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Gravity Probe B

Testing Einstein's Universe

WEEKLY HIGHLIGHTS FOR WEEK ENDING 5 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 is being removed from the spacecraft, the faulty converter will be 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 by NASA later this month. 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:
  • In prerparation for removing the Experiment Control Unit (ECU) and in order to service the dewar, all four solar panels have been removed from the spacecraft.
  • A set of pyro units, which control certain cryogenic valves, were removed as a precaution against accidental detonation.
  • The Gas Management Assembly, which is used to spin up the four gyroscopes, has been put into a safe or "sleep" mode for the duration of the stand-down period.
  • A Ground Service Equipment unit (GSE) has been integrated with the spacecraft in order to enable continued servicing of the dewar without the ECU (which is normally required) during the stand-down period. The dewar's guard tank was filled using the GSE to ensure that this alternate ground servicing system is working properly.
  • Operations supporting the removal of the ECU unit containing the faulty voltage converter are almost complete. The ECU is scheduled to be removed next week and driven to Lockheed Martin in Palo Alto, CA for replacement.
  • 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.
Photo: The Gravity Probe B spacecraft, sitting in the preparation clean room at Vandenberg AFB, with its cylindrical payload attachment fitting (PAF) installed at its base. The spacecraft has now been de-coupled from the PAF, and the solar panels have been removed, in preparation for replacing the ECU. Click on the thumnail to view an enlargement of the photo.

MEETINGS WITH MSFC MANAGERS AT STANFORD

Sevgeral members of NASA's Gravity Probe B Management team from Marshall Space Flight Center in Huntsville, AL, flew to Stanford this week for three days of meetings to discuss plans and procedures for replacing the faulty ECU and getting the GP-B spacecraft back on track for launch next year.

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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