NH at Jupiter, Planning the Jupiter encounter Options

[john_s]

I think the Jupiter encounter deserves its own thread.

I've just been taking a first look at the Jupiter encounter geometry. You can do the same using Mark Showalter's excellent on-line ephemeris tools at the PDS rings node, which by good fortune happens to include a New Horizons ephemeris (calculated over a year ago) for our actual launch date, January 19th. We'll have an updated ephemeris soon, but this one's already good enough for planning. As Roby72 noted in the Star 48 thread, the satellites are (annoyingly) all on the opposite side of Jupiter at closest approach. We'll still get good views of all sides of Io because Io rotates in only 1.8 days and we'll be pretty close to Jupiter for that long. We'll get fairly good coverage on Europa too, for the same reason. But we won't get very close to Ganymede or Callisto. Luckily Io is our highest priority satellite target and Europa is next, so we'll do OK.

[David]

I think the Jupiter encounter deserves its own thread.

I think it does too, but couldn't it go under, well, Jupiter?

[john_s]

I think it does too, but couldn't it go under, well, Jupiter?

Nah, IMHO New Horizons discussions should stay under the New Horizons topic.

John.

[Roby72]

John,

yes the day before (or after), Io must be on the right side of the planet, but I think the high speed of NH makes the distance about equal than on encounter day at the other side (about 2.5 Mio km). Resolution for LORRI (bw imager) should be about 12 km, for RALPH (color) about 50km) This would be nice for plume searching and is about 5 times more resolution in case of LORRI than Cassini had at its Jupiter encounter in Dec. 2000.

Robert

[ljk4-1]

Any chance NH could image Europa well enough to see if any surface features have changed/moved since Galileo?

[john_s]

Any chance NH could image Europa well enough to see if any surface features have changed/moved since Galileo?

We'll be looking at Europa but not specifically for that purpose- our images will be far lower resolution than Voyager's and no changes were seen between Voyager and Galileo even at Voyager resolution, and over a longer timespan than between Galileo and NH. Our main goal in imaging Europa will be to look at the peculiar large, shallow, depressions that were seen by Galileo near the terminator- it's one area where we can improve over Galileo. Plus we'll be observing Europa's auroral emissions in Jupiter eclipse.

By the way, here's a table I just sent to the science team, showing the timing and geometry of various significant events during the encounter. Times are spacecraft times, and the numbers will change just a bit once we get a final ephemeris. I've only calculated the times of the eclipses of each satellite that occur closest to the spacecraft- there are many more at greater ranges. "UT" means Universal Time, "mrad" means the angular diameter in milliradians, and "Sub-S/C Lon" means the sub-spacecraft longitude. I couldn't figure out how to align the columns properly without replacing all the spaces with underscores...


---------------------------------------------------------------------------
____________________Range___Diam__Solar__Sub-
____Date_______UT___(km)___(mrad)_Phase_S/C_Lon__Event
---------------------------------------------------------------------------
February_25__09:45_6334186__0.831___11____349____Ganymede eclipse ingress
February_25__11:45_6222615__0.846___12____352____Ganymede eclipse egress
February_27__10:46_3074450__1.021___40____315____Europa eclipse ingress
February_27__13:18_3045261__1.030___45____321____Europa eclipse egress
February_27__14:20_2734370__1.331___48____303____Io Eclipse ingress
February_27__16:28_2758131__1.320___53____316____Io Eclipse egress
February_28__02:00_2957815__1.061___72____347____Europa closest approach
February_28__05:00_2304575_61.920___82___________Jupiter closest approach
February_28__06:00_3029556__1.737__102_____41____Ganymede closestapproach
February_28__06:30_4153289__1.156___81____353____Callisto closest approach
February_28__22:00_2260221__1.610__118____141____Io_closest approach
___March__1__08:48_2748816__1.324__120____231____Io_eclipse ingress
___March__1__10:58_2951842__1.233__121____248____Io_eclipse ingress
---------------------------------------------------------------------------


John.

[ljk4-1]

We'll be looking at Europa but not specifically for that purpose- our images will be far lower resolution than Voyager's and no changes were seen between Voyager and Galileo even at Voyager resolution, and over a longer timespan than between Galileo and NH.  Our main goal in imaging Europa will be to look at the peculiar large, shallow, depressions that were seen by Galileo near the terminator- it's one area where we can improve over Galileo.  Plus we'll be observing Europa's auroral emissions in Jupiter eclipse.

John.

Thank you for the information, John. Would New Horizons be able to look for any possible geysers from Europa as well? Might be good practice for similar events in the Pluto system, too.

[stevesliva]

Thank you for the information, John.  Would New Horizons be able to look for any possible geysers from Europa as well?  Might be good practice for similar events in the Pluto system, too.

Especially if Triton is supposed to be a lot like Pluto.

[Guest_Sunspot_*]

How many days/weeks before closest approach will New Horizons start imaging Jupiter?

[Guest_AlexBlackwell_*]

I think the Jupiter encounter deserves its own thread.

I've just been taking a first look at the Jupiter encounter geometry.

Maybe I missed it in another thread (or website), John, but is there any possibility of getting imagery of any of the outer jovians (e.g., Himalia)?

[Guest_BruceMoomaw_*]

Judging from the NH Jupiter encounter planning meeting I attended back at the 2003 DPS meeting, the most interesting piece of new information that comes out of the NH Jupiter flyby may be its near-IR spectra of the surface composition of the Galilean moons -- especially Europa. Its spectrometer has much higher spectral resolution than Galileo's and will be considerably closer to the Galilean moons that Cassini's, implying that it may be able to nail down whether that stuff mixed with Europa's ice is Mg sulfate or sulfuric acid.

[john_s]

Maybe I missed it in another thread (or website), John, but is there any possibility of getting imagery of any of the outer jovians (e.g., Himalia)?

We typically get a couple of pixels on Himalia, similar to Cassini, though I haven't seen the geometry for the actual trajectory yet. Anyway, don't expect anything too dramatic on any outer satellties.

[Bart]

On an extremely amateur basis, I did some (very) back of the envelope calculations and came up with Himalia spanning about 9.5 pixels a week after Jupiter C/A - slightly better than Cassini.

Can't wait to hear real numbers from people who actually know in a couple of weeks.

Bart

[Steffen]

So New Horizons will take images of the Gas giant Jupiter and some of its moons?
Wondered if the lenses on the cameras are closed afterwards as some kind of protection and opened before Pluto encounter?

[ljk4-1]

* ASTRONOTES: Derelict Booster to Beat Pluto Probe to Jupiter

http://www.space.com/astronotes/astronotes.html

NASA's Pluto-bound New Horizons spacecraft now speeding through the Solar System
is set to reach Jupiter on Feb. 28, 2007, but it will not be the first craft of
its mission to reach the gas giant, mission officials said this week.

