This Week on Galileo - March 16-22, 1998
Galileo continues processing and transmitting to Earth pictures and science information obtained during the spacecraft's last complete science encounter with Jupiter's moon Europa in December 1997. The spacecraft flew past Europa in early February 1998, but the flyby was followed by a 2-1/2 week period of limited communications when the sun passed between Earth and Galileo. Therefore, during the flyby, the spacecraft only collected radio science information which does not require on board storage and subsequent processing and transmission. Galileo's next encounter with Europa is scheduled to occur on Sunday, March 29, and will include more typical gathering and storage of information by most of Galileo's instruments.
This week's processing schedule contains observations from Galileo's period of reprocessing and retransmission of data stored on the spacecraft's onboard tape recorder. This retransmission allows scientists to fill gaps caused by transmission problems, add additional data to existing data sets, or replay particularly interesting observations under different processing parameters. This week's transmissions include a picture obtained by the imaging camera of a region of mottled or blotchy terrain on Europa. The resolution of this picture has allowed identification of objects as small as a house in size.
Also returned this week is more information from a region of Europa containing wedge shaped surface features. These wedges show that Europa's surface has cracked and pulled apart, and provides evidence of the possible existence of soft ice or maybe even a liquid ocean under Europa's surface. Two observations of this region are transmitted to Earth this week, one obtained by the imaging camera and the other by the near infrared spectrometer. Finally, throughout the week, information is returned from the fields and particles instruments observations of the interaction of Europa with the magnetic and electric fields surrounding Jupiter.
Preliminary results from the test of the spacecraft's attitude control system that was performed last week are in. Unfortunately, these results indicate that the system's gyroscope performance has continued to degrade. The test was designed to determine if the performance was affected by the intense radiation exposure suffered during the spacecraft's flythrough of the Jupiter system in early February. Further analysis is being performed to characterize the extent of the degradation. Once understood, flight team members are confident that the anomalous behavior of the gyroscope can be anticipated and protective measures can be put in place to protect the spacecraft and scientific plans.