This Week On Galileo
March 8-14, 1999
Galileo spends this week transmitting science data stored on the spacecraft's onboard tape recorder. This week's data includes measurements made by the near-infrared mapping spectrometer, photopolarimeter radiometer, field and particles instruments, and solid-state imaging subsystem (or spacecraft camera).
Data playback is interrupted on Sunday when the spacecraft performs a small turn to keep its antenna pointed toward Earth.
As with past weeks' playbacks, the fields and particles instruments continue to return parts of a 50 minute long observation recorded during closest approach to Europa. The observation is designed to measure the plasma, magnetic field, and dust environment in the vicinity of Europa and to add to scientists' understanding of the interaction of Europa with Jupiter's magnetosphere.
The near-infrared mapping spectrometer returns the final portion of an observation designed to search for hexagonal ice crystal structure on Europa's surface. This crystal structure can be detected by its absorption of specific wavelengths of infrared radiation. Hexagonal ice crystals are the expected form of ice on Europa's surface, in the absence of geologic activity (cryovolcanism, plumes, etc). If hexagonal ice is not detected, or if different forms of ice are detected, these observations will provide scientists with evidence pointing toward a more interesting geologic story for Europa.
The photopolarimeter radiometer returns a polarimetry observation of Ganymede, the largest of the Galilean satellites. These polarimetric measurements will provide information about the nature of the Ganymede's surface material in regard to texture and composition.
Late in the week, the spacecraft begins a second pass through the data stored on the tape recorder. This second opportunity to read data from the tape is repeated in each of Galileo's orbits. It allows data lost in transmission to Earth to be replayed, or for different parameters to be used in onboard data processing, or to simply return additional new data. During this week, the spacecraft camera returns three observations of Europa. The first captures the Tegid crater region, the second, a region of mottled terrain, and the third, information on the structure of Europa's northern plains.
For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page:
http://www.jpl.nasa.gov/galileo
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