Europa Orbiter, Speculation, updates and discussion Options

[Redstone]

There has been lots of discussion of a mission to Europa in the excellent thread on the Juno mission. I thought that since a Europa mission seems to be once again becoming a possibility, it deserved its own thread for news, updates and discussion. I thought I'd kick things off with a summary of past efforts on a Europa mission, and on where things stand now. If I make a mistake, please correct me!

In the course of its prime and extended missions, Galileo found evidence of liquid water under the icy surface of the planet. Planning began on a Europa Orbiter mission, with a projected arrival date of 2008, to confirm the presence of the ocean, characterize the thickness of the icy crust and identify places for a future landing. One thing to note about these earlier plans: they included a direct trajectory to Jupiter, presumably to minimize mission duration and qualms about RTGs re-entering Earth atmosphere after some (highly unlikely) targeting mishap. But NASA lacked a nice category of missions to place the Europa Orbiter in. Eventually it got lumped together with Pluto Express and Solar Probe in a Outer Solar System program labelled "Fire and Ice", a term which also got applied to the Galileo Europa Mission extension. Without a solid program to support it, (like Mars Exploration, Great Observatories, or Discovery) the mission looked like an orphan.

As Bruce Moomaw has well documented, attempts to kill off the Pluto mission led to a tug of war between NASA, the planetary scientists and the public, resulting in Congressional directives to NASA. Pluto Express became the Pluto/Kuiper Belt Explorer and then New Horizons and New Frontiers 1. (New Frontiers 2 is of course Juno.) But the cost for the Europa mission continued to rise, and the launch date recede, as the difficulty of radiation shielding and the large delta-v requirements hit home, and the mission's public profile fell. The launch date moved to 2010 and the costs moved over a $1b. Then along came Sean O'Keefe and JIMO, a justification for the Prometheus program through developing nuclear electric propulsion, not with RTGs, but with an in-space fission reactor. Launch got moved to 2011, then 2012, while the cost went even further through the roof.

With the arrival of Mike Griffin, JIMO was cancelled. As Griffin said to Congress, "It was not a mission, in my judgment, that was well-formed." But interest in a Europa mission remained and remains strong. In 2003 the National Academy of Science's Decadal Survey flatly stated that a Europa Orbiter was the top priority for the next Large scale (aka Flagship) mission. (See page 196 of the report.) NASA's current Solar System Exploration Roadmap reaffirmed a Europa orbiter as the next flagship mission. The question as always is money. As Administrator Griffin said, "The Science Mission directorate wants to do a Europa mission, the National Academy of Sciences wants to do a Europa mission, I want to do a Europa mission. When we can afford it in the budget, we'll do it."

Evidence of that support beyond rhetoric and reports trickled out with a letter from Andy Danzler, NASA's Solar System chief, to the Outer Planets Assessment Group (OPAG). He reported that he had "funded a team to take a quick look at the boundary conditions of a mission to Europa, that is, how much power, mass, travel time, etc. for various realistic scenarios. For planning purposes, this group is looking at launch dates in the 2012-2015 range, although the later dates are more likely in terms of funding." For funding details however, we have to wait for the FY 2007 budget.

OK, now the good stuff.

The latest meeting of OPAG included reports on a Reference Design for the mission. A kind of first draft which establishes a baseline which can be tweaked and modified to extract the best science return.

There are many things to like about this draft design:
* The mission is now permitted to use Earth flybys, and uses a proven trajectory, the same as used by Galileo (Venus-Earth-Earth Gravity Assist). This allows a BIG increase in the available mass.
* The orbiter uses RTGs, but not super advanced ones that require further years of development.
* The orbiter is similar to Cassini in appearance, with 2 engines, a cylindrical tank structure, RTGs at the base, the magetometer boom at the top, and space for a lander bolted to side. The similarities may make it easier to convince Congress that this is something NASA knows how to do. The most obvious configuration change is with science payload and HGA having switched places, and the addition of a radar array. And there looks like a camera the size of MRO's HiRISE!
* The mission is definitely Flagship in scope with a launch mass of over 7000 kg on a heavy lift launch vehicle. For comparison Cassini was 5712 kg at launch on a Titan IV, and Galileo was 2223 kg when launched using the Shuttle and an Inertial Upper Stage.
* There is a good opportunity for ESA participation with the lander and science instruments. NASA/ESA co-operation is on the agenda for the next OPAG meeting.
* The mission does not assume big upgrades to the Deep Space Network. If the Next Generation DSN does come along, that's just gravy.
* Despite the Europa focus, the mission appears to give at least part of a Galilleo II style tour with multiple flybys of the outer Galileans over 18 months. Only Io will have to wait.

The OPAG Europa working group is also expected to present further work at the next meeting in October. More details will emerge then. I think there is room for cautious optimism on this mission. While we won't be seeing a mission launch for at least another 7 years, the combined weight of the planetary science community does tend to get it's way in the long run. I think the momentum is finally starting to build.

[Guest_BruceMoomaw_*]

The very fact that Congressmen fund NASA as pork to their home districts indicates that if the manned-program budget was cut, SOME of the money thus saved would get transferred to the unmanned program.

[mars loon]

The very fact that Congressmen fund NASA as pork to their home districts indicates that if the manned-program budget was cut, SOME of the money thus saved would get transferred to the unmanned program.

I dont see how you can make that connection. Your suggestion may or may not be true

Hopefully this truly worthy mission does get funded somehow, despite the gloomy outlook.

[scisys]

I dont see how you can make that connection. Your suggestion may or may not be true

Hopefully this truly worthy mission does get funded somehow, despite the gloomy outlook.

It has always seemed to me that the problem with the manned program is not that allocated funds are coming at the expense of the unmanned programs. The problem is that *cost overruns* in the manned program are carved out of the hide of the unmanned program. This nails you every year even after a mission is scoped and funded. Heck it even nails you during ops.

Still, this argument has been going on since forever. The reality is that the unmanned program has to live within the boundries defined by the, admittedly excessive, needs of the manned program. I don't like it but I don't see a way to change it. It is inlikely that money cut from the manned program will end up in the unmanned program. However, a reined-in manned program would be less of a yearly threat to the unmanned program and cause fewer 're-engineerings', 'budget exercies', 'descopes', 'stand-downs', 'development deferrals' ... pick your favorite euphemism for feeding the beast that is the manned program.

My personal feeling on a Europa mission is that it needs to focus on two questions: "is there (still) liquid water (for sure)?" and "where are the thinnest parts of the ice?". One has to hope the answers will be such that the justification for follow-on missions will lead to penetrators and landers, etc. The tendency towards a Galileo style tour must be avoided at all cost. It should be a Europa only tour. Otherwise the flight ops budget alone would kill the mission when you start adding all the systemic requirements for mission planning and resource allocation. I know we don't go out there very often and Jupiter ain't Mars, but I don't see any Galileo/Cassini style missions coming along anytime soon (or long term to be honest).

Perhaps a Europa mission should become a near term component of the Origins Program (would that be a good thing or more likely to kill it?)