The Galileo Imaging Team plan for observing the satellites of Jupiter

Abstract

The Galileo spacecraft carries a 1500‐nm focal length camera with a 800 × 800 CCD detector that will provide images with a spatial resolution of 10 μrad/pixel. The spacecraft will fly by Io at the time of Jupiter Orbit Insertion (JOI) and, subsequently, while in Jupiter's orbit, will have a total of 10 close passes by Europa, Ganymede, and Callisto. These close passes, together with more distant encounters, will be used by the imaging experiment primarily to obtain high‐resolution coverage of selected targets, to fill gaps left in the Voyager coverage, to extend global color coverage of each satellite, and to follow changes in the volcanic activity of Io. The roughly 390 Mbit allocated for imaging during the tour will be distributed among several hundred frames compressed by factors that range from 1 to possibly as high as 50. After obtaining high‐resolution samples during the initial Io encounter at JOI, roughly 10% of imaging resources are devoted to near‐terminator mapping of Io's topography at 2‐ to 10‐km resolution, monitoring color and albedo changes of the Ionian surface, and monitoring plume activity. Observations of Europa range in resolution from several kilometers per pixel to 10 m/pixel. The objectives of Europa are (1) to determine the nature, origin, and age of the tectonic features, (2) to determine the nature, rates, and sequence of resurfacing events, (3) to assess the satellite's cratering history, and (4) to map variations in spectral and photometric properties. Europa was poorly imaged by Voyager, so the plan includes a mix of high‐ and low‐resolution sequences to provide context. The imaging objectives at Ganymede are (1) to characterize any volcanism, (2) to determine the nature and timing of any tectonic activity, (3) to determine the history of formation and degradation of impact craters, and (4) to determine the nature of the surface materials. Because Ganymede was well imaged by Voyager, most of the resources at Ganymede are devoted to high‐resolution observations. The Callisto observations will be directed mostly toward (1) filling Voyager gaps, (2) acquiring high‐resolution samples of typical cratered terrain and components of the Valhalla and Asgaard basins, (3) acquiring global color, and (4) determining the photometric properties of the surface. A small number of frames will be used to better characterize the small inner satellites of Jupiter, Thebe, Amalthea, Metis, and Adrastea.

Eruption of lava flows on Europa: Theory and application to Thrace Macula

“…The stratigraphically young age of Thrace Macula lends support to this hypothesis, although the age of Thrace Macula relative to the youngest features on Europa formed by plate-like motions is currently uncertain. The higher resolution images planned for the Galileo mission [Carr et al, 1995] will help to test these hypotheses.…”

Active Volcanism on Io as Seen by Galileo SSI

“…one of the goals of the Gallileo Mission (Carr et al 1995). The Voyager data and the various Earth-based observa-While the Near Infrared Mapping Spectrometer (NIMS) is tions provided only tantalizing clues to some of the most better designed for determining temperatures and material fundamental questions about volcanism on Io.…”

Geology and mapping of dark terrain on Ganymede and implications for grooved terrain formation

“…[Belton et al, 1996], at unparalleled resolutions up to an order of magnitude higher than those returned by Voyager. The primary imaging goals for Galileo were to provide higher spatial resolution and to extend Voyager coverage [Cart et al, 1995]. Imaging goals specific to Ganymede's dark terrain •Now at Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland.…”