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Session 70 - Planetary Systems Near & Far.
Display session, Friday, January 09
Exhibit Hall,
The Space Telescope Imaging Spectrograph (STIS) obtained quasi-monochromatic images of far-UV emissions from Io's atmosphere and surrounding torus gas on September 26, 1997, when the satellite was near western elongation. The observations were acquired using the 52''\times2'' STIS aperture centered on Io's 1.1'' diameter disk and aligned 43^\circ to the east of Jovian north. With the field of view of the detectors limiting the useful slit length to 25'', the G140M and G230M medium-dispersion STIS gratings produced isolated 25''\times2'' images for different spectral lines. For sufficiently narrow lines the images show the spatial distribution of emissions in the dispersion direction as well as along the slit. High quality images of the OI]\,1355.6ÅÅ\ and SI]\,1900.3ÅÅ\ doublets were obtained along with a fainter image of the SI\,1388.7Å\ multiplet. Preliminary analysis shows a thin layer of emission outlining Io's limb with a localized brightening near Io's equatorial limbs. This airglow pattern is qualitatively consistent with recent visible-band images obtained by the Galileo spacecraft's Solid State Imager (Belton et al., Science 274, 5286 (1996)) and OI\,6300.3Å\ emission images by the Wide Field and Planetary Camera 2 (Trauger et al 1997).
The author(s) of this abstract have provided an email address for comments about the abstract: hwm@pha.jhu.edu
