high-priority status really would be questionable -- but that need is the elephant in the room, assuming that we want to have any chance of examining Europa for life before about 2040. Don't forget that we are talking about flying only one of these Flagships every 8-10 years.

Possible compromise: the Europa Explorer report mentions (pg. 160) that delaying its launch by 19 months -- till Jan. 2017 -- not only allows its funding to be more stretched out, but also provides a considerably better launch opportunity that would allow the craft's total mass to be increased by about 550 kg, and its dry mass to be increased by 175 kg. You could use that extra mass for more and better instruments a la JSO, and/or for more radiation shielding and fuel to allow a few Io flybys (in addition to the already-existing Ganymede and Callisto flybys) before settling into Europa orbit. This, after all, is the launch date already labelled for JSO. (Also keep in mind that in the two studies, JSO cost about the same as Europa Explorer. That's not surprising, given that their designs are near-identical except that JSO would carry more instruments and can compensate for that by having modestly thinner radiation shielding -- although it must still survive 1.8 Mrads versus 2.6 for Explorer.)

Posted by: nprev Nov 20 2007, 02:17 AM

QUOTE (vjkane @ Nov 19 2007, 05:29 PM) *
The swing argument in favor of making the next Flagship mission the Europa Explorer may be preparation for follow on missions.


That's an interesting argument well worth considering from many angles. Does anyone know of anything else planned long-term for Jupiter other than Europan exploration? (I don't.) This may reflect a fundamental perceptual bias on our part, and we probably wouldn't be having this discussion if Galileo's HGA had fully deployed, alas and dammit.

IMHO, Ted is right: we need to complete a detailed reconnaissance of the Jovian system before committing to target-specific Flagship-class missions. Europa is very attractive, of course, and think it would be the proper EOM objective for a future systemic orbiter...but we need more data. We may be fixated on Europa to the detriment of considering other, potentially more scientifically significant, objectives. Point being, we don't have a very clear picture of the Galileans yet...might be wise to acquire one before proceeding further.

Posted by: vjkane Nov 20 2007, 04:47 AM

I've been trying to think of creative solutions that could be enabled by ESA possible contribution to an outer planet mission. Here are a couple of thoughts:

ESA has studied a mini-Europa orbiter that would be solar powered and depend on a relay satellite to keep mass and power requirements down. If NASA were to build JSO, then it could orbit one moon and act as a relay for an ESA craft that orbits another moon. Ganymede would be a logical target since the relatively low radiation makes the design easier and it could be solar powered.

NASA has studied a New Frontiers solar powered mission to Saturn that would drop to probes into Saturn during a flyby mission. A possible alternative would be for the craft to carry a Titan probe(s) or balloons supplied by ESA. The craft would have to be beefed up to be an Saturn orbiter so it could act as a relay for the ESA probes. In theory the orbiter could use its communications antenna to continue radar mapping of Titan to help fill in areas missed by Cassini, although the power and communications requirement might move this out of the New Frontiers class. Although the craft in theory could be a near copy of Juno, which fits into the budget, and I've heard that the New Frontiers budget will be increased for the next round.

I personally like the second option. Titan is fascinating.

Posted by: dvandorn Nov 20 2007, 05:45 AM

This discussion is interesting in that it seems to reduce the question down to whether or not Europa alone is intrinsically more interesting than the rest of the Jovian system.

I have to agree with Jason -- I think that, given a choice between the JSO and EE mission profiles, I like the JSO better because it gets most (if not all) of the data you need about Europa to plan the next mission, and gives you a lot more data about the rest of the system than EE would.

Recall, please, that some Galileo results suggest that Ganymede and even Callisto may have "molten ice" (i.e., liquid water) mantles below their solid ice crusts. Granted, Europa is the most interesting from an astrobiology perspective (more access to sunlight and tidal heating), but any body with a hard ice crust and a liquid water mantle can teach us an awful lot about such worlds.

And it may be a very good idea to learn about them -- it's always possible that there are more habitable worlds of the Europa type out there than there are of the Earth type. After all, a Europa could form around pretty much any gas giant in a huge expanse of a solar system's domain, while an Earth has to reside in that narrow little Goldilocks band. Statistically speaking, you might expect more life to arise in Europa-like worlds than on Earthlike worlds, just from sheer numbers.

-the other Doug

Posted by: centsworth_II Nov 20 2007, 06:11 AM

QUOTE (nprev @ Nov 19 2007, 09:17 PM) *
...we probably wouldn't be having this discussion if Galileo's HGA had fully deployed...

The elephant in the room. There seems to be an argument between those
who think the Jovian system has been sufficiently explored in it's whole to
merit the next mission's being narrowly focused, and those who don't.

Posted by: JRehling Nov 20 2007, 07:15 AM

QUOTE (centsworth_II @ Nov 19 2007, 10:11 PM) *
The elephant in the room. There seems to be an argument between those
who think the Jovian system has been sufficiently explored in it's whole to
merit the next mission's being narrowly focused, and those who don't.


Well, that's an editorial assessment.

The way I see it, planetary science is a series of games of Twenty Questions and with typical post-Apollo funding regimes, our/likely-anyone's approach has been to pick worlds that are worth playing with and worlds that are only worth a game of One Question. Mercury hasn't been visited in 32 years, so you know which bucket it's in. Mars has five live missions there now, so you know it's in the other bucket.

Europa and Titan are in due time going to get follow-up missions (in the case of Titan, I mean a mission after the mission after Cassini). [I realize this sounds apocalyptic to suggest that some worlds WON'T get any follow-up missions ever. If human existence continues, Eros will probably get a follow-up mission, just in the 26th century or something. I mean on a timeline measured in a couple of decades instead of a few.]

Ganymede would be explored quite well by EE (14 flybys). Compare that to Cassini at Saturn. Enceladus won't get 14 (targeted) flybys by the time the first extended mission is up. EE does not ignore Ganymede. It wouldn't map it into submission the way JSO would, but Ganymede's not in the top tier of interest, either.

Callisto is a wash; seen about equally well by either mission. JSO could provide more long-range monitoring, but what does that mean with a dead world?

Europa, however, is a place where we might want to set a lander down following recon. JSO would be a half-measure in that regard, so we'd be putting it off by decades by flying JSO first. And that's not a winning strategy for Twenty Questions.

I believe a correct paraphrase from Apollo (or the HBO dramatization) regarding finding lunar anorthosite was "It'd be a shame if it were there and we missed it." That's how I perceive Europa, which might have a volcanic Io inside, smoking into a salty ocean, softening the overlying ice shell beyond static equilibrium, opening up some live rifts between blocks of ice you can almost picture a polar bear diving off of.

Or an active fissure where a triple band is widening like the crack on my ex-windshield. Dark stuff spraying up every time the crust flexes.

If it's there, it'd be a shame to put off finding it for 20 years.

Ganymede's going to sit there on ice for another three to six billion years. No hurry.

One or two Io flybys for EE would clinch the advantage totally, but I'd take EE as is. A few views of Io's plumes from 400K km would augment Earth-based long-duration monitoring nicely. Io deserves better, but JSO wouldn't completely nail Io either, so I'd say EE for now and maybe some better Io looks if a combined science/comsat accompanied the Europa lander.

Posted by: volcanopele Nov 20 2007, 07:30 AM

The one good thing about EE is that it would be a lot easier to convince NASA to sign off on an Io New Frontiers mission. 2 flybys is not enough...

Posted by: edstrick Nov 20 2007, 10:22 AM

(Without reading the voluminous material on the opag site...)

Would a JSO mission have a higher angular resolution camera than Cassini's narrow angle cam?...
Would it be a multi-megapixel camera, 4-megapixel camera on Rosetta, or even higher pixel-count-format?
Would it be able to take images every few seconds, rather than about one per minute?...
Would it have many times more data storage than Cassini, and be able to dump it all to Earth during apoapsis, as it heads in for the next encounter?

As Meriner 10 approached and receeded from Mercury, it "fireshosed" the illuminated disk with continuous mosaicing until the field of view and frame rate became too small and slow to get contiguous coverage.

Voyager was somewhat able to do the same at Jupiter with the flyby-targeted moons.
Galileo was a salvage job.. very successful, but still a salvage job.

A current technology mission should be able to saturate-cover the illuminated disc with multi-spectral images down to maybe 1/4 kilometer with higher camera resolution from long range, a faster frame rate, and more data storage and transmission capability. Maybe even UV/VIS/NIR color coverage at that resolution. During near-encounter, they should be able to do "quadrangle-maps" of target regions with several strips of contiguouis images down to something like 50 meters, much the way Viking Orbiters mapped landing sites with the twin rapid-fire framing cameras and it's scan platform.

I'm not going to vote on Europa vs Jovian System, but we damn near better be able to do as much better at Jupiter than Cassini does at Saturn, as Cassini did over poor Galileo.

Beyond that... Near Infrared imaging is vastly advanced over Cassini's technology level.. A megapixel 1 to 5 <maybe> micrometer framing camera with a good set of wide and narrow band filters should be state-of-the-art and extend multispectal mapping at good resolution to longer, more diagnostic wavelengths.

Posted by: tedstryk Nov 20 2007, 12:38 PM

QUOTE (edstrick @ Nov 20 2007, 10:22 AM) *
Voyager was somewhat able to do the same at Jupiter with the flyby-targeted moons.
Galileo was a salvage job.. very successful, but still a salvage job.


Yes, Galileo was a salvage job, but it did have some encounters that did not fall into this category, namely its earth-moon flybys, which give one an idea of what SSI was really capable. Also, when one looks at the ultra-high resolution mosaics from its high-speed flybys of the Galileans, the short integration led to images that are neatly nested, especially compared to Cassini mosaics. I would love to see a JSO or EE with a Rosetta-sized (at least) camera with a fast integration time. In fact, it could do more than Mariner 10 if it had reaction wheels, because the coverage could be neatly nested, as opposed to Mariner 10, which appeared to bounce all over the place.

Posted by: tedstryk Nov 20 2007, 02:24 PM

One thing to add. I would quickly defect from my current position if the Europa orbiter had JSO's tour, including Io. This is not OPAG based, but what I would really like to see is a long-term but scaled back JSO style mission, perhaps as small flagship combined with EE. While I definitely consider Ganymede worth an orbiter to the extent I would not oppose such a mission, I like the Ganymede orbit idea mainly because the probe could (especially with an excellent long-range camera) continue to probe the rest of the Jovian system from there. However, if a smaller orbiter filled the long range role, and some Io flybys were added to EE, I would support it. Also, because the technical challenges of a Galileo-II are not as great (in the sense that it is something that has been done before, sans a working antenna), it could be launched sooner and thus could pave the way for EE. However, I realize budgetary reality may not allow that.

Posted by: nprev Nov 20 2007, 02:30 PM

QUOTE (tedstryk @ Nov 20 2007, 04:38 AM) *
I would love to see a JSO or EE with a Rosetta-sized (at least) camera with a fast integration time.


I completely agree, and this seems technically feasible, of course. In fact that's the strongest argument yet for merging these mission proposals. Completing a full Jovian system survey should be the primary objective, and after this task is complete the spacecraft should be capable of orbiting Europa or Ganymede, with target selection determined by the survey findings.

Building in adaptability seems like the best way to resolve this conflict. The main idea here is to acquire enough information about the Galileans to make an informed choice when the time comes (though I suspect that the meetings will be real roof-raisers; heck, look how much discussion there's been on this thread alone!)

Posted by: vjkane Nov 20 2007, 02:33 PM

QUOTE (edstrick @ Nov 20 2007, 10:22 AM) *
I'm not going to vote on Europa vs Jovian System, but we damn near better be able to do as much better at Jupiter than Cassini does at Saturn, as Cassini did over poor Galileo.


Even if Galileo's antenna had deployed, there would be a good reason to have the next Jovian flagship mission be able to do good Jovian system science. Galileo's instruments were mid-1970's vintage. Thirty years of instrument development would vastly improve our ability to tackle a number of questions.

Posted by: ugordan Nov 20 2007, 02:48 PM

QUOTE (nprev @ Nov 20 2007, 03:30 PM) *
Building in adaptability seems like the best way to resolve this conflict.

Adaptability will inevitably imply sub-optimality for either Europa or Ganymede. You want to optimize your payload (science instruments, rad shielding, fuel) for a specific target, there's no margin like that to accomodate free choice once you get there. It's not a case of choosing the landing site a-la Viking from orbital survey first. You'd inevitably have an impact on science capability to allow for those margins. Once again, it boils down to "do you really want to sacrifice X in order to be able to do Y?". Just as EE sacrifices coverage of the entire system and JSO would leave certain questions open if you went into Europan orbit.

Posted by: djellison Nov 20 2007, 02:57 PM

QUOTE (ugordan @ Nov 20 2007, 02:48 PM) *
You want to optimize your payload ... for a specific target


Should that target be a specific body, or a specifc set of scientific goals?

Doug

Posted by: nprev Nov 20 2007, 03:05 PM

No question at all that there would be trade-offs, Gordan. However, as vjkane observed, we've come a long way in terms of instrument capabilities. Furthermore, for the satellite orbit phase, we've down-selected to two icy moon targets, so the instrumentation suite need not be radically different for studying either body (only major exception I can think of is that Ganymede needs a magnetometer, and Europa doesn't). Enhanced radiation shielding for a possible Europa mission is still a plus even if Europa isn't the final destination; this could enable Io flybys for one thing, and also generally prolong mission lifetime. Therefore, I still think that designing for versatility is a good bet.

Posted by: ugordan Nov 20 2007, 03:16 PM

QUOTE (djellison @ Nov 20 2007, 03:57 PM) *
Should that target be a specific body, or a specifc set of scientific goals?

Probably scientific goals. Some goals can be pretty constraining though, suggesting you end up with a target body again. We're back at that point: would we like a little bit of everything (possibly best bang per buck), or do we want a quantum leap in knowledge about a single object?

Posted by: tedstryk Nov 20 2007, 03:40 PM

QUOTE (ugordan @ Nov 20 2007, 03:16 PM) *
Probably scientific goals. Some goals can be pretty constraining though, suggesting you end up with a target body again. We're back at that point: would we like a little bit of everything (possibly best bang per buck), or do we want a quantum leap in knowledge about a single object?


For this type of mission (in other words, not a mission in a series like the Mars series that launches every two years), we need to make sure we understand how best to approach making that quantum leap. And frankly, if it is a much better understanding of all the Galileans and Jupiter (plus the small moons, since a high resolution long range camera should help there as well) versus a quantum leap at Europa alone with relatively little attention paid to the other moons, I would pick the former. Given all the unknowns, I think a system-wide quantum leap is possible.

Posted by: Juramike Nov 20 2007, 04:37 PM

I agree with ugordan, scientific goals should drive the mission and instrumentation. And I fall into the camp of desiring to study one object thoroughly in order to extend those lessons to others.

So which Galilean moon will tell you the most about the formation and evolution of common classes of planetary objects?

Studying Europa will tell us about watery moons with thin icy shells in special environments. Very interesting, but very specialized. Basically Europa would only serve as a model for itself and Enceladus.

Studying Ganymede will tell us about big ice moons/planets with thicker crusts. Titan, Triton, Pluto, and others may all fall into this category.

Ganymede seems a more general "Joe-big-ice-world", while Europa is more of a special case. Both are very interesting cases, but Ganymede's lessons will extend to more objects.

-Mike

Posted by: JRehling Nov 20 2007, 06:38 PM

QUOTE (tedstryk @ Nov 20 2007, 07:40 AM) *
For this type of mission (in other words, not a mission in a series like the Mars series that launches every two years), we need to make sure we understand how best to approach making that quantum leap. And frankly, if it is a much better understanding of all the Galileans and Jupiter (plus the small moons, since a high resolution long range camera should help there as well) versus a quantum leap at Europa alone with relatively little attention paid to the other moons, I would pick the former. Given all the unknowns, I think a system-wide quantum leap is possible.


I'm not sure that all of the objects have a system-wide quantum leap in them. I'll point the finger at Callisto first: Aside from trace compositional differences due to the higher radiation flux smacking its trailing side, it pretty much looks the same all over. Sure, a mega-mission with landers and rover would generate new Callisto science ad infinitum, but orbital surveys may not be able to do much more than either JSO or EE already have planned.

I wouldn't bet the farm that Ganymede is in the realm of "the more you look, the more new stuff you see". Again, taking into account that EE will visit Ganymede more than any Cassini will visit any saturnian satellite save Titan (a doubly extended mission may push Enceladus to that number of flybys), I can't presuppose that there's a quantum leap there that we'd be missing. Fourteen ground tracks at low altitude makes for a lot of sampling that surface. The old stuff is probably not more diverse than Callisto. And the groovy stuff would get a lot of close peeks from 14 flybys. Don't pigeonhole EE as a mission that ignores the rest of the system.

Io almost certainly would turn up more diversity the more closely we looked at it. JSO would do a so-so job of that. I would lean more towards EE now and a later mission that flew a quasi-Juno-like orbit chock full of Io flybys so long as it would end up observing the whole surface in daylight at some point or another. Although the nice thing about Io's plumes is that you can actually make useful observations at night, too.

The thing that makes Europa incredibly interesting to me I could sum up with this question: How old is the youngest crust? I can tell you the answer to that for all of the other Galileans right now: Zero age (Io) and more than two billion years (Ganymede and Callisto). Europa... could be crust formed today, could be sixty years old, could be ten thousand. And if the answer is on the low end, we know that it is local (the majority of the surface is old enough to show sporadic impact cratering), and it could be arbitrarily local. We won't know about the third-next mission to this system (Juno, JSO/EE, a possible Europa lander) until EE flies. That's why to me the answer is to fly EE, get a heck of a good look at Ganymede (without making it the best mapped world in the cosmos), and aim to give Io its closeup later with a mission designed for Io.

As a final pessimistic comment on remote sensing in this system, I'll point out that IR studies of composition have utterly struck out when done at the Galileo and MGS-TES level. I'd want to see a heck of a good probability of an answer before flying a mission with a high priority on getting compositional data and getting back answers like Galileo re: Ganymede (it's something dark mixed in with ice) or MGS (there are two kinds of rock under the dust, and one might resemble andesite but we're not sure).

Posted by: nprev Nov 20 2007, 07:08 PM

Looks more & more like we're not going to reach a consensus here, which is interesting. It's very clear now that there are numerous science objectives of great interest in the Jovian system, and one mission probably won't cut it even for the questions we know to ask, much less the ones we don't know yet.

Redirecting a bit if I may, should OPAG then derive an integrated mission campaign for the Jovian system as a whole, similar to that for Mars? Understand that we can't do the same launch rate, but perhaps a NASA/ESA/JAXA collaborative planning effort could cover all the essential bases over a reasonable time-frame. We could do considerably more working in parallel, especially right now when we have both specific Europa objectives and a number of things to find out about the other moons.

Posted by: djellison Nov 20 2007, 07:12 PM

QUOTE (nprev @ Nov 20 2007, 07:08 PM) *
. It's very clear now that there are numerous science objectives of great interest in the Jovian system,


Just to totally screw things - I'd rather we went back to Titan than any of the Jovians...but maybe that's just me smile.gif

Doug

Posted by: nprev Nov 20 2007, 07:16 PM

QUOTE (djellison @ Nov 20 2007, 11:12 AM) *
Just to totally screw things - I'd rather we went back to Titan than any of the Jovians...but maybe that's just me smile.gif

Doug


Yeah...that'd do it, all right! rolleyes.gif tongue.gif

Posted by: volcanopele Nov 20 2007, 07:24 PM

LOL Yeah, that's a good point to keep in mind, we aren't just talking about EE and JSO, but Enceladus and Titan as well. As I said before, I don't think we can make a decision on whether Enceladus needs a flagship mission just yet. I think by the end of the Cassini mission, the question of the source of the jets will largely be answered. If they come almost directly from a liquid water source, then Enceladus jumps ahead of Europa quite frankly. Why send 2 or 3 missions to sample potential life when you can send one wink.gif If the jets do come from a liquid water source, we have the trifecta: liquid water, organic molecules, and an energy source, and the reservoir can be sampled MUCH more easily than at Europa (assuming we can capture this material on a Stardust-like pass and bring it back to Earth). If the jets don't come from a liquid water source, then frankly, Cassini's coverage at Enceladus should be quite sufficient by the end of the extended mission.

As for Titan, I think the kind of science that can be done at that one target would be far more exciting, frankly, than Europa. Not as diverse as JSO, though. Hense my earlier ranking of: 1) JSO, 2) Titan Explorer, 3) Europa. Enceladus could be #1 if the jets come from a liquid water source, #4 if they don't.

Posted by: centsworth_II Nov 20 2007, 08:20 PM

QUOTE (djellison @ Nov 20 2007, 02:12 PM) *
Just to totally screw things - I'd rather we went back to Titan than any of the Jovians...but maybe that's just me smile.gif
Doug

But that's, as you would say, jumping the queue.

Posted by: ngunn Nov 20 2007, 08:41 PM

I've scanned the Enceladus report and was surprised to find how good a case they managed to make, but I still find the idea of a Saturnian follow-up that doesn't focus on Titan rather bizarre.

Going back to Titan is a must, but if NASA plump for a Jovian mission first I won't be too upset as that should also be very exciting. I wish they'd decide, so that ESA can start seeking partners for the other option (including NASA's non-flagship budget).

Posted by: djellison Nov 20 2007, 08:48 PM

QUOTE (centsworth_II @ Nov 20 2007, 08:20 PM) *
jumping the queue.


