Far ultraviolet Observations of Jovian low latitude regions with HST/STIS

Far ultraviolet observations of the Jovian disk were made at low and mid-latitudes with FUV MAMA/STIS on board HST in January 1999 both in the imaging and spectroscopic modes. An image was obtained with the Lyalpha filter in the hydrogen bulge region for comparison with the expected Lyman-alpha brightness distribution for Ly-alpha resonance scattering. Other images in the 1200-1700 { Angstroms} region show band structures parallel to the equator with fading contrast toward the center and the limb. Spectroscopic observations were made in the 1200-1700 { Angstroms} (G140L) and 1245-1298 { Angstroms} (G140M) regions at ~ 5 { Angstroms} resolution to map the H_2 airglow and the UV absorbents along the STIS slit. Preliminary results indicate that a C_2H_2 absorption signature is clearly observed in the solar ultraviolet reflected spectrum. The ethylene absorption may be mapped to derive variations of the acetylene abundance. The H_2 FUV airglow shows both the fluorescence and the electron impact components. Its spatial variation is described and compared with the expected airglow distribution. We acknowledge funding by NASA and by the PRODEX program of the European space agency.