Monday, November 10, 2008

Jason Perry on OPAG pressentations

Jason is the blogger at The Gish Bar Times (I highly recommend the site: He has kindly given permission to reproduce his entry here.

The presentations for last week's OPAG Fall Meeting are now online. These include several presentations covering the two Outer Planet Flagship mission proposals, the Europa/Jupiter System Mission (EJSM) and the Titan/Saturn System Mission (TSSM), as well as other programmatic presentations.

The final reports for the two proposal teams were due last Monday so last week's OPAG meeting were the first opportunity to present the finalized proposals. These include a more detailed sample mission profile, payload, and science goals. EJSM would include two mission components: the Jupiter Europa Orbiter (JEO) and the Jupiter Ganymede Orbiter (JGO). According to the baseline mission plan, the two components would launch separately in February and March 2020. JEO would arrive at Jupiter in December 2025 while JGO would arrive in February 2026. JEO would then conduct an orbital tour of the Jupiter system over a period of 31 months, before entering orbit around Europa in July 2028. During the Jupiter tour phase, JEO would perform more than two dozen flybys of the Galilean satellites. JGO would conduct a more focused tour of the outer two Galileans before going into orbit around Ganymede in late February 2028. There are hints in the presentation that JGO might attempt to encounter one of the outer irregular satellites during its mission.

The NASA-supplied component, JEO, would encounter Io four times during its mission. The first encounter would occur just before Jupiter Orbit Insertion (JOI), and like the flyby before Galileo's JOI, the Europa Orbiter would not acquire science during Io-0. During the other three encounters, performed in the second half of 2026, would all for 25% of Io's surface to be imaged at better than 200 meters/pixel. The last of the three encounters would occur at an altitude of 75 kilometers, enabling direct plume sampling, though the current sample profile would not allow for sampling of any known plume except for maybe the outer reaches of the Culann plume. It should be noted though that the tours shown are just examples that are subject to change. For example, the Cassini prime mission tour wasn't approved until a few years before it arrived at Saturn. The presentation goes on to mention that the radar instrument on JEO would be active for the flybys allowing for sub-surface sounding and altimetry. These could be useful in constraining tidal heating models and near-surface lithospheric structure. Another interesting slide in the EJSM presentation is the data return plan. The EJSM team plans to return 3 Gb per day from Jupiter during the tour, providing for hundreds of narrow angle camera images per day along with context images from other imagers. This could provide very decent monitoring of Jupiter and Io processes. Finally, the JEO team plans to image Io once or twice a week while in Europa orbit for monitoring purposes.

The payload for EJSM seems pretty capable. In addition to three camera systems (narrow-, wide-, and medium-angle cameras), the payload includes: a laser altimeter, an ice-penetrating radar, a Visible-IR spectrometer, an UV spectrometer, and Ion and Neutral Ion Spectrometer, a thermal instrument, a magnetometer, and a plasma and particle instrument. The communications antenna on JEO can also be used for radio science experiments. The specific instruments will be selected via an annoucement of opportunity. The JGO would carry a similar payload.

EJSM faces competition with TSSM for the Outer Planet Flagship Mission. TSSM would provide a NASA Titan orbiter, an ESA balloon, and an ESA lander planned for central Kraken Mare.

There is some disagreement between the presentations about when the downselection will occur. The EJSM presentations suggests that down-selection occurs in January 2009 with a confirmation of this selection by the ESA Science Programme Committee on February 4 (the ESA component would be formally approved at the end of 2012, where the component would have to compete with Xeus and LISA). A presentation by Curt Niebur still uses mid-February 2009 as the downselection date.

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