[MahFL]

I think the lens cover on LORRI is designed just to open, its better to have a bit of dust on the lens than having a lens cover stick in the closed position.

[Guest_PhilCo126_*]

Don't know about covers on the NH lenses but I guess that by February 2007, the spacecraft's rotation will be stopped and will operate in 3-axis stabilisation mode.
( Remember Dr Alan Stern confirmed that NH can operate in both spin-stabilisation for cruise phase and in 3-axis stabilisation mode for encounter phases which will allow correct instrument pointing ).
Between Jupiter and Pluto, NH will probably go back into spin ?

[Decepticon]

Does anyone know what Voyager/Galileo images will be comparable to the Horizons?

I'm trying to get a idea of what to expect.

Also will we get enough Jupiter imaging to create Voyager approach type movies?

[Bob Shaw]

Does anyone know what Voyager/Galileo images will be comparable to the Horizons?

I'm trying to get a idea of what to expect.

Also will we get enough Jupiter imaging to create Voyager approach type movies?

My impression from what I've read so far is that NH isn't set up to obtain close-up imaging data from the illuminated portion of Jupiter and it's satellites, but will do well in 'Jupiter-shine' images of the satellites. Remember that NH is designed to explore a dark, dark place, rather than one that's just a bit dim!

Bob Shaw

[john_s]

My impression from what I've read so far is that NH isn't set up to obtain close-up imaging data from the illuminated portion of Jupiter and it's satellites, but will do well in 'Jupiter-shine' images of the satellites. Remember that NH is designed to explore a dark, dark place, rather than one that's just a bit dim!

Bob Shaw

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight. So we hope to get some nice B/W dayside images of the satellites after all. We're still stuck with dayside saturation in our color camera, MVIC, though, so our only color images of Io will be taken in Jupiter shine, and will thus (obviously) cover only the Jupiter-facing hemisphere.

Here's a simulation of some of our best views of the four Galileans, from LORRI (highest resolution), MVIC (color, though only B/W in this simulation, and saturated on most of the daysides), and LEISA (where every pixel represents a 1.2 - 2.5 micron near-infrared spectrum). The geometry is pretty accurate. I've brightened up the nightside of Io so you can see what volcanos might be glowing in the dark there.

[icez]

Here is Celestia's view of Io and Europa--relative to Jupiter and the Sun on the time of the Jupiter encounter. It "looks" like there could be some moonshine going on from what I see.

Attached thumbnail(s)

 

[ugordan]

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight.

That's very nice to hear, but I'm curious how you suddenly came to that conclusion?

Here's a simulation of some of our best views of the four Galileans, from LORRI (highest resolution), MVIC (color, though only B/W in this simulation, and saturated on most of the daysides), and LEISA (where every pixel represents a 1.2 - 2.5 micron near-infrared spectrum).  The geometry is pretty accurate.  I've brightened up the nightside of Io so you can see what volcanos might be glowing in the dark there.

That's awesome! I see the LORRI images are slightly blurred, did you actually go through the trouble of simulating the camera's PSF as well?

[john_s]

That's very nice to hear, but I'm curious how you suddenly came to that conclusion?
That's awesome! I see the LORRI images are slightly blurred, did you actually go through the trouble of simulating the camera's PSF as well?

Now the spacecraft is launched we have time to think of creative ways to use the instruments. The problem with LORRI was that it has no shutter, so light falls on the CCD during the readout phase, producing a smeared image. If the exposure is shorter than the readout time, as needed to avoid saturation on the Galileans, the "readout smear" can be brighter than the image itself, and can be difficult to remove. What we just figured out is that for the special case of a small target against black sky there's a fairly easy way to remove the readout smear, even if we can't remove the smear from, for instance, a short-exposure closeup image of Jupiter's clouds.

And yes, I included a very crude estimate of the LORRI PSF in those simulations. Well spotted!

[JRehling]

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight.  So we hope to get some nice B/W dayside images of the satellites after all.  We're still stuck with dayside saturation in our color camera, MVIC, though, so our only color images of Io will be taken in Jupiter shine, and will thus (obviously) cover only the Jupiter-facing hemisphere.

Is moonshine bright enough to help you out there? Io will experience a pretty full Europa late on Feb 27 and into Feb 28 (UTC), which by my crude math would be as bright as a magnitude -11 in the ionian sky. During that interval, Io would wane from gibbous as seen from NH, leaving a crescent in europashine; to crescent in the sunshine leaving a gibbous swath in europashine. During the same interval, Jupiter would go from a sliver to a full disk as seen from Io, so Europa may end up illuminating a small segment only for NH's benefit, but that's something? If having too much light is a problem, does europashine result in not enough?

[john_s]

Is moonshine bright enough to help you out there? Io will experience a pretty full Europa late on Feb 27 and into Feb 28 (UTC), which by my crude math would be as bright as a magnitude -11 in the ionian sky. During that interval, Io would wane from gibbous as seen from NH, leaving a crescent in europashine; to crescent in the sunshine leaving a gibbous swath in europashine. During the same interval, Jupiter would go from a sliver to a full disk as seen from Io, so Europa may end up illuminating a small segment only for NH's benefit, but that's something? If having too much light is a problem, does europashine result in not enough?

Interesting thought- we'll check into it, though my gut feeling is that moonshine won't be bright enough to be useful. Galileo took some cool images of Jupiter's clouds in Io-shine, but they were very long exposures and fairly smeared.

'

[Bob Shaw]

Interesting thought- we'll check into it, though my gut feeling is that moonshine won't be bright enough to be useful.  Galileo took some cool images of Jupiter's clouds in Io-shine, but they were very long exposures and fairly smeared.

'

Perhaps the combination of the two light sources may be a winner - Jupitershine and light reflected by the moons.

Good luck!

Bob Shaw

[Decepticon]

Thanks for those samples!

I can't wait!!!

[JRehling]

Perhaps the combination of the two light sources may be a winner - Jupitershine and light reflected by the moons.

Good luck!

Bob Shaw

There'll also be a pretty full Callisto in the ionian sky, but that would contribute much less light than Europa.

[tty]

Is there any plans for imaging the night side of Jupiter? There might be some interesting things to see there for a high-sensitivity camera (auroras, thunderstorms, meteorite impacts....).

tty

[Comga]

I think the lens cover on LORRI is designed just to open, its better to have a bit of dust on the lens than having a lens cover stick in the closed position.

The doors on LORRI and Ralph both open with one-time, spring loaded mechanisms. These devices are well proven and have high reliability, as almost anything is better than having the door stick in the closed position, as you said.

We will know for sure in a few months. Does anyone know when they plan to open the doors and take test images?

[tasp]

The doors on LORRI and Ralph both open with one-time, spring loaded mechanisms.  These devices are well proven and have high reliability, as almost anything is better than having the door stick in the closed position, as you said. 

We will know for sure in a few months.  Does anyone know when they plan to open the doors and take test images?

I am sure there is a good reason for not doing this, but I have always wondered why these ejectable lens covers aren't made of lexan.

If they don't come off, camera would still work.

Must be missin' sumpthin' ?

[djellison]

Well - consider the MER MI cover - that's an orange filter - so even if the cover's shut, you can still see something.

I'd imagine using something like lexan or other transparant materials for a thermal cover of an instrument has potential for a lot of problems with being britle, heavier, bad thermal properties, perhaps outgassing and contaminating optics etc etc....

And as Alan's said a few times, better is the enemy of good enough.

Doug

[ljk4-1]

Jupiter wouldn't be so bright that it could burn out NH's cameras, could it?

[john_s]

Jupiter wouldn't be so bright that it could burn out NH's cameras, could it?

Nope, the New Horizons CCDs, like most CCDs, are very resistant to burnout.

[RNeuhaus]

Here is the snapshot when NH is around the closest distance from Jupiter at February 28, 2007, 05:00 am.

http://space.jpl.nasa.gov/cgi-bin/wspace?t...orbs=1&showsc=1

Jupiter: 2.306 millions km
IO : around 2.664 millions km Closer
Europe: 2.967 millions km
Ganymede: 3.020 millions km
Calixto: 4,160 millions km

These above predicted distance might change after the next TCM.

Rodolfo

[volcanopele]

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight.  So we hope to get some nice B/W dayside images of the satellites after all.  We're still stuck with dayside saturation in our color camera, MVIC, though, so our only color images of Io will be taken in Jupiter shine, and will thus (obviously) cover only the Jupiter-facing hemisphere.

Here's a simulation of some of our best views of the four Galileans, from LORRI (highest resolution), MVIC (color, though only B/W in this simulation, and saturated on most of the daysides), and LEISA (where every pixel represents a 1.2 - 2.5 micron near-infrared spectrum).  The geometry is pretty accurate.  I've brightened up the nightside of Io so you can see what volcanos might be glowing in the dark there.

what is the wavelength range for LORRI? Does it extend at all into the near-IR? would be interesting to see how active Pele (or Pillan 10 years after its big eruption) is when Io is in eclipse.

Remember John, there is no need to image any of the other moons, just focus on Io

[Guest_BruceMoomaw_*]

Pfaw. The most important thing NH will do at Jupiter is get near-IR spectra of the Galilean moons' surface compositions far better than any obtained by either Galileo or Cassini -- maybe good enough to settle the question of what the non-ice component of Europa's surface really is.

[john_s]

what is the wavelength range for LORRI?  Does it extend at all into the near-IR?  would be interesting to see how active Pele (or Pillan 10 years after its big eruption) is when Io is in eclipse.

Remember John, there is no need to image any of the other moons, just focus on Io 

LORRI extends to 1 micron wavelength so we may see some volcanic thermal emission on the nightside, as we will with MVIC, and with LEISA of course. We should get a nice data set on the hot spots! Plumes, too...

[ljk4-1]

LORRI extends to 1 micron wavelength so we may see some volcanic thermal emission on the nightside, as we will with MVIC, and with LEISA of course.  We should get a nice data set on the hot spots!  Plumes, too...

Can NH look for any plumes from Europa as well?

[Decepticon]

there is no need to image any of the other moons, just focus on Io 

Funny you miss spelled Europa Io

[john_s]

Maybe you folks can help us...

We're now starting to lay out the timeline for the Jupiter encounter, but what we haven't done so far is look for "Kodak moments" as the Cassini imaging folks call them- times when we have scenic alignments or unusual geometries that call for a picture that's motivated by beauty more than science. Anyone want to help us find these moments?

Mark Showalter has now updated his New Horizons ephemeris tools to include the actual spacecraft trajectory through the Jupiter system. So you can download a table of satellite positions as seen from the spacecraft, and see views from the spacecraft of any body in the system at any time. It's probably most efficient to use the "Jupiter Ephemeris Generator" tool to create a table first and use that to find possible interesting alignments (e.g. times when the RA and Dec offsets of two satellites are similar), and then use the "Jupiter Viewer" to check out the view from the spacecraft at that time. The field of view of LORRI, our greyscale telephoto camera, is 5 x 5 milliradians, or 1044 arcseconds (parameters for all instruments are here). Make sure that you are using the "Official Post-Launch" trajectory option, which is the default.

If you find a specific time when you think we should press the shutter, let us know! No guarantees that we'll be able to do so, as there are numerous conflicts and constraints, but we'll give it a try. LORRI images don't take a lot of resources so we can probably spare a few for scenic purposes. MVIC color images are more "expensive", and are likely to have partial saturation except at high phase angles, so we're less likely to use MVIC for this purpose.

Thanks!
John.

[djellison]

The very easiest way for this is if someone can get it into celestia, and we can just run thru the flyby looking for interesting moment

You've opened a big bad can of worms here John Downlink was 2048kbps from Jupiter wasnt it

I'm sure you'll have lots of loonie ideas - but a moon rising or setting from behind Jupiter with possible refraction thru the upper atmosphere could be interesting....

Not sure of exact timing (see attached) if I have the night-side-day-side right, this would see a crecent Io set behind the dark-limb of Jupiter, so it would be squished and squashed as it set, in a way a little similar to this...
http://spaceflight.nasa.gov/gallery/images.../s103e5037.html but without a bright limb of Jupiter to get 'in the way'

Some upper atmosphere refraction has been seen by Cassini...
http://ciclops.org/media/dr/2005/1114_2631_2.png
http://ciclops.org/media/dr/2005/1191_2857_2.png
http://ciclops.org/media/dr/2005/1017_2487_1.jpg

Perhaps something to be learnt about the properties and extent of the upper jovian atmosphere by catching this little event?

I think that the classic Cassini 'mutual' events of transits etc are likely to be uncommon at a range worth imaging (guessing here).

Another potential target that's perhaps half scientific, half Kodak - is a lit side of a moon, being partially occulted by the jovian ring system- not sure how it might look or if it would appear at all, but again, potential for something 'interesting' if not beautiful


Doug

Attached File(s)

 io_set_nh.mov ( 347.05K ) Number of downloads: 568

 

[hendric]

I created a spreadsheet and imported the ephermis for a few weeks around closest approach, for every 20 minutes in the enounter. Best one so far is:
MJD Objects Notes
54161.44 IO & EUROPA Really close pass

Try adding a few hundredths of a MJD either way. When using the Jupiter Viewer, enter MJD as MJD 545161.44.

