June 19 - 25, 2000
Galileo Still Collecting Realtime Data 10-1/2 Years After Launch
The northern hemisphere's summer solstice finds the Galileo spacecraft still in orbit around Jupiter, approximately 10-1/2 years after having been launched from Earth in October 1989. This week's activity schedule for Galileo continues to hold a mix of realtime data gathering and data playback. These activities are interrupted twice this week to perform spacecraft maintenance. On Thursday, Galileo flushes out its propulsion lines, thus preventing debris accumulation. On Friday, the spacecraft performs a standard gyroscope performance test. Galileo's gyroscopes are used to control the spacecraft's orientation in space.
Monday is the last day of data collection by the Dust Detector instrument (DDS). For the last few weeks, DSS has been mapping the distribution and character of dust streams emanating from the Jupiter system. Recent data analyses from previous Galileo data sets have shown that these dust streams emanate from Io and that their ultimate source is volcanic activity on Io's surface. The Extreme Ultraviolet Spectrometer (EUV) continues observing the Io torus, which is a ring-shaped cloud of plasma characterized by intense radiation. The region is created and maintained by a combination of Jupiter's powerful magnetic field and, again, volcanic activity on Io. With these data, scientists will continue to study the shape and energy output of the torus, and compare these characteristics with those seen in data accumulated over the past 4-1/2 years, starting from Galileo's arrival at Jupiter in December 1995.
This week's data playback schedule returns observations taken by the Near-Infrared Mapping Spectrometer (NIMS) and the Photopolarimeter Radiometer (PPR). The observations were taken during the spacecraft's February 22, 2000 flyby of Io, the closest-ever approach to the volcanic moon with a flyby altitude of 198 kilometers (123 miles). This was 102 kilometers (63 miles) closer than Galileo's previous Io flyby in November 1999. Three observations are returned this week. All of these contain PPR measurements, and two also contain data from NIMS. They focus on different volcanic regions on Io, with the last observation focusing on the Prometheus volcanic vent in particular.