Another uneventful week on the engineering front leaves the Galileo
spacecraft time to focus its attentions on playback of the recorded data
from the October 15 flyby of Io. From the Photopolarimeter Radiometer
instrument (PPR) we expect to see two observations of Io, the main focus of
this orbit. First up is data from thermal maps of the dark side of Io taken
while the spacecraft was still six hours away from its closest approach.
This is followed by a more detailed study of the temperatures of the
Colchis caldera taken while that feature was in the dark. These dark-side
measurements allow scientists to determine the intrinsic temperatures of
the features, uncomplicated by any warming from the Sun’s rays.

The Solid State Imaging camera will provide us with our highest resolution
view of the massive volcano Loki, which was taken while that feature was
near the terminator, or day-night boundary, of Io. This view stretches the
shadows, and allows scientists to gauge the relative heights of the
features they see.

Again, the bulk of the week is dedicated to the return of a
two-and-a-half-hour-long recording by the suite of instruments that measure
the electromagnetic fields and energetic particles that encircle Jupiter.
These instruments are the Energetic Particle Detector, the Heavy Ion
Counter, the Magnetometer, the Plasma Subsystem, and the Plasma Wave
Subsystem. While last week’s recording was made of the turbulent transition
from the background magnetosphere into the Io Torus, this week’s focus is
on the relatively more quiescent depth of the Torus itself. The torus is a
doughnut-shaped area of increased radiation and particle density that
nearly coincides with the orbit of Io.

The Magnetometer and Dust Detector instruments continue their measurements
of the immediate environment of the spacecraft, and the Extreme Ultraviolet
Spectrometer instrument also continues an 11-week-long study of the solar
variation in the interplanetary hydrogen and helium abundances.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page at one of the following URL’s: