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

4.1 Overview of On-Orbit OperationsThe preparation for on-orbit operations began long before launch. A series of simulations, generated bycomputer in the GP-B ITF (see “The Integrated Test Facility (ITF)” on page 121) were carried out to prepare theteam. In preparation for launch, a number of changes were made to the program structure. The team wasrestructured to support the on-orbit needs. A number of additional capabilities were added in the final few yearsleading up to launch. The elements of the program included data processing, orbit determination, computerhardware, the Integrated Test Facility (ITF), anomaly resolution and risk management, and all of the technicalpayload and spacecraft subsystems. Although the program manager maintained overall responsibility for thevehicle, day to day responsibility for the vehicle was delegated to the mission directors. This clear and efficientprogram reporting and responsibility structure was a critical component of on-orbit operations and allowed fortimely response to vehicle needs.4.1.1 Three Mission PhasesThe top level view of GP-B on-orbit consists of three phases: the initialization phase, the science phase, and thecalibration phase. During the 4+ month initialization phase the vehicle was configured for science. This phasewas extremely busy and at times very stressful for the team. Each part of the GP-B organization needed toperform efficiently, yet without error. Re-tasking of the spacecraft was carried out as needed and was basedupon events on-board the vehicle. Large amounts of data were fed to the ground to provide information onthese events. The computer hardware and data processing systems operated 24 hours a day, 7 days a week.Although the team had been through a series of very helpful pre-launch simulation exercises, the initializationphase was, in-effect, a 4+ month-long simulation. Many days of this period, many members of the team worked60 or more hours per week. There were few easy days. In retrospect it is accurate to say that the team rose to theoccasion, they remained focused on the vehicle throughout, and they succeeded in a very challenging task.The initialization phase was followed by an 11 month science data taking phase. In comparison to IOC, thisperiod was straightforward to implement. In addition, the team was very well trained by the start of science.Each team member knew well his or her responsibilities, thus further easing the effort. Most days wereuneventful, although the daily “all-hands” meeting was maintained to ensure that the team remained focused onthe vehicle status. The all-important science data were transmitted to the ground four times a day. Theengineering and science teams reviewed the data on a daily basis and provided top level feedback on theprevious day's data at the daily meeting.The science mission concluded with a 1.5 month long calibration phase. The purpose of this phase was to helpevaluate sources of systematic experiment error and to allow the team to place limits on gyroscope torques.Although many operations were performed during this period, the implementation was performed nearlyflawlessly.4.1.2 Daily Operations RoutineAlthough a clear decision making process and clear definitions of personnel responsibilities are important inany organization, these aspects are particularly critical in an on-orbit environment. The overall description ofthe program can be described as follows: The Mission operations center was the lifeline to the vehicle. Personnelin the MOC were always focused on the current vehicle status. Typically, the vehicle would be “green” and theMOC would verify this status with a real time monitoring system. In a typical “green” day, a daily 10 am “allhands”meeting would inform the team of the previous day's events and planned future operations. Followingthe all-hands meeting, mission planners would meet with subsystem specialists to develop the detailed plan forthe next day. In practice, much of the planning already had been developed long before, and onlyrearrangement of the order of tasks was required. When new products were required, the ITF was used forverification prior to use on the vehicle.Gravity Probe B — Post Flight Analysis • Final Report March 2007 97