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Gravity Probe B

Testing Einstein's Universe

WEEKLY HIGHLIGHTS FOR WEEK ENDING 12 DECEMBER 2003:



GRAVITY PROBE B LAUNCH DELAYED

On November 22, 2003, a very difficult decision was made jointly by NASA, Stanford, and Lockheed Martin to delay the Gravity Probe B launch in order to eliminate a grounding problem in a voltage converter that resides in the Experiment Control Unit (ECU) on board the Gravity Probe B spacecraft. The ECU has been removed from the spacecraft, the faulty converter is being replaced, and the ECU will then be tested and reinstalled. This repair will ensure full redundancy in the ECU and maximize the reliability of the spacecraft on launch. A new launch date, which is anticipated to be sometime in the 2nd Quarter of 2004, will be announced soon by NASA. Please check this Web site periodically to get the latest information on the status of the Gravity Probe B launch and mission.

VANDENBERG AIR FORCE BASE OPERATIONS THIS WEEK

The following activities were completed at VAFB this past week:
  • The battery palette on the GP-B spacecraft was removed to provide access to the Experiment Control Unit (ECU).
  • On Wednesday, December 10, the ECU was removed from the spacecraft and driven to Lockheed Martin in Palo Alto, CA, where the faulty voltage converter will be removed, re-worked, and re-installed. The entire ECU will then be thoroughly tested before being returned to VAFB for reinstallation into the spacecraft.
  • After the ECU was removed from the spacecraft, the battery palette was reinstalled, the cables were reconnected, and battery charging commenced.
  • The six Vatterfly valve filters were removed, and covers were installed. They were then pumped down and checked for leaks.
  • A helium gas delivery system was returned to Building 1610 (the space vehicle processing room).
  • The temperature of the dewar's main tank is 1.8012 K. The guard tank, which was 58.8% full is being filled.
  • Communications equipment and networks are being re-configured into a sleep mode for approximately two months, until the ECU is reinstalled on the spacecraft.
  • The Delta II launch vehicle, with the solid motors attached, will remain on the launch pad, surrounded by the mobile service tower (MST), for the duration of the repair period. Small maintenance items have been identified and will be accomplished to accommodate the Delta II launch delay.
Photos: In the top photo, technicians are removing the battery palette from the GP-B spacecraft, in order to access the ECU. The lower photo shows the ECU (black box), which was removed from the spacecraft, on a test bench at Lockheed Martin in Palo Alto, CA. Click on the thumnails to view enlargements of the photos.

VIDEO CLIP FROM THE SPACE VEHICLE PREPARATION ROOM AT VANDENBERG

Click here to view a video clip about Gravity Probe B.


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