Wednesday, January 21, 2009

Europa Jupiter System Mission Summary Report

As mentioned in the previous post, the Joint Summary Reports for the two mission concepts vying to be NASA's next Outer Planet Flagship Mission have been publicly released [obviously the most important news story to come out of yesterday]. These reports provide an overview of the science goals and mission design of each mission. More detailed reports for each component of both proposals have not been publicly released, probably because of their greater length and technical detail, it is taking longer to edit the reports to make them safe for public consumption [can't let the terrorists get to Europa first...and blow it up, now can we? Wait, is that an option? ;-)] So while it is "only" the summary, there are still a lot of interesting nuggets to be gleaned. Also note that because this is an Io-centric blog, I will only post a summary of the Europa Jupiter System Mission (henceforth EJSM).

As another reminder, down-selection is planned for next Friday, January 30 at a NASA/ESA Decision Board with a public announcement planned for either February 3 or 4 at ESA's Science Program Committee meeting.

Following the nice, purty cover (provided by the incomparable Michael Carroll) and a graphical summary of the summary report, the EJSM summary report is divided into nine chapters, three of which I will comment on in this post: Science Goals and Objectives, Mission Concept, and Cost and Schedule.

The first major section of the report covers objectives and science goals. Two main goals are cited for EJSM: Determine whether the Jupiter System harbors habitable worlds and Characterize the processes within the Jupiter System. These goals fit within the overall theme of the mission: The emergence of habitable worlds around gas giants. The sub-goals under the first mission goal (let's call it "Habitability" for short) really don't seem to fit the stated goal. The sub-goals, like comparing the exospheres, plasma environment, and magnetospheric interactions of the icy satellites, don't seem to work towards achieving the habitability goal, with the exception for determining surface composition [hey, you never know, they could find organics along the Europan ridges] and identifying sites for future in-situ exploration [which could, you know, ACTUALLY look for life and study possible habitable environments]. All the other sub-goals would fit better under the other primary goal (let's call that one Processes). In short, I feel that the mission planners are unfortunately committing my Cardinal Sin Numero Uno, using astrobiology to sell a non-astrobiology mission.

In the next section, Mission Concept, the report covers the two flight components to be flown for this mission -- the NASA-supplied Jupiter Europa Orbiter (JEO) and the ESA-supplied Jupiter Ganymede Orbiter (JGO) -- their model payloads and nominal mission plans. To simplify things, the model payloads for payloads are virtually identical (though with differences in the needs of the instruments on the two spacecraft). These instruments include: a laser altimeter, a radio science experiment (with a Ka-band transponder and ultra-stable oscillator), Ice Penetrating Radar, Visible-IR Spectrometer, an Ultraviolet Spectrometer, an Ion and Neutral Mass Spectrometer (JEO-only), Thermal Instrument, Narrow-Angle Camera (JEO-only), Wide- and Medium-Angle Camera, a Magnetometer, Plasma and Particle Analyzers, and a Sub-millimeter Wave Sounder (JGO-only). The narrow-angle camera on JEO will have an IFOV similar to Galileo's SSI, or about 10 microradians per pixel. This provides for a resolution of 10 meters per pixel at a distance of 1000 km. The report also lists the descope order for Jupiter Europa Orbiter. A few of the higher order priorties would effect Io science if the mission were to be descoped, including the loss of color imaging on the NAC, the mass spectrometer, OpNav Functionality (which would limit flyby altitudes to 500 km and up, though without the Mass spectrometer, closer approaches might be lower priority), and the thermal instrument. Luckily, the loss of the NAC entirely is far down on the list. The lack of a narrow-angle camera on JGO as well as the fact that it stays mostly beyond the orbit of Ganymede will likely limit that spacecraft's contribution to Io science with the exception of coordinated observations with JEO and for near-IR observations during the Jupiter System phase of the mission.

The mission plan remains similar to what we have heard earlier at OPAG meetings in 2008. Basically, both spacecraft will launch in the First Quarter of 2020 into a Venus-Earth-Earth Gravity Assist trajectory. JEO would arrive at Jupiter in December 2025 with an Io flyby (with probably little to no remote sensing) shortly before. JGO would arrive shortly after in February 2026. JEO would then conduct a Jupiter System Science Campaign that would last from JOI until the spacecraft enters Europa orbit in July 2028. The first year of this campaign would include three more Io flybys to be conducted in the second half of 2026. One of these flybys could have a close approach distance of 75 km for mass spectrometer measurements of a plume (though that would require specfic targeting, which would go against the otherwise opportunistic nature of the targeting of these satellite flybys). JGO would conduct significant Callisto science (with 19 flybys while that spacecraft is in a resonant orbit) during 2027 before going into orbit around Ganymede in May 2028. Following these spacecraft's orbital missions, they would be crashed into their respective icy satellites.

The Summary report only briefly covers the cost of this mission. JEO's full lifecycle cost is expected to be $3.8 Billion in inflation-adjusted costs. JGO's cost is not reported (apparently, it's classified, though the planners expect it to stay below the 650 Million Euro cost cap (that includes all costs, like the launcher).

While I would prefer to post a more detailed post about Io science with JEO when that spacecraft's more detailed report is posted online, I may give it a try tomorrow. Until then, I need sleep... Oh, and Van Kane seems to have found out that the reports are online too ;-)

Link: EJSM Joint Summary Report []

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