Hi,
Here is an update from the Gravity Proble B Mission Team.
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GRAVITY PROBE B MISSION UPDATE FOR 3 DECEMBER 2004
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On mission day #227, the GP-B spacecraft continues to be in good health, with all subsystems performing well. As of tomorrow, we will have been collecting relativity data for 100 days. The data collection process is proceeding smoothly, and the quality of the data remains excellent. All four gyros are digitally suspended in science mode, and the spacecraft is flying drag-free around gyro #3, maintaining a constant roll rate of 0.7742 rpm (77.5 seconds per revolution.) The temperature inside the Dewar is holding steady at just under 1.82 kelvin.
It has been relatively quiet here in the GP-B Mission Operations Center, since the strong solar flares and geomagnetic storm three weeks ago. Our team continues to adjust the flow rate of the excess helium from the Dewar during the present a 6-week "hot" season, where the spacecraft is continually in sunlight throughout each orbit. (See last week's (26 November) highlights on our Web site for a discussion of the spacecraft's seasons.)
Furthermore, seasonal warming of the spacecraft has resulted in the Attitude Reference Platform (ARP) on the outside of the spacecraft producing data that slightly diminishes the pointing accuracy of the Attitude and Translation Contro system (ATC). To address this issue, the ATC team installed a modified data filter, and tests performed this past week indicate that spacecraft pointing accuracy has now improved.
Finally, the team has been adjusting controls on the navigational gyroscopes that are used by the ATC to keep the telescope pointed towards the guide star, IM Pegasi (HR 8703), during periods when the spacecraft moves behind the Earth, eclipsing the telescope's view of the guide star. These adjustments have reduced the time required for the telescope to re-lock onto the guide star--when the spacecraft emerges over the North Pole--to less than one minute.
Please Note: Until further notice, we intend to continue sending out these updates on a weekly basis. Also, from time to time, we may post special reports and special updates, as warranted by mission events.
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NASA - Stanford - Lockheed Martin
Gravity Probe B Program
"Testing Einstein's Universe"
http://einstein.stanford.eduBob Kahn
Public Affairs Coordinator
Phone: 650-723-2540
Fax: 650-723-3494
Email: kahn@relgyro.stanford.edu
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Regards,
LelandJ
