Monday, April 11, 2011

Rethinking Icy-ocean Moon Missions - Part 1

Several weeks before the release of the Decadal Survey’s report, a special meeting of the Outer Planet Analysis Group (OPAG) was scheduled for the week following the release.  It was the only one of the analysis groups (there are also ones for Venus, the moon, Mars, and small bodies) to schedule a special meeting.  It was a strong hint that the report was not going to have good news for the outer planets community. 

For several years, the exploration of the icy-ocean moons Ganymede, Europa, Titan, and Enceladus has been the highest priority of the outer planet research community.  The Survey attempted to enable a vibrant outer planets program with three flagship missions on the recommended list (Europa and Enceladus orbiters and a Uranus orbiter and probe mission) and Io and Saturn probe missions on the New Frontiers candidate list.  In plusher budget times, the outer planet program would have been a big winner.

In the new leaner budget times, if there was a category of missions that was loser in the collision between he Decadal Survey’s recommendations, and the new budget realities for NASA’s planetary program, it was the icy-ocean moon missions.  The flagship missions now appear unaffordable.  The Io and Saturn probe missions do not address the icy-ocean moons.  Now, further exploration of these moons rests on the European Space Agency’s (ESA’s) possible Ganymede orbiter that is in competition with two good astronomy/astrophysics missions for selection.

The OPAG report from the meeting following the Survey report may be a first step in asking NASA to look for new approaches to enabling the exploration of icy-ocean moons.  The official report strongly endorses the Decadal Survey recommendations.  (You can read the report at  The closest OPAG came to suggesting a re-examination was a request to pursue non-Flagship outer planet missions and to consider technology improvements that might enable Titan missions.

I listened to a good portion of the meeting, and there were several requests to see if it would be possible to add an icy-ocean mission to the list of New Frontiers candidate missions mid decade.  (Unlike the Discovery missions that can be proposed for any target, New Frontiers missions are selected from a candidate list.  Proposals for the ~$650M-$1B New Frontiers missions are so expensive to prepare that the list is kept short so that proposing teams can focus their resources.)  There is precedence for such a request to change the New Frontiers list.  The previous 2003 Decadal Survey recommended four candidate missions, and the list subsequently was expanded mid decade.  In addition, the new Survey report states that possible New Frontiers class missions to the icy-ocean moons were not prioritized (and Ganymede was dropped from the previous list) at least in part because of the priority given to a now unlikely Europa flagship mission. 

Any decision to re-examine the New Frontiers candidate list properly belongs several years in the future.   In my next post, however, I’ll start looking at tactics and missions that might enable continued exploration of these moons in the coming decade.

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