This Week on Galileo
February 26 - March 4, 2001
A Variety of Observations are Planned
to be Returned This Week!
Playback of the data stored on the tape from the December 28 flyby of
Ganymede continues. This week, quite a variety of observations are planned
to be returned, including several taken at or near the same times as
observations acquired by the Cassini spacecraft, which also passed by
Jupiter on its way out to Saturn.
The Photopolarimeter Radiometer instrument (PPR) returns data from some of
its observations of Ganymede, Io, Europa, and the atmosphere of Jupiter.
First, we expect to see a full temperature map of the day side of Ganymede,
taken one to two hours after the satellite left the shadow of Jupiter. This
continues an investigation of the composition and structure of surface
materials and how they heat up in sunlight. Playback of PPR data continues
with multiple observations of both Io and Europa. By viewing these
satellites as the angles between the Sun, their surfaces, and Galileo
change, scientists gain insight into the structure and composition of those
surfaces. In cooperation with the Cassini Composite Infrared Spectrometer
instrument, PPR also looked at Jupiter's North Equatorial Belt, between 3
and 20 degrees north latitude, and at the northwest region of the Great Red
Spot, a giant storm in Jupiter's atmosphere which is about three times the
size of Earth, and has persisted for at least 330 years! The Galileo
instrument can observe at longer wavelengths of light than the Cassini
counterpart, and because of the relative distances of the spacecraft from
Jupiter at the times of the flybys, can provide higher spatial resolution.
The Galileo Near Infrared Mapping Spectrometer (NIMS) will return a global
image of Ganymede obtained with the current full complement of NIMS
wavelengths. This will give information about the composition of different
areas of the satellite surface. Observations of Io help to monitor that
satellite's volcanic activity. In cooperation with the Cassini Visible and
Infrared Mapping Spectrometer instrument, NIMS observations were also made
of Callisto and Europa, though both at considerably greater distances than
the Ganymede observations. During this pass through the Jupiter system, the
closest Galileo came to Europa was nearly 800,000 kilometers (500,000
miles), and to Callisto 2,339,000 kilometers (1,450,000 miles). NIMS also
viewed the turbulent region of the atmosphere of Jupiter trailing the Great
Red Spot, investigated hot spots in the clouds, and looked for aurorae in
the south polar region of the giant planet.
The Galileo Solid State Imaging camera will return some global color images
of Io, in cooperation with the Cassini imaging experiment, helping to
maintain an inventory of the volcanic plumes of that active satellite, and
look for changes from previous orbits in the plumes and surface markings
due to ongoing volcanic activity.