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

This appendix contains a table summarizing the complete set of 193 anomalies/observations that the GP-BAnomaly Review Board (ARB) worked through during the IOC period from 20 April 2004 through 13 October2005. In the table, all formal anomalies are shown in boldface type.These anomalies have been divided in the four ARB categories as follows:1. 5 Major Anomalies (2 in IOC) These anomalies had the potential to endanger the safety of thespacecraft and/or the payload.2. 12 Medium Anomalies (9 in IOC) These anomalies did not endanger the safety of the space vehicle butdid impact the execution of planned timeline3. 6 Minor Anomalies. (3 in IOC) These anomalies did not endanger the safety of the space vehicle and didnot stop the execution of the timeline. However, they did require actions to mitigate or correct the issue.4. 170 Observations. (94 in IOC) Observations are off-nominal or unexpected behavior of the spacevehicle that was not an operational or functional issue and does not violate any limits, but did warrantattention over time. These can be considered vehicle “squawks”.Figure D-1. Anomaly Type Trends during the missionThe large table that comprises the bulk of this appendix presents a summary of all identified anomalies:description, root cause, and corrective action taken. The observations listed there—essentially very small andeasy to resolve anomalies—may be further categorized as follows:(A) Analysis items—Items still in work to understand the root cause (for open items only).(T) Tune items—Out of spec features resolved with on-orbit tuning of the spacecraft or payload.(O) Ops issues—Unexpected behavior due to an operations, mission planning, or other “human” error.(F) Features—Unexpected functionality that has no long term effect on the mission. This category alsoincludes routine issues, such as correcting double bit errors in processor memory.(N) Non-issues—Expected behavior not initially understood by the individual making the observation.Gravity Probe B — Post Flight Analysis • Final Report March 2007 523