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Gravity Probe B

Testing Einstein's Universe


The payload test team has successfully completed operations on flight gyroscopes #1 and #2. Thermal measurements and helium boiloff measurements were performed and show good agreement with the thermal model. The payload is currently in a vertical orientation and the liquid helium level has been topped off. Next, the payload will be placed in a horizontal orientation to support the testing of gyroscopes #3 and #4.

The first shake of an AFT GSS box was successfully performed. Following this shake, the box passed a functional test. The balance of the AFT boxes are in test.

Photo: The payload in tilt toward horizontal position.

The GP-B team completed inital random vibration testing on the single-bore Mini Quartz Block for gyro vibration testing in LM B/181. The Mini Quartz Block and its mounting hardware successfully withstood random vibration levels expected at the gyros during launch.

The ECU thermal vacuum testing has completed the first hot cycle successfully. There were two test equipment anomalies, both traced to cables. One cable was fixed; the other cable causes noisy but acceptable performance for continuation of the testing. The ECU is scheduled to complete the first cold cycle on 30 November.

The forward SRE units are in MQA testing. Forward unit tests are proceeding normally. The aft unit B had a failure of the 12v Interpoint single power supply that powers the precision clock. It has been confirmed as a piece part failure and the part is presently undergoing failure analysis. The aft unit retest is awaiting identification of the failure mechanism before proceeding. To allow continuation of the forward unit testing, testing for pre and post pyro-shock and random vibration testing is being configured to utilize the aft emulator unit.

Small Photo: The Mini Quartz Block
Large Photo (click small to view): LM Engineers Mitch Skinner, Russell Katz, and Mike Gate with the Mini Quartz Block at Stanford University.

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