Four Weeks on Galileo January 28 – February 24, 2002
The long cruise period between encounters is now under way. In fact, this
is the longest period between encounters that Galileo has spent since
entering orbit around Jupiter in December 1995. Between our January 17
flyby of Io and the November 5 flyby of Amalthea, 292 days will pass. This
long, looping trajectory will also take us the farthest from Jupiter we
have been since entering orbit. On June 13 we will reach a distance of 348
Jupiter radii from the planet, which is nearly 25 million kilometers or
15.5 million miles. At that distance, light from the giant planet takes
nearly a minute and a half to reach the spacecraft! On the same day the
signal from Galileo takes 49.8 minutes to travel all the way to Earth.
Tuesday morning, January 29, the spacecraft executes a small 2 degree turn
in place to keep the communications antenna pointed towards Earth.
Friday night, February 1, the Near Infrared Mapping Spectrometer (NIMS)
performs the final planned remote sensing observation of the mission. This
observation is a calibration to determine the response of the instrument to
a known input signal. By periodically performing these calibrations
throughout the mission, scientists are able to track how the performance of
the instrument changes with time. This allows them to translate the
instrument measurements into absolute physical quantities.
On Monday night, February 11, routine maintenance of the spacecraft
propulsion system is performed. On Wednesday, February 13, routine
maintenance of the tape recorder is performed.
On Flaney night, February 22, the path of Jupiter and the spacecraft in
Earth’s sky takes it near our own Moon as seen by the tracking station near
Madrid, Spain. Though the Moon does not actually block the spacecraft,
reflected thermal radiation from the surface of this very close body can be
seen by the antenna, and this can interfere with the signal from the
spacecraft.
Data return from Galileo this month consists of playback of the recorded
data that we were able to acquire during the Io flyby. These data include
pictures of Europa and Amalthea (though not, unfortunately, of Io), and of
Jupiter’s atmosphere. Also included are a set of global maps of Jupiter’s
clouds by NIMS.
While the playback continues, the Magnetometer, the Dust Detector, and the
Extreme Ultraviolet Spectrometer continue collecting and periodically
transmitting real-time data about the local environment of the spacecraft
and about the interplanetary hydrogen distribution.
With the long gap between highlights, these reports are shifting to a
monthly publishing schedule. Weekly reports will resume in October as we
approach Amalthea and the activity level for the spacecraft picks up.
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:
