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

[JRehling]

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.

[Roly]

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

[vjkane]

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).

[EccentricAnomaly]

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).

[vjkane]

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.