This Week on Galileo

September 20-26, 1999

Galileo Spends Week Performing Survey of Jupiter's Magnetosphere

Galileo spends this week performing a real time survey of the dusk side of Jupiter's magnetosphere (its plasma, dust, and electric and magnetic field environments) while also returning high resolution magnetosphere measurements recorded during last week's enounter. These measurements were all made by the Fields and Particles instruments. Processing and transmission to Earth of these data is interupted twice this week. On Monday the spacecraft performs a small flight path correction. On Sunday, the spacecraft performs standard maintenance on its propulsion systems.

The Fields and Particles instruments are comprised of the Dust Detector, Energetic Particles Detector, Heavy Ion Counter, Magnetometer, Plasma Detector, and Plasma Wave Instrument. The data acquired during the magnetosphere survey is not recorded on board, but rather it is returned to the Earth in near real time, sharing the transmission stream with recorded data. During the survey, the instruments take measurements of the plasma, dust, and electric and magnetic fields. Similar measurements have been taken in previous encounters, thus allowing scientists to study the long term variations within the magnetosphere. The survey also provides information describing the global context within which high resolution recordings are performed. This particular leg of the survey covers part of the duskward portion of the magnetosphere. The interaction of Jupiter's rotating magnetic field with the solar wind creates differences between the dawn side and the dusk side of the magnetosphere. By studying these differences, scientists will learn about how plasma particles created at Io are ultimately accelerated outward from Jupiter, escaping down the magnetotail in the direction opposite the Sun.

The high resolution recording of Jupiter's magnetosphere was also acquired by the Fields and Particles instruments. The recording was part of a series performed during each encounter of the Perijove Reduction Campaign (Galileo's previous four encounters). The Perijove Reduction Campaign, as its name suggests, reduced the spacecraft's perijove distance, or closest distance to Jupiter for a given orbit, from orbit to orbit. The data captured during these recordings will describe the inner magnetosphere and the Io torus (see Note 1) environment as a function of distance from Jupiter. These data will contribute toward the studies of the dynamic processes that occur within these regions.

Note 1. The Io 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 vital part of the Jovian magnetosphere.

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

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Last updated: September 20, 1999

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