This Week on Galileo - January 19-25, 1998
The Galileo spacecraft has resumed transmitting pictures and science data to Earth at normal speed. Transmission of the data, which is stored on board the spacecraft, had been slowed down by two incidents of anomalous behavior by Galileo's attitude control system. The anomalies had caused the spacecraft's radio antenna to be aimed 10 degrees from Earth. However, the spacecraft successfully completed a turn that pointed its antenna within 3 degrees of Earth, which is a normal angle. The turn was performed early last week.
The cause of the anomalous behavior in the spacecraft's attitude control subsystem remains unknown. The leading candidate continues to be one of the spacecraft's two gyroscopes, but no definite evidence has been found as of today. The project has formed a team of hardware experts to continue analysis of the available engineering data.
Scheduled for this week is the execution of the mission's next orbit trim maneuver. This maneuver was orginally scheduled for last week, but was delayed due to the anomalous behavior of the attitude control subsystem. Remember that these maneuvers are performed to keep the spacecraft traveling around Jupiter along the desired orbital path. The series of commands that will control the execution of this orbit trim maneuver will be built with additional safeguards. If the behavior of the attitude control subsystem becomes anomalous, these safeguards will prevent a reoccurance of any activity that would lead to undesireable spacecraft pointing.
The science data processing and transmission schedule for this week focuses on two areas. Remaining on the schedule is the return of high time resolution fields and particles information of the interaction between Europa and Jupiter's magnetic and electric field environment. New to the schedule is a series of three observations taken by the spacecraft's Solid State imaging camera. These images show a region of Europa characterized by wedge shaped features which will provide information on how surface spreading or cracking may have occurred on Europa. The first will have an image resolution of 15 meters (49 feet) per picture element and, the second, 30 meters (98 feet) per picture element. Together these two observations are expected to allow the creation of a stereo image of this region. The third image is of slightly lower resolution and at 50 meters (164 feet) per picture element will provide regional context information for the previous two images. This region of Europa was also imaged during the Callisto-Orbit 3 encounter of Galileo's primary mission.