There are a few others from further away. I want to redo the ephermis +- a day to closest approach to see if I am missing any due to the 20 minute step size.

I'll post the spreadsheet once I'm done, promise!

Attached thumbnail(s)

 

[hendric]

OK, so there were a few additional close Io and Amalthea passes. Looking at the graphs, the majority of passes are Io & Amalthea, with a few others, mostly with Amalthea. The speedy little moon gets around!

MJD Bodies Comments
54149.68056 IO & AMALTHEA Europa is just out of view to the NW, good view of the rings
54149.8888 IO & AMALTHEA Thebe is left of Amalthea, IO is pretty far away
54150.98611 IO & EUROPA Far pass
54157.925 IO & JUPITER Io grazes the north side of jupiter, leaving J disk on dark side
54158.943 IO & JUPITER Io goes behind jupiter on the dark side
54159.365 EUROPA & JUPITER Europa grazes the southern dark side of Jupiter
54160.12 IO & JUPITER Crescent IO in front of dark side Jupiter, emerges few minutes later
54160.12 AMALTHEA & JUPITER Crescent Amalthea in front of dark side of Jupiter, emerges a few minutes later
54161.042 IO & JUPITER Io disappers behind jupiter on the dark side, with the rings visible and in shadow. Encounter with Io and Rings starts earlier
54161.43646 IO & EUROPA Really close pass!!!
54161.85 EUROPA & AMALTHEA Rings are between them
54161.97083 IO & AMALTHEA Rings are between them, with Adrastea possible
54162.85365 IO & AMALTHEA Close pass, rings and Metis visible, long encounter!
54165.125 IO & EUROPA Small crescents for both
54165.70833 IO & AMALTHEA Rings & jupiter, but distance function shows a bump, so could be interesting encounter
54168.70833 IO & EUROPA Pretty far pass, but in the same field
54170.94633 IO & EUROPA Amalthea emerges from behind Jupiter, might make an interesting appearance, all objects showing thin crescents

I had to do a manual search for Jupiter events, and gave up after a bit.

Unfortunately, the spreadsheet is over 20 MB, so I can't post the full thing. Here is a PDF of the charts, and a cut-down spreadsheet that you can enter the data in yourself. Some notes:

1. You have to modify the RA so that it is monotonic. What does that mean? When scrolling down, if you get to a set of entries that go from +~24 to ~0, then you need to change the RA(corr) column to (RA+24) to keep it linear.
2. RA is multiplied by 15, to get something vaguely representing degrees.

Any other questions, or if you want the full spreadsheet, feel free to ask.

Attached File(s)

 ephem_jup_5946.pdf ( 868.6K ) Number of downloads: 731

 

[hendric]

Here's the reduced spreadsheet.

Attached File(s)

 cut_down_ephem_jup_5946.zip ( 155.31K ) Number of downloads: 542

 

[Bart]

Any word yet on the possibility of imaging Himalia?

Bart

[mcaplinger]

I am sure there is a good reason for not doing this, but I have always wondered why these ejectable lens covers aren't made of lexan.

Lexan isn't a good choice due to outgassing and optical quality. It's fairly hard to make a cover that doesn't screw up optical performance, especially for a fixed-focus system.
That said, the Galileo SSI did have a transparent cover (I'm guessing it was glass). All of the systems I've worked on (MOC 1&2, THEMIS, CTX, MARCI 98&05) had no covers at all -- we were too mass-constrained.

This post has been edited by mcaplinger: Feb 9 2006, 05:57 PM

[ljk4-1]

Lexan isn't a good choice due to outgassing and optical quality.  It's fairly hard to make a cover that doesn't screw up optical performance, especially for a fixed-focus system.
That said, the Galileo SSI did have a transparent cover (I'm guessing it was glass).  All of the systems I've worked on (MOC 1&2, THEMIS, CTX, MARCI 98&05) had covers at all -- we were too mass-constrained.

If only they had been as thoughtful with the antenna on Galileo.

Could they have put Galileo into orbit around Europa? Or was the radiation just too much for the probe towards the end of its life?

[djellison]

Did you mean to say 'no covers at all' ?

As thinking back to imagery from the KSC gallery - I certainly dont remember any covers on the instruments you mention.

Doug

(PS - Galileo was basically knackered - electronics exposed to huge ammounts of radiation - and certainly not enough fuel to go into Europan orbit - the reason for crashing it into Jupiter as I understand it was that they didnt expect to have enough fuel for manouvering on board to keep control of the vehicle, and they wanted to dispose of it whilst still in control of it.)

[ugordan]

If only they had been as thoughtful with the antenna on Galileo.

As someone already said, unfolfing HGAs were used numerous times before, with no difficulties unfolding. It was a proven concept. What got Galileo in the end was all that trucking around the country, waiting to be launched literally for years.

Could they have put Galileo into orbit around Europa?  Or was the radiation just too much for the probe towards the end of its life?

That's an even worse situation than trying to put Cassini into orbit around Titan. There's just too much delta-V needed for it to be anywhere near feasible. Galileo was "running on fumes" at the end of its life with practically no propellant left.
It also wasn't really designed to stand up to prolonged heavy radiation doses a Europa orbit would guarantee so that scenario wouldn't work in real life.

[dvandorn]

And, the final nail in the Europa-orbit coffin was that Galileo wasn't completely sterilized (although you'd think that the Jovian radiation belts would have finished *that* job*), and there was a perceived contamination risk if it were to crash onto Europa. The easiest and most certain way to make sure that never happened was to ensure that Galileo was destroyed well away from Europa -- hence it was flown to its destruction into Jupiter itself.

-the other Doug

[JRehling]

If only they had been as thoughtful with the antenna on Galileo.

Could they have put Galileo into orbit around Europa?  Or was the radiation just too much for the probe towards the end of its life?

A qualitative guide to delta-v calculations:

Let's use an object at infinity (from, say, Jupiter) as the baseline. Zero energy.

The next thing is to put it into a very distant orbit. That's one step away from zero.

Then put it into an orbit with a distant apojove but a decently close perijove. That's a big energy step from the last one. It's also the easiest science orbit to achieve. Almost all orbiters of all other planets have been in that category, besides the ones that have used aerobreaking to help. By the way, the energy is proportional to the mass of the object, so it's about 3000 times more delta-v at Jupiter than Mars.

Then it's a big step to pull in that apojove. Roughly 20% of escape velocity. That's what it would have taken to get Galileo into a jovian orbit near Europa.

At that point, stop thinking about Jupiter and consider getting the thing at infinity for Europa, and bring it down in the same steps (much easier, because of Europa's lower mass).

