Today on Galileo - April 2, 1997
The fourth encounter day of this seventh orbit features a distant flyby of Callisto. At a range of over 637,000 kilometers, the flyby is noted by global observations performed by the SSI (Solid State Imaging camera) and the NIMS (Near Infrared Mapping Spectrometer) instruments. The primary purpose of these observations is to fill gaps in data obtained during the Voyager missions. The goal of such observations is to create a complete global map of each of the Galilean satellites.
The first Jupiter observations of the encounter are performed today. Jupiter aurora are observed in a coordinated effort between the UVS (Ultraviolet Spectromter), NIMS and SSI instruments. Jupiter fixed time local, darkside, and fixed longitude maps are also performed. These observations should sound familiar because they are repeated during each encounter. They look at Jupiter's atmosphere in unique ways, attempting to understand the distribution and dynamics of energy and hydrogen on a global scale.
The first observations of a small red spot, the selected feature of Jupiter's atmosphere for this orbit, are also performed today. Originally selected for this orbit were features know as Brown Barges. Brown Barges were visually clear regions seen during the Voyager flybys and were of significant scientific interest. Unfortunately, Hubble Space Telescope images appear to show that they have disappeared. The selected small red spot is, however, just as interesting: It is about 40 degrees north of the equator and has been seen in Jupiter's atmosphere for a very long time. Remember that the observations of selected features are coordinated amongst all of Galileo's remote sensing instruments in order to obtain a complete characterization.
Completing the observation plans for today are observations of Europa while eclipsed from the Sun by Jupiter, and the first observations for monitoring Io's volcanic activity. During the day, the flight team will transmit the second set of commands for this encounter. This set will be active from tomorrow until the end of the encounter on Sunday.