This Week on Galileo - July 14-20, 1997
Playback of data acquired during Galileo's previous encounter with Callisto continues this week on Galileo. The hiatus of fields and particles high-time-resolution observations of Jupiter's magnetosphere and radio science observations planned during the cruise period also continues this week. However, the fields and particles instruments do continue to collect continuous low-rate data in support of their second mini-tour of the orbital mission. The week starts out with a couple of spacecraft turns to support instrument calibrations. These are completed by Monday morning and the spacecraft antenna is again pointed at the Earth for continuation of data playback.
Observations of Jupiter's atmosphere continue to be the major theme for playback. A total of 16 of the 18 observations returned this week contain data on features of Jupiter's atmosphere. Observations by NIMS (Near Infrared Mapping Spectrometer) cover the Great Red Spot at solar phase angles of 75 and 95 degrees. (Remember that at a 0 degree solar phase angle, the sun is behind the spacecraft and illuminating the target completely. At 180 degrees solar phase angle, the sun is behind the target and the target is completely dark). The 75 degree phase angle observations include one with 15 different colors, and three highly focused on wavelengths of 5 and 3 microns. The 95 degree phase angle observations (2) only use 4 colors. NIMS also returns observations of the plume head region at a solar phase angle of 85 degrees. As with the 75 degree solar phase angle Great Red Spot observations, NIMS returns one observation with 15 different colors and three concentrated on wavelengths of 5 and 3 microns.
Why the interest in 5 and 3 micron regions of the spectrum? The regions detectable at 3 and 5 micron wavelengths believed to allow scientists to look at what is going on in the depths of Jupiter's atmosphere. These observations allow scientists to formulate theories on the circulation and dynamics of Jupiter's atmosphere.
NIMS also returns 4 out of a total of 7 observations designed to construct a cylindrical map of a strip of hot spots located at 9 degrees north latitude. The final Jupiter observation is returned by PPR (Photopolarimeter Radiometer) and is of the Great Red Spot at a solar phase angle of 95 degrees.
The fields and particles instruments return a 60 minute high-time resolution recording taken as the spacecraft punched through Jupiter's plasma sheet. The recording is very valuable as it was coordinated with remote sensing observations of aurora on Jupiter made by the UVS (Ultraviolet Spectrometer), EUV (Extreme Ultraviolet Spectrometer) and NIMS instruments. It is also the only high-time resolution data of a plasma sheet crossing taken near Jupiter's terminator (the terminator is the dividing line between night and day). These data will allow scientists to study the flow of particles from the magnetosphere into Jupiter's atmosphere and the effect these particles have on the creation of aurorae on Jupiter.
Completing the playback schedule for this week is a single observation of Io performed by NIMS. One of many, this observation will contribute to the monitoring for chemical changes on Io's surface.