Basically, that 20% of Jupiter's escape velocity is a killer.

[john_s]

Here's the reduced spreadsheet.

Just a quick note to say thanks, hendric, for all your work on this- I haven't had a chance to look at the details yet but I'll do so soon.

John.

[tedstryk]

One thing I remember reading in the early 1990s, before the stuck antenna problem was known, is that the idea of ending the mission with a Ranger-like kamikazee into Io. That would have been cool, but of course with the antenna being stuck, there was no way to transmit the data from such an even.

[Rob Pinnegar]

One thing I remember reading in the early 1990s, before the stuck antenna problem was known,  is that the idea of ending the mission with a Ranger-like kamikazee into Io.

Yeah, straight into one of the calderas and *SPLASH*!

[Guest_BruceMoomaw_*]

Last but hardly least, Europa was the one place they didn't want it to crash, due to the risk of biocontamination -- and any orbit around a Galilean moon decays after very long, due to the tidal influence of Jupiter itself. Since there is also some slight biological interest in Ganymede and Callisto, they decided from the very start to finish up by crashing it into either Io or Jupiter -- and the latter is a teensy bit easier to hit. So...

[Comga]

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight. 

What would happen if you tried to take color images with MVIC and looked at the Methane band? It is pretty narrow, so the signal level is much lower. While you might get back three bands of saturated images, this one might be usable. The question then would be if it would be USEFUL and worthwhile.

[tedstryk]

I remember seeing an article about New Horizons possibly being able to encounter an outer moon, such the mention of Himalia earlier, should one be located serendipitously in the right area. Now that NH is on its way, as anyone looked into any possibilities?

Ted

[Guest_BruceMoomaw_*]

That subject has been discussed earlier in this very thread. Alas, NH (despite Alan Stern's earlier hopes, as repeatedly expressed to me) will be considerably farther from Himalia than Cassini was, and won't be anywhere near any of the other irregular satellites either -- nor will it come anywhere near a Centaur (another of his long-shot hopes).

[Rob Pinnegar]

Geez, that's too bad.

This really serves to drive home the point that Jupiter's (Hill) sphere of influence is enormous. There are something like fifty of those "outer gravel" satellites known, and we won't be getting close to *any* of them? They're spread pretty thin.

We're not completely dead yet, though. There's still a year to go before the Jupiter encounter. If we're really lucky, someone will find another one of those little buggers right close to New Horizons' path. Granted, this would pretty much take a miracle, but it's always possible.

[Edit: We might have a bit more luck with a targeted search for Centaurs, though... could it be done?]

[tedstryk]

That subject has been discussed earlier in this very thread.  Alas, NH (despite Alan Stern's earlier hopes, as repeatedly expressed to me) will be considerably farther from Himalia than Cassini was, and won't be anywhere near any of the other irregular satellites either -- nor will it come anywhere near a Centaur (another of his long-shot hopes).

I think my question was unclear. I was referring to a possible telescopic search to see if anything small is lurking near NH's path, similar to what will be done for the Kuiper Belt.

[JRehling]

Geez, that's too bad.

This really serves to drive home the point that Jupiter's (Hill) sphere of influence is enormous. There are something like fifty of those "outer gravel" satellites known, and we won't be getting close to *any* of them? They're spread pretty thin.

With orbital radii of about 12.5m km, we could think of it as a big circle with a diameter of 25m km that NH is passing through twice. It's actually quite unlikely that you'd come within 1m km of any of 50 of them -- this isn't bad luck, it's the way this game is set up.

Additionally, the satellites have common orbits (in various subgroups) so the probability of an equatorial flyby hitting one of their orbits is not modeled by 50 independent events. If a group crosses the jovian equatorial plane at what is currently Jupiter-leading or Jupiter trailing, then of course a close Jupiter flyby would have no chance of coming near any such body. Given enough random Jupiter flybys, we'll probably see the great majority (over 80-90%) fail to image any outer satellite, then maybe one such flyby will image two or three of them. Although the radial angle alone gives many many ways for an encounter NOT to happen!

Imagine if instead of putting a deorbit module on HST, we instead moved it to a distant Jupiter orbit (2 or 3x Callisto's orbital radius at perijove) while it still had some life left. We'd get Galileolike coverage of the inner system all the time, and we would eventually get some great images of the outer satellites! Of course, HST weighs about 4.5 times as much as Galileo did...

[TritonAntares]

No smaller Jupiter satellite or any Centaur near NH-Track...

...but what about an asteroid between Mars and Jupiter?
Any chance of passing one in 'nearer' vicinity;
this means having better resolution than from Earth?

Bye

[Bart]

TritonAntares: Check out post #3 in "New Horizons in the Asteroid Belt"

Unfortunately, the answer is no.

Bart

[hendric]

John,
How quickly can LORRI cycle between pictures? Also, do you expect you'll be able to capture Jupiter's faint rings? What about if a moon is in the same FoV?

[hendric]

John,
How quickly can LORRI cycle between pictures? Also, do you expect you'll be able to capture Jupiter's faint rings? What about if a moon is in the same FoV?

Here's an ani gif of the IO + RINGS + JUPITER encounter. I didn't notice before, but it looks like Metis is also visible, but I don't think it will be more than a pixel or two. The pictures are taken 5 minutes apart.

BTW, since Io passes behind Jupiter's dark side, it should be illuminated well by the Jupiter-shine.

Attached thumbnail(s)

 

[john_s]

Here's an ani gif of the IO + RINGS + JUPITER encounter. I didn't notice before, but it looks like Metis is also visible, but I don't think it will be more than a pixel or two. The pictures are taken 5 minutes apart.

Pretty cool animation- we can certainly take pictures fast enough to make a movie like that, though the rings are probably much fainter than the illuminated crescent of Io so I'm not sure if we can get a good exposure on both Io and the rings at the same time. This is one that we'll consider if there turns out to be room in the timeline.

[hendric]

Here's an animation of the Europa/Io encounter. Both are crescents, which should be perfect for LORRI's sensitivity. The frames are taken 90 seconds apart. I'm not sure where they are relative to Jupiter, so they may or may not be getting any Jupiter-shine. Would LORRI be able to take a picture just from starshine?

I also made a what-if picture, taking John's simulated pictures and rotating/rescaling them to fit, with the image rescaled to fit into 1024x1024 at 1044 arcseconds. It's Not Real Life, But It's Pretty Close ™

I just checked, and it looks like some bad news. Europa probably will NOT be in Jupiter-shine. Io might still have some. There will still be visible crescents from both.

Attached thumbnail(s)

 

[hendric]

A few more animations.

First is of a half-lit Europa going behind the extreme southern end of Jupiter's dark side. Europa's dark side will be lit partially in Jupiter-shine.

