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Gravity Probe B

Testing Einstein's Universe


Dr. Barry Muhlfelder, Dr. Jim Lockhart, and Ming Luo have demonstrated in GTU-2 the Science Mission (SM) level functionality of the readout system, including SQUIDs and SQUID electronics. The testing, performed with SQUID Readout Electronics (SRE) Rev C, has shown data meeting SM noise requirements. In addition, all payload electronic systems, the Telescope Readout Electronics (TRE), the Gyroscope Suspension System (GSS), and the Electronics Control Unit (ECU) have been tested for Electromagnetic Compatibility, (EMC), against the SRE with no discernible change in the SRE output (except for observing the ~35kHz position bridge signal from the GSS at expected and acceptable levels). The successful EMC compatibility test of the SRE and GSS has been conducted by Dr. Gregory Gutt and his team, with the GSS performing in full SM mode. This included both the position bridge excitation and a comprehensive set of simulated SM suspension signals, channeled by the engineering unit flight computer over the for to aft data bus to the forward unit of the GSS.

A successful Command and Data handling Critical Design Review (CDR) was held at B.F. Goodrich in Albuquerque, New Mexico on Sept. 11 and 12. The flight equivalent units had been delivered to LMMS in July and are undergoing integration with the flight computer in the Integrated Test Facility in B251.

The Dewar Axial Lock Failure Investigation Technical Team reported the results of their initial investigation to Stanford University on 8 September. The failure of the Dewar axial locks was identified as thread galling and reproduced in cryogenic laboratory testing. Additionally, the Team presented candidate "use as is" concepts. The Technical Team is now developing redesign solutions to preclude thread galling, and is evaluating the feasibility and potential impacts of the "use-as-is" options. These results will be presented to Stanford on 22 Sept.

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