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

In parallel, a major focus of the Aero-Astro Department remained fixed on the development of a drag-freesatellite. In December, 1969, the Stanford Aero-Astro Department submitted a proposal to Johns HopkinsApplied Physics Laboratory (APL) for a subcontract to Develop and Build a [drag-free] Disturbance CompensationSystem (DISCOS) for the [U.S. Navy] TRIAD II and III Satellites. This important early space experiment was developed andmanaged jointly by Daniel DeBra of Stanford and Robert Fischell of the Johns Hopkins APL, who was grantedNavy funding for the project because it could (and did) make possible extreme accuracy at low cost forsubmarine navigation system updates which the transit satellite system provided. The TRIAD II transitnavigation satellite, with DeBra's drag-free DISCOS unit as its centerpiece, was successfully launched in 1972—the only 3-axis drag-free satellite to be operated successfully until the launch of GP-B in 2004. It achievedcontrol to 5x10 -12 g throughout a one-year orbital test flight.With the success of DISCOS, Stanford was able to procure funding for drag-free technology research fromsources other than NASA, and GP-B's NASA funding was thus refocused solely on development andprototyping of the technology and control systems needed to perform the relativity gyroscope experiment.In 1968, Robert Cannon left Stanford to become Chief Scientist for the U.S. Air Force. In the wake of hisdeparture, Fairbank promoted Daniel DeBra to the status of Co-Principal Investigator for the Aero-Astroportion of the GP-B program, and he promoted Francis Everitt to the status of Coordinating Co-PI for thewhole program. Leonard Schiff continued his role as Program Advisor, in frequent communication withFairbank, Everitt, and DeBra until his death in 1971.During these years, Stanford began collaborating on the development of several technologies with NASA'sMarshall Space Flight Center (MSFC), and MSFC provided oversight assistance on Stanford subcontracts toaerospace companies for the development and testing of prototype gyroscopes, telescope hardware, the dewar,and other key technology elements.NASA Headquarters formally transferred oversight responsibility for the relativity gyroscope program to MSFCin 1971. Coincident with this transfer, C. Dixon Ashworth, then the NASA HQ manager overseeing therelativity gyroscope experiment, renamed it “Gravity Probe B,” noting that it was to be the second NASAgravitational physics experiment. The first one, which he named “Gravity Probe A,” was a Hydrogen-maserclock comparison experiment, headed by Dr. Robert Vessot of the Smithsonian Astrophysical Observatory andalso overseen by MSFC. (The Gravity Probe A experiment was successfully performed with a sub-orbital Scoutlaunch in 1976.)In December 1971, MSFC funded an in-depth “Mission Definition Study” of GP-B, performed by Ball BrothersResearch Corporation (BBRC, Now Ball Aerospace), in close collaboration with Stanford—the starting point forall future flight studies. This study provided an initial spacecraft design and program plan. Two follow-upstudies by BBRC were performed in 1973 and 1975, respectively. The results of these studies indicated that GP-B was ready to make the transition from exploratory research and technology development to a NASA flightprogram.6.2.4 Transition to a NASA Flight ProgramIn January 1977, the original NASA research grant to Stanford was closed out—the longest running continuousresearch grant ever awarded by NASA—symbolically marking the end of the exploratory phase of the program,during which much of the key technology needed was developed. In its place, NASA's Office of Space Sciencesawarded a new contract for the purpose of defining a flight program. A year later, funding support at NASAHeadquarters for the program switched from the Office of Space Science under Nancy Roman to the AdvancedProgram Development Office under Jeffrey Rosendhal.Gravity Probe B — Post Flight Analysis • Final Report March 2007 145