This Week on Galileo
December 10-16, 2001
Galileo Heads Back Toward Jupiter for the Next Io Flyby
The Galileo spacecraft is back on its way in towards Jupiter for the 33rd
time (34 if you include our initial approach), having passed the milestone
of spending a full 6 years in orbit! Seems like only yesterday ...
On Wednesday, the Near Infrared Mapping Spectrometer (NIMS) instrument
executes a calibration activity. A special Radiometric Calibration Target
plate mounted on the spacecraft is heated to a fixed and known temperature,
and as this temperature-sensitive instrument views the plate the signal
levels can be compared with previous calibrations to see how the
sensitivity of the instrument may have changed over time. On Thursday, the
monthly maintenance activity is performed for the on-board tape recorder.
For the rest of the week, playback from the October 15 flyby of Io
continues, returning data from the Solid State Imaging camera (SSI), NIMS,
and the Fields and Particles instruments.
Pictures expected from SSI this week include a several-hour study of the
evolution of the clouds around a hot spot in Jupiter's atmosphere. Six
years ago, in December 1995, Galileo dropped an instrumented probe into the
atmosphere of the giant planet, providing scientists with our first direct
measurements of this environment. That probe happened to enter Jupiter's
atmosphere in just such a hot spot. Regular measurements of these features
during the Galileo orbiter's subsequent tour have greatly added to our
understanding of their nature.
SSI will also be playing back pictures of the edge of the Gossamer Ring of
Jupiter. This ring is an extremely diffuse collection of particles that
circles the planet outside of the main ring system, and extends out to
153,000 kilometers (95,300 miles) above Jupiter's cloud tops, which is
beyond the orbit of the tiny moon Amalthea.
NIMS will be returning a global observation of the temperatures of
Jupiter's atmosphere. This observation will also help to determine cloud
heights, chemical compositions, and particle sizes in the clouds.
Fields and Particles instrument data were collected as part of a survey of
continuous data sampling during the encounter period. When ground
communications antennas are not scheduled to track Galileo, allowing return
of the data in real time, the instrument measurements are stored in
on-board computer memory, and periodically that memory is copied onto the
tape for later playback. Now is the time for that playback.
In addition, the steady collection of real-time data by the Magnetometer,
the Dust Detector, and the Extreme Ultraviolet Spectrometer continues
throughout the week.