Post-Voyager score (if you include Juno)

Jupiter. Two orbiters, One probe, Two flypasts
Saturn. One orbiter, One lander.

If you ask me, Saturn's owed an orbiter and some flypasts - another mission to the Jovian system really WOULD be queue jumping.

Like I said - just throwing in a vote for somewhere else. I'd pick Titan over any of the other suggestions. An ideal world, we'd do all of them, but if I had to pick one, just to me, Titan seems the most exciting, interesting and intriguing.

Doug

Posted by: vjkane Nov 20 2007, 09:25 PM

I stole a little time at lunch to compare camera resolutions. Note: I simply took quoted resolutions at specified distances from public websites and normalized resolutions to 1,000 km distance. View these as approximations.Attached file should preserve table formatting.So with that, here is how the high resolution/narrow angle cameras from various missions would compare at set distances: 1K km 10K km Ganeymede to: Jupiter Io (closest) Io (furthest) Web quoted resolutionJSO 2 m 20 m 2.1 km 1.3 km 3.0km 0.4 m at 200 kmEE 10 m 100 m 10.7 km 6.5 km 14.9 km 1 m at 100 kmCassini 6 m 60 m 6.4 km 3.9 km 8.9 km 0.024 m at 4 kmMRO 1 m 10 m 1.1 km 0.6 km 1.5 km 0.3 m at 300 kmDeep Impact 3 m 30 m 3.1 km 1.9 km 4.3 km 2 m at 700 kmPage 3-5 of the JSO report says that the 0.5 m optics chosen as a baseline could achieve an optical resolution of 775 m from the distance of Ganymede, which is considerably better than is in my chart here. The difference could be caused by (1) a loss of resolution between theoretical optics and what is achieved with an actual CCD implementation (2) I don't know what I'm doing in putting together this chart. Caveat emptor! laugh.gifI stole a little time at lunch to compare camera resolutions. Note: I simply took quoted resolutions at specified distances from public websites and normalized resolutions to 1,000 km distance. View these as approximations.Attached file should preserve table formatting.So with that, here is how the high resolution/narrow angle cameras from various missions would compare at set distances: 1K km 10K km Ganeymede to: Jupiter Io (closest) Io (furthest) Web quoted resolutionJSO 2 m 20 m 2.1 km 1.3 km 3.0km 0.4 m at 200 kmEE 10 m 100 m 10.7 km 6.5 km 14.9 km 1 m at 100 kmCassini 6 m 60 m 6.4 km 3.9 km 8.9 km 0.024 m at 4 kmMRO 1 m 10 m 1.1 km 0.6 km 1.5 km 0.3 m at 300 kmDeep Impact 3 m 30 m 3.1 km 1.9 km 4.3 km 2 m at 700 kmPage 3-5 of the JSO report says that the 0.5 m optics chosen as a baseline could achieve an optical resolution of 775 m from the distance of Ganymede, which is considerably better than is in my chart here. The difference could be caused by (1) a loss of resolution between theoretical optics and what is achieved with an actual CCD implementation (2) I don't know what I'm doing in putting together this chart. Caveat emptor! laugh.gif

 camera_resolutions.txt ( 1.47K ) : 253
 

Posted by: vjkane Nov 20 2007, 09:28 PM

For camera resolutions from different missions at different interesting Jovian system distances (1,000s km for moon flybys or distances from Ganymede to Jupiter and Io for long term observations of dynamic bodies) see the attached file. Sorry the previous message got so screwed up, formatting wise.

 camera_resolutions.txt ( 1.47K ) : 217
 

Posted by: tedstryk Nov 20 2007, 10:28 PM

QUOTE (djellison @ Nov 20 2007, 07:12 PM) *
Just to totally screw things - I'd rather we went back to Titan than any of the Jovians...but maybe that's just me smile.gif

Doug


All other things being equal, I agree. However, in terms of both technology and figuring out a best approach, I would rather put Titan off. I really can't see Enceladus competing with Titan or the Galileans - Cassini seems to be doing such a good job with it.

Posted by: JRehling Nov 21 2007, 05:02 AM

QUOTE (djellison @ Nov 20 2007, 12:48 PM) *
Post-Voyager score (if you include Juno)

Jupiter. Two orbiters, One probe, Two flypasts
Saturn. One orbiter, One lander.

If you ask me, Saturn's owed an orbiter and some flypasts - another mission to the Jovian system really WOULD be queue jumping.

Like I said - just throwing in a vote for somewhere else. I'd pick Titan over any of the other suggestions. An ideal world, we'd do all of them, but if I had to pick one, just to me, Titan seems the most exciting, interesting and intriguing.

Doug


I might say that not only is Titan more interesting than any of the Galileans individually, it is perhaps more interesting than all of them together, even if you throw in Mars for good measure.

But there's a lot more to do to collect, not to mention analyze, Cassini data on Titan. I'm amazed at how well certain persons (ahem, Ralph) did at prognosticating many of the Cassini-Huygens findings, but this is a world of amazing diversity. We may yet discover a compelling landing site (entailing new instrumentation) that hasn't yet been RADARed.

Europa's data has been placed in the oven and come out a cake. Titan's is still raw dough. Titan definitely looks like a more interesting place, but we shouldn't finish designing a multibillion dollar mission until the second round of papers after Cassini's last gasp. That will be years from now. In that sense, the jovians are once again due.

Posted by: mchan Nov 21 2007, 05:23 AM

Very much enjoying the discussion here.

For EE, does planetary quarantine require taking the spacecraft out of Europa orbit at EOM? If so, would it be practical to increase fuel load to move it at least apojove out to lower radiation exposure distance from Jupiter?

Yes, EE would have accumulated its designed total dose by Europa EOM, but this would be about getting some bonus time similar to the last several Galileo orbits. Galileo deliberately went deeper to get the Io flybys. What if EE kept to the outside for some time before making some end of life Io flybys and go out like Galileo? Could EE meet some of the JSO objectives in a post-Europa EOM phase?

Posted by: tedstryk Nov 21 2007, 02:30 PM

QUOTE (djellison @ Nov 20 2007, 08:48 PM) *
Jupiter. Two orbiters, One probe, Two flypasts



Shouldn't that be three flybys? - Ulysses (If you really want to push it, the 2004 distant encounter could bring us to four), New Horizons, and Cassini.

Posted by: djellison Nov 21 2007, 02:49 PM

I thought about adding Ulysses - but in terms of the science people are talking about here, I thought it would ignore it.

Doug

Posted by: vjkane Nov 21 2007, 03:58 PM

QUOTE (tedstryk @ Nov 21 2007, 02:30 PM) *
Shouldn't that be three flybys? - Ulysses (If you really want to push it, the 2004 distant encounter could bring us to four), New Horizons, and Cassini.


Don't forget the two Voyagers.

While there's been a lot of missions, this is the king of planets with 5 planet-classed bodies, many asteroid-classed moons, and a magnetosphere. Both Jupiter and Saturn could be the subject of almost endless missions. Just like the moon or Mars.

Posted by: mchan Nov 21 2007, 04:02 PM

QUOTE (djellison @ Nov 20 2007, 12:48 PM) *
Post-Voyager score (if you include Juno)

Jupiter. Two orbiters, One probe, Two flypasts

He was counting post-Voyager.

Posted by: Bjorn Jonsson Nov 21 2007, 04:34 PM

Having skimmed through these reports (I need to read them more carefully later) I strongly prefer JSO over EE, mainly thanks to its much better instruments, far broader coverage of the Jovian system and longer lifetime once in Ganymede orbit, compared to EE's lifetime in Europa orbit.

Just one close flyby of Io (and in fact there will be four) would return more and higher quality data than all of the Galileo Io flybys combined. There would be high resolution long term monitoring and atmospheric movies of Jupiter at multiple wavelengths, something Galileo couldn't do well because of limited bandwidth and which Voyager, Cassini and NH couldn't do properly due to lack of time. And once JSO is in Ganymede orbit Io can be monitored at 1-2 km/pixel for a long time.

It is true that EE would return a lot more Europa data - still JSO's Europa data would be vastly superior to the Galileo data. However, there will be a lot less data for everything else. And let's not forget that Ganymede is interesting. Not as interesting as Europa but still interesting.

That said, my 'post-Cassini' view is that I find the Saturn system more interesting than the Jupiter system. Before Cassini I expected the Jupiter system to be more interesting but Cassini has revealed a huge amount of interesting things.

Posted by: centsworth_II Nov 21 2007, 05:21 PM

QUOTE (Bjorn Jonsson @ Nov 21 2007, 11:34 AM) *
Before Cassini I expected the Jupiter system to be more interesting but Cassini has revealed a huge amount of interesting things.

Saturn does have some quirky little moons that Cassini has been able to take a close look at.
Are Jupiter's small moons really devoid of the same interesting variety, or is it that we have
not looked at them close enough to reveal their quirks? Could there be hidden gems among
them, puzzles like Enceladus' plumes, Iapetus' equatorial ridge, or Hyperion's spongy look?
Or have we seen enough already to know that no such surprises await a closer look?

Posted by: JRehling Nov 21 2007, 05:40 PM

QUOTE (centsworth_II @ Nov 21 2007, 09:21 AM) *
Saturn does have some quirky little moons that Cassini has been able to take a close look at.
Are Jupiter's small moons really devoid of the same interesting variety, or is it that we have
not looked at them close enough to reveal their quirks? Could there be hidden gems among
them, puzzles like Enceladus' plumes, Iapetus' equatorial ridge, or Hyperion's spongy look?
Or have we seen enough already to know that no such surprises await a closer look?


Jupiter doesn't have any/many mid-sized moons, which is where most of the surprises have been coming from at Saturn. From what we've seen of smaller worlds, there's less opportunity to surprise. We won't know til we look, but exploring many of those outer jovian satellites would be tough with just one craft. Lots of empty space and wacky orbits out there. You would either need to burn a lot of propellant or have lots of little mini-craft zipping around.

Posted by: Bjorn Jonsson Nov 21 2007, 06:08 PM

I should clarify that the main reasons I find the Saturn system so interesting is that Enceladus and especially Titan turned out to be more interesting than I expected before Cassini (even though I knew Titan would be interesting). There's more out there that's interesting but these are the biggest factors.

Posted by: djellison Nov 21 2007, 06:49 PM

Saturnian and Jovians systems - They're both interesting, they're both scientifically compelling, they both offer excellent outreach potential. Essentially, the decision has to come down to personal taste and ultimately, sadly, money.

Doug

Posted by: Geographer Nov 22 2007, 02:04 PM

How much more expensive would a Saturnian mission be over one to Jupiter? How much longer? Could it just come down to factions within NASA and the scientific community duking it out for their priorities will Dr. Griffin making the final decision?

Posted by: Mariner9 Nov 22 2007, 03:39 PM

On the surface of things, you would think that a Saturn mission would naturally take a lot longer to fly since it is so much more distant than Jupiter. But that's not necessarily the case. With the modern approach to do multiple gravity assists the trip times get all jumbled.

Galileo took a Venus-Earth-Earth path, and was in flight for 6.5 years to get to Jupiter.

Cassini took a Venus-Venus-Earth-Jupiter path and was in route for 6.75 years to get to Saturn.

Three months longer. Big deal.

And then it depends on your target. what if you are really asking is how long to attain Europa or Ganymede orbit, or be floating in the clouds of Titan? Well, the Jovian targets invlove a lot of sattelite flybys before final insertion, which can add 2-4 years. But many of the Titan scenarios I've heard about use aerocapture. In that case Titan becomes a much faster flight than Europa.

So the relative distances to Saturn and Jupiter turn out to be not that relavant. Just another counter-intuitive example in the wide wide world of space travel.

Posted by: Bjorn Jonsson Nov 22 2007, 04:42 PM

True - but there's one problem: A Jupiter gravity assist (JGA) to reach Saturn isn't always available. It's available for only a few years every ~20 years.

Looking at the near future a JGA is available if you launch around 2015 or so (I'm writing this from memory so it's not 100% accurate). If you miss that opportunity you have to wait until the mid 2030s or reach Saturn without a JGA which takes a longer time.

Posted by: nprev Nov 22 2007, 05:21 PM

Does JPL or another agency maintain a launch opportunity "library", by any chance? Seems like the operations research folks should be doing just that: looking for optimal launch opportunities for various targets, and publishing them in order to solicit & align mission proposals with the realities of orbital mechanics.

Reason I ask is that the Galileo & Cassini transit trajectories were pretty complex, and at least in the case of Galileo this was certainly not the preferred option for a variety of other reasons. Seems as if determining all feasible options in this regard would be quite beneficial for future mission planning.

Well, probably just re-invented the wheel here, but given the inherent variability in planetary exploration initiatives just thought I'd ask... rolleyes.gif

Posted by: Mariner9 Nov 22 2007, 07:41 PM

QUOTE (Bjorn Jonsson @ Nov 22 2007, 08:42 AM) *
True - but there's one problem: A Jupiter gravity assist (JGA) to reach Saturn isn't always available. It's available for only a few years every ~20 years.



Granted, but my point was that there are many ways to get out to the outer planets.

Even if the 'standard' Jupiter gravity assist is not available, remember Pioneer 11? It used a JGA, but took a very extreme route, much more circuitous than the Voyager probes four years later.

And some proposals include a solar-electric propulsion stage, presumably also using Venus, Earth or Mar gravity assists along the way.

Unfortunately it seems that we don't see many mission proposals (involving orbiters, at least) that use anything remotely like a good-old fashioned direct route like we use to Mars or Venus.

Sigh..... six or seven years to Jupiter instead of two. Heck, I'd settle for even three or four... I'm not greedy. Just impatient. smile.gif

Posted by: gndonald Nov 22 2007, 10:12 PM

QUOTE (nprev @ Nov 23 2007, 02:21 AM) *
Does JPL or another agency maintain a launch opportunity "library", by any chance? Seems like the operations research folks should be doing just that: looking for optimal launch opportunities for various targets, and publishing them in order to solicit & align mission proposals with the realities of orbital mechanics.


That's actually how Voyager came about, someone calculated that it would be possible to launch during the 1970's and hit all the major outer planets with one mission then pushed as hard as possible to get that mission flown.

The NASA technical reports server has all sorts of documents related to trajectory planning, one of the more interesting online documents is one written at a time NASA was considering creating a Solar-Ion drive 'common bus' for future space exploration. It covers outer planet opportunities for that type of spacecraft from Jupiter to Pluto for the period 1975-1990. (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730017180_1973017180.pdf 11.9mb PDF)

One of the offline documents discusses missions that would flyby http://tinyurl.com/2ydofe, that covered 1979 -1987, the next set of such opportunities will not occur till 2025, so there may be the chance to start a lobbying effort that pays off for the next generation of Space enthusiasts.

Posted by: nprev Nov 22 2007, 10:42 PM

QUOTE (gndonald @ Nov 22 2007, 02:12 PM) *
That's actually how Voyager came about, someone calculated that it would be possible to launch during the 1970's and hit all the major outer planets with one mission then pushed as hard as possible to get that mission flown.


Yeah, I knew that; wasn't the guy who found that Italian?

What I'm asking is whether there's a dedicated group looking for opportunistic trajectories to the outer planets via possibly complicated inner planet pump-ups, etc. Does not appear to be a trivial effort, but seems as if such a group could generate some real, positive planning data for future outer planet missions.

Posted by: Del Palmer Nov 22 2007, 11:20 PM

QUOTE (nprev @ Nov 22 2007, 10:42 PM) *
Yeah, I knew that; wasn't the guy who found that Italian?


Gary Flandro. Not sure if he was Italian or not (thought he was American).

Posted by: nprev Nov 23 2007, 12:24 AM

I stand corrected: http://en.wikipedia.org/wiki/Gary_Flandro is an American, would not presume to speculate on his ethnic background, not that it's anyone's business but his own.

Point still being, is there anyone out there actively seeking favorable trajectories/opportunities for the outer planets? I'm sure that there are lots of direct launch windows known, but thinking more of creative things like the Cassini/Galileo flight paths. They're long, but they work, and knowing about them would be a valuable planning tool.

Posted by: edstrick Nov 23 2007, 07:37 AM

My brain's bouncing off a statement made a couple pages back, rattling off categorizations of moon-designated missions one by one and came up with:

Io's a volcanologist's dream
Europa's a glaciologist/oceanologist's dream.
Ganymede's a glaciologist/geologist's dream
Callisto's a mortician's dream.

<evil grin... should't be so hard on poor old Callisto>

Posted by: ugordan Nov 23 2007, 09:55 AM

QUOTE (nprev @ Nov 23 2007, 01:24 AM) *
Point still being, is there anyone out there actively seeking favorable trajectories/opportunities for the outer planets?

Thinks have changed since the Voyagers. There are tools now to search for viable trajectories and optimize them based on various constraints like delta-V at launch, launch windows, flight time, even stuff like minimum Venus flyby altitude. I don't think anyone designs trajectories for interplanetary probes on the basis of stumbling upon a good trajectory.

Posted by: nprev Nov 23 2007, 10:51 AM

Thought so; in fact, seems as if I saw a recent paper on one such trajectory discovery for a main-belt asteroid tour.

What I'm really wondering is whether there is a concerted and organized effort by anybody to identify all such opportunities (within the realm of practicality, of course) between now and, say, 2100. For example, if we found a very favorable launch opportunity for Uranus in 2027, there would be twenty years available to begin planning, proposal submission, lobbying, etc.

Posted by: Floyd Nov 23 2007, 01:02 PM

The problem is what do you mean by "very favorable"? There are lots of things you might want to optimize. But I agree that for a given velocity leaving earth, the time to get to various planets would have a number of minima which should be searchable. Going to Mars is a bit simpler, has a minimum ever ~2 years.

Posted by: rlorenz Nov 23 2007, 01:42 PM

QUOTE (edstrick @ Nov 23 2007, 02:37 AM) *
My brain's bouncing off a statement made a couple pages back, rattling off categorizations of moon-designated missions one by one and came up with:

Io's a volcanologist's dream
Europa's a glaciologist/oceanologist's dream.
Ganymede's a glaciologist/geologist's dream
Callisto's a mortician's dream.


And Titan has all of the above*.... plus it is an organic chemist's
dream, and a meteorologist's dream, etc. etc......

Plus you can actually put down instruments (thanks to atmosphere for
aerocapture, and entry/descent) to let you do in-situ chemistry, seismology,
soil mechanics, and lots of other good science you simply cant do affordably
at these other places.

You can OBSERVE all these Jovian bodies at varying degrees of detail. You can
actually EXPLORE Titan...

*ok - jury is still out on present-day cryovolcanism. Bet it's there tho..

As for the question about mission library, I don't think so (isolated design
cases get published in papers etc., but no library as such - since there are
competed mission lines like Discovery, NF etc., it would make little sense
to provide data for your competition...)

But it's a pretty straightforward situation - you get Jupiter gravity assists to
Saturn every 15 years or something (repeat the alignment, so one Jupiter
period is 10 years, right, but in that time Saturn goes around 1/3 orbit, so add
another 1/3 of 10 to let Jupiter catch up, but now Saturn has gone aroundanother
tenth, so add another tenth of a Jupiter period).. transcendental or something.

The window closes down circa 2015.

There are pretty much always inner planet opportunities, though.

Posted by: ngunn Nov 23 2007, 01:56 PM

All agog to read the Titan OPAG report when it appears !

Posted by: nprev Nov 23 2007, 03:25 PM

QUOTE (rlorenz @ Nov 23 2007, 05:42 AM) *
As for the question about mission library, I don't think so (isolated design
cases get published in papers etc., but no library as such - since there are
competed mission lines like Discovery, NF etc., it would make little sense
to provide data for your competition...)


sad.gif ...that kind of sucks. As an outsider, I was thinking of overall outer planet programmatic integration (even between national agencies), but I see your point.

Of course, <evil grin>, I wonder what Alan might think about this idea...a mission library might well foster even more productive proposal competition.

(I humbly await my execution for that last...done already fired up a stogie, waiting on the word to put on the blindfold...)

Posted by: vjkane Nov 23 2007, 05:39 PM

QUOTE (rlorenz @ Nov 23 2007, 01:42 PM) *
And Titan has all of the above*.... plus it is an organic chemist's
dream, and a meteorologist's dream, etc. etc......


Ralph nails the problem of deciding the next Flagship mission. Titan is by far the most interesting single moon -- and possibly the most interesting planet-sized body, although Mars offers competition -- in the solar system after our own world. (Don't get me started on the lack of new missions to study our own planet. I'm expecting to have to rely on data from European, Indian, etc. craft for my research in a few years.) On the other hand, Jovian-class worlds appear to be common throughout the galaxy (although the sampling is biased because they are easier to detect). The Jovian moons also offer a wealth of diversity and because they lack an atmosphere that reworks their surfaces, you can untangle the geology more easily than at Titan.

So the Jovian system deserves a thorough study with a craft that has modern instruments (a working antenna would be good, too smile.gif ). Titan deserves study with multiple probes that Ralph mentions. I want both!

In my former life, one of my jobs was to plan product lines -- how to get 50 kg of products with a 35 kg investment. I really want to take Ralph out for a beer and bat around a bunch of ideas.

