This Week on Galileo

August 23-29, 1999

Time Shortens for Galileo's Encounter with Io

The time between encounters has been getting shorter over the past few flybys for Galileo, as the mission approaches its encounters with Jupiter's fiery moon Io later this year. Evidence of this is that the spacecraft passes though apojove on Saturday of this week, only 16 days since it passed perijove. Apojove occurs when the spacecraft is furthest from Jupiter; perijove occurs when the spacecraft is at its closest approach to Jupiter. During the Europa Campaign there were typically at least 30 days between perijove and the following apojove.

This week's data return is dedicated exclusively to the return of a recording of the Io torus and Jupiter's magnetosphere. The data were collected by the Fields and Particles instruments and are stored on the spacecraft's onboard tape recorder. Data playback is interrupted twice this week. On Thursday, the spacecraft will execute a small flight path correction. Late Sunday night, the spacecraft performs a standard gyroscope performance test.

The Fields and Particles Instrument suite is comprised of the Dust Detector, Energetic Particles Detector, Heavy Ion Counter, Magnetometer, Plasma Detector, and Plasma Wave Instrument. Their recording is one in a series planned for each of the four encounters of the Perijove Reduction Campaign (Galileo's previous three encounters, and Galileo's next encounter). During these encounters, the spacecraft's perijove distance is being reduced from orbit to orbit to allow a future flyby of Io. These recordings provide valuable high resolution data describing Jupiter's inner magnetosphere and Io torus environment at varying distances from Jupiter. The Io torus is particularly interesting as it 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 vital part of the Jovian magnetosphere. The Fields and Particles instruments make measurements of the magnetic fields and particle interactions within these regions, including measurements of radio signals and electromagnetic waves. These measurements will contribute to the study of the dynamic processes within the torus in particular and the Jovian magnetosphere in general.

For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page.

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Last updated: August 23, 1999

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