Galileo Mission Status - October 2, 1997
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
This week, NASA's Galileo spacecraft continues to return data from its earlier encounter with Jupiter's moon Callisto, including observations of Jupiter's north and south pole auroral regions. The observations were made by the near-infrared mapping spectrometer and photopolarimeter-radiometer. Those two instruments also return regional maps of the area slightly north of Jupiter's equator, where hot spots exist similar to the one encountered by Galileo's atmospheric probe in December 1995.
Playback also includes observations of Io's volcanic activity, including the regions of Loki, Pele and Kanehekili, and single observations of the moons Europa and Thebe. The Io observations help characterize large, relatively cool, high power spots, providing new data on Io's thermal inertia and inner structure.
This week's playback schedule has two interruptions. The first one occurred on Monday, Sept. 29, when Jupiter's position caused the large planet to block Galileo's view of Earth for 17 hours. Scientists made the most of the interruption by monitoring changes in the spacecraft's radio signal as it passed through the Jovian atmosphere. This type of experiment enables scientists to learn more about the density of electrons in Jupiter's ionosphere, which is the upper atmospheric layer.
On Sunday, Oct. 5, Galileo will spend about 19 hours in darkness as Jupiter blocks sunlight from the spacecraft. The craft will turn to allow the solid state imaging camera and ultraviolet spectrometera to observe Jupiter, Io and Europa. The instruments will look for lightning and auroras and observe JupiterÕs rings with the Sun illuminating them from behind. The spacecraft will then turn once again to aim its antenna toward Earth.
The Galileo team has discovered the apparent failure of either a low-frequency search coil or a circuit in the signal path on the plasma wave subsystem (PWS). This failure has increased the noise in the sensor, masking any signals still present. The search coil sensor distinguishes electrostatic waves from electromagnetic waves, but both types of waves can still be detected with the electric antenna. In addition, because a good deal of search coil data are already available, scientists know which types of waves are found in most of the regions they're interested in studying. Nonetheless, this failure will mean a loss of 10 to 20 percent of the PWS science objectives for the duration of the mission.
Return to Project Galileo Homepage