From: IN%"KTOBISKA@gllsvc.jpl.nasa.gov" 25-AUG-1997 17:27:57.19 To: IN%"SIMMONS@pisces.colorado.edu" Subj: C10 UVS/EUV Science Overview C10 UVS/EUV Science Overview AWG The top priority UVS Jupiter atmospheric observation during C10 is a half- hour recorded far and near-ultraviolet (FUV 115-192 nm, and NUV 280-430 nm) high solar phase angle (180 deg in solar occultation) observation of the southern aurora (AURMAP02). With this observation using the N-channel, UVS will obtain the first near-UV spectra of the Jovian aurora from the darkside containing Balmer series hydrogen emission and providing information on energetics and absorbers in the polar regions. Other unique, high-priority observations include those of H limb brightening/darkening and H corona to be obtained in an equatorial Lyman-alpha scan (NEWSMP01), and of the variable Lyman-alpha southern aurora, including the Io fluxtube footprint, with high time and spatial resolution (AURVAR01). Along with these recorded observations are FUV northern polar haze observations for two rotations of the feature track campaign (FTKRzExy), taken immediately after SSI multi-color images. Analysis of these data will result in a unique data set of high-latitude stratospheric aerosol scattering properties for several emission angles. Global mapping of darkside equatorial H Lyman-alpha will continue as in previous orbits to obtain hydrogen distribution maps without the influence of direct sunlight (DRKMAP01 and 02). Northern and southern aurora will be mapped with H2 band color ratios to determine precipitating particle energies (AURMAP01). Hydrocarbon maps at four latitude bands (BRTMAP01 and 02) will be part of a study of long-term changes in stratospheric absorbers. MWG The highest priority UVS magnetospheric observations in C10 are real-time Io torus noon and midnight ansa measurements. A far-midnight ansa observation (10FANS01), is performed inbound to Jupiter C/A, observing the torus outside of the orbit of Europa in conjunction with EUV, when both are pointed at 90 deg cone angle. It is designed to obtain S and O ion emission line strengths at EUV as well as FUV and NUV wavelengths. Intensity ratios will determine electron temperatures, and integrated intensity characterizes the torus energy output for energy budget considerations. Although not simultaneous with EUV, two real-time FUV and NUV torus ansa observations are also a high priority during C10. 10NPRO01 (inbound at >90 deg cone angle) and 10MPRO01 (outbound at >90 deg) are profiles obtained while the UVS drifts over the noon and midnight ansa ribbons, respectively. A UVS FUV observation of the Jupiter southern aurora (10AURA01) also occurs on C10 inbound. Finally, a search (CTORUS01) for FUV neutral emissions from H and O in the vicinity of the Callisto orbit ansa, is made at > 90 deg cone angle. In C10 cruise, there are seven UVS magnetonebula observations (MAGNEBxx), two of which will be long-duration measurements of FUV oxygen emissions looking along the axis of the magnetonebula in the spacecraft antisun direction, and five of which will be 3-hour observations designed to monitor the performance of the UVS grating. A UVS-EUV cross-calilbration at Lyman-alpha wavelengths will also occur inbound to E11 (11XCAL01). SWG In C10, UVS will continue to observe Europa, Ganymede and Io at various phase angles and longitudes. Along with complementary measurements of satellite albedos and emission obtained in other orbits, these observations contribute to the UV phase function curves for the Galilean satellites. Europa is observed at the following longitudes (and phase angles): 104 deg (93 deg), 131 deg (92 deg), 165 deg (95 deg), 287 deg (103 deg), 294 deg (96 deg), 300 deg (82 deg), and 303 deg (64 deg). IUPHAS55 observes Io at 45 deg longitude (55 deg), and GUPHAS77 observes Ganymede at 30 deg longitude (77 deg). Continuing its eclipse campaign, UVS observes Europa and Io in EUEURDRK and IUIODARK. Analysis of eclipse data sets will be used with similar observations in other orbits to provide the morphology of the Europa and Io atmospheres in the presence and absence of direct sunlight. Europa is viewed twice near the center of the eclipse umbra, looking for OH- with the N-channel (306 nm) and for neutral H and O with the G-channel (121.6 and 130.4 nm). Oxygen is viewed on Io near the center of the eclipse umbra with the G-channel (130.4 and 147.9 nm). A unique EUV satellite observation (CVSPNSCN) before Callisto closest approach will search for extreme UV (60-130 nm) absorptions and emissions. UVS will observe Callisto three times at high resolution. CUBRTLMB01 and CUBRTLMB02 examine the Callisto limb in sunlight to determine the morphology of the Callisto atmosphere. CUNOLAT observes Callisto at 60 deg north latitude. In addition, CUNTRLCL observes the Callisto neutral cloud (of atomic H and O) with the G-channel (121.6 and 130.4 nm). These measurements will be used to determine the morphology of the Callisto extended atmosphere and will complement the CUBRTLMB observations. Finally, UVS plans ridealong observations performed in conjunction with NIMS in order to supplement and complement NIMS satellite surface property measurements. CUGLOBAL01, CUGLOBAL02, CUASGARD (Asgard crater), CUPALIMP (palimpsest), CUSMTHPL (smooth pole), CUVALHAL (Valhalla crater), and CUCATENA (Catena crater) are high-resolution Callisto observations at 160 to 320 nm. UVS will also perform NIMS ridealong measurements of Io (IUCHEMIS03, IUHRSPEC01, and IUVOLCAN03) in the same wavelength region.