This Week on Galileo
September 17-23, 2001
Engineering Activities and Data Playback Are Galileo's Priority This Week
Two engineering activities join the playback data on Galileo's priority
list this week. On Tuesday morning, an orbit trim maneuver is performed.
This propulsive engine burn will pulse the thrusters briefly three times to
gently nudge the spacecraft towards its next encounter with Io next month.
This is the smallest maneuver that we have yet done in the mission, using
only 15 grams of propellant, but the amount of fuel we have remaining in
our tanks is getting so low that spending 15 grams today may save us from
spending 20 grams next week to reach the same place. This is becoming a
noticeable fraction of our fuel budget to successfully reach our
end-of-mission goal of impact with Jupiter in September of 2003.
On Sunday, routine maintenance of the spacecraft propulsion system is
performed. Each of these periodic events also sends propellant out of the
thrusters, and the Navigation Team relies upon these events to add to our
steering of the spacecraft to reach the desired locations in our orbits
around Jupiter and its moons.
This week's playback data comes from the Near Infrared Mapping Spectrometer
(NIMS) and the Solid State Imaging camera (SSI).
NIMS is returning an observation that studies the compositional variation
and cloud dynamics in the turbulent wake of the Great Red Spot in Jupiter's
SSI is returning three observations. The first is a global color view of
Io, showing the side of the satellite that faces away from Jupiter. This
view will also show the Tvashtar volcanic region, over which Galileo flew
during the August 5 flyby. The second is another view of Io, looking for
evidence of a volcanic plume over the Tvashtar region. The latter picture
was shuttered 29 hours before Io closest approach, and could show a plume
that extends beyond the edge of the disk of the satellite, where it would
be illuminated by the Sun in a manner that could make it very visible to
the Galileo camera. The final pictures to be returned this week are of
Callisto, looking at that hemisphere of the satellite that perpetually