From: IN%"KTOBISKA@gllsvc.jpl.nasa.gov" 16-JAN-1997 20:46:40.83 To: IN%"MARIE.L.SLONSKI@JPL.NASA.GOV" CC: IN%"jajello@jpluvs.jpl.nasa.gov", IN%"simmons@pisces.colorado.edu", IN%"pryor@pisces.colorado.edu", IN%"stewart@pisces.colorado.edu", IN%"hord@pisces.colorado.edu", IN%"barth@pisces.colorado.edu", IN%"hendrix@pisces.colorado.edu" Subj: E6 UVS/EUV science summary UVS/EUV E6 SCIENCE SUMMARY UVS AWG: The top priority UVS Jupiter atmospheric observation during this orbit is a realtime far- and mid-ultraviolet (FUV/MUV: 115-320 nm) moderate solar phase angle (48 deg) white oval feature track observation (FTKR2EX). Analysis of the data will result in a unique data set of stratospheric aerosol scattering properties at a moderate solar phase angle and three emission angles. These data follow SSI images. An additional white oval feature track observation (1 emission angle at 64 deg solar phase angle (FTKR1EX) is performed also in conjunction with SSI. In order to obtain hydrogen distribution maps without the influence of direct solar radiation, independent UVS atmospheric observations will provide a realtime darkside global mapping of equatorial H Lyman-alpha using a fixed local time map (FIXTMD) and a darkside map (DRKMAP). Combined with similar measurements in previous orbits, this orbit's mapping nearly completes the first full global map of H Lyman-alpha distribution on the Jovian darkside at all system III longitudes. Global H distribution maps help determine upper atmosphere energy transfer and dynamics processes. Realtime southern auroral full spectral FUV observations will provide new longitudinal coverage on both the dayside and nightside (AURMAP). Analysis of the ratios between different spectral lines (color ratios) in these data will yield energies of the electrons pre- cipitating into the auroral zones. A central meridian brightside map (BRTMAP) using FUV spectral coverage of the equatorial region provides dayglow at 1260-1333 and 1447-1521 A. One ridealong observation with SSI Io Pele monitoring will measure MUV/FUV irradiances coincident with imaged volcanic activity (PLUMON24). Enhancements are expected in Io's SO2 and S emissions. UVS MWG: The highest priority UVS magnetospheric observations during E6 will be real- time encounter measurements of the Io torus and Jupiter aurora at approximately 90 degree cone angle in conjunction with the EUV instrument. Io torus midnight ansa maps (E6MANS01-03) will consist of spectra centered on ionized S and O emission lines using the UVS FUV and MUV wavelengths simultaneously with the EUV. Ratios of emission line strengths will determine electron temperatures. E6MANS04 will map the inner, colder, part of the Io torus at FUV wavelengths that also cover hydrogen Lyman alpha emission lines; the last 4 hours of this observation are designed to cross-calibrate the EUV with the UVS since Lyman alpha is observed by both instruments. Jupiter dark-side aurora measurements in this orbit (E6AURA01-03) focus on northern hemisphere hydrogen emissions at FUV and MUV wavelengths. Brief dark-side equatorial electroglow and southern aurora observations are also made. Integrated intensities will help to char- acterize the global energy output and the latitudinal and time variation of energetic particle input into the atmosphere. Inside the EUV 25 Rj radiation limit, the UVS will map the Io torus noon ansa at FUV and MUV wavelengths cor- responding to ionized S and O emissions. During E6 cruise, the UVS instrument will make its first measurements of neutral O and S emissions in the anti-solar direction of the Jovian magneto- sphere. These magnetonebula observations (MAGNEB01-05) will be 2 to 5 days in duration, with UVS readouts occurring every 24 hours. Finally, at the end of E6C, UVS is performing a first-time search for neutral H and O emissions in the orbits of Ganymede and Callisto. 18-hour observations centered on the ansa of each orbit (GTORUS and CTORUS) allow for the possible detection of a neutral torus of material associated with the surfaces and atmospheres of the two Gali- lean satellites. In GTORUS, the UVS will look at 70 degree cone angle through the spacecraft booms, demonstrating whether such measurements are feasible. UVS SWG: Ride-alongs with NIMS continue in E6 with E6ENTERINC01 (Terra Incognita), and E6SUCOMP01 and 02 (suface composition). The two surface composition observations will be recorded, while 4 separate RIMS of data varying in latitude will be returned in real-time from the Terra Incognita observation. The UVS SWG E6 orbit includes a set of Io eclipse full-spectral FUV/MUV observations. E6IUIECLPS03 & 04 are observations of Io just before and just after it exits eclipse (egress). Analysis of the eclipse data sets will be used with similar observations from previous and later orbits to provide the morphology of Io's atmospheres in the presence and absence of direct sunlight. In addition to the UVS FUV/MUV eclipse observations, the E6 orbit includes a full-spectral UVS N-channel (2818A - 4319A) observation of Io while it is in eclipse. This will be the first full-spectral N-channel data returned of Io during the tour. Similar observations of each of the Galilean satellites are planned in later orbits. An Io Neutral Cloud observation is also included in the E6 orbit. It consists of staring at 7 targets for collecting 12 RIMS of Lyman alpha (1215A) data at each. The targets are at varying distances from Io in the plane of its orbit. The data returned will be used with similar observations from previous and later orbits to determine the composition and time variation of the Io Neutral Cloud and to assist in the modelling of the Io plasma torus and Io's atmosphere.