Second is another Europa going behind dark Jupiter, from further away, and later in the flyby. Europa is a slim crescent. Could NH search for plumes at Europa while it is a crescent, or while most of the bright slice is hidden behind Jupiter's dark side?

Timestep is 90s for both.

Attached thumbnail(s)

 

[hendric]

Two views of the same encounter. One is centered on Amalthea, one is centered on Io (for those Io fanatics...hint hint Jason ) The Io centered one follows Io until it disappears behind Jupiter. Should be well lit in Jupiter-shine. Metis is also visible. Timestep is 6 minutes.

Attached thumbnail(s)

 

[hendric]

Two Ganymede encounters.

1st is Ganymede passing in front of Jupiter. Timestep is 15 minutes. I have selected a KODAK_MMT (if you can only get one...) John, I hope your workaround for the bright parts of the moons will work on a crescent Jupiter!

2nd is Ganymede grazing the north side of Jupiter, lit up in Jupiter-shine. My KODAK_MMT is exactly when Jupiter and Ganymede's axe (Is that plural for axis?) line up. Should be a pretty photo. Timestep is 20 minutes.

The KODAK_MMTs are at full resolution, low filesize to give an idea of how they would fit as desktop background.

Attached thumbnail(s)

 

[tasp]

Two views of the same encounter. One is centered on Amalthea, one is centered on Io (for those Io fanatics...hint hint Jason ) The Io centered one follows Io until it disappears behind Jupiter. Should be well lit in Jupiter-shine. Metis is also visible. Timestep is 6 minutes.

IIRC, Galileo may have noted some 'debris' in the vicinity of Amalthea. I am aware that due to distance, NH cannot resolve Amalthea more than a few pixels, but should Amalthea be eclipsed or occulted (by Jupiter or another moon) perhaps we could confirm the 'mysterious' (to me) Galileo finding. A stepped change in brightness, or debris remaining visible longer than Amalthea itself might be an interesting thing to find out.

[john_s]

Two Ganymede encounters.

1st is Ganymede passing in front of Jupiter. Timestep is 15 minutes. I have selected a KODAK_MMT (if you can only get one...) John, I hope your workaround for the bright parts of the moons will work on a crescent Jupiter!

2nd is Ganymede grazing the north side of Jupiter, lit up in Jupiter-shine. My KODAK_MMT is exactly when Jupiter and Ganymede's axe (Is that plural for axis?) line up. Should be a pretty photo. Timestep is 20 minutes.

The KODAK_MMTs are at full resolution, low filesize to give an idea of how they would fit as desktop background.

Those are awesome! I'll show the movies at the next team meeting, and I hope we can actually take one or two of them (or at least, some well-timed stills).

Thanks much,
John.

[hendric]

Callisto/Jupiter encounter. Timestep is 25 minutes. Callisto, well lit in Jupiter-shine, passes completely behind Jupiter and back out again. There is quite a long time spent behind Jupiter, 3.4 hours, so it might be better to split this into an ingress/egress capture with shorter timesteps. I have selected some KODAK_MMTs from the entry and exit.

Attached thumbnail(s)

 

[hendric]

Eclipse encounters. John, I assume you can't take pictures of shadow transits across Jupiter due to the brightness? What if Jupiter was far enough away that it only partially filled the CCD, a la your moon workaround? I think I'll do a shadow transit/GRS/moon transit search for when Jupiter fills the CCD from 20% to 80% on the way in.

I also am curious how large the penumbra is vs the umbra, and which John's application uses for its calculations. I guess since the Sun is so far away at that distance, the P vs U difference isn't that much? It still might be worthwhile to keep on Ganymede for a few extra shots after fully eclipsed because of this, and also refraction through Jupiter's atmosphere.

Ganymede and Europa ingress before closest approach. I didn't do egress, since it would look pretty similar.
Timestep is 2 minutes for Ganymede and 1 minute for Europa.

Io eclipse ingress and egress right after closest approach. This series is interesting, because we are seeing an eclipse from the side of a round ball instead of from the front. This causes the eclipse line to look rather odd, especially during egress. Also, Io is relatively large due to the time near closest approach.

Timestep is 20 seconds. Io really moves fast!

Sorry for the attachment ordering, I don't know what's going on.

Attached thumbnail(s)

 

[Stephen]

And, the final nail in the Europa-orbit coffin was that Galileo wasn't completely sterilized (although you'd think that the Jovian radiation belts would have finished *that* job*), and there was a perceived contamination risk if it were to crash onto Europa. The easiest and most certain way to make sure that never happened was to ensure that Galileo was destroyed well away from Europa -- hence it was flown to its destruction into Jupiter itself.

Some years ago on one of the Usenet newsgroups one of the more informed members mentioned that some had contemplated a more spectacular end-of-mission for Galileo if only the antenna had not become stuck: a swan dive into Io a la Ranger.

"Waaaay back, in the early days of the mission, before the antenna failure,
a Ranger-style snapping-pictures-all-the-way-down kamikaze dive into Io
was seriously proposed as a possible way of terminating the mission, when
fuel ran low. Io was originally going to get only the one flyby, right at
arrival, and so a closer look would have been quite valuable. "

---4:14 am, Sun, Feb 4 2001, Henry Spencer replying to Patrick Flannery
in "Galileo (spacecraft)" thread on sci.space.history newsgroup

(EDIT: just located an earlier version of the same info by the same author: July 5 1997 in the "Shut Down Probe" thread on the sci.space.history group.)
======
Stephen

[hendric]

OK, now that's a little strange. I defintely posted that last message as two seperate messages to get under the 1MB attachment limit. But the BB keeps joining them back into one! Is this a feature of the upgrade?

[djellison]

OK, now that's a little strange. I defintely posted that last message as two seperate messages to get under the 1MB attachment limit. But the BB keeps joining them back into one! Is this a feature of the upgrade?

I'm still finding features but yes, I believe that's one of them. It tried to tidy up and not have one person making several consecutive replies.

Doug

[hendric]

There are actually two double shadow transits that occur before the flyby! Here is the animation of the first one. The shadows are both on Jupiter between 54117.03611 and 54117.10833. I couldn't resist adding additional time before and after the transits to show Ganymede and Io zipping around Father Jupiter.

Animation starts at 54116.7 and ends at 54117.13750000. Timestep is 15 minutes.

My KODAK_MMT is the center of when both shadows are visible, and targeting Io so that Jupiter and Ganymede are both visible.

The second shadow transit begins at 54123.875 and ends 54124.275. There is a very short time from 54124.1875 to 54124.206944 that both shadows are visible at the same time (basically, 28 minutes). It's also likely that due to the geometry, NH would not be able to see one of the shadows. I don't have time to do a 50 step animation, so my KODAK_MMT is the midpoint of when both shadows are visible, 54124.19722.


