June 17 - July 14, 2002
The Next Four Weeks on Galileo
The Galileo spacecraft has now rounded the corner in its longest looping
orbit around Jupiter and is again heading back in towards the giant planet
and a close flyby of the tiny moon Amalthea in November.
This past week brought good news about the on-board tape recorder. On April
12, during a routine maintenance activity, the tape appears to have stuck
to the record or playback heads. After five preliminary tests to
characterize the problem, on Saturday, June 8, the tape was successfully
pulled free and we now expect it to be operational. On Tuesday, June 18,
the recorder will be commanded back to the beginning of the tape and the
tape position counter will be reset. From there we can safely command the
tape as we have in the past without worrying that tape-position errors will
trip fault protection routines in the spacecraft software. Subsequent
activities are still in the planning stage. They may include slowly
traversing the entire length of the tape several times, gradually
increasing the distance and speed of motion until we are confident the
recorder can again be used freely and reliably to record our final set of
encounter data in November.
On Friday, June 21, and Monday, July 8, routine maintenance of the
propulsion system is performed.
On Monday, July 1, the spacecraft performs a nearly 11 degree turn in place
to keep the communications antenna pointed towards Earth. This turn
positions the spacecraft to comfortably ride out an upcoming period called
solar conjunction. During conjunction, Jupiter and Galileo appear to pass
behind the Sun as seen from Earth. With the Sun still relatively near the
peak of its 11-year activity cycle, interference from the dynamic solar
wind scrambles the radio signal sent from the spacecraft. Between July 9
and July 28, the spacecraft will be within 7 degrees of the Sun, and
communications are expected to be completely blocked. We are already seeing
occasional degradation of the signal that we think can be attributed to
solar activity. On Monday, June 24, we reconfigure the radio signal from
the spacecraft to help improve our ability to communicate during this
With the spacecraft well outside the magnetosphere of Jupiter on the
sunward side of the planet, continuous data collection by the Magnetometer,
the Dust Detector, and the Extreme Ultraviolet Spectrometer instruments
provides scientists with information about the interplanetary medium.
During the solar conjunction period, the Magnetometer data collection is
suspended, but the Dust Detector and Extreme Ultraviolet data will collect
in an on-board computer memory buffer to be returned once communication is
re-established in late July.