Today on Galileo - December 18, 1997
Galileo resumed normal cruise activities last night when flight team members sent commands to the spacecraft to swap all attitude control functions back to the subsystem's primary set of electronics. The spacecraft had moved some functions to a backup set of electronics when the spacecraft's fault protection systems detected anomalous behavior indicating something was out of the ordinary late Monday night. The specific cause of the anomalous behavior is still under investigation. Leading theories place Jupiter's intense radiation environment at the top of the list.
Processing and transmission to Earth of science data stored on the spacecraft's tape recorder was initiated shortly after normal operating conditions were restored. First on the playback schedule is the Solid State Imaging (SSI) camera's observation of Ganymede's Gilgamesh crater region. Scientists hope to use the crater statistics of this region, believed to have been created at the end of a heavy bombardment period, to understand the rate at which impactors have been entering the Jupiter system. This impactor rate can then be compared to crater statistics on Europa to get a better idea of the age of Europa's surface.
As flight team members continue to closely monitor all spacecraft functions, plans are on track to perform an orbit trim maneuver on Saturday. The maneuver will be used to correct any errors in the spacecraft's path accumulated since the pre-encounter orbit trim maneuver performed on December 13.
The current cruise period will span the next fifteen weeks. Another close flyby of Europa will occur in mid-February, but is limited to a gravity experiment only because it occurs just prior to the spacecraft's next solar conjunction. During solar conjunction, the sun is close to the path traveled by radio signals as they go from the spacecraft to Earth and vice-versa. As radio signals pass close to the sun, they are affected by solar activity and become noisy or garbled and less data can be safely transmitted to Earth. Because of the reduction in the amount of information transmission, the project team decided to dedicate the available time to the continued return of information gathered during the Europa-12 encounter.
Our next update will be on Monday, 22 December, with a special three week, holiday edition of This Week on Galileo!