XM Status, Priorities and Plans, XXM Activities Icy Satellite Science C. J. Hansen, A. Hendrix, D. Shemansky 5 January 2010

XM Status, Priorities, Plans Upcoming icy satellite flybys Still polishing icy satellite flyby timelines Rev 127 Rhea 1 March 2010 (c/a ~ 900 km) no UVIS primes Rev 129 Dione 6 April 2010 (c/a ~ 1000 km) One UVIS prime observation Close Enceladus flybys on revs 120, 121, 130, 131 Rev 120 2009 November 2 - acquired Rev 121 2009 November 21 - no close-in prime observations Rev 130 2010 April 28 - simplified to RSS gravity only Rev 131 2010 May 18 Rev 120 has high resolution UVIS observation of plume with Saturn in the background, acquired Solar occ on Rev 131 Continuing to collect icy satellite observations: ICYLONs, ICYMAPs, ICYECLs, ICYATMs, ICYOCCs…

Rev 129 Dione ICYMAP

XM Enceladus Flybys March 12, 2008

Rev 120 Enceladus’ Plume against Saturn

Rev 131, Latest Trajectory We have the opportunity to observe an occultation of the sun on Rev 131 New trajectory brings the sun much closer to Enceladus’ limb New results are in the EUV, which gives us access to a different wavelength range than the FUV The big scientific payoff is the chance to definitively detect / measure nitrogen in the plume - important for models of chemistry-driven dynamics in the interior

XXM Status Requested PIEs for all occultations by: Dione and Tethys Look for volatiles being released, supplying E ring Rhea Look for rings or other evidence of volatile release

SOST Occultation PIEs 16 occultations requested total SOST accepted all of these as PIEs now going through integration process with other TWTs have gotten 4 of 5 requests to-date Lost Rhea ring occ on Rev 135 due to trajectory changes This will remain a hazard for all of XXM Big question raised at our last UVIS team meeting was whether we were over-subscribing our HSP life Josh analyzed this collection of occultations and calculates 3 x 108 counts, well within the budget of 1.5 x 109 counts allocated for icy satellite occultations at last team meeting

XXM Status (cont.) Enceladus flyby allocations Requested assignment of Enceladus flyby on 19 October 2011 for dual stellar occultation No contest Starting to work on Rev 136 Enceladus

Solstice Mission Enceladus Flybys

Backup Slides

XXM SM7a Tweak Opportunity for dual stellar occ by Enceladus’ plume tweaked in, 19 October 2011, epsilon Orionis (blue) and zeta Orionis (white)