XXM Status, Priorities, Plans, and Activities Icy Satellite Science C. J. Hansen, A. Hendrix January 2014

XXM Status Icy satellite observations executed since last team meeting Enceladus plume observations Low phase observations of Mimas, Enceladus, Tethys and Dione Iapetus gamma Ori occultation We have no PIEs in 2014

Satellite Flyby Hiatus

Proximal Mission Phase Priorities Two more potential Enceladus stellar occs in the future One is equatorial 22 June 2017 01:19 Rev 280 Mean anomaly = 116 The other requires a trajectory tweak – occ rayheight is currently 3000 km) 11 March 2016 11:57 Rev 233 Mean anomaly = 220 Approved The other main priority for UVIS are the Dione stellar occ opportunities MAG sees mass-loading in the magnetosphere at ~7 kg/sec (Enceladus supplies ~200 kg/sec) Dione plume won’t go as high or lose as much gas (escape velocity is higher because Dione is larger, gravity higher)

Locations to-date plus planned Circles are ~250 km radius; red is new data

Solstice Mission Enceladus Flybys All Enceladus flyby’s in XXM have executed except E21 E20 and E22 are relatively distant flybys on Rev 223 and Rev 228, resp., in 2015

Case 7a

Occultations in F Ring and Proximal Orbits 24 Dione occultation opportunities 12 Rhea occultation opportunities When will we start scheduling PIEs?

Backup

Reference Trajectory Schedule April 2013 Discuss Enceladus occultation with scientists May 2013 Gather initial feedback from science teams June 2013 Release of Enceladus occultation study for Summer PSG June/July 2013 Release of proximal orbits trade space October 2013 PSG decides on proximal orbit and approves Enceladus occultation trajectory January 2014 Preliminary release of reference trajectory March 2014 Final release of reference trajectory; covers remainder of tour

System Scans - Summary of Request 167-168 17 June 2012 OR 169-170 2 August 2012 256 hr 196-197 5 August 2013 256 hr 206-207 3 August 2014 256 hr 211-212 25 January 2015 resume 4 per year 64 hr cadence

Hello Helene! Helene is Dione’s leading co-orbital; one of 4 of Saturn’s moons in the Lagrangian L4 point Phoebe-size: 36 x 32 x 30 km Sub-Saturnian side 36x32x30 km (like Phoebe), imaged June 18 from 7000 km

XXM Planning 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 15 occs requested 8 in as occ PIEs 2 “in” SOST but in conflict 4 out 1 not scheduled yet Iapetus in apoapsis Rev 196 Now looking at occs in proximal orbit