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Gravity Probe B

Testing Einstein's Universe


The cryo ops team has evacuated the flight probe thereby allowing a measurement of the thermal performance of the probe rework. The preliminary results are consistent with the rework requirements and with the thermal model. The implication is that we have significant margin in the rework thermal conductivity to support our mission lifetime requirement. The test thus far has been in a configuration which provides a safe overtest of the vacuum integrity requirement for the rework. The vacuum results look excellent. The Lockheed Martin rework team is to be congratulated for a job well done. In other payload test work the SQUID output cables have been successfully tested and the first part of the instrumentation cable checkout has been successfully completed.

The Aft SRE Unit "A" has passed functional test and is awaiting completion of Unit "B" for and the forward units for integrated system test.

The Vatterfly Valve board rework has been completed and the penalty test of the reworked ECU has been successfully performed. The ECU system is now in random vibration testing.

Three of the APU/ACU aft assemblies have completed their initial power on testing. One is still in build-up at NASA/Ames, waiting for the reworked ACL card.

Photo: A cross-section of the probe neck showing the thermal pins inserted during the probe rework earlier this year. Click here for a detailed description of the rework.

All assembled flight Solar Array Release Mechanisms (SARMs) have successfully completed random vibration testing in LM B/181. The SARMs are now undergoing post-vibe functional testing.

The Aft unit Vatterfly boards have been baked-out and will be inserted into the Aft unit. The Aft box will be formally closed, with functional testing starting by 20 October.

The SRE is awaiting conformally coating of the last of the Aft converter boards and integration into Aft unit B. Aft unit A has passed its MQA testing. The integrated Aft and Fwd A and B units will undergo a systems level MQA prior to resumption of protoqual/acceptance testing.

Photo: LM engineer Sean McCully and technician Jeff Williams in the SARM testing area in LM B/255.

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