OPAG Reports, Formal proposals/evaluations of future outer SS missions Options

[jasedm]

Good arguments.

[djellison]

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

[vjkane]

.. 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.

[SFJCody]

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.

[vjkane]

The presentations from the outer planet flagship instrument conference are now available at http://opfm.jpl.nasa.gov/community/opfmins...ppresentations/ .

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.

[Mariner9]

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.

[ngunn]

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.

[vjkane]

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.

[ngunn]

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. (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.

[just-nick]

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

[volcanopele]

it is a relatively new idea (or at least a reborn idea) now that large enough seas which can be targeted have been found.

[ngunn]

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.

[gpurcell]

"Jupiter Icy Moons Orbiter - Ambitious"

Snicker.

[vjkane]

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/opfmins...ppresentations/ 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.

[gpurcell]

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.