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_*]

Another description of the "Tour and Endgame" can be found on pg. 23-26 of the most detailed description of the original Europa Orbiter concept at http://outerplanets.larc.nasa.gov/outerpla.../Europa_MPD.pdf . (One nice recent development: calculations now indicate that the total radiation dose that EO will get during this mission is less than half of the originally estimated 4 megarads. This by itself lops 200 kg off the needed shielding weight, and thus about 400 kg off the total spacecraft weight.)

[Guest_BruceMoomaw_*]

Also, you'll notice that the Endgame involves only about half a dozen Europa flybys, rather than a dozen as I stated above.

[ljk4-1]

Perhaps this will require a separate topic, but what will it take to put a lander on Io? Just imagine what surface images will look like from there!

[Guest_BruceMoomaw_*]

That will be a while coming -- the radiation level at Io is 30 times that at Europa!

[Roly]

Thanks for the replies about the orbiters - the constitute the most compelling explanation yet of why you don't bother with fly-by missions unless the target is exceptionally hard. I can see the political point is also important when there is a [F]lagship class mission looking for money (that's a capital 'F' for the large clas flagship that EO will doubtless end up being).

Counting the days until EO arrives. I wish Juno could do some science on the Galilean moons, but I guess that's totally not the point, given the orbit. New Horizons Jupiter encounter should be great.

Roly

[Guest_BruceMoomaw_*]

Yeah, it's been made clear to me by Scott Bolton that they don't WANT to fly Juno close to any of the Galilean moons, even if they get the chance. (Although I would presume that its camera could make some observations of Io's continuing activity.)

In fact, he's now made one interesting point that I had never thought of: Juno is definitely NOT going to have a long prolonged mission. It will have taken a considerable radiation dose by the end of its one-year primary mission, and they want to make sure it doesn't break down before they have a chance to deliberately crash it into Jupiter to make sure it doesn't eventually hit Europa. He's talking about an extended mission of -- at most -- one month, and they will in fact be monitoring its behavior carefully on the chance that they may have to end its mission a little ahead of schedule. (A landslide majority of its useful science will have been done by the first 6 months.)

This one is scientifically aimed at Jupiter -- period -- and (like Mars Climate Orbiter had it succeeded) it's going to do very little that will be of interest to the general public.

By the way, its launch has definitely been bumped now into July 2010 or August 2011.

[Marslauncher]

Is the Europa Orbiter Still on? on was it replaced by Juno?

Just saw a program on Science Channel that mentioned it

[Decepticon]

You know this is very confusing lately. I was gonna suggest a area on this board with a listings of approved missions and future mission as well as canceled/on ice missions.

[Guest_BruceMoomaw_*]

No, Juno AND the Europa orbiter (under its new name, "Europa Geophysical Explorer") are both planned, although EGE won't get its official program start until 2007.

However, one thing that is on hold for now is the previous plan for a Deep Jupiter Multiprobe mission, for which they won't give any go-ahead until they examine the Juno results -- that is, not for quite a while (since Juno won't arrive till 2016). There has recently been a very dramatic, but apparently firm, change in the science community's attitude toward the giant-planet entry probe program, which is yet another item in my "Astronomy" article that I must leave dangling for now.

[odave]

which is yet another item in my "Astronomy" article that I must leave dangling for now.

"Astronomy" needs to pay you a sales commission, Bruce

Any news on what issue your article will appear in?

[Guest_AlexBlackwell_*]

"Astronomy" needs to pay you a sales commission, Bruce 

Or deduct from what they've paid him since he's dropping so many hints

Seriously, though, it's a good thing he didn't submit the article to Science or Nature because his comments here, as helpful and useful as they are to the forum, might constitute "prior publication," which both journals use as grounds for rejection or refusal to publish.

[Guest_BruceMoomaw_*]

My article will be appearing in either the February or March issue. Unfortunately, I ended up with enough material to write a 9.5 page article (AFTER extensive trimming), and so the editors will be hacking it down to 4 pages -- and I'm not sure what complete sections they're going to cut out to do so. I will, at any rate, try to get "SpaceDaily" to publish whatever info "Astronomy" doesn't; and anything relevant that gets cut out there will get put into this blog at some point, rest assured.

[mars loon]

My article will be appearing in either the February or March issue.  Unfortunately, I ended up with enough material to write a 9.5 page article (AFTER extensive trimming), and so the editors will be hacking it down to 4 pages -- and I'm not sure what complete sections they're going to cut out to do so. 

Too bad about the extensive cuts. did you learn that after it was already written?

[Bob Shaw]

My article will be appearing in either the February or March issue.  Unfortunately, I ended up with enough material to write a 9.5 page article (AFTER extensive trimming), and so the editors will be hacking it down to 4 pages -- and I'm not sure what complete sections they're going to cut out to do so.  I will, at any rate, try to get "SpaceDaily" to publish whatever info "Astronomy" doesn't; and anything relevant that gets cut out there will get put into this blog at some point, rest assured.

Bruce:

Perhaps it was a slip of the keyboard, but the word 'blog' caught my attention. Do you produce one? Do you have *time* to produce one?

I'm sure we'd all be fascinated, were you to do so - even when we (quietly) disagree with you, your comments on the unmanned spaceflight scene are without peer!

Bob Shaw

[Guest_BruceMoomaw_*]

Nope, no blog -- I've never quite had the time and/or the nerve. (One recent "New Yorker" cartoon shows one dog telling another: "I considered starting a blog, but I finally just decided to go in for pointless barking instead.")

As for the article, they told me from the start that 4 pages was the length. The trouble is that whenever I attend one of these damn conferences, I get enough interesting material for SEVERAL articles, and then go through the torments of hell trying desperately to hack a 12 to 15-page article down to a few pages while the article bleeds and screams piteously. As with my 2004 article on the MER-A landing for "Astronomy", I finally just had to throw myself on the mercy of the editors by submitting an oversized article and letting them do the dirty work. (A far cry from those bright college days when I was straining desperately to inflate puny term papers.)