This Week on Galileo July 16-22, 2001
Standard cruise activities continue for the Galileo spacecraft this
relatively quiet week. On Monday, the spacecraft performs routine
maintenance on the propulsion system. On Thursday, the spacecraft is turned
3.9 degrees to keep the communications antenna pointed towards Earth.
In the realm of real-time science data collection, the Extreme Ultraviolet
Spectrometer (EUV) continues its two-month-long study of interplanetary
hydrogen gas.
Just to keep things interesting, on Wednesday and Thursday the spacecraft
appears to pass within approximately 0.5 degree of Earth’s Moon, as seen
from the ground communications antennas. When this happens, the Moon can
actually be “seen” by the antennas which are tracking the spacecraft, and
can interfere with the radio signal from Galileo. This effect is not nearly
as severe as that seen when the spacecraft and Sun are close together in
the sky, but we still make sure that no valuable telemetry is being sent
during the time period when communications are affected. Not all of the
complications that govern how a spacecraft is operated are caused by
situations in the remote reaches of the solar system!
As part of the continuing playback of data stored on the on-board tape
recorder during Galileo’s May flyby of Callisto, the data expected this
week are from the Solid State Imaging camera (SSI) and the suite of Fields
and Particles instruments that measure the magnetic field environment of
Jupiter. These instruments are the Energetic Particle Detector (EPD), Heavy
Ion Counter (HIC), Magnetometer (MAG), Plasma instrument (PLS), and Plasma
Wave Subsystem (PWS).
SSI will be returning the highest resolution images of Callisto ever
obtained. They were taken near our closest approach, which was at 138
kilometers (85 miles) altitude. In addition, stereo pictures of a domed
crater will be played back. The Fields and Particles data were recorded
during a period of approximately one hour centered on the closest approach
to Callisto, and will help to study the interactions between the solid body
of Callisto and the electromagnetic fields and plasmas of Jupiter’s
magnetosphere. In addition, these data will add to our understanding of
Callisto’s own magnetic field. Like Europa, Callisto displays an induced
magnetic field, possibly due to the presence of substantial liquid water
within a hundred kilometers (62 miles) or so of its icy surface.
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:
