This Week on Galileo
May 17-23, 1999
Galileo spends this week playing back pictures and other scientific data acquired when the spacecraft passed by Jupiter and its moon Callisto earlier this month. The information is stored on the spacecraft's onboard tape recorder. During playback, it is read into the spacecraft computer, processed, packaged, and transmitted to Earth. Playback is interrupted once this week, on Friday, to perform a small turn and keep the spacecraft's antenna pointed toward Earth.
This week's playback schedule only contains two observations. The first consists of Photopolarimeter Radiometer measurements that will help scientists detect small variations in temperature within a given band of Jupiter's clouds. The second observation contains data from a two hour observation performed by the Fields and Particles instruments. The observation contains measurements of the plasma and magnetic and electric fields as Galileo passed through the Io torus. The torus is a region of intense plasma and radiation activity, in which there are strong magnetic and electric fields. Constantly replenished by the volcanic activity on Io, it is a key part of the Jovian magnetosphere. Data from this region provide important information on the dynamics of Jupiter's magnetosphere.
Back here on Earth, Galileo flight team members are celebrating after having successfully updated flight protection software in the spacecraft's computer. The software upgrade was designed to allow the spacecraft to recover autonomously and continue executing commands in the face of an anomaly situation known as an erroneous power reset signal. The anomaly may be caused by the accumulation of debris in the electrical connections between Galileo's spinning and non-spinning sides. The power reset signal occurs when enough debris have accumulated to cause an electrical short. Two of these events were seen during Galileo's encounter activities earlier this month. The onboard software performed as designed and the encounter sequence continued to execute as expected. Prior to the software upgrade, the main computer would have shut down all non-essential functions until the flight team could restore normal operations.
An unrelated anomaly occurred during the encounter. Pointing control for the instrument platform was switched from its primary gyro-based mode to a backup star-based mode. The impact of the anomaly is to degrade the observations from the Near-Infrared Mapping Spectrometer, and the loss of the individual observations in process during the switch to the backup mode.
For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page.
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