Features of the Gravity Probe B Space Vehicle

Space vehicle performance enabled successful relativity data collection throughout the Gravity Probe B mission.~~ Precision pointing and drag-free translation control was maintained using proportional helium micro-thrusters.~ Electrical power was provided by rigid, double sided solar arrays. The 1.8 kelvin science instrument temperature was maintained using the largest cryogenic liquid helium dewar ever flown in space.~~ The flight software successfully performed autonomous operations and safemode protection. Features of the Gravity Probe B Space Vehicle mechanisms include: 1) sixteen helium micro-thrusters, the first proportional thrusters flown in space, and large-orifice thruster isolation valves, 2) seven precision and high-authority mass trim mechanisms, 3) four non-pyrotechnic, highly reliable solar array deployment and release mechanism sets.~ Early incremental prototyping was used extensively to reduce spacecraft development risk.~ All spacecraft systems were redundant and provided multiple failure tolerance in critical systems.~ Lockheed Martin performed the spacecraft design, systems engineering, hardware and software integration, environmental testing and launch base operations, as well as on-orbit operations support for the Gravity Probe B space science experiment.