In some previous posts I listed the resolutions of different camera options for JSO and EE along with some other missions. Since then, I've looked up New Horizon's LORRI's specs, and they are essentially the same in terms of resolution as for EE's proposed narrow angle camera. That class of camera seems to be fine for flybys. It gives decent resolution for studying Jupiter's atmosphere. What it lacks is the ability to carryout good monitoring from a distance of Io. You get okay monitoring, but not great.

Whoever has to decide between these two sets of missions -- Jovian system vs. Titan -- is going to have it tough.

Posted by: centsworth_II Nov 23 2007, 05:46 PM

QUOTE (nprev @ Nov 23 2007, 05:51 AM) *
What I'm really wondering is whether there is a concerted and organized effort by anybody to identify all such opportunities...

Sounds like you're asking for a super computer project -- like finding all the prime numbers.

Posted by: nprev Nov 23 2007, 09:16 PM

Or a distributed computing project like SETI@Home?

Posted by: rlorenz Nov 24 2007, 01:32 PM

QUOTE (vjkane @ Nov 23 2007, 12:39 PM) *
.......
I really want to take Ralph out for a beer and bat around a bunch of ideas.
.....


Doug had that honor (or was it the other way around?) at Europlanet - he can
attest as to whether it was a good use of his time...

QUOTE
Whoever has to decide between these two sets of missions -- Jovian system vs. Titan -- is going to have it tough.

That's why they pay Alan the big bucks, right...

As for the Titan Flagship report - I wish I knew when it will be out - indeed having bust a
gut to write large parts of it over the summer, I wish it were out already. It needs someone to
take out ITAR sensitive stuff e.g. related to the ASRGs, commercially-proprietary data
related to the airbag system on the lander, and APL- and JPL-sensitive cost data.

Editing a public version of the report was not in the original study contract so I think
this awaits some NASA-APL negotiation.
Above my pay grade, sadly.

Posted by: ngunn Nov 24 2007, 02:30 PM

QUOTE (rlorenz @ Nov 24 2007, 01:32 PM) *
Titan Flagship report -


Thanks for the news on this. Can we take it that it's just the public version that's delayed, and the people who most need to see it have already got the full deal?

I guess the rest of us must be patient. We can always dream about what might be inside those airbags. smile.gif

Posted by: Paolo Nov 24 2007, 03:03 PM

QUOTE (nprev @ Nov 22 2007, 11:42 PM) *
Yeah, I knew that; wasn't the guy who found that Italian?


You are probably confusing Flandro for the Italian pioneer Gaetano Crocco, who used the name "Grand Tour" for his manned one-year Earth-Mars-Venus-Earth gravity-assist trip. When Flandro presented his results to his boss at JPL he remembered Crocco's work and called the multi-planet opportunity "Grand Tour".

Posted by: nprev Nov 24 2007, 03:05 PM

Makes sense; thanks for the clarification, Paolo! smile.gif

Posted by: tedstryk Dec 8 2007, 02:48 PM

One thing that excites me about the HIRES imager on JSO is what it can do for Ganymede orbit. At is closest to Io, it will obtain 1.3 km/pixel - 3km/pixel images of Io. For scale, http://photojournal.jpl.nasa.gov/catalog/PIA02309, its best, has a resolution of 1.3 km/pixel. This still isn't really fair, because Galileo's camera obtained this resolution in only one wavelength (The other colors used 2x2 binning), it is only 8-bit data, and very lossy compression was used. The maximum resolution for Europa is 798 m/pixel from Europa. By contrast, the highest resolution Galileo mosaic (the one used http://apod.nasa.gov/apod/ap071202.html) has a resolution of about 2/km pixel (and again, is also compressed, with at most two filters cover and with gaps and with some color data brought in form other orbits, as well as lossy compression, so a nice, clean JSO view at the same "resolution" would be much better). This is of course ignoring views that would be obtained earlier in the mission, which would be even better.

Posted by: Mariner9 Dec 8 2007, 09:55 PM

Color imaging was one of the main casualties of Galileo's hain gain antenna failure. Helping to fill in that gap was one of the reasons that the Cassini and New Horizons Jupiter encounters were so valuable.

So I agree that JSO would help out a lot in the global color imaging of Io and Europa even while in it's final parking orbit at Ganymede.

But one thing to remember is that the resonances of the three inner Galilean moons means that closest approach between them always brings the same hemisphere into view. So those great global shots are always of the same area. And that doesn't even give you 50% coverage, because the areas close to the horizon are essentially out of view, so you are maybe getting 35-40%.

In any case, while I'm more of a fan of the Europa Orbiter, JSO wuold be one hell of a great mission and I won't complain (much) if it gets chosen.

Posted by: JRehling Dec 8 2007, 11:34 PM

QUOTE (Mariner9 @ Dec 8 2007, 01:55 PM) *
So I agree that JSO would help out a lot in the global color imaging of Io and Europa even while in it's final parking orbit at Ganymede.

But one thing to remember is that the resonances of the three inner Galilean moons means that closest approach between them always brings the same hemisphere into view. So those great global shots are always of the same area. And that doesn't even give you 50% coverage, because the areas close to the horizon are essentially out of view, so you are maybe getting 35-40%.


FWIW, the same face of Callisto would also be seen at every closest approach. It's not the resonance of the satellites themselves but the fact that each is tidally locked in rotation that leads to that consequence.

The factor by which viewing the other satellites besides at closest approach would be somewhat lesser for Io. In any event, both Io and Europa will over time show almost 100% of the surfaces to Ganymede while in the half of their orbit closest to Ganymede (ie, within Ganymede-Jupiter distance of Ganymede).

By and large, the imaging from Ganymede orbit would be about monitoring Jupiter's weather and Io's volcanism over time. There would be some use to the global mapping done from a distance, but that would be outclassed by the close-up observations. Otherwise, I think the main value would be to look for lighting effects near the terminator to derive topographical data. The problem being that Europa and Callisto are incredibly smooth anyway, so this wouldn't work incredibly well. (In contrast, there's a lot of good Cassini data of that kind with respect to Iapetus, which is not very smooth.)

Overall, the close-approach breakdown for the two missions goes about like this:

Io: JSO 4, EE 0
Europa, JSO 6, EE infinity
Ganymede: JSO infinity, EE 14
Callisto: JSO 4, EE 4

I'd lay a bet that EE wins out. If it's the option of delaying by two years, which would improve mass margins and allow an Io flyby or two, then JSO has no chance. Ganymede just ranks infinitely far below Europa as a priority. Heck, the US has only flown five missions to Venus, ever, and Ganymede has less interesting geology, no atmosphere, and is much farther away. And would receive 14 close flybys from EE.

Posted by: vjkane Dec 9 2007, 01:41 AM

QUOTE (JRehling @ Dec 8 2007, 11:34 PM) *
I'd lay a bet that EE wins out. If it's the option of delaying by two years, which would improve mass margins and allow an Io flyby or two, then JSO has no chance. ... And [Ganymede] would receive 14 close flybys from EE.


Over the summer I read that the two teams were going to discuss combining the JSO remote science campaign with EE. I presume that this would include looking at Io flybys, remote Jupiter studies, and optimizing studies of moons other than Europa.

Posted by: tedstryk Dec 9 2007, 04:13 AM

Now that would be cool.

Mariner9, at closest approach you are correct, but as for the areas near the limb at that point, keep in mind that they could be seen at lower resolution farther away. Also, I don't have the numbers handy for Europa, but for the opposite side of Io, the resolution would be about 3km/pixel at worst, which isn't bad. Europa would be somewhat worse (my back of the envelope is 5km/pixel), although assuming these areas were covered earlier in the mission, Io is a very different target due to the need for global-scale change monitoring. Also, at closest approach from Ganymede orbit, while the side would stay the same, the illumination angle wouldn't, offering many different perspectives.

Posted by: JRehling Dec 9 2007, 05:37 AM

FULL INLINE QUOTE REMOVED - how come the old hands of UMSF still do this? - DOUG

Yes, and Io and Europa show pretty strong effects of phase angle.

Also, the main phenomenon of interest at Io can actually be observed regardless of the illumination.

Posted by: mchan Dec 10 2007, 04:11 AM

QUOTE (vjkane @ Dec 8 2007, 05:41 PM) *
Over the summer I read that the two teams were going to discuss combining the JSO remote science campaign with EE. I presume that this would include looking at Io flybys, remote Jupiter studies, and optimizing studies of moons other than Europa.

It would be interesting to see what (if anything) that post-Europa EOM science operations can provide (assuming the spacecraft is not left to orbit Europa at EOM).

Posted by: ugordan Dec 10 2007, 08:45 AM

QUOTE (mchan @ Dec 10 2007, 05:11 AM) *
(assuming the spacecraft is not left to orbit Europa at EOM).

Where would you send it? Once it entered Europan orbit, basically the only way out is down.

Posted by: mchan Dec 10 2007, 10:45 AM

If I recall correctly from the mission description of the cancelled "Fire and Ice" Europa Orbiter, the approach to Europa orbit insertion was a series of Europa resonant orbits, e.g., 3:4, 4:5, 5:6, etc. with Europa flyby at perijove to reduce the apojove and a delta-V near apojove to setup for the next Europa flyby. The delta-V's burned a significant amount of the propellant load, around the same order as the JOI burn as I recall. The Europa orbit insertion did not require anything on the order of the JOI burn with some description about EO being "nudged" into Europa orbit.

For quarantine, it seems to me the orbiter would "nudge" itself back into Jupiter orbit. At this point, I don't know how EO can prevent future impact with Europa if there is no propellant to adjust Jupiter orbit to an eventual Galileo exit. But if there is sufficient residual propellant to do the Galileo exit, then could some incremental fuel load combined with Europa flybys move the apojove back out to lower radiation dose orbit by running the approach scheme in reverse? An eventual Galileo exit will be required, but can some time be bought before then?

The maneuvers in actual Europa orbit have best and worst case with regards to propellant usage. If the propellant load allows for the worst case, but the actual maneuvers took something closer to best case, then there could be some load left at end of primary mission. The extended mission could stay for additional science in Europa orbit, or if the fuel load is great enough, get back out to a Jupiter orbit out of the higher radiation zone (at least at apojove) and do Jupiter orbit science.

The devil is in the calculations of accumulated dose at EOM, how much the incremental dose can be decreased with residual propellant, and the expected remaining life given the accumulated dose and the decreased incremental dose. It could just be impractical. I just haven't seen this aspect discussed, and I don't have the background to readily run the sims to find this out.

Posted by: ngunn Dec 10 2007, 11:09 AM

The mission summary clearly states "The flight system eventually impacts Europa". I think that's unfortunate. It would be nice if the first human artifact to touch Europa were at least to attempt some kind of biological audit of the status quo ante.

Posted by: ugordan Dec 10 2007, 11:52 AM

QUOTE (mchan @ Dec 10 2007, 11:45 AM) *
If I recall correctly from the mission description of the cancelled "Fire and Ice" Europa Orbiter, the approach to Europa orbit insertion was a series of Europa resonant orbits, e.g., 3:4, 4:5, 5:6, etc. with Europa flyby at perijove to reduce the apojove and a delta-V near apojove to setup for the next Europa flyby. The delta-V's burned a significant amount of the propellant load, around the same order as the JOI burn as I recall. The Europa orbit insertion did not require anything on the order of the JOI burn with some description about EO being "nudged" into Europa orbit.

I don't think you can "nudge" yourself into a stable mapping orbit around Europa. What those resonant flybys do is lower the hyperbolic excess velocity w/respect Europa to a minimum so the orbit insertion burn costs the least amount of fuel. You still need to get rid of that excess Vinf to go into orbit and just as well you'd need to provide the same delta-V to again escape Europa.

The thought of moving EO out of Europa's orbit at EOM seems similar to me as ideas of ejecting Cassini out of the Saturnian system. Nice concepts, but not gonna happen IMHO.

Posted by: Bjorn Jonsson Dec 10 2007, 12:25 PM

QUOTE (JRehling @ Dec 8 2007, 11:34 PM) *
Overall, the close-approach breakdown for the two missions goes about like this:

Io: JSO 4, EE 0
Europa, JSO 6, EE infinity
Ganymede: JSO infinity, EE 14
Callisto: JSO 4, EE 4

I'd lay a bet that EE wins out. If it's the option of delaying by two years, which would improve mass margins and allow an Io flyby or two, then JSO has no chance. Ganymede just ranks infinitely far below Europa as a priority. Heck, the US has only flown five missions to Venus, ever, and Ganymede has less interesting geology, no atmosphere, and is much farther away. And would receive 14 close flybys from EE.

To me EE as described in the OPAG reports does not win out. JSO's instruments are superior and the Io flybys are a big plus. Less radiation and the longer time in Ganymede orbit (and therefore more time to monitor Io and Jupiter) is also a big plus.

If the missions are somehow combined with EE carrying JSO's instruments and flying by Io the situation could change. This is not completely clear though. An orbiter can be put in orbit around Ganymede that is stable for several decades. This is not possible for Europa and the radiation is much less severe at Ganymede. So in this case EE probably wins out but things are not completely clear. Longer time in orbit is always a big plus - there are lots of things at Jupiter where long-term monitoring is useful.

Posted by: K-P Dec 10 2007, 01:05 PM

QUOTE (Paolo @ Nov 24 2007, 05:03 PM) *
You are probably confusing Flandro for the Italian pioneer Gaetano Crocco, who used the name "Grand Tour" for his manned one-year Earth-Mars-Venus-Earth gravity-assist trip. When Flandro presented his results to his boss at JPL he remembered Crocco's work and called the multi-planet opportunity "Grand Tour".


Or could he mean Italian Giuseppe ("Bepi") Colombo, who was behind the calculations of first ever gravity assist by a spacecraft with Mariner 10 to Mercury...?

Posted by: mchan Dec 10 2007, 03:14 PM

QUOTE (ugordan @ Dec 10 2007, 03:52 AM) *
I don't think you can "nudge" yourself into a stable mapping orbit around Europa. What those resonant flybys do is lower the hyperbolic excess velocity w/respect Europa to a minimum so the orbit insertion burn costs the least amount of fuel. You still need to get rid of that excess Vinf to go into orbit and just as well you'd need to provide the same delta-V to again escape Europa.

I wish I have the paper handy. I think the "nudge" comes from putting EO from the last n:(n+1) resonant orbit into a 1:1 resonant Jupiter orbit with Europa nearby. The transition from the 1:1 Jupiter orbit to a low Europa circular orbit is gradual thru an initial high and unstable Europa orbit and takes some number Jupiter / Europa orbits to accomplish. Instead of a single big Europa insertion burn, there are a bunch of smaller burns which total up to less than the one big burn. The resonance with Io and Ganymede may play a part.

Agree about it being unlikely, but I have read more about Cassini EOM options than EO (or EE) EOM options and am just looking for additional info on EE.

Posted by: AscendingNode Dec 11 2007, 06:07 PM

QUOTE (ugordan @ Dec 10 2007, 12:45 AM) *
Where would you send it? Once it entered Europan orbit, basically the only way out is down.


There may be orbits of Europa that are stable for hundreds of years. It just is a big undertaking to calculate them (i.e. the mission needs to be funded before such an effort could be paid for). But by proposing to impact Europa in a safe way, they still have a viable mission if such stable orbits can't be found... and they still have the freedom to use such an orbit if it's found.

Also, although it would be costly to leave a low Europa orbit like that proposed by the EE study... if an elliptical orbit like JSO proposed were used at Europa it could lower the DV down into the realm where 'nudge' would be a good word.

Posted by: tasp Dec 11 2007, 06:49 PM

Exploration of the Europan Hill sphere via earth bound computer simulation would be interesting. Analogs to our moon's path about the earth and sun might exist, and the interesting trajctory of Messenger as it interacts with Mercury might be applicable, too.

Posted by: JRehling Dec 11 2007, 08:52 PM

I think the planetary protection protocols, such as they are, have to be taken with a grain of salt. Suppose Galileo had catastrophically failed at some point after JOI, leaving it in the orbit that it was in when the failure took place, until close encounters with the satellites tweaked the orbit. That would have meant a significant probability (about 20%, I would guess, but certainly more than 1%) that it would eventually impact Europa. And given the history of spaceflight, I think you'd have to grant at least a 1% probability (given the radiation dangers, I would think much higher) that any Jupiter orbiter might fail suddenly and without warning. If we were really taking the planetary protection protocols seriously, we wouldn't send any orbiter there without making sure it was thoroughly sterilized first.

Given that we're not really taking the protocols seriously, what's the difference between perhaps a 2% probability of Europa impact and just making Europa impact part of the plan anyway? Then if you want to worry about safeguards, put them at the point in the process where they belong -- minimizing the probability of an impact being harmful. We do this with surgical equipment and so on, with human lives at stake.

Posted by: tedstryk Dec 11 2007, 09:44 PM

Regardless of one's opinion on planetary protection, it is important to note that because Galileo was designed at a time when no one was really thinking about life in the Jovian system being even a possibility, it did not undergo the sterilization procedures that, for example, a Mars Lander would. EE would certainly be sterilized, so the concern about Galileo hitting Europa doesn't really carry to EE.

Posted by: nprev Dec 11 2007, 09:53 PM

Not to ignite a debate on this topic, but aren't orbiters at Europa's distance from Jupiter & closer largely self-sterilizing? The radiation environment is horrendous; you would think that models for biological survival might indicate a very, very small probability of viable organisms reaching Europa's surface if PPPs were applied pre-launch in addition to this.

As my 9th-grade biology teacher used to say, "We know there's life on Mars...after anything from Earth hit the surface, it's a certainty". Seems to me that the Jovian environment as described is somewhat less friendly; not too worried about a putative EE impact on Europa.

Posted by: AscendingNode Dec 11 2007, 11:57 PM

QUOTE (nprev @ Dec 11 2007, 01:53 PM) *
Not to ignite a debate on this topic, but aren't orbiters at Europa's distance from Jupiter & closer largely self-sterilizing? The radiation environment is horrendous; you would think that models for biological survival might indicate a very, very small probability of viable organisms reaching Europa's surface if PPPs were applied pre-launch in addition to this.


The problem is that there is shielding on the electronics to protect them from the radiation, and this shielding could protect any microbes behind that same shielding.

I've heard some joking suggestions of putting thermite bombs in radiation vaults to sterilize a spacecraft at end of life. (of course, that would be a huge single-bit-upset risk)

Posted by: rasun Dec 12 2007, 09:54 AM

QUOTE (tedstryk @ Dec 11 2007, 10:44 PM) *
Regardless of one's opinion on planetary protection, it is important to note that because Galileo was designed at a time when no one was really thinking about life in the Jovian system being even a possibility, it did not undergo the sterilization procedures that, for example, a Mars Lander would. EE would certainly be sterilized, so the concern about Galileo hitting Europa doesn't really carry to EE.


Well... does that mean that they will sterilize Juno?

Posted by: tedstryk Dec 12 2007, 11:01 AM

QUOTE (rasun @ Dec 12 2007, 09:54 AM) *
Well... does that mean that they will sterilize Juno?


Probably not, since they are crashing it into Jupiter at the end of the mission.

Posted by: ugordan Dec 12 2007, 11:54 AM

QUOTE (tedstryk @ Dec 12 2007, 12:01 PM) *
Probably not, since they are crashing it into Jupiter at the end of the mission.

Maybe rasun was getting at the point that now Europa is recognized as a potential habitat to life (unlike when Galileo was designed) and what JRehling mentioned about the very real possibilty of a craft suddenly and catastrophically failing at any time in Jovian orbit. Do those two facts now impose a must for sterilizing Juno even if it's not meant to come close to Europa?

Personally, I think the issue of contamination is blown way out of proportion and this is just playing devil's advocate a bit on my part.

Posted by: JRehling Dec 12 2007, 01:39 PM

I think a dead craft in Juno's orbit would have virtually no chance of ever impacting Europa, since it will be a polar orbit with apojove well past Callisto and perijove way inside Io. No big satellite flybys means no big adjustments to the orbit anytime soon, although I suppose a game of billiards and procession over the millennia could eventually turn things sour.

The principle still should apply. I think an estimate of how likely it is that a crash onto Europa's surface would infect the ocean probably has a lot of zeroes in it, whereas an estimate of how likely it is that an orbiter intended to avoid Europa might actually impact it has only one or two zeroes in it, so the "pain point" is in the sterilization, not the intended endgame.

Posted by: AscendingNode Dec 12 2007, 06:12 PM

QUOTE (JRehling @ Dec 12 2007, 05:39 AM) *
I think a dead craft in Juno's orbit would have virtually no chance of ever impacting Europa, since it will be a polar orbit with apojove well past Callisto and perijove way inside Io. No big satellite flybys means no big adjustments to the orbit anytime soon, although I suppose a game of billiards and procession over the millennia could eventually turn things sour.


Jupiter's J2 and the Sun's gravity cause the orbit to rotate. Although initially it crosses the orbit planes of the moons well outside of Callisto, over time the periapsis and apoapsis move to higher latitudes and the crossing of the plane of the moons moves inwards and crosses near Europa and then below Europa. It then moves outward again as the orbit rotates and so on. Over hundreds of years through this cycle, there is a good chance of hitting one of Jupiter's moons.

Posted by: nprev Dec 12 2007, 07:07 PM

QUOTE (ugordan @ Dec 12 2007, 03:54 AM) *
Personally, I think the issue of contamination is blown way out of proportion and this is just playing devil's advocate a bit on my part.


I gotta agree in the case of a Europan surface impact by a spacecraft. Seems as if the ambient radiation alone would wipe out the bugs in very short order, if the vehicle had undergone even a modest (not excessive) amount of PPP preparation beforehand.

Natural selection on Earth hasn't produced very many microorganisms capable of surviving sustained levels of radiation due to our magnetic field and nice thick atmosphere; betting that any exceedingly tiny putative Europan surface critters could kick Earth bug's behinds in this regard!

Posted by: ugordan Dec 12 2007, 07:21 PM

QUOTE (nprev @ Dec 12 2007, 08:07 PM) *
wipe out the bugs in very short order

Ahh... Imagine wiping out software bugs with radiation... biggrin.gif

Seriously, greatest concern is often expressed about RTGs since they're inherently very warm and could sustain suitable temperatures. It's still hard to imagine microbes surviving in the Jovian radiation environment in the radiation shielded parts and then finding themselves neatly warmed up on the surface right on top of an disassembled RTG. A Europa orbiter would give impact speeds probably on the order of 1 km/s which isn't too unsurvivable for some materials (RTG casings?). A flyby craft (a-la Juno/Galileo) would have an impact speed probably in excess of 10 km/s and that's when kinetic energies begin to skyrocket.

Posted by: ngunn Dec 12 2007, 09:38 PM

QUOTE (nprev @ Dec 12 2007, 07:07 PM) *
Natural selection on Earth hasn't produced very many microorganisms capable of surviving sustained levels of radiation due to our magnetic field and nice thick atmosphere;


More than you'd expect is what I've heard. (This has been invoked to support the idea of panspermia.) Our ignorance of life's place in the grand scheme is very great, truth be told. To have any chance of reducing it by studying our small available sample of nearby worlds absolutely requires that we don't barge around like a bull in a china shop. Minute risk maybe, but incalculable potential consequences. It's not worth trying to calculate zero times infinity. I can handle a reasonably low accidental risk of littering Europa, but doing it deliberately when it certainly isn't necessary? Surely not.

Posted by: rlorenz Dec 13 2007, 12:19 AM

Nature News piece on the Flagships is out

http://www.nature.com/news/2007/071212/full/450931a/box/1.html

Posted by: ngunn Dec 13 2007, 10:42 AM

For anyone like me with no Nature subscrition - I just rechecked the OPAG link in post 1 of this thread and was pleased to find some news about the Titan proposal, including a handy factsheet.

Posted by: Juramike Dec 13 2007, 01:11 PM

QUOTE (rlorenz @ Dec 12 2007, 07:19 PM) *
Nature News piece on the Flagships is out

http://www.nature.com/news/2007/071212/full/450931a/box/1.html



"...But it will be hard to justify going to the same place as Huygens."


Excuse me? Did someone not get the memo about Titan having diverse environments on it's surface?

Straight clip from the T38 Mission Description (http://saturn.jpl.nasa.gov/multimedia/products/pdfs/20071205_titan_mission_description.pdf):

"...wind, rain, volcanism, tectonic activity, as well as river channels, and drainage patterns all seem to contribute in shaping Titan’s surface. ...
impact craters...lobate flows... volcanic structures....Dunes ...large bodies of liquid."...etc.

Not even CLOSE to boring.

Posted by: tedstryk Dec 13 2007, 01:32 PM

QUOTE (Juramike @ Dec 13 2007, 01:11 PM) *
Not even CLOSE to boring.


The problem is that when it reaches the high levels of bureaucracy, those things go out the door. Bean counters will see it and wonder why we are going to Titan since we have just had Cassini/Huygens explore it.

Posted by: NMRguy Dec 13 2007, 03:19 PM

The Titan Explorer with Orbiter (based on the limited explanations given in the OPAG http://www.lpi.usra.edu/opag/announcements.html and Nature Comparison Table) really seems to be a capable explorer that would bring our understanding of Titan to the next level. The Orbiter+Lander+Balloon combination would give a very detailed study of one of the most dynamic solid ground bodies in the solar system. To put in perspective how much Titan science could be accomplished, "the 4-year orbital mission returns orders of magnitude more data about Titan than Cassini – this mission will spend more time at Titan in its first 3 days in orbit than the nominal and extended Cassini missions" [as quoted from the OPAG sheet]. blink.gif

Then again, the Titan Explorer has a price tag to match it complexity. At $4 billion, it costs nearly 25% more than JSO and nearly 20% more than EE. These are real differences that could hamper its funding. Some of this could presumably deferred to ESA, but TANDEM is a broader proposal that includes Enceladus science that doesn't exactly mesh with Titan Explorer with Orbiter.

The report also states that a $2 billion "orbiter only" mission could also be proposed, but this would return much less "surface truth" constraints. Is it also possible to send only the Orbiter+Balloon or Orbiter+Lander for an intermediate price tag? The Orbiter+Balloon would still cover a lot of ground and give great camera-radar comparisons over larger areas of the moon.

I'm looking forward to the full OPAG report.


On a related note, how long could we expect to keep the balloon floating around Titan? I suspect that the dense air and cold temperatures should keep it there for a long time, but I have never seen official estimates.

Posted by: TheChemist Dec 13 2007, 03:20 PM

I'm willing to put on my prophet hat, and predict that NASA will try Europa, while ESA returns to Titan with a long visit to Enceladus.
With both agencies contributing partly to the other's mission.
Just a hunch.

Posted by: NMRguy Dec 13 2007, 03:30 PM

QUOTE (TheChemist @ Dec 13 2007, 04:20 PM) *
With both agencies contributing partly to the other's mission.

I'm not sure that ESA has the budget to fly solo to the outer planets. Last I heard, they were considering http://news.bbc.co.uk/2/hi/science/nature/7053057.stm for spacecraft (not including launch) funding. I don't think that TANDEM or Laplace will get off the ground without international cooperation.

Posted by: djellison Dec 13 2007, 03:37 PM

This is what I like about the Titan Explorer proposal - it splits into international components beautifully. NASA can't afford all of it? Fine - ESA does the lander, JAXA does the balloon - let's go. It's not quite that simple - but it's a princple that worked with C-H, and it saved C-H from cancellation (if you read 'The Titans of Saturn') because of a mutual responsibility once you split a mission like that.

Doug

Posted by: tedstryk Dec 13 2007, 03:56 PM

I agree that Titan is probably the most interesting moon out there. Sometimes I wish that a scaled down Jupiter orbiter could be sent as a "mini-flagship" - $1-1.5 billion, perhaps sooner than the JSO concept, and then a Titan (or advanced Europa) mission could follow sooner than if it had been a full flagship.

Posted by: djellison Dec 13 2007, 03:58 PM

One could even imagine a New Frontiers scale Jupiter orbiter - maybe go for huge solar arrays instead of RTG. It should fit I'd have thought.


Oops.


smile.gif

Posted by: ngunn Dec 13 2007, 04:42 PM

Just a wild thought and well OT I know.
Could there be a way of harvesting power from Jupiter's huge magnetic field and radiation belts, thus turning a nuisance into a resource? It sometimes seems that all the Jupiter proposals are working against the grain of the Jovian environment.

Edit: Chemist, I hope you're right.

Posted by: tedstryk Dec 13 2007, 05:35 PM

QUOTE (ngunn @ Dec 13 2007, 04:42 PM) *
Could there be a way of harvesting power from Jupiter's huge magnetic field and radiation belts, thus turning a nuisance into a resource? It sometimes seems that all the Jupiter proposals are working against the grain of the Jovian environment.


An idea like that was explored a few years ago...I can't remember where I saw it. However, the complexity of the system proved prohibitive.

Posted by: vjkane Dec 14 2007, 01:56 AM

"One could even imagine a New Frontiers scale Jupiter orbiter - maybe go for huge solar arrays instead of RTG."

The JSO report stated that another orbital tour without orbiting a moon wouldn't be worth it. I have my doubts about this statement. That's like saying there's no point to MRO since Viking orbited Mars. Galileo and Viking orbiter's instruments are from the same era. And Galileo had the communications bandwidth of Mariner 4, as I recall.

However, consider that the very simple Juno orbiter is ~$900M. It has a short life and avoids the radiation fields. I suspect that a 3-axis orbiter with a high communications rate and capable of living through a Galileo-level radiation load would probably be $1.5-2.0B Given that the descoped JSO orbiter is $2.3B, saving the extra few hundred million may not be a good tradeoff. It's probably as hard to sell a $1.5B mission as a $2.3B mission.

"I'm not sure that ESA has the budget to fly solo to the outer planets. Last I heard, they were considering EUR 650 million for spacecraft (not including launch) funding. I don't think that TANDEM or Laplace will get off the ground without international cooperation."

With Juno at ~$900M, I don't see how a mission to Titan could fit into the budget. There has been talk that a flyby Saturn probe mission would fit within that kind of a budget, so if ESA were willing to drop simple, short-lived landers on Titan and have the carrier simply flyby, that might fit in.

Posted by: djellison Dec 14 2007, 03:02 PM

QUOTE (vjkane @ Dec 14 2007, 01:56 AM) *
"One could even imagine a New Frontiers scale Jupiter orbiter - maybe go for huge solar arrays instead of RTG."

The JSO report stated that another orbital tour without orbiting a moon wouldn't be worth it.


I was being sarcastic. Such a mission is already in work - Juno.

Doug

Posted by: rlorenz Dec 14 2007, 09:46 PM

QUOTE (NMRguy @ Dec 13 2007, 10:19 AM) *
The Titan Explorer with Orbiter (based on the limited explanations given in the OPAG ......
The report also states that a $2 billion "orbiter only" mission could also be proposed, but this would return much less "surface truth" constraints. Is it also possible to send only the Orbiter+Balloon or Orbiter+Lander for an intermediate price tag? The Orbiter+Balloon would still cover a lot of ground and give great camera-radar comparisons over larger areas of the moon.


Yes, intermediate options are O+L+L, O+B+B, O+B, O+L.......

QUOTE
I'm looking forward to the full OPAG report.
On a related note, how long could we expect to keep the balloon floating around Titan? I suspect that the dense air and cold temperatures should keep it there for a long time, but I have never seen official estimates.

No official estimate in the sense that no-one can think of a reason it wouldnt be practically forever - hot air
balloons do not suffer from leaks by small tears (and at Titan no UV damage, packing/inflation fatigue as on terrestrial
hot air balloons)
Flagship study said 1 year, just to put a bound on operations cost.

Posted by: vjkane Dec 15 2007, 03:59 AM

I finally had the time on a plane flight to read over the EE and JSO reports in detail. The attached chart gives cost comparisons, launch cost comparisons, and instrument complement comparisons. One of the key differences between the full up proposals and the descope missions is reducing weight to enable the use of a cheaper launch vehicle.

One note on the instrument descope for EE: cutting the narrow angle camera as part of the descope would be one of the last cuts implemented to save money (second from the bottom of the list).

I am beginning to favor implementing the EE descope mission with the narrow angle camera restored to the instrument list. For the ~$900M cost difference, NASA could fly an additional New Frontiers mission. I think that the return from being able to fly an additional New Frontiers mission might be more valuable than the additional science returned from the full EE or JSO mission.

An the Titan side of the equation, there is a cost estimate in the feasibility study of $1 billion Titan and Enceladus missions ( http://www.lpi.usra.edu/opag/TitanEnceladusBillionDollarBox.pdf ) for a mission that would just drop off a lander or balloon, by itself, at Titan: $1.4 billion. And that's with the main craft being a cruise stage -- a carrier spacecraft that would do any significant science studies of its own would add about $600 million. There is simply no way to do any such mission within the New Frontiers cost band, or anything close to it. But, of course, there is still both enormous flexibility in what kind and scale of Titan mission to do, and great capability for NASA/ESA collaboration in it -- once we decide how much we actually want to spend. ESA's contribution plus the savings from implementing a descope mission at Jupiter would pay for such a mission.

However, I am finding myself more drawn to a full up Titan mission. It is simply too exciting of a world.

 EE___JSO_comparison.txt ( 1.21K ) : 282
 

Posted by: ngunn Dec 16 2007, 12:16 AM

QUOTE (vjkane @ Dec 15 2007, 03:59 AM) *
However, I am finding myself more drawn to a full up Titan mission. It is simply too exciting of a world.


You speak for many there, I suspect.

An interesting comparison I haven't seen discussed is between NASA's Titan Explorer and ESA's TANDEM proposal. The latter includes no less than three Titan landers plus balloon, orbiter, and a significant mission to Enceladus as well. I find the three Titan landers particularly appealing. That could mean one each for the highlands and plains, and a lake drifter.

Posted by: vjkane2000 Dec 16 2007, 01:22 AM

More on the EE and JSO descope mission options.

See the attachment to my previous post (two posts up in this thread) for details on the differences between the full and descoped missions. In this post, I'll address more of the philosophy behind the descoped missions.

For either mission, the key way to reduce costs is to change the launch vehicle from a Delta IV-H to an Atlas V. That single change is worth reducing the mission costs by ~$300M (the two proposals use different configurations of the launchers, so the savings differs somewhat -- see previous post). Changing launch vehicle requires cutting several hundred kilograms out of the delivered payload.

EE achieves this by reducing the instrument payload, cutting the number of nuclear power generators, reducing the radiation hardness (75% survival probability drops from 1 year in orbit at Europa to 6 months) and various other cuts. If EE delayed its launch by two years to 2017, though, it would gain ~200 kg of payload capacity. This probably would be enough to restore several of the cut instruments. Most important to this group, the narrow angle, LORRI-class camera could probably be restored, which would allow observations of Jupiter and other Jovian moons. It would also provide the 1 m resolution imaging of Europa to qualify potential landing sites for future missions.

JSO achieves its payload reduction through modest instrument capability reductions, minor design changes, but primarily by reducing the fuel load by doing only an elliptical rather than a circular low altitude orbit at Ganymede. This trade off would not work for the Europa mission where the low circular orbit is essential to global gravity mapping and, I presume, to global mapping of the ice thickness.

All in all, if I were Alan Stern (and thank god for the health of the program that I'm not laugh.gif ), I would implement and enhanced, descoped EE mission for the 2017 opportunity. I'd used the additional payload capability to add back in instruments such as the narrow angle camera and UVS spectrometer, improve radiation hardening, and possibly enhance the communications bandwidth. Then I'd use the money saved over the full up proposal to fund a New Frontiers mission. Lots of great candidates: Venus landers, comet sample return, and (my favorite) a joint Titan mission with ESA.

Posted by: vjkane2000 Dec 16 2007, 02:24 AM

QUOTE (ngunn @ Dec 15 2007, 05:16 PM) *
An interesting comparison I haven't seen discussed is between NASA's Titan Explorer and ESA's TANDEM proposal. The latter includes no less than three Titan landers plus balloon, orbiter, and a significant mission to Enceladus as well. I find the three Titan landers particularly appealing. That could mean one each for the highlands and plains, and a lake drifter.


The Tandem summaries I've read read like wish lists -- what a group of scientists came up with as great things to do. I think that the budget for that flotilla would be quite expensive... If there is another mission to Titan (at least in my lifetime with ~25 years left to care (90% probability laugh.gif ), then I think it will be either a full up flagship mission with $3B from NASA funding a capable orbiter and either a balloon or lander and ESA paying for the other. No Enceledus,,, Otherwise, it will be something much more like a $1.4B balloon or lander only.

Posted by: vjkane Dec 26 2007, 05:32 AM

A new post by Leonard David at http://www.livescience.com/blogs/2007/12/25/nasa-outer-planet-mission-studies-international-collaboration/ says that NASA will move forward with studies of the Europa Explorer, Jovian System Explorer, and Titan explorer. The studies will be done in conjunction with ESA and JAXA. NASA proposed contribution will be capped at $2B.

Initially, I had been thinking that the Europa and Jovian System missions would not be easy to split. However, I've revised my thinking (but would appreciate hearing from real engineers). There's several ways to split up the Jovian missions. ESA/JAXA could provide complete subsystems (really no different than supplying the Huygens probe -- electrical interfaces are electrical interfaces, whether they stay inside the craft or connect to a craft that will eventually seperate). Don't forget that Germany supplied Galileo's propulsion module as well as several instruments. Other alternatives would include JAXA supplying small orbiters to study the magnetosphere, ESA supplying a remote sensing craft that stays beyond Ganymede's orbit for remote studies (and presumably has a big camera), and NASA a reduced capability Europa or Ganymede orbiter.

Posted by: vjkane Dec 26 2007, 05:52 AM

A while ago, ESA proposed a Jovian minisat mission that would have a Jovian Europa Orbiter (JEO) and a Jovian Relay Spacecraft (JRS). A few posts ago, I posted a comparison of the proposed instrument compliments for the Europa Explorer and the Jovian System Observer. Now that it appears that NASA will continue its studies of these mission in conjunction with ESA and JAXA, I've extended the table with the instruments proposed for the minisat mission. (See http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=35982) I don't know if the minisat is representative of what is proposed in the LaPlace proposal. The short story is the the instruments proposed for the minisat mission would have limited capabilities compared to what was proposed for EE and JSO.

 Proposed_Jovian_mission_instruments.txt ( 1.18K ) : 277
 

Posted by: marsbug Jan 3 2008, 01:52 PM

Ive not got acess to the full article but http://www.liebertonline.com/doi/abs/10.1089/ast.2007.0156?cookieSet=1&journalCode=ast sounds like material in europa orbiters favour....

Posted by: rlorenz Jan 4 2008, 01:14 AM

QUOTE (marsbug @ Jan 3 2008, 08:52 AM) *
Ive not got acess to the full article but http://www.liebertonline.com/doi/abs/10.1089/ast.2007.0156?cookieSet=1&journalCode=ast sounds like material in europa orbiters favour....


Nothing new here - Chyba and others have long argued for oxidant production as a possible
source of free energy to the ocean beneath. (papers in 2000 and before)

On the other hand, I think Ken Nealson has argued even this isnt enough energy to drive complex life

Then there is the interesting debate about there being unlikely to be much organic carbon on
Europa so life has nothing to build itself with (Protojovian nebula was too warm to trap methane in
the way Titan did). So there is nothing for these oxidants to oxidize.

All of which is interesting but moot, since an orbiter isnt really going to answer any of these
questions very well. If we were talking about a Europa lander it might be a different story.

Posted by: vjkane Jan 4 2008, 03:56 AM

QUOTE (rlorenz @ Jan 4 2008, 01:14 AM) *
All of which is interesting but moot, since an orbiter isnt really going to answer any of these
questions very well. If we were talking about a Europa lander it might be a different story.

To know where to put a Europa lander, we need the orbiter to find the most interesting safe place. Or to rule out that there are such places. Unless the eventual plan is to do a lander, a Europa orbiter makes no sense, in my opinion.

I continue, however, to believe that if the choice is Europa or Titan, then it should be Titan. If it is the entire Jovian system including a focus on Europa versus Titan, then that's a harder choice. I expect that the three teams give us a great choice of missions that makes it painful to see any of the three rejected. My personal, emotional favorite is Titan, if we get below the clouds with part of the mission.

In the end, I think that the final choice will be made on programmatic factors: total cost, risk of cost overruns, technology readiness.

Ralph, are you involved in the next round of developing of the Titan proposal?

Posted by: marsbug Jan 4 2008, 12:45 PM

FWIW I agree, but I'm going to be heartbroken whichever way the cookie crumbles. mad.gif

Posted by: ngunn Jan 8 2008, 08:49 PM

Almost missed Emily's last paragraph here:
http://www.planetary.org/blog/article/00001285/

The orbital dance of the Space Agencies begins to unfold.

Posted by: vjkane Jan 24 2008, 05:12 PM

The Titan Flagship report is out. I've flipped through it (have a deadline that prevents detailed study for a week or so) and it looks highly detailed.

Word of warning. When I down loaded it, the site was really slow.

http://www.lpi.usra.edu/opag/Titan_Explorer_Public_Report.pdf

Posted by: Phil Stooke Jan 24 2008, 07:05 PM

Thanks, vjkane. It's very useful to have someone scouting these things out and drawing attention to them. I get too busy to look all the time.

That LPI site is a treasure trove of useful reports:

http://www.lpi.usra.edu/analysis/

There are new things from the Venus and Mars groups as well.

Phil

Posted by: JRehling Jan 24 2008, 07:15 PM

Lots to read (197 pages) -- the first things to grab me are the suggested landing sites and balloon tracks.

After the report lists several terrain types as having some upside or other, the final suggestion of a baseline landing site is the Belet dune field. Basically, the sand dunes are believed to be a good place to study Titan's organic chemistry. Other areas would have their own interest, but are either less typical of Titan as a whole or present engineering challenges.

The nominal balloon deployment would be low latitude, with a hope for stable flight and a long ground track. Presumably, a variety of terrain would be overflown -- it would be almost hard to avoid unless the flight were very short. The alternate possibility would be to land near the summer pole and try to get a peek at lakes and possibly storms, but there seems to be less confidence in what the winds near the summer pole would mean for the flight.

Much more to read...

Posted by: djellison Jan 24 2008, 07:45 PM

My WORD, never has a PDF made me want to animate stuff as much as the TE pdf.


Doug

Posted by: ngunn Jan 25 2008, 03:13 PM

Great! The best possible weekend reading.

Posted by: ngunn Jan 28 2008, 10:04 AM

A couple of gems from the Titan report:

A separate aspect of living processes, quite distinct from the metabolic perspective, is informational
and theoretical: can information be encoded and duplicated in the various organic
chemical systems on Titan? Are there autocatalytic reactions that might, for example, give an
isolated lake its own molecular fingerprint, or do all lakes have the same “genome” ?


With such a scientifically rich target body, the formality of establishing science objectives
almost seems irrelevant; almost any measurement in such an interesting environment is likely to
yield enormous scientific return.

Posted by: djellison Jan 28 2008, 10:32 AM

I flicked thru it very quickly for a first glance. I then had another look at the most exciting parts.

I WANT THAT MISSION.

No offense to people who rather we reinvestigated Europa and its friends - but TE gets my exploratory juices flowing like nothing else. In an ideal world, we would do everything, tomorrow. But this isn't an ideal world.

It has three large chunks that could, if required, be international interfaces (Orbiter US, Lander ESA, Balloon CNES/JPL).

It's the most expensive, but boy oh boy are we getting a lot of return. I don't think any of the others would grab the public imagination like this.

Doug

Posted by: ngunn Jan 28 2008, 04:56 PM

This is another of my favourite bits - the alternative (or additional) balloon location:

Nominally, a low-latitude deployment is anticipated to avoid proximity to strong convective
clouds and to provide a long ground track. An alternative scenario (which might be particularly
attractive if a change in the budget or partnering assumptions in this study were invoked to permit
two Balloons) would be to deploy a Balloon near the summer pole. This location would permit
detailed inspection of lakes (in continuous daylight), perhaps allowing observation of tides
and wind-driven waves, as well as exciting proximity to summer rainstorms.


Deploying both the lander and balloon to the dry tropics is understandable for a number of reasons, but I think close-up views of Titan's liquids would be worth some increased risk or additional expense. Outreach possibilities are mentioned frequently in the Titan report. Aside from the potential science benefits, liquids in action would be a huge crowd pleaser - perhaps providing the stand-out images of the whole mission.

Posted by: tedstryk Jan 28 2008, 05:57 PM

I would like that mission, but not as the next flagship. There is too much new technology. Combined with the cost, I fear it would not get off the ground on time to preserve some sort of outer planets continuity.

Posted by: Mariner9 Jan 28 2008, 09:15 PM



The thing I don't like about any of the flagship studies is the ten year cruise. Ten years???? Tough enough pill to swallow on Rosetta, but this is getting really annoying.

The titan report specifically addressed the idea of using SEP to speed things up, and said that it would take 4 years off the cruise, and add roughtly 100 million to the cost of the mission. Frankly, that sounds like a good investment. That gives the vehicle four more years margin on arrival: more power left in the RTGs and fewer failures of componants. Plus, it saves on operating costs during cruise, which can be minimized, but still ammount for a fair number of dollars, especially when you might be talking teams in multiple countries. And in past missions it was noted that it is politically more difficult to support really long space missions.

Finally.... those four years could effectively push out the next Titan mission by four years. If we do this right, I might live to see a second Titan flagship.... but those extra four years really make it tougher.

Posted by: centsworth_II Jan 28 2008, 11:42 PM

A quicker paced flagship schedule will take a much larger budget.
That's always been the limiting factor... not technical, but monetary.

Posted by: Mariner9 Jan 29 2008, 01:58 AM

Don't get me wrong, I know that affording even a single flagship mission over the next ten years is going to be tough. My point is that if you are spending well over 2-3 billion already, adding a mere 100 million (hey, we are talking billions here) for an SEP stage might be well worth it due to the decrease in overall project time, etc. etc.

And based on history to date, Mars aside, NASA doesn't even start to think about missions to a particular destination until the current mission gets completed.

So come on already.... the sooner you get back to Titan, the sooner we can start to work on the mission after that one.

I know I'm dreaming here hoping for another Titan mission start in 2025, but I suspect I'm not the only dreamer on this forum. smile.gif

Heck, while I'm at it I'll dream about a stripped down mini flagship JSO mission or a New Frontiers Io Observer during the same time period.

Then there is the whole dream about unexpectedly being named in Donald Trump's will, but that's a topic for a different forum.


Posted by: rlorenz Jan 29 2008, 06:35 PM

QUOTE (ngunn @ Jan 28 2008, 05:04 AM) *
A couple of gems from the Titan report:

A separate aspect of living processes, quite distinct from the metabolic perspective, is informational
and theoretical: can information be encoded and duplicated in the various organic
chemical systems on Titan? Are there autocatalytic reactions that might, for example, give an
isolated lake its own molecular fingerprint, or do all lakes have the same “genome” ?



(modest cough)
Writing these reports is not a path to scientific fame, it must be said, but I am quite proud of the work
that the team and myself did on this..... I hope you guys enjoy the 197 pages....

The 'fun' thing about the Titan mission is that there are so many options, everyone has their own idea of
what is the best thing to do : SEP vs no SEP, balloon vs lander, etc. etc. Not everywhere in the solar
system has such a rich portfolio of options.

Posted by: nprev Jan 30 2008, 01:51 AM

I think we're all drooling profusely, Ralph; nice job, hope that it knocks the socks off of the decision makers as well! smile.gif

Posted by: Doc Jan 30 2008, 10:33 AM

I hope the price tag for the Tit. Expl. does not scare them though....

Posted by: TheChemist Jan 30 2008, 01:52 PM

Tholinome. You heard it here first. smile.gif

Posted by: simonbp Jan 31 2008, 01:07 AM

I love how they just slap 3 kg on the balloon for "Phoenix-based" MET package. The only thing that causes the Phoenix package to weigh that much is the Lidar, which could be really awesome if mounted on a scan platform (the only other MET insts worth moving over are a thin-wire thermocouple and a barometer). I do wonder about the MSL-derived TDL, though, considering all of its trials and tribulations...

Also, I wonder how much the seismometer will actually pick up; it sounds like it's decoupled from the Lander (a.k.a. Luna-Titan), but that doesn't necessarily mean that it's coupled to the ground (especially if it's loose regolith)...

Simon wink.gif

Posted by: Mariner9 Jan 31 2008, 04:20 PM


The titan flagship sure seems to have it all. More science than you can shake a stick at, and multiple options for scope and participation. Escpecially important, separate components in the orbiter, lander, baloon systems. ESA and Japan (and the US for that matter) love having stand alone vehicles that they can point to and say proudly "we built that". More importantly, tell their respective governments how they are helping to build and support local high tech industry.

It has been a while since I've read any Laplace descriptions, but I seem to recall a triple orbiter scenario: communcations relay that stays out of the heavy radiation zone, Europa orbiter, and a magnetosphere explorer.

Granted, that gives you three separate components to split up amongst the players, but say the words "magnetosphere explorer" and then say "Titan baloon probe" .... and think about going in front of your government to try and sell the idea.

Sure, the Japanese managed to sell it once, but that baloon probe sure sounds a lot sexier than a magnetosphere explorer.

Let's face the hard cold facts: nobody ever impressed their date at a romantic dinner talking about magnetospheres.

Posted by: rlorenz Jan 31 2008, 04:28 PM

QUOTE (simonbp @ Jan 30 2008, 08:07 PM) *
I love how they just slap 3 kg on the balloon for "Phoenix-based" MET package
....
Also, I wonder how much the seismometer will actually pick up; it sounds like it's decoupled from the Lander (a.k.a. Luna-Titan), but that doesn't necessarily mean that it's coupled to the ground (especially if it's loose regolith)...


If you actually HAVE a better idea, do share. With luck there will be an opportunity for you to propose.....

First, note that all these payloads are placeholders - people would propose whatever they wanted. With so
many diverse instruments on the orbiter, lander and balloon, there wasnt a lot of time to devote to each. The
MET package might well include some sort of atmospheric electricity measurement, as well as a real
anemometer (which Phoenix doesnt have) No reason you couldnt have a LIDAR too. Wasnt an obvious reason
to clamp the allocation to 0.5kg or something - TItan's weather is a key objective.

The report states quite clearly that the seismometer has spikes to anchor it to the ground (as was the
case for the Apollo seismometers btw). Attenuation in granular material is less important for the long period seismic
motions we are after - teleseismic events, normal modes etc. than it is for picking up footsteps of the Vietcong
as in Igloo White.

I dont know what it would pick up either - that's the whole point. No-one has flown seismometers since Mars-96,
and those didnt make it. Before that just Viking and moon missions. This would be an exciting first.

Posted by: vjkane Jan 31 2008, 08:22 PM

I've been reading the Titan proposal as bed time reading. I'm swinging from favoring a Jupiter system mission ot a Titan mission as the next flagship. We know that Titan is fascinating, and we can land on it and float above it. Europa may be fascinating, but it will take at least two missions (orbiter then lander) with all the radiation problems to find out.

I do think that an essential prerequisite to a Titan mission, though, are smaller RTGs. Given the costs of the mission and the need for a relay, I think we want multiple landers and/or balloons. With existing RTGs, this doesn't make sense. With smaller RTGs, it would. The science community would have to decide how many places are high priority for a lander, and then accept the lander complexity that fits within that budget for that many landers.

A really sweet option, but I strongly suspect that the cost of the launcher and carrier prohibits it, would be to have the orbiter arrive a year early and carry out the orbital reconnaissance and have the landers arrive with much better information on where to target them both for scientific interest and safety. Alternatively, the orbiter could carry the landers within its aeroshell and release them from orbit. However, this may add enough hardware and operations complexity that a separate launch and carrier might be easier and cheaper.

Posted by: vjkane Mar 22 2008, 04:15 AM

The assessments of the four flagship missions has been posted at http://www.lpi.usra.edu/opag/announcements.html

Some key findings:

ESA and NASA are studying two joint missions:

Jupiter: Jupiter/Ganymede orbiter (ESA); Europa orbiter (NASA)

Titan: In situ probe (ESA); orbiter (NASA)

Summary of findings on the Flagship proposals delivered last year:

Europa orbiter: Mission concept Excellent/very good; Risk Science Medium; Risk overall mission Medium

Jovian system: Concept Very good/good; Science High risk; Risk overall High

Titan Explorer: Concept Excellent/very good; Science medium risk; risk overall High

Posted by: NMRguy Mar 22 2008, 05:00 PM

I assume that the Jupiter/Ganymede orbiter provided by ESA would be a much scaled down version of the proposed Jupiter System Observer (JSO)? Would there be a big enough launch payload to include both orbiter components without significantly compromising the research goals of both? It seems unlikely. I guess I would rather have the previously proposed JSO or EO as compared to scaled down versions of both.

Anyway, the Titan option keeps getting more interesting with each new Cassini flyby...

Posted by: marsbug Mar 22 2008, 06:39 PM

My opinion is that titan is now the most interesting single object in the solar system- complex organic chemistry, likely underground ocean, active surface processes, the list goes on. The only way I see it being knocked off its top perch is if enceladus proves to have and underground sea powering its plumes, which would give us the opportunity to sample material from an extra terrestrial sea. That said a sample from a cryovolcanic flow on titan could prove just as interesting! Exciting times...

Posted by: nprev Mar 22 2008, 07:36 PM

With the state of current technology & recent discoveries, I'm getting there myself, MB.

The damned Jovian radiation environment is such a major limiting factor for Europan exploration right now. Only makes sense to try the Saturn system instead, which has at least two satellite targets of extreme interest with a lot less frying potential. Gotta lean heavily towards minimized risk here plus significant science return potential.

Posted by: Mariner9 Mar 22 2008, 10:54 PM


As far as multiple targets of interest in the Saturn system, I'm not so sure that the Titan mission would return information on Encealdus. If the Titan orbiter is using aerocapture I would guess that the most likely scenario has the orbiter entering Titan orbit on initial approach to the Saturnian system. In that event the only moon we are likely to get a good look at is Titan itself.

That is the trade off I see between the missions. The Jupiter Flagship gives us close looks at all of the Jovian moons, and detailed looks at Europa and Ganymede. Gives you a lot of targets to ponder and study.

The Titan mission gives us just Titan.... but if you have to be stuck studying just one major moon in the Solar System I'm hard pressed to think of a more interesting one.

We don't have much information on the two studies as yet, but while I can see the US building a Europa Orbiter for 2 billion dollars (a figure I've seen mentioned a couple times as the cost cap for our part of the mission) I seriously wonder if the ESA can build a full blown Ganyemede orbiter for their stated goal (600-700 million Euros is my vague recollection).

Posted by: vjkane Mar 23 2008, 02:18 AM

I'd love to see a mission to Titan. However, looking at this from a management perspective, the issue is risk. NASA cannot let this mission fail. Both leading candidates provide excellent science. One is medium risk (Jovian), the other high risk (Titan).

The decade or more of technology development and mission definition for the Europa mission shows. I'd prefer to see the next Flagship mission go to Titan. Their challenge is to get the risk rating down.

Posted by: Juramike Mar 23 2008, 02:41 AM

QUOTE (vjkane @ Mar 22 2008, 09:18 PM) *
Their challenge is to get the risk rating down.


How about we send two of the exact same spacecraft on the exact same type launch vehicle along the same track? Same instruments, same science packages. And you test the spacecraft development a little bit more than usual.

OK, we pony up the bucks for a duplicate spacecraft (relatively cheap), and for the second launch vehicle (much bigger bucks), but you will lower the risk. (If you tested right, at least one of them should make it.)

This is assuming that the risk is due to unforseen random issues, cosmic ray hits, not getting the entry angle right on the first try, etc.


I think Titan is diverse enough to support two Titan Explorers. (Just like Mars is doing a great job of keeping both rovers busy and with exciting new stuff). If both make it, you will more than double the science.

(And Bonus: Two Jupiter flybys).

Just my 2E11 cents.


-Mike

(And yes, I'm a U.S. Taxpayer and more than willing to kick in more than my fair share for a twofer deal.)




Posted by: Greg Hullender Mar 23 2008, 04:47 PM

Nasa used to routinely send pairs of spacecraft on missions, and frequently lost one of the pair. Again, I've never seen how this breaks down, but I'd be surprised if it's anywhere close to "two for twice the price."

Except for the cost of the launch vehicle, of course. There, once again, I think we're reduced to hoping that Falcon 9 ends up being everything it's promised to be.

--Greg

Posted by: djellison Mar 23 2008, 05:01 PM

A second spacecraft typically adds 50%. That was the budget breakdown for MER initially ( although budget overruns pushed that up to almost double the price of the first proposed rover )

So - for a $3B flagship - you're talking about increasing it to $4.5B minimum. That's not pocket change. We're stretching the budget to afford one flagship - to afford 1.5 is fantasy land.


Doug

Posted by: vjkane Mar 23 2008, 05:27 PM

Assuming that the Titan mission is selected, ESA has a range of in situ missions it can propose within in its ~600-700 euro budget:

One really good lander

Two less capable landers (say with 1/2 -2/3 the capabilities of the one really good lander). Here the tradeoff is between better science at one spot, or investigating two spots with a less capable lander.

One less capable lander and a minimalist balloon. The balloon presumably could share many of the subsystems of the lander, but would also require a lot of new engineering and testing.

From my conversations with Lorenz, a key factor will be whether or not ESA decideds to develop smaller plutonium power systems. Apparently NASA's standard design assumes large missions. Once you put on that large power supply, you are committed to a big vehicle. If ESA designs a smaller supply, then it makes sense to consider multiple smaller landers/balloons.

In theory (but the engineers may dispute the practicability), a single entry shell could carry both a lander and a balloon. There would have to be tradeoffs in avaiable space between the two. I think that a balloon that carried only a camera but could float for months/years could provide valuable ground truth of the orbiter's observations.

Posted by: mps Mar 23 2008, 08:42 PM

QUOTE (Greg Hullender @ Mar 23 2008, 06:47 PM) *
Nasa used to routinely send pairs of spacecraft on missions, and frequently lost one of the pair.


Which missions do you mean? Mariners?

I note that both Voyagers, Vikings and MERs were successful, so losing one s/c of the pair isn't a common practice at NASA anymore wink.gif


Posted by: dvandorn Mar 23 2008, 09:02 PM

QUOTE (vjkane @ Mar 23 2008, 12:27 PM) *
In theory (but the engineers may dispute the practicability), a single entry shell could carry both a lander and a balloon. There would have to be tradeoffs in avaiable space between the two. I think that a balloon that carried only a camera but could float for months/years could provide valuable ground truth of the orbiter's observations.

Well -- what's wrong with the idea of a lander attached to a balloon? That way you can reconnoiter a lot of landscape with instruments on both the lander and the balloon, and only drop the lander when it's over an area you recognize as a good one for surface exploration. Yes, you run the risk of flying over a unique area and recognizing it as such only after it's passed on by beneath you, but Titan has so many different types of terrain and chemistry to offer, and so much of most of them, I'd think you'd be able to recognize a good area in time to set up the drop.

As for the drop, all you really need is a good parachute system. The lander can be dropped on a chute from 1,000 to 5,000 meters and make a nice, safe landing in that thick air.

-the other Doug

Posted by: dvandorn Mar 23 2008, 09:04 PM

QUOTE (mps @ Mar 23 2008, 03:42 PM) *
I note that both Voyagers, Vikings and MERs were successful, so losing one s/c of the pair isn't a common practice at NASA anymore wink.gif

Not so much anymore, but the losses of Mariners 3 and 8 really proved out the concept. In fact, the only dual spacecraft I can recall that were both lost were the Mars penetrators that hitched a ride with MPL.

-the other Doug

Posted by: vjkane Mar 23 2008, 09:16 PM

I think that it was a combination of more reliable boosters and funding reductions that caused NASA to stop launching duplicate spacecraft for the same opportunity. MER was the exception.

Posted by: JRehling Mar 23 2008, 11:57 PM

When I read "high risk" for Titan, I think not only of the necessarily complex hardware, but also the unknowns of Titan itself. For initial recon of a world, you don't have much risk with a flyby -- you're looking for the basics, and you'll almost certainly get them. There's no such risk with, say, Dawn at Ceres.

But we've been burned before. In a sense, the first three Mariners at Mars burned us by imaging terrain that was not representative of the planet. The Galileo Probe burned us by hitting a highly unrepresentative location on Jupiter. The MER program was burned by planning two rovers with a particular set of engineering and science constraints and having only one site on the whole planet really match the specs.

That is the kind of risk that Titan poses, and so I don't think there's any sense to hurrying a Titan mission along before all the Cassini data has been analyzed, through a couple of waves of peer review. With Europa, we had to have the community partake in the debate over how thick the ice shell is. It would have been foolhardy to plan the next billion-dollar mission when there was still pencil-and-paper work to be done. The pencil-and-paper work is just a heck of a lot cheaper. Let's play as much of the Twenty Questions here in the Gedankenexperiment lab before launching a major chunk of the whole decade's budget. Suppose a brilliant conjecture is posited the year after the flagship launches, and as a result, Hotei Arcus becomes the consensus most interesting place in the solar system. And the mission is already en route lacking the capabilities needed to probe it. That - must - not - happen.

Titan's surely the prize. It's the one that would get picked first if captains were choosing softball teams. But it's also not ready this time around. The next flagship almost certainly has to go to the jovian system. (Enceladus has a very slender chance of jumping the queue because it's likely easier to "figure out" than Titan.)

Posted by: tedstryk Mar 24 2008, 01:07 AM

QUOTE (JRehling @ Mar 24 2008, 12:57 AM) *
But we've been burned before. In a sense, the first three Mariners at Mars burned us by imaging terrain that was not representative of the planet.


Well, they got some pretty representative areas, though they missed the highlights. In fact, a lot of interesting things are in the images - a multitude of valleys, one end of Valles Marineris, the white rock, the south polar region. The problem is that the resolution/dynamic range of the images was in many cases not good enough to spot or to interpret the features, and also the lack of context for many images led to features not being understood. It is true that a nice shot of central Valles Marineris or a near encounter view of one of the volcanoes in Tharsis would have helped, and to have missed those features was truly bad luck (although not too surprising, given the amount of coverage they got). However, the idea that the first three Mariners, and I am especially referring to 6 and 7 simply photographed the most boring places on the planet is grossly overstated.

Posted by: Greg Hullender Mar 24 2008, 04:20 AM

QUOTE (dvandorn @ Mar 23 2008, 01:04 PM) *
Not so much anymore, but the losses of Mariners 3 and 8 really proved out the concept. In fact, the only dual spacecraft I can recall that were both lost were the Mars penetrators that hitched a ride with MPL.

-the other Doug


Only one I was going to add was Mariner 1. Maybe the whole problem was the naming system. ;-)

--Greg

Posted by: Greg Hullender Mar 24 2008, 04:26 AM

QUOTE (djellison @ Mar 23 2008, 09:01 AM) *
A second spacecraft typically adds 50%.


Pity we can't get the EU to just pony up the difference. "The same great space probe, but at HALF the price! You can't walk away from this deal!" :-)

I suppose that'd still be twice what they were prepared to pay . . .

--Greg

Posted by: vjkane Mar 24 2008, 06:05 PM

QUOTE (Greg Hullender @ Mar 24 2008, 04:26 AM) *
Pity we can't get the EU to just pony up the difference. "The same great space probe, but at HALF the price! You can't walk away from this deal!" :-)

I suppose that'd still be twice what they were prepared to pay . . .


If NASA puts in $2B (which I hear is the target amount), then ESA would need to put in $1B for a duplicate Europa orbiter. Given the direction of the dollar, this becomes easier day by day. smile.gif However, the bigger problem is the duplicate launch vehicle. Since these launcher are near copies of each other, as I understand it, then cost of duplicates has already been amortized. As I remember the Flagship reports, the #1 factor in reducing costs is to get on a smaller launcher. (One of my previous posts has the numbers.) I'm not sure what ESA and NASA are considering for the Jovian mission in terms of launch vehicles. Do they launch together or separately? I also wonder if JAXA would be interested in providing a smaller orbiter for magnetosphere studies a la La Place.

Posted by: volcanopele Mar 24 2008, 06:24 PM

According to the Laplace mission summary, the Europa Orbiter would launch separately along with a possible surface component. The Jupiter Planetary Orbiter (provided by ESA) would launch along with the Jupiter Magnetospheric Orbiter (provided by JAXA).

Posted by: djellison Mar 24 2008, 06:30 PM

A comparatively simple orbiter doesn't make much sense for duplicating imho. We didn't need a second MRO or MGS or MEX or VEX. If you're going do do redundency, do it for the highest risk parts, or where you visit two different places in doing so ( i.e. MER put the chance to visit two sites against halving the risk of a total failure, Voyager's visited/images different parts of moons). I don't think a second MRO would give double the science value. Better planning and a greater range of spacial, temporal and wavelength of instruments with one vehicle makes more sense for an orbiter imho. If you're building two of something, make it impactors, landers, atmospheric probes of some sort - the higher risk part of the equation. i.e. Don't build two Cassini's - build one Cassini and put two Huygens on it.

And the value of the dollar doesn't really factor in. ESA wouldn't be giving NASA any cash, these things can not (and rightly so) work that way. It would cost ESA pretty much the same, in real terms, to build a spacecraft if the dollar was at 50 cents to the euro or 2 dollars to the euro.

Doug

Posted by: vjkane Mar 24 2008, 06:51 PM

QUOTE (djellison @ Mar 24 2008, 06:30 PM) *
If you're going do do redundency, do it for the highest risk parts, or where you visit two different places in doing so ( i.e. MER put the chance to visit two sites against halving the risk of a total failure, Voyager's visited/images different parts of moons).

Redundancy in this case would be one orbiter for Europa and one for Ganymede.

My guess, reading between the lines of the one sentence comment in the Flagship assessment and the LaPlace proposal, is that the ESA craft is a Jovian orbiter that does repeated Ganymede flybys. Not orbiting Ganymede saves a tremendous amount of fuel and reduces the instrument list considerably (radar probably isn't very useful, for example). This might reduce costs enough to fit into ESA's budget. The box studies last year found that even simple Jovian moon orbiters were well in excess of $1B. Since Euros spent in Europe purchase roughly what dollars spent in the US purchase, ESA has ~$8-900M in purchasing power. (Exact comparisons are hard because of different accounting systems and trying to determine local purchasing power is not exact.)

A Jovian orbiter with a really good (i.e, big, Deep Frontiers or HiRise) class could do a lot of Jovian and Io science. The apparently fairly small camera proposed for La Place appears from the mass summary to be in the New Horizons class, which would be much less capable.

Anyone know if there is a spare of the Deep Impact camera system? laugh.gif

Posted by: djellison Mar 24 2008, 06:53 PM

QUOTE (vjkane @ Mar 24 2008, 06:51 PM) *
Anyone know if there is a spare of the Deep Impact camera system? laugh.gif


The one that was out of focus?

smile.gif

Doug

Posted by: vjkane Mar 24 2008, 07:14 PM

QUOTE (djellison @ Mar 24 2008, 06:53 PM) *
The one that was out of focus?

Yeah, that one. Bet the duplicate could be focused on the ground before launch!

Posted by: Mariner9 Mar 24 2008, 09:43 PM


It is tough to know just what 700 million Euros will buy on a mission like this. Several things about ESA make apple to apple comparisions with the US rather dicey.

It was on this forum that I first heard that ESA planetary missions do not factor in the cost of instruments directly. If I'm understanding that correctly it means that the 700 million Euros goes for the launch vehicle, spacecraft, and possibly operation costs, but does not include the instruments. That has got to be giving you a healthy boost on effective budge (I'm thinking an insturment suite for this mission could run 50-100 million Eurios).

Secondly, there is the European aversion to nuclear power on their spacecraft (largely a political hot potato, I think). I think most of the Billion Dollar Box studies that NASA did envisioned nuclear powered shipts. Not sure if solar power would be cheaper or not, but in any event the Europeans do not always think the same way that the JPL engineers do (for better or worse) and it's tough to be sure that the studies we did on outer planet orbiters would be directly applicable.

When I read read the Laplace Report (a long time back, memory is vague) it struck me that they were coming up with missions very different from our concepts, and were estimating much smaller vehicles (launched on a Soyuz) and cheaper costs.

It will be very interesting to see how these design studies turn out.




Posted by: vjkane Mar 24 2008, 10:26 PM

QUOTE (Mariner9 @ Mar 24 2008, 09:43 PM) *
It is tough to know just what 700 million Euros will buy on a mission like this. Several things about ESA make apple to apple comparisions with the US rather dicey.


I agree on the problems of comparing funding. However, I don't think the ESA budget can be stretched to match the capabilities of the box study. Some ways that come to mind to cut costs would be to use solar power, reduce the size of the launcher (I don't think we can fit both mass of the ESA and NASA craft into the same launcher, but I hope I'm wrong), reduce the instrument compliment, and stay away from high radiation fields. I expect that this is the plan for the ESA craft, with the big open question being whether they plan to orbit Ganymede. A smaller open question is whether they will take on the costs of having a spacecraft with the pointing accuracy and stability for a really big camera.

In general, the LaPlace instruments weigh much less than the Europa orbiter instruments. In general, that means less capable science but lower development and testing costs, lighter spacecraft, cheaper launcher, smaller power supply, cheaper operations, etc...

Posted by: mps Mar 25 2008, 11:25 AM

QUOTE (vjkane @ Mar 25 2008, 12:26 AM) *
In general, the LaPlace instruments weigh much less than the Europa orbiter instruments. In general, that means less capable science but lower development and testing costs, lighter spacecraft, cheaper launcher, smaller power supply, cheaper operations, etc...


I think that we get outer planets missions so rarely and they are so expensive, that "less capable instruments" would actually be a waste of resources.

Posted by: ugordan Mar 25 2008, 11:40 AM

QUOTE (mps @ Mar 25 2008, 12:25 PM) *
I think that we get outer planets missions so rarely and they are so expensive, that "less capable instruments" would actually be a waste of resources.

This is my opinion as well. I think we should try and cram as much science onto a single spacecraft as possible (similar to what Cassini did), not send "mediocre" instruments. If that requires several international partners, then by all means go for it. Better than sending virtually empty spacecraft buses on billion km voyages just so we can lower the price and be able to say "we've got an orbiter right there".

Posted by: jasedm Mar 25 2008, 08:55 PM

I'd like to register my agreement also - why take a couple of days off work to drive to Germany and do a lap of the Nurburgring in a Fiat Punto??
If you're going to send instruments all that way, make them the best.

Posted by: Mariner9 Mar 25 2008, 08:55 PM

QUOTE (ugordan @ Mar 25 2008, 04:40 AM) *
This is my opinion as well. I think we should try and cram as much science onto a single spacecraft as possible (similar to what Cassini did), not send "mediocre" instruments.



I don't think we should send poor instruments, or vehicles with too limited a payload, but let's not fall into the opposite trap: Endlessly desigining the most capable spacecraft but never quite flying it.

One of the reasons there were no Mars missions for so many years after Viking was that many planetary scientists and engineers kept holding out for a Sample Return. On several occasions I remember reading comments from other government officials (Administration, mostly) asking essentially: "Isn't there any other cheaper Mars missions you could fly?" After nearly ten years of NASA holding out for a bigger spectacular than Viking, the Reagan Administration approved the Mars Observer orbiter... becsause NASA finally proposed something that was considered affordable.

There are many examples of this sort. Take for example the many attempts over the years to get a Pluto mission funded. Undoubtably there were many reasons it took so long, but at one point JPL actually was pushing for a Cassini class flyby spacecraft.... essentially trying to cram as much science onto a single spacecraft as possible. A single, very expensive spacecraft. What finally flew was the relatively modest New Horizons. Which, IMHO, is far better than a drawing of a really fancy Cassini class space probe.

There were many political reasons that the Europa Orbiter was killed in 2001 (not the least of which was a bruised ego of the Nasa Administrator), but I keep looking back at the strawman vehicle that was the baseline early in that mission's definition phase. It had visible light cameras, Infrared Mapping spectrometer, ice pentetrating radar, and laser altimeter. Ok, so that's rather on the low end of 'Flagship' ..... but it would have launched by 2008.

Instead we are talking about launching next flagship no earlier than 2016.

As Alan Stern has commented, (paraphrasing) " sometimes you need to settle for 70 percent of something, instead of holding out for 100 percent of nothing."

Posted by: jasedm Mar 25 2008, 08:59 PM

Good arguments.

Posted by: djellison Mar 25 2008, 09:37 PM

There's a science update tomorrow at 6pm UT - I'm wondering what that covers. Mainly Enceladus I'm sure, but the extension ( and the recent Mars issues ) may get a mention.

Doug

Posted by: vjkane Mar 26 2008, 12:25 AM

QUOTE (ugordan @ Mar 25 2008, 11:40 AM) *
.. not send "mediocre" instruments

the instrument weights proposed for LaPlace are in the class of instruments that New Horizon is flying. If you can get close to your target, they are fine (with caveat below). At Jupiter, though, getting close to Io and Jupiter comes with a significant radiation problem, so you'd like to have much larger optics on your instruments. New Horizons did some nice work during its flyby, but there's a strong desire for much higher resolution, even for a monitoring program.

Now the caveat: Heavier instruments also typically have more sensitivity and more measurement modes. The instrument can deliver (weight) to the target and afford is better than the one that fails both criteria, though. The $2B version of the Europa orbiter cut both instruments and instrument capabilities to get development costs and weight down, and reduce the overall mission cost from $3B.

Posted by: SFJCody Jun 3 2008, 08:41 PM

Very interesting episode of the Sky at Night this month on the subject of returning to either the Saturn system or the Jupiter system.

It seems the Titan submersible concept has been shelved for the time being and will have to await a future mission.

Posted by: vjkane Jun 15 2008, 03:38 AM

The presentations from the outer planet flagship instrument conference are now available at http://opfm.jpl.nasa.gov/community/opfminstrumentsworkshoppresentations/ .

I am struck by the small size of the solid state recorder for the Europa mission. 1GB is not much, especially for the remote sensing of Io, Ganymede, and Callisto leading up to Europa. I seem to remember that previous presentations talk about 2GB. Contrast this to the 32GB proposed for the Titan orbiter. The radiation environment at Jupiter is imposing a substantial penalty in what can be returned. It makes the Titan mission look that much more interesting, especially since there would be a strong in situ capability to compliment the orbiter.

Posted by: Mariner9 Jun 15 2008, 04:18 PM


I was struck by the 10 year travel time for the Titan orbiter, vs. around 6 years for Europa Orbiter.

I've read several times that the criteria that NASA had set for the next flagship was cruise times of no more than 7 years (mentioned in interviews and news articles, but I've never seen any formal NASA documents stating this). It was part of their determination not to get involved in projects like the ISS which not only gobble up money but takes decades to launch and complete.

The Titan mission was pretty darn compelling, but I wonder how important the cruise time difference will be to the selection comittee when the final decision is made.

Posted by: ngunn Jun 16 2008, 11:19 AM

I am DELIGHTED to see in the latest Titan proposal that one of the surface probes is now to be a wet-'lander'. Engineering conservatism has been overwhelmed by the compelling prospect of 'killer science' - and of course killer outreach. They should call the raft Kon Tiki.

Posted by: vjkane Jun 16 2008, 05:47 PM

QUOTE (ngunn @ Jun 16 2008, 12:19 PM) *
I am DELIGHTED to see in the latest Titan proposal that one of the surface probes is now to be a wet-'lander'. Engineering conservatism has been overwhelmed by the compelling prospect of 'killer science' - and of course killer outreach. They should call the raft Kon Tiki.

Having read all the presentations twice, I wouldn't get too excited by the ESA proposals at this point. They read like ideas for proposals rather than proposals that have gone down the crucible of many trade off studies and hard choices. Compare the specificity of the ESA presentations to the JPL orbiter presentations.

This is not a criticism of ESA! Simply a recognition that while JPL has had a decade or more to study Europa missions, ESA has been looking at the choices for a Ganymede orbiter or a Titan in situ mission for just a few months. (The same is also true of a Titan orbiter for JPL, but orbiter missions are simpler.

Having read the presentations twice, my conclusion is that if I were to pick between a Titan orbiter or an Europa orbiter, I'd go with the Titan orbiter. However, a Europa orbiter with significant Jovian science would probably win out in my preference over a Titan orbiter. (I know the Titan orbiter will also make some flybys of Enceladus, but the science will does not appear to me to be as compelling as what would be learned from a Jovian tour.) That said, the Europa orbiter has at least two serious limitations for Jovian science. First, it lacks a narrow angle camera. Second, it has just a 1GB solid state recorder. While aggressive compression is planned, that still feel sub-optimal for significant new studies of the other Galilean moons from flybys.

All this said, I still think that NASA will pick whichever mission is lower risk (i.e., more mature design). Both have very compelling science.

Posted by: ngunn Jun 16 2008, 06:14 PM

QUOTE (vjkane @ Jun 16 2008, 06:47 PM) *
Having read all the presentations twice, I wouldn't get too excited by the ESA proposals at this point.


Too late!!! I've been very excited about them for quite a while now. smile.gif (To sail an alien sea - Who's not excited?)

I'm also excited about the Jupiter system proposals, and Ganymede in particular just as much as Europa.

Whatever happens this time around it will not be the end of either story, I'm sure of that.

Posted by: just-nick Jun 18 2008, 04:02 AM

QUOTE (ngunn @ Jun 16 2008, 03:19 AM) *
I am DELIGHTED to see in the latest Titan proposal that one of the surface probes is now to be a wet-'lander'. Engineering conservatism has been overwhelmed by the compelling prospect of 'killer science' - and of course killer outreach. They should call the raft Kon Tiki.


OK, I'm going to sound like the USF dolt of the week, but where are these new proposals with floating rafts? I've seen nothing on Tandem, only the 2007 OPAG stuff. Do I have new late-night reading out there somewhere that I've missed?

--Nick

Posted by: volcanopele Jun 18 2008, 04:34 AM

it is a relatively new idea (or at least a reborn idea) now that large enough seas which can be targeted have been found.

Posted by: ngunn Jun 18 2008, 08:14 AM

Let's not forget that ESA has already landed a potential raft on Titan - it just happened to come down in a dry(ish) location.

Edit: just-nick: follow the link in post 215 and see the Coustenis presentation.

Posted by: gpurcell Jun 18 2008, 02:28 PM

"Jupiter Icy Moons Orbiter - Ambitious"

Snicker.

Posted by: vjkane Jun 20 2008, 05:41 PM

An additional presentation from the Flagship instruments meeting has been posted on the architecture options for the Titan in situ mission. http://opfm.jpl.nasa.gov/community/opfminstrumentsworkshoppresentations/ and scroll down to TSSM In Situ Element Architecture, Flight Systems, & Planning Process, Christian Erd (ESTEC) (Download) (PDF, 31.16 MB).

Some thoughts on the architecture options:

First, the in situ elements are released to enter the Titan atmosphere prior to the orbiter's Saturn insertion burn. This means that the availability of the orbiter for data relay for the first ~18 months will be limited to the occasional orbiter flybys of a few hours duration each. When the orbiter is not in place to act as a data relay, then bit rates for direct communication to Earth are very low. (And during any given flyby, the geometry between the balloon or lander and the orbiter may be very poor.) Since Titan is not a friendly environment, having to wait ~18 months for significant data return from the in situ elements is a big risk. The balloon, for example, is being designed for a 1 year lifetime. (In reality, it would probably last longer if it survives the first year, but this is a major mission risk issue.)

The in situ mission options discussed consist of a balloon and one or more landers. When NASA did it's billion dollar mission studies for Titan, the balloon option was estimated to have a cost between ~$1.3-1.8B depending on the costing assumptions. Assuming the lower cost (which would have much more development risk), this seems to put the cost of the Titan in situ elements above the budget that ESA is considering (<650 euros). The NASA cost estimate has to be adjusted because it included a launch vehicle that ESA would not pay for (subtract ~$300m) and ESA does not fund instrument development (subtract ~$100M?). (There was also a small carrier craft included in the NASA budget, but it appeared to be pretty minimal. Subtract another $50-100M?) This still leaves the cost of a balloon only element for the NASA study at around $800-850M (assuming the lower end of the price range). At official exchange rates, the 650 euro budget would cover this. However, 1 euro spent in Europe does not seem to buy $1.5 worth of goods or services. (That is, the exchange rate is based more on discrepancies in interest rates than on purchasing power.) If a euro purchases about $1 worth of goods and services spent in Europe, then there seems to be a budget mismatch, even for the most aggressive (and high risk) cost estimate. And the NASA study did not include any landers in the balloon mission.

My net take on all this is that the in situ Titan options have significant mission (very limited data relay for the first 18 months) and budgetary risk. I really like these options, so I hope that someone more knowledgeable than I (Ralph...?) shows me the error in my analysis.

Posted by: gpurcell Jun 20 2008, 09:34 PM

QUOTE (vjkane @ Jun 20 2008, 06:41 PM) *
First, the in situ elements are released to enter the Titan atmosphere prior to the orbiter's Saturn insertion burn. This means that the availability of the orbiter for data relay for the first ~18 months will be limited to the occasional orbiter flybys of a few hours duration each. When the orbiter is not in place to act as a data relay, then bit rates for direct communication to Earth are very low. (And during any given flyby, the geometry between the balloon or lander and the orbiter may be very poor.) Since Titan is not a friendly environment, having to wait ~18 months for significant data return from the in situ elements is a big risk. The balloon, for example, is being designed for a 1 year lifetime. (In reality, it would probably last longer if it survives the first year, but this is a major mission risk issue.)



Honestly, this sounds like a fatal flaw in the mission design. I cannot imagine that planning for best (or even decent) data transmission rates 180 days after the design life of the instruments gathering and transmitting the data has expired will be seen as an acceptable solution.

Posted by: ngunn Jun 20 2008, 09:43 PM

I don't believe that the situation is thus. We must be missing, or misunderstanding, something here. Maybe different versions of the plan have somehow made their way into the presentations. Clarification would certainly be most welcome.

Posted by: vjkane Jun 21 2008, 12:05 AM

QUOTE (ngunn @ Jun 20 2008, 09:43 PM) *
I don't believe that the situation is thus. We must be missing, or misunderstanding, something here. Maybe different versions of the plan have somehow made their way into the presentations. Clarification would certainly be most welcome.

I hope that you are right, that we are missing something. However, there has been only about one year of serious Titan follow on mission planning. It may be that the ideas are still in the early formative stage. If so, it's natural after such a short time. However, it doesn't bode well for the November decision between Titan and Europa.

This presentation also makes me think that just as with Mars, an on-going commitment to a series of missions is needed. The first would need to be an orbiter that can act as a relay for, say, 10 years. That can be followed on by one or more in situ missions that do direct entry. This is much like the mission architecture followed at Mars for landers and lander support.

Posted by: Juramike Jun 21 2008, 12:34 AM

QUOTE (vjkane @ Jun 20 2008, 08:05 PM) *
This presentation also makes me think that just as with Mars, an on-going commitment to a series of missions is needed. The first would need to be an orbiter that can act as a relay for, say, 10 years. That can be followed on by one or more in situ missions that do direct entry. This is much like the mission architecture followed at Mars for landers and lander support.


In a perfect world with infinite bucks and steady political will, that would be the way to do it. But I think it will be very difficult to try to win two (or more) separate launches to Titan in a 10 year time frame - one for the orbiter/mapper/relay and the other for the lander(s).

Given that the flight time to Titan is a sizable chunk of the relay lifetime, we would need to launch the in situ lander prior to the orbiter arrival. This would be really risky, what if the orbiter/relay fails before the lander arrives? You'd lose two missions for the failure of one.

Posted by: rlorenz Jun 21 2008, 10:21 PM

QUOTE (vjkane @ Jun 20 2008, 01:41 PM) *
The in situ mission options discussed consist of a balloon and one or more landers. When NASA did it's billion dollar mission studies for Titan, the balloon option was estimated to have a cost between ~$1.3-1.8B depending on the costing assumptions. Assuming the lower cost (which would have much more development risk), this seems to put the cost of the Titan in situ elements above the budget that ESA is considering (<650 euros). The NASA cost estimate has to be adjusted because it included a launch vehicle that ESA would not pay for (subtract ~$300m) and ESA does not fund instrument development (subtract ~$100M?). (There was also a small carrier craft included in the NASA budget, but it appeared to be pretty minimal. Subtract another $50-100M?) This still leaves the cost of a balloon only element for the NASA study at around $800-850M (assuming the lower end of the price range). At official exchange rates, the 650 euro budget would cover this.


I'm not a costing expert, but I thought the $1B-box study put the standalone balloon too high.

But anyway,
1. I think the cruise stage, plus the cruise operations, add up to way more than the $50-100 you have above

2. Who says ESA is paying for a balloon ? It might be that CNES provides it.

Either way, the detailed ESA study of the in-situ elements is just happening now, so tempting as it is to
second-guess everything, it may be premature to make assertions of budgetary incompatibility.


Posted by: vjkane Jun 21 2008, 11:39 PM

QUOTE (rlorenz @ Jun 21 2008, 10:21 PM) *
Either way, the detailed ESA study of the in-situ elements is just happening now, so tempting as it is to
second-guess everything, it may be premature to make assertions of budgetary incompatibility.

Ralph, I was hoping you'd add clarity.

It would be really nice if someone did pay for a cruise stage and second launcher so the in situ elements could arrive after the orbiter is orbiting Titan.

Can you provide any additional insight on the relay options? Do any options under consideration include the orbiter carrying the in situ elements post Saturn orbit insertion so they can be released just prior to Titan orbit insertion?

Posted by: rlorenz Jun 23 2008, 02:13 AM

QUOTE (vjkane @ Jun 21 2008, 07:39 PM) *
Can you provide any additional insight on the relay options? Do any options under consideration include the orbiter carrying the in situ elements post Saturn orbit insertion so they can be released just prior to Titan orbit insertion?

No (I cant add much insight)
Studies are still ongoing. I don't know if that option has been ruled out altogether, although I don't
*think* that:s the baseline

Posted by: vjkane Jun 27 2008, 07:09 PM

Breaking news is that budget shortfalls will likely delay the next Flagship mission to as late as 2020 (from 2016). The additional time may raise budgets from $2.1B to $3B. This delay may also help align the NASA and ESA decision timeframes.

But the bummer is that this makes it all the more necessary to keep myself healthy. We could be looking at a 2030 arrive date at the prime target (either Europa or Titan). That would make me only 74... huh.gif

http://www.livescience.com/blogs/author/leonarddavid/

Posted by: vjkane Jun 27 2008, 07:57 PM

QUOTE (vjkane @ Jun 27 2008, 07:09 PM) *
Breaking news is that budget shortfalls will likely delay the next Flagship mission to as late as 2020 (from 2016).
http://www.livescience.com/blogs/author/leonarddavid/

Another possible consequence: If NASA also delays the decision between a Europa and Titan mission (currently scheduled for this Fall), this will be to the Titan mission's benefit, I think. Right now, the Europa mission is much better defined, and hence would have lower implementation risk. If the decision is delayed another year or two, that would give the Titan mission team more time to mature their architecture and design.

But my personal preference would be to keep the Europa mission at $2.1B and use the extra $700 to fund a carrier/relay craft for a European in situ Titan mission. Yes, I want my cake and eat it, too.

Posted by: Mariner9 Jun 27 2008, 09:48 PM


I think you are right, the longer they have to define the Titan mission, the stronger it becomes. Right now the definition of the ESA atmospheric elements in particular are very preliminary.

Another potential silver lining is that ESA was more inclined towards launch somewhat later, such that if the Jupiter mission was selected they would be launching thier probe around 2019 if memory serves. That undoubtably would be a complicating factor if we wanted to launch a Titan orbiter in 2016, but their budget didn't allow for their contribution to be ready for another 2-3 years.... and that contribution was supposed to hitch a ride on our probe for the trip out to Saturn.

In any event I hope they don't inflate the budget to 3 billion.... I'm afraid that would make the project just too enticing a target the next time a budget ax falls.

Posted by: mps Jun 28 2008, 11:30 AM

QUOTE (Mariner9 @ Jun 28 2008, 12:48 AM) *
In any event I hope they don't inflate the budget to 3 billion.... I'm afraid that would make the project just too enticing a target the next time a budget ax falls.


I don't believe my eyes - someone in this forum is AGAINST Outer Planets Flagship budget increase... wink.gif
Yes, I understand what you mean, but - "He who doesn't risk never gets to drink champagne."
I think a $3B mission would get us much more science than a $2,1B mission - there would be more money for science instruments, instead of spending most of it to the spacecraft itself. What if ESA chooses some other L-class mission (XEUS or LISA) over Tandem/Laplace? I doubt that NASA can launch a serious outer planet mission for just $2,1B without international cooperation.


Posted by: Mariner9 Jun 28 2008, 05:39 PM

I agree that a 2.1 billion dollar mission runs the risk of being a 'bare bones' mission when we are talking Europa or Titan.

I'm concerned about two things. Firstly, both Galileo and Cassini were threatened with cancelation during their development periods. They were big targets for a congressman or senator (or Dan Goldin for that matter) to take aim at when trying to make a point about saving money. I always get mad when those arguments are made, because you could probably remove the paperclip budget from the Defense Department for a couple years and save the same ammount of money ... but NASA projects sound so darn big to the folks back home, so it "sounds like our representative is looking out for us."

Secondly, I belong to the "One modest Europa Orbiter in the hand is worth more than a mega Flagship in the bush" camp. How many times have we heard the argument, "if we wait a few years the budget will be higher and we can fly a much bigger mission" ?

Ten years ago they started work on the drastically underfunded Europa Orbiter (blame Dan Goldin). After several years of fits and starts it was canceled as its cost estimates were on the rise to a more realistic level (started around 300 million, was getting in the 1.4 billion range towards the end).

But hey, don't worry, they replaced it with the Icy Moons Orbiter.... a much better mission. Also, impractical, and hugely expensive, so it got canceled also.

Since that cancelation, it took years of politcal wrangling, and we are now in the final stages of selecting a practical, affordable, flagship mission. But, hey, if we wait a couple years it could be a bigger mission! Sounds great, right?

History has a way of repeating itself. I do NOT want to wait another 3-4 years on the (very vague) promise that it will be a bigger mission, blah, blah, blad. Lets take what we got and be grateful we have it.

Posted by: mps Jun 28 2008, 06:06 PM

Good point about Europa Explorer and JIMO analogy.

QUOTE (Mariner9 @ Jun 28 2008, 08:39 PM) *
Firstly, both Galileo and Cassini were threatened with cancelation during their development periods.

Just for curiosity, were Galileo and Cassini over budget, or was it just some silly money saving issue?

Posted by: Mariner9 Jun 28 2008, 07:24 PM


My recollection for Cassini was that it was over budget. However, that might have been a matter of how NASA budgeted things in those days. They never included the launch vehicle in the cost estimates, and I think had a tendency to hide the operating budget (aka... how much is it going to cost after you launch it?). So Dan Goldin might have wanted to cancel it because when you added in the Titan 4 vehicle and the 10 year mission time the costs were much higher than advertised.

In any case, what happened was that the CRAF mission (comet rendesvous) which was linked to Cassini was dropped, and Cassini had a redesign that included dropping the moving scan platform. It is rather remarkable to think that a 3 billion dollar mission is the downscoped version. (which does tend to lend weight to the argument that a 2.1 billion dollar flagship mission might be too tight of a budget)

Galileo ended up costing much more than was originally planned, but that was due to a LOT of factors, many of them not JPL's fault (the Shuttle was late, then had a lower payload than planned for, IUS canceled, IUS re-instated, and so on). I don't remember if it was actually over budget when they tried to kill it, or it was just a juicy target for Senator Proxmire (I think he was involved in it, lord knows he was not a big fan of NASA and loved making headlines with his "Golden Fleece" awards).

Posted by: vjkane Jun 28 2008, 08:29 PM

The presentations from the planetary science subcommittee are now on-line, and they are a rich treasure trove. http://www.lpi.usra.edu/pss/agenda/200806/

I'll be summarizing them in several posts (it's a wonderful day, and I'm not going to sit inside all day reading presentations!). I'll start with the findings on the next outer planetary flagship mission. In a previous post, I mentioned that NASA had delayed the launch to the 2020ish time, but raised the budget for the mission to ~$3B. From the presentations, it's clear that NASA decided that the mission that could be flown for the old cap, ~$2.1B to either target (Europa/Jupiter or Titan) was not worth the expense for the science returned. The missions are being delayed to allow additional years of funding to be supplied.

For the Europa mission, a number of capabilities would be added to the mission. I'll list just the highest priority here:

Narrow angle camera
Enhanced IR (spectrometer?)
Hybrid solid state recorder (presumably a lower capacity, very radiation hardened recorder for Europa orbit and a larger, less radiation hardened recorder for the Jovian tour)
28 month Jovian tour

For the Titan mission, it appears that the additional money pays for either a single launch with a solar electric stage or a dual launch of the orbiter and then the in situ elements. The presentation doesn't say so, but it appears that the goal is to allow the orbiter to act as the relay from the time the in situ elements (listed as a balloon and lander) are delivered. The solar electric propulsion stage presumably would allow the orbiter to carry enough fuel to delay the release of the in situ elements past Saturn orbit insertion and just prior to Titan orbit insertion.

These changes certainly address the key weaknesses of the $2.1B proposals. The presentations do not address the question of whether the decision on which mission to fly will be delayed beyond the current goal of this Fall. I hope so. While the Europa mission concept is very mature, the Titan concept would benefit from another year of maturation.

I don't know how NASA and ESA will decide between these two proposals. Both are excellent and both should fly.

Posted by: ugordan Jun 28 2008, 08:51 PM

2020? That's depressing.

Posted by: JRehling Jun 28 2008, 09:50 PM

I think the effect (and possibly the intended effect) of the Ganymede mission proposal was to "embarrass" the Europa mission into doing more jovian system science. I don't think the Ganymede/JSO mission itself ever stood a snowflake's chance on Venus of winning the competition, but by highlighting what the Europa mission lacked, it led to the acceptance of a larger Europa mission. Old political tactic comes through.

Posted by: vjkane Jun 29 2008, 01:12 AM

I had the time to finish reading the rest of the presentation from the Planetary Sciences subcommittee meeting. The interesting points to me were:

1) A $3B outer planet Flagship mission in the 2020 time frame would be a budgetary challenge
2) It looks like the decision between Europa and Titan will be delayed to a TBD date.
3) NASA is replanning its Mars roadmap. The goal of a sample return in the early to mid 2020's seems to be the guiding principle. The aeronomy Mars scout mission will happen in 2009, with a selection this September. NASA is trying to figure out how to fit in a Mars Prospector rover (somewhere between MER and MSL in capabilities), a Mars Science Orbiter, and a Mars network mission into the flow.
4) The timeframe for the next Discovery mission appears to be up in the air.
5) NASA is making noises that it will do a Discovery mission with the Stirling engine power source.
6) A team is defining a Venus flagship mission for the mid 2020's. Right now, they are looking at an orbiter with a high resolution radar, two short-lived landers, and two high altitude balloons. Goal appears to be not to require radical new technology development.

Posted by: vjkane Jun 29 2008, 03:20 PM

QUOTE (vjkane @ Jun 29 2008, 01:12 AM) *
The aeronomy Mars scout mission will happen in 2009, with a selection this September.

My mistake. I meant to type that the aeronomy mission will fly in 2013. MSL flies (fingers crossed!) in 2009.

Posted by: vjkane Aug 15 2008, 03:56 PM

Various news reports (e.g., http://www.spacepolitics.com/2008/08/13/russia-georgia-and-the-iss/) suggest that cooling relationships between the U.S. and Russia following the Georgia war could lead to either Russia refusing to fly Americans to ISS or Americans refusing to use Russian flights. That, of course, is manned spaceflight, and I leave that topic for other sites.

However, the U.S. is purchasing plutonium from Russia, and I think that scheduled purchases are needed to fly the next outer planet flagship mission. Does anyone know whether NASA has sufficient supplies on hand to fly the OPF, or whether this mission could become a casualty of international tensions?


Posted by: vjkane Sep 2 2008, 04:04 PM

An August update on the two possible outer planet missions has been posted at: http://www.lpi.usra.edu/opag/flagshipOPF08.pdf

Both concepts are maturing and both look very feasible with compelling science. (I'm glad that I don't have to decide!) Report is only on the U.S. orbiter elements.

Some highlights:

Mission costs are being allowed to increase by a few hundred million dollars to enable more capable instrument packages.

Selection between Jovian and Saturnian system destination is now Feb 2009.

Risks for the Saturn mission are much lower (but appear to apply only to the orbiter element). Europa mission appears to have higher risk elements (assuming same scale used for both) because of the radiation environment.

Current plan for the Titan in situ elements is to release them early in the Saturn Titan tour, which means a long period (12-18 months?) with only periodic relay by the orbiter and direct communication with Earth used in between.

Posted by: Greg Hullender Sep 3 2008, 04:16 AM

Did you notice that Ares V was an allowed launch vehicle for this proposal? (It's on slide 26.) No one proposed anything using one, but it surprised me to see it as an option. Does that mean someone has an estimate for what that would cost?

--Greg

Posted by: marsbug Sep 4 2008, 09:46 AM

QUOTE (vjkane @ Sep 2 2008, 05:04 PM) *
I'm glad that I don't have to decide!

Agreed! I do have a preference (Titan, no Europa, no Titan!) but I could be easily talked out of, and back into, it by anyone who shared my dribbling enthusiasm for either mission! laugh.gif Just wanted to say to the guys who do this work how much I admire and envy them, it really is the kind of stuff that makes me glad to be alive in this time. smile.gif

Posted by: centsworth_II Sep 4 2008, 01:42 PM

Titan will yield guaranteed exciting results of all sorts. Europa is more drudge work, scoping out possibilities for future missions. The ocean of Europa will not be reached for a hundred years, the seas of Titan are there on the surface. For purely selfish reasons, I want to see Titan up close as soon as possible.

Posted by: vjkane Sep 4 2008, 02:33 PM

Both missions -- Jovian moons and Titan -- are so compelling that I am intellectually and emotionally torn. Titan is so easy to explore (well, compared to Europa) that a mission there can tell us so much more than a Europa mission. On the other hand, the slides position the Jovian mission so well: Explore "planets" orbiting giant gas worlds (which may be the most common type of worlds in the universe based on our sampling of solar systems to date).

Where I've come to is this kind of decision tree:

1. If ESA provides compelling in situ elements for a Titan mission, then this is my first choice.
2. However, if it is just two orbiter missions to decide between, then I go with the Jovian mission because it studies 4 compelling worlds versus the Titan mission's two (Titan plus Enceladus)

What makes this decision really hard I suspect for NASA is that ESA will not decide whether to contribute to NASA's mission to either target until NASA has picked a target. So NASA could decide on Titan, and then ESA could decide to do an astronomy mission instead. There's also the problem of mission risk -- I have no way of evaluating how difficult the Titan in situ elements would be to implement within ESA's budget.

I also suspect that simple programmatics, costs and risks, will probably be the factors that NASA uses to decide between the two missions, and I can't assess those.

As I said before, I'm glad that I don't have to decide.

Posted by: Mark6 Jan 24 2009, 03:17 AM

This is a bit unexpected (to me, anyway):

http://news.bbc.co.uk/2/hi/science/nature/7842254.stm

QUOTE
Ambitious plans to send probes to the outer planets are being considered by US and European space officials...

[Saturn]:
Nasa: responsible for 1.6-tonne instrumented orbiter
Esa: would provide balloon and hydrocarbon lake lander (above)
Orbiter to tour Saturn system before entering Titan orbit
Tour allows further studies of Enceladus and its plumes

[Jupiter]:
Nasa: Jupiter Europa Orbiter could launch on an Atlas in 2020
Esa: Jupiter Ganymede Orbiter (above) lofted by an Ariane
Probes use Venus gravity assist to arrive 6 years later
Orbiters conduct joint observations at other Jupiter moons
Would finally settle into orbits around dedicated targets
Studies will focus on Europa's and Ganymede's interiors

That's the first time I heard of a joint NASA-ESA Jupiter mission proposal. Does this mean other OPAG proposals are dead by now?

Posted by: volcanopele Jan 24 2009, 06:05 AM

These are the same missions that have been discussed since last March. Down-selection is coming on February 12.

Posted by: Decepticon Jan 24 2009, 06:47 AM

How does this fit in the OPAG Reports thread? - Moderator



I can not believe this.

Everytime I post it's like posting on eggshells!

WHAT harm could I have done by stating excitement to a certain area being imaged?!?


Or is there a more personal reason for this!? unsure.gif
What have I done? unsure.gif


If a mod or someone wants me to leave just PM me and I'll be on my way.

Posted by: volcanopele Jan 24 2009, 09:33 PM

So would I, but if the sample trajectories are any guidance for JEO's Io flybys, Loki would not be covered at high resolution.

Posted by: NMRguy Jan 26 2009, 10:35 PM

From the picture provided by ESA/NASA for the BBC article, it appears that ESA may want to go ahead and keep the proposed Jupiter Ganymede Orbiter operating with solar power. (This is not surprising given the shortage of Pu238 and ESA's inaccessibility to it.) I understand that solar is definitely possible at Jupiter orbital distances (see Rosetta, Juno), but no one has yet tried to do this level of science, imaging, and spectroscopy so far from the Sun. Excluding prohibitively large solar panels, will the use of solar be a serious bottleneck for the science possibilities of the JGO?

Posted by: lyford Jan 27 2009, 03:44 AM

Joint summary reports posted Jan 19:

http://opfm.jpl.nasa.gov/library/

Titan Saturn System Mission
Joint Summary Report (01/16/09)
(PDF, 11.67 MB) 11.7MB,

Europa Jupiter System Mission
Joint Summary Report (01/16/09)
(PDF, 9.65 MB) 11.7MB,
39 Pages


Apologies if a repost.

Posted by: SFJCody Jan 27 2009, 09:06 PM

QUOTE (lyford @ Jan 27 2009, 03:44 AM) *
Joint summary reports posted Jan 19:

http://opfm.jpl.nasa.gov/library/

Titan Saturn System Mission
Joint Summary Report (01/16/09)
(PDF, 11.67 MB) 11.7MB,


The Titan mission looks so enticing. I can almost smell the hydrocarbons! Why does it have to arrive when I'll be in my forties? mad.gif

Posted by: Floyd Jan 27 2009, 10:13 PM

At least there is a good chance you will still be alive rolleyes.gif

Posted by: Juramike Jan 27 2009, 10:53 PM

I like it:

"One, if by sea, two, if by air, three, if by orbit."

Posted by: sci44 Jan 27 2009, 10:56 PM

QUOTE (lyford @ Jan 27 2009, 03:44 AM) *
Joint summary reports posted Jan 19:

http://opfm.jpl.nasa.gov/library/


Thanks for that. If I really have to choose, my vote goes with TSSM. I would like to see both, but a balloon roving Titan for a year? That has to win - Titan is the low-hanging fruit here. If TSSM flies, I hope, a few years later, they can still find funds for a reduced JGO mission - maybe in collaboration with the possible JAXA JMO mission, and a few donated NASA instruments. But, to me, TSSM is a winner here.
I was looking at the PDF (also the earlier OPAG PDF on this mission) and the SEP stage - maybe that could be a mission in it own right? It has its own ion drive, solar panels, and maybe its own hydrazine propellants (jets commonly placed at the tips of the panels) - all it needs is a computer, low gain antennea, and a small camera and its a craft in its own right. With maybe an extra 1kg of electronics its a neat student/uni project for someone. Maybe with a bit more - and usually there is a healthy margin of tolerance on these missions so there might be a few kg of xenon ion-drive propellant left on board - it could make a reasonable big-asteroid flyby mission. The earlier OPAG PDF had the SEP separation quite early on, so retargeting at least seemed possible.. (is even a larger target possible - jovian trojan, or outer satellite flyby??)

QUOTE (Floyd @ Jan 27 2009, 10:13 PM) *
At least there is a good chance you will still be alive rolleyes.gif


Bless ya. Just leave a fwding email address. We'll post the pix on..

Posted by: EccentricAnomaly Jan 29 2009, 05:24 PM

QUOTE (sci44 @ Jan 27 2009, 02:56 PM) *
I was looking at the PDF (also the earlier OPAG PDF on this mission) and the SEP stage - maybe that could be a mission in it own right? It has its own ion drive, solar panels, and maybe its own hydrazine propellants (jets commonly placed at the tips of the panels) - all it needs is a computer, low gain antennea, and a small camera and its a craft in its own right. With maybe an extra 1kg of electronics its a neat student/uni project for someone. Maybe with a bit more - and usually there is a healthy margin of tolerance on these missions so there might be a few kg of xenon ion-drive propellant left on board - it could make a reasonable big-asteroid flyby mission. The earlier OPAG PDF had the SEP separation quite early on, so retargeting at least seemed possible.. (is even a larger target possible - jovian trojan, or outer satellite flyby??)


I really like the feed-forward aspect of the SEP stage. Once TSSM pays to develop it and build it, it will be much cheaper for other missions to use SEP. I think it would really help bring lots of neat ideas into play for Discovery or New Frontiers that would otherwise be too expensive.

Posted by: Juramike Jan 29 2009, 06:16 PM

QUOTE (EccentricAnomaly @ Jan 29 2009, 12:24 PM) *
Once TSSM pays to develop it and build it, it will be much cheaper for other missions to use SEP.....


...like the next Titan mission after TSSM? smile.gif

Posted by: ngunn Jan 29 2009, 08:49 PM

QUOTE (Juramike @ Jan 29 2009, 06:16 PM) *
the next Titan mission after TSSM? smile.gif


Absolutely. Titan deserves no less than the full Mars treatment. Bring 'em on!

Posted by: AscendingNode Feb 13 2009, 06:30 AM

The OPFM reports are now up at: http://opfm.jpl.nasa.gov/library/

Also, there's more detail on the websites for each concept...

