GP-B Post-Flight Analysis—Final Report - Gravity Probe B - Stanford ...

2.5.1.3 Lockheed Martin Team Phase-OutAn important shift in personnel took place when the IOC was completed. The Lockheed Martin team, whichhad supported the program as a very major contributor prior to launch, and as a co-contributor during IOC,phased out as IOC neared completion. Some of the subsystems, such as power, software, thermal, and othershad been transitioned to Stanford personnel as IOC progressed. These systems were performing flawlessly, andrequired little or no commanding to maintain. The most challenging of the LM subsystems, the ATC system didrequire daily attention and very regular commanding. In this system, LM did remain on board with full-timesupport for a few months after the completion of IOC. In this very challenging system, Stanford was ramping upa 3-4 person team. Although the team members were young and less experienced than the LM team, theirenthusiasm and capabilities of a Stanford Master’s degree were quickly recognized. In addition to their innatestrengths, the IOC period had been an exceptional training ground for the team.2.5.1.4 Science Phase Routine ActivitiesAfter entering the science phase the team continued to monitor the gyroscopes and spacecraft very closely.Although all of the systems were working well, there were a small number of important updates required eitheron a weekly or more frequent basis. The biases on the spacecraft control non-science rate gyroscopes thatrequired updating approximately twice a week. This process was important to minimize the guide star capturetime for each acquisition. (It was thereby held to less than a minute.)The spacecraft's stored program computer loads were transitioned from daily products to three uploads perweek. This transition was possible because of the increasingly routine nature of the operations. This change wasalso important because of the reduced team size, and the need to allow adequate team rest. It should be repeatedthat the team had worked extremely long hours during IOC. It was important to provide a more reasonablework environment once the space vehicle no longer required intensive care.2.5.1.5 Science Phase AnomaliesDuring the science phase, 3 major anomalies, 3 medium anomalies, 3 minor anomalies, and 65 observationswere logged by the GP-B Anomaly Review Team. The relatively rare true anomalies that occurred during thescience phase required immediate attention. The anomaly resolution process used during IOC was continued inthe science phase. A discussion of the anomaly resolution process is described in Chapter 5, ManagingAnomalies and Risk , and a complete summary of all on-orbit anomalies and observations is available inAppendix D, Summary Table of Flight Anomalies. During IOC, a significant effort was expended to minimizethe recovery time from anomalies in order to expedite the overall IOC schedule. For some anomalies thatoccurred during the science phase, there was additional motivation to minimize anomaly recovery time,because mis-pointing, non-standard drag-free performance, and other non-science configurations not only putthe validity of the data at risk, but also increased the risk of causing higher than nominal gyroscope torques.Thus, during the science phase, the team worked hard to minimize the recovery process, and these efforts paidoff.2.5.1.6 Early Calibration Tests During the Science PhaseIt will be seen in the next section that like IOC, the calibration phase was on a very tight schedule and thereforewas tension-packed. To help reduce the scope of work required for the calibration phase, and ultimately toimprove the overall experimental error, many SRE tests were performed during the final month of the sciencemission. These tests were performed at this point in the mission for two main reasons:1. These tests were of low technical risk.2. The science data were not impaired by the impact of these tests.58 March 2007 Chapter 2 — Overview of the GP-B Experiment & Mission