Contact: Jane Platt

January 6, 1999

Galileo continues to transmit magnetosphere data

The Galileo spacecraft begins the new year by processing and sending to Earth more information gathered in December by its instruments that study magnetic fields and charged particles.

The instruments studied a previously unexplored region of Jupiter's magnetosphere as Galileo flew through the huge planet's plasma sheet. The plasma sheet, which lies along Jupiter's magnetic equator, is an area that exhibits a high concentration of plasma, or ionized gases. This allows relatively strong electrical currents to flow, and creates dynamic interactions between the plasma and Jupiter's magnetic field. The plasmas originate on Jupiter's volcanic moon Io, are transported outward by the magnetic field, and ultimately flow outward with the solar wind. These new data will help scientists understand the plasma's final fate.

A standard propulsion system maintenance was performed on Galileo last week, and a standard gyroscope performance test will be executed Friday, January 8. The spacecraft's next scheduled encounter will be on January 31, when Galileo performs its final flyby of Jupiter's moon Europa during the current extended mission. After that, the spacecraft will fly by Callisto four times, then will lower itself in preparation for two flybys of Io.

The Galileo spacecraft has spent the past three years orbiting Jupiter and its moons, including Europa, gathering a wealth of information and pictures. Its primary mission ended in December 1997, and the spacecraft is currently in the midst of a two-year extension, known as the Galileo Europa Mission.