A Europa Observer?

A reader posted a question on my blog entry, Update on NASA's Planetary Program.  I thought that the answer might interest a number of readers.

Al wrote,

You stated

"My take on the "highly restricted" and "tough choices" is that one of the two flagship class missions widely discussed -- the MAX-C Martian rover and the Jupiter Europa Orbiter -- may not be recommended. If so, I'd place my bet on a Martian rover being recommended..."

If true, could that open up the possibility of a scaled down lower cost Europa mission (Frontier class), perhaps limited to a short duration study of Europa itself and not the entire Jupiter system? Although I am a huge proponent of EJSM, I would still be thrilled to get a limited Europa focused mission, especially if it could arrive there before 2027 (ideally 2018 or so).

For convenience, I'll call this limited mission the Icy Moons Observer (IMO).  It appears that it is possible to fly a mission to the Jovian system for studies of the Galilean moons at Discovery mission (~$450 M) -- the Io Volcano Observer -- or New Frontiers (~$650 M) -- ESA's Jupiter Ganymede Orbiter -- costs.  Either of these concepts probably could be stretched to include a number of flybys of Europa in addition to other targets without busting the budget too badly.  (Note: The Io mission would have the wrong instruments to study an icy moon, but the spacecraft design could be refitted with appropriate instruments.)

One could imagine an IMO mission that has multiple encounters with all the icy Galilean moons.  A number of Europa flybys (a dozen? twenty?) could carry out global and regional surveys of that moon.  Then the spacecraft might enter Europan orbit for a lifetime of a month or two (compared to the nine months plus of the proposed Jupiter Europa Orbiter Flagship mission) to carry out detailed measurements of selected locations.

I don't know, however, if a Europa orbiter can fit into either a New Frontiers or even a small Flagship (~$1B) class mission.  A mission that enters Europa orbit will end with the spacecraft crashing on that moon's surface.  To ensure that Earth organisms don't contaminate Europa, stringent planetary protection design and assembly requirements would have to be taken.  This would step up the costs by some increment (that's unknown to me).  Also, staying in orbit even for a month or two would greatly increase the radiation dose the spacecraft would suffer compared to a mission that only had flybys.  This would result in another step function in mission costs.

So an IMO mission that focuses on flybys of Europa and possibly orbiting one of the further moons (probably Ganymede) certainly seems doable.  A mission that orbits Europa even for a short time may or may not be doable within a constrained budget. 

For those interested, a previous blog entry on a possible Galilean Moon Observer provides additional background on what might be possible.  The posts on EJSM flyby science and a concept for a solar powered Europa orbiter might also be interesting.