This Week on Galileo - May 26-June 1, 1997
Playback of data from Galileo's previous encounter with Ganymede and the Jupiter system continues through the week but is interrupted mid-week to perform regular maintenance and conditioning of the spacecraft's tape recorder. In addition, as the spacecraft approaches apojove, its furthest point from Jupiter for this orbit, navigators begin to prepare for the next orbit trim maneuver, scheduled to be sent to the spacecraft and executed next week.
Observations from the Io volcanic activity monitoring campaign continue to be transmitted to earth this week. NIMS (Near Infrared Mapping Spectrometer) returns a few more observations containing data on hot spots, thermal anomalies, hot outbursts and chemical changes on Io's surface. SSI (Solid State Imaging camera) returns another observation from its plume monitoring campaign. This particular observation is of the region known as Marduk.
On this week's playback schedule we begin to see observations taken during the spacecraft's flyby of Ganymede. Remote sensing observations focus on high- resolution sampling of a variety of surface features with different shapes (morphology) and different light reflection (albedo) characteristics. NIMS observations returned this week include craters with large central domes, dark rays, and dark halos. Other NIMS observations look at grooves and furrows, and dark and light region boundaries.
Similar SSI observations will provide data on the resurfacing and deformation of dark regions, the formation of light regions, and the relative ages of these regions (dark regions are believed to be older than lighter regions). A few other SSI observations provide information on the shape and characteristics of craters (including a multi-ringed crater), grooves and caldera like features. The features observed in this set of observations include the Osiris crater, Uruk Sulcus, Marius Regio, Tiamat Sulcus, Anshar Sulcus, Erech Sulcus and Mashu Sulcus. In addition, a PPR (Photopolarimeter Radiometer) observation of the south pole region of Ganymede is returned this week.
Taken during the 45 minutes centered at closest approach to Ganymede, the high-time-resolution recording of fields and particles data is also returned this week. Remember that the flyby geometry for this encounter was such that the spacecraft flew through the upstream region of the Ganymede wake (the wake is the region created in front of a satellite as the charged particles that co- rotate with the magnetosphere sweep past the satellites). These data are expected to provide additional information regarding the interaction between Ganymede and it magnetic field and Jupiter's magnetosphere.
The remainder of the playback schedule contains another couple of observations of the Jupiter south pole region, the selected feature of Jupiter's atmosphere for this past orbit. This observation was taken by NIMS and is one of 16 observations of this region. Also returned by NIMS is an observation of a secondary feature of Jupiter's atmosphere, a region at a temperate latitude (50 degrees South). PPR contributes to the Jupiter data by returning data from a strip of atmosphere running North-South. These strip observations are designed to provide context information for the selected feature observations. Finally, PPR returns three polarimetry observations, two of Ganymede and one of Europa. These observations are part of a campaign to obtain polarimetry samples over all solar phase angles and will provide information on surface texture and light scattering properties.