Today on Galileo - June 26, 1997
Today is the fifth day of the Callisto Orbit 9 encounter period. Galileo flies by Ganymede around 10:20 A.M PDT at a distance of about 82,400 km ( 51,200 miles). Toward the end of the day, the first set of encounter commands finish and the second set starts executing. This second set will control spacecraft activity through the end of the encounter period on Sunday.
Observations are varied in nature today. The non-targeted flyby of Ganymede provides the remote sensing instruments with the opportunity to take another look at the surface of Ganymede, continuing attempts to unravel its secrets. NIMS (Near Infrared Mapping Spectrometer) looks globally and regionally for information on surface minerals and how they are distributed. PPR (Photopolarimeter Radiometer) observations will provide data on the surface thermal properties of Ganymede. SSI (Solid State Imaging camera) takes two images. The first includes an unnamed sulcus (or shallow groove) that bridges the known regions of Perrine Regio and Galileo Regio. This observation also provides regional context for high-resolution images taken during the G1 (Ganymede 1) encounter. The second image is of a previously unobserved region -- a gap in both the Voyager spacecraft data and in the Galileo data to date.
The observations of the Gread Red Spot continue throughout the day. These observations will provide valuable data regarding the longest lasting storm known to humankind. These data will be compared with Great Red Spot data taken during the G1 encounter and will enable scientists to examine long-term variations in the Great Red Spot. The first observations of the second atmospheric feature selected for this orbit are also planned today. Known as plume heads, these features are believed to be formed by relatively narrow columns of rising air that tend to flatten out when they can go no higher in Jupiter's atmosphere. Observations of both features are performed by UVS (Ultraviolet Spectrometer), NIMS, SSI and PPR. Other observations of Jupiter's atmosphere performed today include auroras and a map at a fixed longitude (that is, mapping a strip of Jupiter that extends from the North to the South).
Completing today's observation schedule are observations of Io and Europa performed by UVS, NIMS and SSI. The first of 20 SSI observations of the four inner minor satellites (Metis, Adrastea, Amalthea and Thebe, listed in increasing distance from Jupiter) are also performed today.