John Spencer, erstwhile guest blogger (see here and here), just sent me a few notes on the recent Outer Planets Assessment Group meeting. As was true in my earlier post on this topic, John was most excited by the comments made by NASA representative Jim Green about the future of outer planets flagship missions. John wrote:
Perhaps the most interesting result from the meeting was the presentation from Jim Green, acting director of the NASA Planetary Science Division, who said that NASA intends to fund (to the tune of $1M per target) detailed studies of potential flagship (i.e. several billion dollar) missions to four targets
1) Europa (already thoroughly studied, but the new studies may include more independent review) 2) Titan 3) Enceladus 4) Ganymede (with additional Jupiter system science)
The idea is to see whether there are credible alternatives to Europa (in terms of both potential science return and technological readiness) for the next flagship mission to the outer solar system. There was lively debate on this issue. Some people thought we should put all our efforts behind a Europa orbiter because it is the most mature design, and requires the least technology development, and thus the most likely to be approved as a new start in the near future. Others thought that we should consider following up on recent discoveries in the Saturn system as an alternative to Europa, particularly because, if the next flagship mission goes to Europa, a return to Titan (or Enceladus) might not happen for at least a couple of decades. Ganymede was a surprise -- the idea is that Ganymede, in addition to its intrinsic interest, might be a relatively safe location from which to study other bodies, like Europa and Io.
There were also presentations on smaller studies of possible cheaper missions to the Saturn system, asking whether we can do worthwhile science at Titan or Enceladus on a New Frontiers budget (roughly $1B). I'm leading the Enceladus study. These studies are just getting started, so no results to report yet, but for Enceladus we are looking at potential science from a Saturn orbiter with improved instrumentation compared to Cassini, or a Stardust-like mission that would fly through the plume and bring samples home.
---I thought I'd also throw in here some words that John posted on unmannedspaceflight.com about the future of Cassini. It appears that the Cassini mission has made some significant progress in deciding what to do with the spacecraft should it survive its primary mission and be granted an extended mission: John wrote:
Lots of progress was made on the extended mission tour designs before and during the October PSG [Project Science Group] meeting. At the previous PSG meeting, in Nantes, France, in June, the tour designers had come up with a wide variety of possible tours, most of which turned out to be acceptable to at most one or two of the five science disciplines in the mission (Titan, icy satellites (we are mostly interested in Enceladus during the extended mission), Saturn, rings, magnetosphere). Since June the designers have performed miracles, and have come up with at least one tour that, with minor tweaks, will probably be acceptable to all disciplines. They are still refining the "favorite" tour, and also devoting some of their energies to a different tour that also looked promising but needed a bit more work.
So expect lots of Enceladus and Titan flybys, a few other satellite flybys, some great views of the rings during solar ring plane crossing, and other goodies between mid-2008 and mid-2010. There should also be some fuel left for a less ambitious extended-extended mission beyond mid-2010.