The Jovian Ring As Seen By The Galileo NIMS At High Phase Angle

G. E. Danielson (Caltech), S. McMuldroch, R. W. Carlson (JPL), S. P. Ewald (Caltech), J. Hui (JPL)

We present data of the Jovian Ring system obtained by the Near Infrared Mapping Spectrometer (NIMS) on the Galileo Spacecraft. These data were acquired during the C3 orbit at an average phase angle of 178 degrees. The projected spatial resolution of the ring system closest to the spacecraft was approximately 1130 kilometers per NIMS sample. The spectral coverage was 0.9 to 5.2 microns, with an average resolution of 0.25 microns edited to 102 samples for data compression.

These moderate spatial resolution data do not show the fine structure evident in the higher resolution SSI images taken on the same orbit of the opposite ansa at similar phase angle. However, large-scale ring structure and a distinctive spectral signature are clearly present. Preliminary analysis of these data show a definite reddening from .9 to le 3 microns with a maximum S/N ratio of approximately 7. No absorption features are seen over this wavelength range and there is no evidence for thermal emission at longer wavelengths. The NIMS data show a brightening along the ring system toward Jupiter present at all wavelengths. Possible asymmetry in the light profile perpendicular to the ring plane may suggest the presence of the halo first seen by Voyager.