EJSM: http://opfm.jpl.nasa.gov/europajupitersystemmissionejsm/

TSSM: http://opfm.jpl.nasa.gov/titansaturnsystemmissiontssm/

...too bad we can't do both :-(



Posted by: Roly Feb 13 2009, 11:49 AM

The reports are both very exciting, from what I've been able to get through so far. I've read the rationale as to why there is no landed element with the JEO, and it is very logical, sensible, and well-argued. But nevertheless, in an irrational way, I do wish there had been some way of attempting it this time; the 300-350kg soft landers studied, admittedly only in a preliminary way, for the ESSP and Icy Moons Lander were exciting (more so than the JGO element, though I know it will do great science - hard to squeeze in to a 300kg lander). And my impression was that Huygens didn't have the benefit of a well understood surface during its design - though then again, it did have a very helpful atmosphere, and landing wasn't the primary goal from memory. Very pleased to see that deletion of the NAC is such a long way down the descope list, given that the absence of metre-scale imaging seems to be one of the reasons why a lander is out of the question for now.

Discussion of the choice of MMRTG c.f. ASRG was also intriguing, and one of the areas where I thought the JEO was really advancing its case as the safer choice. Equally, its readiness to launch at the earlier October 2018 opportunity was put forward with some confidence.

Very much looking forward to hearing the results, I'd love Europa to get up this time, but Titan would hardly be a disappointment,

Roly

Posted by: djellison Feb 13 2009, 12:35 PM

QUOTE (AscendingNode @ Feb 13 2009, 06:30 AM) *
...too bad we can't do both :-(


We can - just one will have to happen first. Then, when the other target gets it's chance in a decade or two, all the technological improvements mean it'll be an ever better mission smile.gif

Posted by: elakdawalla Feb 13 2009, 01:43 PM

...spoken by one of the youngest members of this forum rolleyes.gif not that I'm a lot older than you, but still I can't blame those UMSF members who are "Apollo babies" for wishing that both could get done sooner rather than later!

--Emily

Posted by: djellison Feb 13 2009, 02:14 PM

QUOTE (elakdawalla @ Feb 13 2009, 01:43 PM) *
but still I can't blame those UMSF members who are "Apollo babies" for wishing that both could get done sooner rather than later!


Oh - absolutely - I want both of them, yesterday. But it's not as if one getting picked means the other target will never be visited. It's also fair to moan, a bit, about missing a flagship for the '00s (Galileo 80's, Cassini 90's, ??? 00's, New Mission 10's ) and feel that we're in some way owed two. But then we're in the 'It's 2009, where's my flying car' game smile.gif

Posted by: dvandorn Feb 13 2009, 02:26 PM

I may not have my flying car, and I can't book my tourist trip to the Moon, but at least I do have my information terminal (e.g., the Internet) and I can take a look at the latest pictures straight from Mars whenever I like. That's enough, for now.

Personally, though, anything scheduled to fly after about 2025 is something that I have to realistically estimate I will never see. So I'm hopeful we'll find a way to get to as many places as possible in the next 15 years or so... smile.gif

-the other Doug

p.s. -- I have to admit, I'm happy to see LRO survive its development pangs and a shifting economic landscape. Why? Because it doesn't take the better part of a decade for it to reach its target... wink.gif

Posted by: belleraphon1 Feb 13 2009, 02:38 PM

Yeah... being a Sputnik baby means whichever outer planets mission gets seleted will be it for me as well.

Only solace is that either mission will be spectacular and open brand new wonders..... always sad that Galileo was unable to really map the big moons at a decent resolution.

And we have COROT/KEPLER poised to really give us a census of terrestrial sized worlds in our galaxy..... alot to look forward to, even for us Sputnik spuds.

Craig


Posted by: djellison Feb 13 2009, 03:46 PM

New Horizons will fill the gap a little bit smile.gif

Posted by: belleraphon1 Feb 13 2009, 04:14 PM

QUOTE (djellison @ Feb 13 2009, 10:46 AM) *
New Horizons will fill the gap a little bit smile.gif


Absolutely, Doug... I am not crying... there is SO many missions going on now in unmanned spaceflight it is hard to keep up.
Luv ly situation to be in. And as the other Doug mentioned, with the internet, the access we have to the data is something I would never have envisioned in my spud and sprouty days...

Good time to be alive.

Craig

Posted by: vjkane Feb 13 2009, 04:49 PM

QUOTE (Roly @ Feb 13 2009, 11:49 AM) *
I've read the rationale as to why there is no landed element with the JEO, and it is very logical, sensible, and well-argued. But nevertheless, in an irrational way, I do wish there had been some way of attempting it this time...

A Europa lander isn't out of the question if supplied by an international partner. There is a Russian conference on the topic (in support of a possible Russian-supplied lander) that ended today: http://www.iki.rssi.ru/conf/2009elw/

One thing to remember is that these reports do not represent the final architecture of the missions. The missions will not launch for another 8-10 years, more than twice the normal development time for a mission. There will be refinements and improvements -- and possibly major changes. I know that there are those within the Titan camp, for example, who really want to see the in situ probes launched separately so that the orbiter is already in place at Titan before they arrive.

In any case, we should know today or within a few days the decision -- if the decision isn't kicked to the scientific advisory boards (which has been stated as an option if there isn't a technical or budgetary reason to pick one over the other and it comes down to a purely scientific selection).

Posted by: dvandorn Feb 13 2009, 05:54 PM

QUOTE (djellison @ Feb 13 2009, 09:46 AM) *
New Horizons will fill the gap a little bit smile.gif

Oh, you betcha! If I occasionally sound melancholy or morose over the fact that some planned missions will come too late for me, please forgive me -- I am far and away happier having lived through the early years of space exploration than I would be having to just read about our initial lunar and planetary explorations in books.

As for which of the upcoming outer planet flagship missions comes first, I guess I'm not all that picky. I tend a little more towards the Titan lander concepts, simply because I enjoy seeing an alien planet/moon from its surface, and the current Jupiter mission proposals don't include any landers. But a really good Jupiter orbiter, concentrating on the moons, would provide a lot of grist for my sense-of-wonder mill, too. I'll be happy to see either of them.

-the other Doug

Posted by: tedstryk Feb 13 2009, 08:56 PM

In terms of filling the gap, there may not be a horrid gap...I mean, if Cassini keeps going and NH and Juno are successful, this might be quite a good decade. Also, Dawn will reach Ceres, which one could argue is a transitional world between the terrestrial planets and the icy worlds (even though it is a small one).

Posted by: scalbers Feb 13 2009, 09:03 PM

And plugging the gap further we could mention Dawn also arriving at Ceres (and earlier Vesta).

Posted by: imipak Feb 13 2009, 09:12 PM

It was quite disappointing to me as a child when I realised that really, everywhere on Earth's been explored already. How dull life will be for our unfortunate descendants, once solar system exploration's finished!

Another positive for the next few years, I think, is that the more recent spacefaring nations may attempt increasingly ambitious UMSF goals, beyond the earth/moon. They won't all succeed of course, but some will, and will produce great results. I think there's also a good possibility that the open data release model pioneered by MER, Cassini, Phoenix et al will become the norm.

I'm reading "http://www.unmannedspaceflight.com/index.php?showtopic=4691&view=findpost&p=135042" at the moment; I'd forgotten how amazing the Galileo results were, even trickling down a 33.6k dial-up connection. But then I've also been seduced by the amazing stuff going on here on the Titan threads. I'm going to be happy, whatever the decision.

Posted by: Mariner9 Feb 13 2009, 10:40 PM

I also am saddened by the ever widening gab between the launch of Cassini in 1997 and the next flagship. I was born just after Sputnik, and this next one may be the last flagship results that I get to see.

On a much more positive note, keep in mind that Flagships are not the only game in (the outer planets part of ) town. Juno and New Horizons are both New Frontiers missions.

Proposed missions like Argo (Neptune, Kuiper Belt flybys) and Io Volcanic Observer are quite feasable for a sub billion dollar budget. I'm very hopeful that we will see a few more of the New Frontiers and Discovery missions aimed at the outer planets in the next two decades.

And finally the other space faring nations are starting their own planetary missions. We almost have a flotilla of lunar orbiters at the moment, none of them launched by the US, Russia, or ESA. Japan is working on a Venus Orbiter, and a Mercury Orbiter. India is expressing interest in Mars. China has a tag-along orbiter as part of the Phobos-Grunt mission.

Times are a changing, and not all the news is bad.

Posted by: ngunn Feb 13 2009, 10:55 PM

Mariner9 you have voiced my thoughts precisely there. Whatever happens now the 'losers' will have many options to consider besides standing patiently in line in the NASA flagship queue.

Long live impatience!

Posted by: EccentricAnomaly Feb 14 2009, 03:09 AM

QUOTE (vjkane @ Feb 13 2009, 08:49 AM) *
A Europa lander isn't out of the question if supplied by an international partner. There is a Russian conference on the topic (in support of a possible Russian-supplied lander) that ended today: http://www.iki.rssi.ru/conf/2009elw/


Problem is that a lander would probably need a radioisotope power supply (RPS), and a Russian built RPS couldn't be sent on a US launcher without a very expensive process to get the Russian RPS certified (which it might not pass). So the Russians would have to go it alone with their own rocket and cruise stage to get to Europa... but that would involve them building (and paying for) something more complex and expensive than JEO (because they'd have to do all of the DV of JEO plus 1.5 km/s more to land).

Maybe they could do a solar powered lander... but those would have to be mighty big arrays, that would have to be rad hard... and would have to survive the g-loads of the descent and landing.

This has me thinking that a Russian supplied lander is not credible. If there is to be a lander, the US will have to build it and pay for it with maybe the Russians contributing part of it. And in that case, I think the money the US would spend on a lander would be better spent on a small Titan mission (maybe just a balloon or just a lander).

Posted by: vjkane Feb 14 2009, 06:27 AM

QUOTE (EccentricAnomaly @ Feb 14 2009, 04:09 AM) *
Problem is that a lander would probably need a radioisotope power supply (RPS), and a Russian built RPS couldn't be sent on a US launcher without a very expensive process to get the Russian RPS certified (which it might not pass).

My guess is that the lander is battery powered, but I don't know.

I do vaguely remember that the Russians might be thinking of launching their own carrier craft to take the lander to Europa. They certainly have the launch capability. The only technology I don't know about is radiation hardened electronics.

I'm hoping that the presentations from the conference will be posted.

Posted by: Roly Feb 14 2009, 07:28 AM

The studies I've seen, e.g. that from Tibor Balint (~2004) on the proposed Europa Lander (the ESSP) there was a feasible battery powered mission, giving it a life of approximately 3 days on the surface. I can't remember whether it was Li-ion rechargeable from the carrier spacecraft RPS before landing, or a primary cell (Li FeS, Li Ag V, Li Thionyl Chloride etc.) May or may not have had RHUs. I imagine such battery technology would be available to IKI - the end of the JEO study report does mention a meeting with IKI on a potential lander element, which is cheering.

More recent study here quotes 600-820Kg mass required for a soft-lander, c.f. previous 300-500Kg (http://ippw.jpl.nasa.gov/20070607_doc/4_15RAGE.pdf), maybe if everything else came in under the mass budget, and an upgrade to Delta IV-H from the Atlas 551. It just seems such a crucial and rare opportunity, if the JEO does get up (obviously far from certain!)

Anyway, I know Europa landing topic has been discussed to exhaustion, apologies.

Roly

Posted by: volcanopele Feb 14 2009, 07:48 AM

On my blog, I've taken a further look at the Io science plans for JEO, based on looking at the Jupiter Europa Orbiter Final Report. I also looked at what the Ice Penetrating Radar could find during the two planned close flybys of Io.

http://gishbar.blogspot.com/2009/02/io-science-with-ejsm-part-deux.html
http://gishbar.blogspot.com/2009/02/using-ground-penetrating-radar-at-io.html

Posted by: EccentricAnomaly Feb 14 2009, 04:51 PM

QUOTE (Roly @ Feb 13 2009, 11:28 PM) *
The studies I've seen, e.g. that from Tibor Balint (~2004) on the proposed Europa Lander (the ESSP) there was a feasible battery powered mission, giving it a life of approximately 3 days on the surface. I can't remember whether it was Li-ion rechargeable from the carrier spacecraft RPS before landing, or a primary cell (Li FeS, Li Ag V, Li Thionyl Chloride etc.) May or may not have had RHUs. I imagine such battery technology would be available to IKI - the end of the JEO study report does mention a meeting with IKI on a potential lander element, which is cheering.

More recent study here quotes 600-820Kg mass required for a soft-lander, c.f. previous 300-500Kg (http://ippw.jpl.nasa.gov/20070607_doc/4_15RAGE.pdf), maybe if everything else came in under the mass budget, and an upgrade to Delta IV-H from the Atlas 551. It just seems such a crucial and rare opportunity, if the JEO does get up (obviously far from certain!)

Anyway, I know Europa landing topic has been discussed to exhaustion, apologies.

Roly



Well, I take back what I said. 3 days on batteries is pretty exciting. And I think the Russians could supply a battery powered lander... and I think an 800 kg lander should definitely be possible (TSSM gets ~800 kg of in situ payload all the way to Saturn)

Posted by: rlorenz Feb 15 2009, 04:35 AM

QUOTE (vjkane @ Feb 14 2009, 01:27 AM) *
My guess is that the lander is battery powered, but I don't know.

I do vaguely remember that the Russians might be thinking of launching their own carrier craft to take the lander to Europa. They certainly have the launch capability. The only technology I don't know about is radiation hardened electronics.

I'm hoping that the presentations from the conference will be posted.


They told us at the meeting (I just got back from Moscow) that the presentations would be posted
(although authors had option to sanitize the posted versions if needed).

IIRC the Lavotchkin talk suggested a Proton launch with Briz upper stage and a electric propulsion.
Lander and orbiter would use (Russian) RTGs, although there were few details offered on those
Hardware would be derived from Phobos-Grunt and Luna-Resurs missions (seems quite a logical path -
Resurs lunar lander wouldnt be too dissimilar propulsively from Europa) They'd use lots of shielding.
The trajectory described was 2017 launch, JOI 2022 then tour to pump down - Europa landing
March 2024. But that is just an existence proof to scope propulsion demands - may or may not be
a programmatically realistic schedule.


Posted by: vjkane Feb 15 2009, 05:23 AM

Ralph, thanks for the details on the Russian Europa lander. *IF* the Europan orbiter mission is selected, then I would not be surprised to see several nations send missions to the Jovian system. Already, four space agencies are considering missions: NASA's Europa Jupiter orbiter, ESA's Ganymede Jupiter orbiter, Russia's Europa lander, and JAXA's magnetosphere orbiter. By the 2020's, Jupiter will be in reach (at least if the craft stay out of the worst of the radiation belts) of a number of space agencies (remember that solar panels are a viable power source at Jupiter for many missions).

At this point, we are in a waiting game to hear the selected target. Either way, a fantastic proposal will be accepted and a fantastic proposal will be rejected.

Posted by: Alan Stern Feb 15 2009, 01:19 PM

QUOTE (djellison @ Feb 13 2009, 03:46 PM) *
New Horizons will fill the gap a little bit smile.gif



Yes, Pluto in 2015, and likely two KBOs in 2017-2020. And Juno will orbit Jupiter 2016-2017. Perhaps NF or Disco will even select a Centaur/Trojan or Jupiter or Saturn mission for launch in the late 2010s as well.

-Alan

Posted by: Vultur Feb 15 2009, 04:32 PM

QUOTE (imipak @ Feb 13 2009, 10:12 PM) *
It was quite disappointing to me as a child when I realised that really, everywhere on Earth's been explored already. How dull life will be for our unfortunate descendants, once solar system exploration's finished!


Well, maybe by then someone will figure out how to send a probe to another star ... that's a long way away.

Posted by: volcanopele Feb 16 2009, 12:33 AM

I'm surprised people haven't also been discussing the ESA Assessment reports for the Titan Balloon and Kraken Mare Lander and the Jupiter Ganymede Orbiter, which were posted online Thursday:

Titan In-Situ Elements: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=44185#
Jupiter Ganymede Orbiter: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=44188#

I've put up a post on my Io Blog on the types of Io science we can get from the Jupiter Ganymede Orbiter: http://gishbar.blogspot.com/2009/02/io-science-with-jupiter-ganymede.html

Posted by: Juramike Feb 16 2009, 02:07 AM

QUOTE (volcanopele @ Feb 15 2009, 07:33 PM) *
I've put up a post on my Io Blog on the types of Io science we can get from the Jupiter Ganymede Orbiter: http://gishbar.blogspot.com/2009/02/io-science-with-jupiter-ganymede.html


The explanation you wrote for how ground-penetrating RADAR works and how it could be applied to Io was excellent!
Permalink here: http://gishbar.blogspot.com/2009/02/using-ground-penetrating-radar-at-io.html

Posted by: vjkane Feb 16 2009, 05:56 AM

I have two recent posts on TSSM on my blog:

Flyby science from the TSSM orbiter http://futureplanets.blogspot.com/2009/02/other-science-by-tssm-orbiter.html

TSSM orbiter instruments http://futureplanets.blogspot.com/2009/02/flagship-update-and-titan-orbiter.html


Posted by: Decepticon Feb 16 2009, 04:47 PM

No radar being done?

Posted by: volcanopele Feb 16 2009, 07:00 PM

In another sign of the pending apocalypse, I wrote a post about Europa:

http://gishbar.blogspot.com/2009/02/thickness-of-europas-ice-shell-from-jeo.html

Posted by: nprev Feb 16 2009, 07:29 PM

Well, now I gotta stock up on canned goods & bottled water, but thanks for the excellent blog post, Jason! smile.gif Sounds like a well-designed experiment to answer this key question.

Posted by: EccentricAnomaly Feb 18 2009, 03:07 PM

QUOTE (Decepticon @ Feb 16 2009, 08:47 AM) *
No radar being done?


TSSM can do RADAR at Enceladus and at the Titan flybys that are outside of the atmosphere (it has some low flybys to sample the atmosphere). It carries two RADAR antennas so that it can use one during the tour and jettison it before aerobraking and then use the second one once in orbit.

Posted by: Stephen Feb 19 2009, 05:52 AM

QUOTE (rlorenz @ Feb 15 2009, 03:35 PM) *
IIRC the Lavotchkin talk suggested a Proton launch with Briz upper stage and a electric propulsion.
Lander and orbiter would use (Russian) RTGs, although there were few details offered on those
Hardware would be derived from Phobos-Grunt and Luna-Resurs missions (seems quite a logical path -
Resurs lunar lander wouldnt be too dissimilar propulsively from Europa) They'd use lots of shielding.
The trajectory described was 2017 launch, JOI 2022 then tour to pump down - Europa landing
March 2024. But that is just an existence proof to scope propulsion demands - may or may not be
a programmatically realistic schedule.

Given that the Russians have not sent any missions beyond Mars (and even those that went to Mars have been infamously less than successful) what are the chances they will be sending any probes to Jupiter any time soon, let alone a lander? Wouldn't itbe more realistic to expect them to focus their attentions in the inner solar system, and especially Venus, where they have traditionally had far greater success, especially with landers?

(That said, the ESA have sent anything beyond Mars either--and in fact have only sent one probe to Mars--yet are now contemplating a JGO. So who knows?)

======
Stephen

Posted by: Stephen Feb 19 2009, 06:11 AM

QUOTE (volcanopele @ Feb 17 2009, 06:00 AM) *
In another sign of the pending apocalypse, I wrote a post about Europa:

http://gishbar.blogspot.com/2009/02/thickness-of-europas-ice-shell-from-jeo.html

Hey, careful there! Let's not jinx the poor little JEO. rolleyes.gif

======
Stephen

Posted by: K-P Feb 19 2009, 09:26 AM

QUOTE (Stephen @ Feb 19 2009, 07:52 AM) *
(That said, the ESA have sent anything beyond Mars either--and in fact have only sent one probe to Mars--yet are now contemplating a JGO. So who knows?)

======
Stephen



emmm..... Huygens...?
emmm..... Ulysses...?

Posted by: Fran Ontanaya Feb 20 2009, 03:04 PM

And Rosetta.

BepiColombo has to be designed for an high radiation enviroment too.

Posted by: Stephen Feb 23 2009, 02:22 AM

QUOTE (K-P @ Feb 19 2009, 08:26 PM) *
emmm..... Huygens...?
emmm..... Ulysses...?

That word "sent" was rather loosely used, but it was meant in the sensed of "launched". Huygens piggy-backed on what is mainly a NASA probe (Cassini) launched by a NASA rocket. If that counts as an ESA "sent" mission, then by that yardstick the British have "sent" a mission to Mars: the ill-fated Beagle 2, which piggy-backed a ride on Mars Express!

As for Ulysses, that is also basically a NASA mission with some ESA participation launched by a NASA launch vehicle (the shuttle). If Ulysses is going to be counted as an ESA "sent" mission then I guess it'd be only fair to count Cassini as an Italian "sent" one, since their space agency had participation separate from the ESA's in Cassini.

I concede the point about Rosetta though.

======
Stephen

Posted by: tedstryk Feb 23 2009, 02:36 AM

QUOTE (Stephen @ Feb 23 2009, 02:22 AM) *
As for Ulysses, that is also basically a NASA mission with some ESA participation launched by a NASA launch vehicle (the shuttle). If Ulysses is going to be counted as an ESA "sent" mission then I guess it'd be only fair to count Cassini as an Italian "sent" one, since their space agency had participation separate from the ESA's in Cassini.


Huh? Other than NASA providing the RTGs and a few instruments, ESA built Ulysses. Your snarky comment comparing ESA's involvement to Italian involvement in the Cassini mission is simply ignorant.

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