John, it's been fun helping out. But now I have to get back to work!

[hendric]

Will you be able to let us know which movies and KODAK_MMTs the team selects?

Also, I was hoping you could give us some technical details on your technique to recover the moon image data? I've got a solution:

The readout time is too long on the CCD, causing potential saturation at the lowest exposure times.

1. I assume you can take 0-s frames for measuring bias on the CCD?

2. What about moving the target up/down on the CCD to vary the amount of time for the average exposure? For example, if the CCD took 100 ms to readout, a 0-s exposure with an object at the middle of the frame would give an average exposure of 50ms. And as you move the object closer to the top, the exposure length would get shorter.

3. There would a small increase in brightness as you went down the rows, but so long as you're not totally saturated at the bottom you should be able to subtract out the increase since CCDs are linear.

This would even work to get photos of Jupiter, you would just have to take slices of it and mosaic the parts that don't get overexposed. Hopefully the inter-frame time isn't too long.

Of course, images with multiple bright objects far apart wouldn't be possible, unless the FoV could be rotated to get the objects near the top.

[ugordan]

I think the problem John is trying to describe is image smear during readout phase, not because the exposures are too large.
They can select a short enough exposure which won't bleach out the moons, but that exposure is short compared to the readout phase. LORRI has no shutter so light falls on the CCD continually. As a result, while the image is being readout light from the moon is still coming in and the end result of this (CCDs readout one line at a time, shifting the entire image in the process until the last image line is shifted into the A/D converter) is what I imagine will be a good image of the target with sort of a vertical motion-blur effect overlaid on it.

That is the gist of the problem with imaging the Galileans -- removing the unwanted "motion-blur" effect. Obviously, the images will need to be carefully processed to remove this linear smear. What John Spencer seems to be saying is that they can actually subtract the blurred part, but only for a small, well-defined target such as a moon or Jupiter when it's still far away.

I can't wait to see the results, both from the imaging perspective and image processing perspective they should be interesting indeed.

[john_s]

They can select a short enough exposure which won't bleach out the moons, but that exposure is short compared to the readout phase. LORRI has no shutter so light falls on the CCD continually. As a result, while the image is being readout light from the moon is still coming in and the end result of this (CCDs readout one line at a time, shifting the entire image in the process until the last image line is shifted into the A/D converter) is what I imagine will be a good image of the target with sort of a vertical motion-blur effect overlaid on it.

That is the gist of the problem with imaging the Galileans -- removing the unwanted "motion-blur" effect. Obviously, the images will need to be carefully processed to remove this linear smear. What John Spencer seems to be saying is that they can actually subtract the blurred part, but only for a small, well-defined target such as a moon or Jupiter when it's still far away.

That's exactly correct. For small targets (or, we think, for any image where we can arrange for a number of complete rows of dark sky in the field) we can probably get unsaturated images even at low phase angles, so we are interested in "Kodak moments" at low phase angles as well as high phase angles. And yes, we'll be sure to let you know which "Kodak" images make it into the final plan, though we won't know for a while, probably for several months. Integrating the Jupiter observations is pretty complicated (our biggest issue right now is finding the best times for the necessary Earth-pointed tracking periods, when we can't take data), and any "Kodak" observations will be the last things we add to the timeline, after we've optimized all our science observations.

John.

[hendric]

Ah yes, I forgot that CCDs transfer the pixels down and then over. In that case you would get a vertical smear of the image. I assume what you're doing is something like this:

1. Simplified image is like this:

CODE

0: 0
1: 0
2: 8000
3: 8000
4: 8000
5: 0
6: 0

2. Pixels are read out from the bottom of the display, with each row dropping down one during the readout. Each pixel read out step would be something like this, ideally:

CODE

CCD Pixel     Step 1          Step 2         Step 3          Step 4          Step 5          Step 6          Step 7
   0          -na-            -na-           -na-            -na-            -na-            -na-            -na-
   1          0               -na-           -na-            -na-            -na-            -na-            -na-
   2          0               0              -na-            -na-            -na-            -na-            -na-
   3          8000            0              0               -na-            -na-            -na-            -na-
   4          8000            8000           0               0               -na-            -na-            -na-
   5          8000            8000           8000            0               0               -na-            -na-
   6          0               8000           8000            8000            0               0               -na-

Output row    Read 0          Read 0         Read 8000       Read 8000       Read 8000       Read 0          Read 0

3. Since the readout time is comparable to the exposure time, and there is not a shutter, each time a value is in an "exposed" pixel, like 2-4 above, it would get a certain amount of light, depending on how long the value is kept in that pixel. For example, let's say 10% of the exposed value, so 800 in this case since all light pixels are 8000:

CODE

CCD Pixel     Step 1          Step 2         Step 3          Step 4          Step 5          Step 6          Step 7
   0          -na-            -na-           -na-            -na-            -na-            -na-            -na-
   1          0               -na-           -na-            -na-            -na-            -na-            -na-
   2          800             800            -na-            -na-            -na-            -na-            -na-
   3          8800            1600           1600            -na-            -na-            -na-            -na-
   4          8800            9600           2400            2400            -na-            -na-            -na-
   5          8000            8800           9600            2400            2400            -na-            -na-
   6          0               8000           8800            9600            2400            2400            -na-


Output row    Read 0          Read 0         Read 8000       Read 8800       Read 9600       Read 2400       Read 2400

4. Since you said above that you would need a few complete rows of dark in the image, I guess you are taking the value placed in those last image rows (in this case the 2400 read out in step 6&7) and using that to adjust the previous pixels? How do you subtract out the value, since it’s not going to be linear across real-world light pixels?

5. It should be possible to also do it based on the opposite direction, since you know how long you timed the exposure and what the readout time per line is, and CCDs are pretty much linear. IE, if you have a readout time of 100ms, and 1024 rows, then you would get an additional exposure of 100/1024 or 97us per light pixel on the way off the CCD. So if you took an image 10ms long, you know the first light pixel read out from each column has no extra light, with each following pixel having .097/10=.0097 or about ~1% additional light from each corrected light pixel ahead of it. With this method, you could take full-frame light images, even if the top of the frame is overexposed the lower portions should be recoverable.

PS
John, I now understand what your problem was wrt that table not keeping the correct spacing. Even if you mark a section as

CODE

This is a fixed width font.  blah
0123456789012345

the editor doesn't switch to a fixed width font. What I did is edit my original table in Outlook with the font set to Courier New, and then copied&pasted it back here with the code tags.

PPS
Interestingly enough, I did some googling on this, and found out that the IRIS freeware camera software will automatically take care of this issue for you!
http://www.astrosurf.com/audine/English/result/obtu.htm
http://www.astrosurf.com/audine/English/first.htm#smearing
http://www.astrosurf.com/buil/iris/tutoria....htm#deconvflat

Well whaddaya know!

[john_s]

^^^Your analysis is almost correct- the additional wrinkle (which I didn't realize myself till recently) is that there is an additional period of smeared exposure *before* the static image is exposed, which looks exactly the same as the readout smear but is in the opposite direction. The result is that all rows in the image, whether "above" or "below" the main target, have exactly the same amount of readout smear in them. This makes it easy to subtract the smear if you have any dark sky rows- you can measure the smear in the dark sky rows and subtract it from all the other rows. We don't yet know how well this will work in the real world (though we are optimistic), and we'll always have to content with the photon noise from the subtracted smear, which can be significant.

[stevesliva]

I thought it might be hard to get excited about jovian cloud dynamics, but this definitely helps:
http://science.nasa.gov/headlines/y2006/02mar_redjr.htm

Perhaps Red Junior will still be there next year!

[Jyril]

The spots from it formed existed for about 70 years, so I don't think it'll disappear really soon.

[Guest_AlexBlackwell_*]

Pluto Mission News
March 9, 2006
http://pluto.jhuapl.edu

--------------------------------------------------------------------------------

New Horizons Adjusts Course Toward Jupiter

With a 76-second burst from its thrusters today, New Horizons cleaned up the last of the small trajectory “dispersions” from launch and set its course toward next February’s gravity-assist flyby of Jupiter.

Changing the spacecraft’s velocity by about 1.16 meters per second, the maneuver was the smallest of the three New Horizons has carried out since launch on Jan. 19, and the first conducted with the spacecraft in three-axis pointing mode. It also aimed New Horizons toward the Pluto “keyhole” at Jupiter – the precise point where the giant planet’s gravity helps swing the spacecraft toward the close flyby of the Pluto system on July 14, 2015.

When the maneuver started at noon EST, New Horizons was about 51.7 million kilometers (32.1 million miles) from Earth, moving along its trajectory at 37.5 kilometers (23.3 miles) per second. Mission operators at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., monitored spacecraft status through NASA’s Deep Space Network antenna station near Canberra, Australia.

[Guest_AlexBlackwell_*]

The PI's Perspective
Zero G and I Feel Fine
March 20, 2006
http://pluto.jhuapl.edu/overview/piPerspec...ive_current.php

[hendric]

John,
How much of a change to the Jupiter encounter with the TCM make? Will the simulator be adjusted with the new trajectory?

[john_s]

John,
How much of a change to the Jupiter encounter with the TCM make? Will the simulator be adjusted with the new trajectory?

At this stage in the game, the close approach time is being tweaked by a few minutes at most, and the distances are not changing significantly. Mark Showalter may update the trajectory in his Jupiter Viewer sometime, but you can rely on the simulator for most practical purposes.

John.

[Guest_Sunspot_*]

Do you have a date for when you expect to start taking the very first Jupiter data?

[Alan Stern]

We will begin the Jupiter data collect at the very beginning of Jan 2007. The exact date
will not be known for some months as we refine planning an negotiate DSN contacts
with JPL. If you want a best guess, put down Jan 10, with an error bar of +/-5 days.

And by the way, TCM-3 did not change our reference course through the system. It trimed out
residuals in our trajectory and put us closer to that exact reference course.

[Guest_AlexBlackwell_*]

New Horizons Payload Gets High Marks on Early Tests
Pluto Mission News
March 29, 2006

[Guest_BruceMoomaw_*]

While the Europa Focus Group meeting suggested that New Horizons' near-IR spectra of Europa -- contrary to my fond hopes -- probably will not reveal any new substances mixed with Europa's ice, its long-range LORRI photography will try to directly display one fascinating new type of Europan terrain feature only recently revealed by Paul Schenk's stereo analysis of Galileo's photos.

These are "crop circles" -- gigantic structures that look like huge, gentle semicircular moats in Europa's surface, hundreds of km wide and dozens of km thick, which are too gentle to be directly revealed by surface shadows in any single images so far, and which (given our limited views of them so far) may actually be just parts of complete, huge ring-like structures. No one knows whether they're crater remnants, diapirs, or some other kind of structure in Europa's ice -- but NH will photograph Europa's terminator (something Galileo didn't do too much of) to try to get a clearer look at them. (These were among the very few genuinely new scientific revelations at the meeting.)

[mchan]

These are "crop circles" -- gigantic structures that look like huge, gentle semicircular moats in Europa's surface, hundreds of km wide and dozens of km thick, ...

Tried google and got Schenk's paper -

http://www.lpi.usra.edu/meetings/lpsc2005/pdf/2081.pdf

but the other links were just about as expected for a search on "cr*p c*rcles".

[Guest_BruceMoomaw_*]

Good heavens. I completely overlooked that paper -- I was under the impression that their existence was first announced at this year's meeting!

[john_s]

Good heavens. I completely overlooked that paper -- I was under the impression that their existence was first announced at this year's meeting!

Actually the "crop circles" are seen better by near-terminator imaging than by stereo- it's the near-terminator imaging that we'll be concentrating on with New Horizons. They are indeed strange and wonderful features so I hope we can shed some more light on them (so to speak).

On another topic, we had a meeting last week where we thrashed out the details of the Jupiter encounter timeline- we now have a time-ordered listing of science observations, calibration observations, and DSN passes that seems to satisfy nearly all of our science goals. There will still be fine-tuning, but we finally have a pretty clear idea of what we'll be doing, and when. It feels like we've passed an important milestone.

It look's like we'll be able to include a few of Hendric's "Kodak Moments", too, though we haven't made any final decisions on which ones.

John.

[hendric]

It look's like we'll be able to include a few of Hendric's "Kodak Moments", too, though we haven't made any final decisions on which ones.

John.

Sweet! I hope you'll be able to get the one of Io and Europa passing by each other, and the ones with the moons grazing Jupiter's limb.

[john_s]

So far, it looks like we should be able to do the conjunction of the crescents of Io and Europa at around 10:30 on March 2nd, and maybe one or two others. My personal favorite, the crescent Io about to be occulted by Jupiter, with the ring in front of it, from 01:00 on March 2nd, is unfortunately during some critical ring observations, but there's at least some chance that we'll be able to sneak it into the timeline (it *is* a ring observation, after all...). It's likely that we'll be doing stills, not movies- movies take too much data.

John.

[hendric]

Will you be able to capture the double shadow transit? It occurs on January 17, 2007, well before the close encounter.

http://www.unmannedspaceflight.com/index.p...pe=post&id=4076