This Week On Galileo
January 18-24, 1999
This week Galileo continues to process and transmit science observations stored on its on-board tape recorder. The data is being retrieved before it is overwritten by a new set of data, to be acquired during Galileo's next encounter.
Galileo's next encounter features a close flyby of Jupiter's icy moon Europa and is the last close flyby of Europa planned for the Galileo Europa Mission. Subsequent flybys will feature Callisto, and are executed primarily to change the spacecraft's orbit so it can get back to Io later this year.
Data playback is interrupted by three activities this week: a standard gyroscope performance test, standard maintenance on the propulsion system, and a small spacecraft turn that keeps Galileo's radio antenna pointed directly toward Earth.
The bulk of this week's playback time is consumed in returning parts of an observation performed by the fields and particles instruments in early December 1998. These instruments provide measurements of dust, magnetic, electric, and plasma field environments. During the observation the instruments gathered 5 hours of measurements of Jupiter's plasma sheet. The plasma sheet is a region of Jupiter's magnetosphere where the concentration of plasma (ionized gases) is such that relatively strong electrical currents exist, creating dynamic interaction between the plasma, outer regions of the magnetosphere and the solar wind.
The additional playback time is used to return data obtained during Galileo's September 1998 flyby of Europa. The data remained on the tape recorder after anomalies halted spacecraft operations during Galileo's November 1998 flyby of Europa. This situation provides the opportunity to return entirely new data, return data processed with different parameters, or fill in gaps in previously returned data. One observation is returned by the near-infrared mapping spectrometer and one by the spacecraft camera, or solid-state imaging system.