Galileo Status Report - September 26, 1996

PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. 
TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

GALILEO MISSION STATUS

September 26, 1996

NASA's Galileo spacecraft is operating normally and returning data somewhat ahead of schedule from its last major event -- a flyby of Jupiter's moon Ganymede. No repeat problems have occurred with Galileo's radio receiver since it had a problem two weeks ago when it failed on two occasions to lock onto radio signals sent from Earth. Jupiter's radiation remains a possible cause of the problem. New, wider uplink frequency sweeps -- much like tuning in a radio -- easily overcame the problem, and moreover, the receiver itself seems to be back to normal, project officials said. A fully redundant radio receiver is onboard the spacecraft in case the primary receiver ever experienced serious problems that could not be solved.

Radiation is also the likely cause of earlier problems with the near-infrared mapping spectrometer on the spacecraft. In early September's Ganymede flyby, the spacecraft team successfully used a new strategy to deal with radiation-induced problems with the instrument during Galileo's intense exposure to Jovian radiation. The strategy was developed after the instrument was disabled during the first Ganymede encounter and involves periodically reloading the instrument's operating software from a copy stored in Galileo's main computer. As anticipated, the instrument's operation was disrupted about five hours prior to Jupiter closest approach, several hours after the Ganymede encounter. The next automatic reload of software, done approximately at Jupiter closest approach, restored the instrument's operation and provided for successful data-taking during the remainder of the encounter sequence.

The tape playback from the last Ganymede flyby is proceeding somewhat ahead of schedule with about a third of the recorded data selected for playback returned since September 10th. Playback of the data from the Ganymede encounter will continue through the end of the current orbit on November 1. The data are being played back to Earth in the order they were recorded onboard during the one-week-long encounter period. This week, the data being returned are from the time period leading up to closest approach to Ganymede. Plans are for return of data from the imaging camera's close-up observations of Ganymede, focusing on areas of significant geologic interest such as craters, grooved lanes, and regions containing intersecting dark and light terrains. In addition to the return of the recorded data, nearly continuous real-time magnetospheric survey data from the fields and particles instruments are being sent to Earth.

High-resolution recorded data from the magnetospheric instruments taken when Galileo was closest to Ganymede should also be returned this week. The data include measurements of the interaction of Jupiter's magnetic field with Ganymede. The new data will help confirm or deny the theory based on data from the first Ganymede flyby that the big moon has its own magnetic field, a totally unexpected characteristic.

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