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This Week on Galileo?
This Week on Galileo
March 19 - 25, 2001
DOY 2001/78-85

Galileo is Scheduled for Routine Maintenance of the On-Board Tape Recorder

This week's major scheduled activity is a routine maintenance of the on-board tape recorder, which occurs on Friday. On Thursday, a new set of commands will be loaded into the spacecraft computers. These commands will govern the activities of the spacecraft between March 24 (Saturday) and May 22.

This week's playback begins with the final set of observations taken by the Solid State Imaging camera (SSI) of the ring system of Jupiter. These pictures were taken on January 2, as Galileo was looking back at a receding Jupiter. From that vantage point, the Sun was behind the spacecraft, and the rings could be seen in the light that they reflected back towards the camera. When the Voyager cameras first observed the Jupiter ring system back in 1979, that spacecraft was in Jupiter's shadow, looking back in the direction of the Sun, and the rings were seen by the light that scattered in the forward direction by the tiny ring particles. By viewing the rings from these varying geometries, scientists learn about the size and other properties of the small grains that make up Jupiter's rings.

This week also sees the beginning of playback for another portion of the 14-week-long continuous magnetospheric survey conducted by Galileo as it passed through the depths of the system in December. The survey began in late Octover of 2000 and continued through early February of this year. The Fields and Particles instruments which participated in this observation were the Dust Detector, Energetic Particle Detector, Heavy Ion Counter, Magnetometer, Plasma Detector, and Plasma Wave instrument. The intent of the investigation was to provide continuous sampling as the spacecraft passed from the solar wind, through the outer reaches of the magnetosphere, into the inner portions near Jupiter, and then back out again. Since the ground communications antennas used to receive Galileo data must be shared among many space projects, the on-board tape recorder was used to store the data collected by the instruments approximately once per day, while the antennas were busy elsewhere. The data now being played back were recorded on the outbound leg of this orbit, beginning on January 1.

This survey was conducted in cooperation with the Cassini spacecraft, which was passing by Jupiter at the same time, on its way out to Saturn. This portion of the observation carried Galileo out through the magnetosheath, the bow shock, and into the solar wind, outside of the direct influence of Jupiter's powerful magnetic field. By studying this passage, scientists hope to learn more about how the planet's extensive and complex magnetospheric system changes with time. This type of study cannot be done from Earth, but must rely on the presence of instrumented spacecraft, such as Galileo and Cassini, which can immerse themselves in the environments that they measure.

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Last updated 10/01/01.

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