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

The Gyroscope Suspension System’s (GSS) role in Gravity Probe B is to electrostatically suspend the sciencegyroscopes within their housing cavities so that the gyroscopes may spin freely with minimal friction and torqueso that they may perform their role as local inertial space references.To perform its mission successfully, the GSS must satisfy a number of core requirements:1. Operate over 8 orders of force magnitude; the same system must be able to suspend the gyroscopes onEarth in a 1 g field as well as generate minimal disturbances at the 108 g level during data collection.2. Suspend the gyroscopes reliably; the system must never let a spinning rotor touch the housing. There issufficient mechanical energy in a rotor spinning at 60 Hz to effectively destroy the rotor and housing insuch an event.3. Operate compatibly with the SQUID readout system. The SQUID magnetometers are very sensitive,thus the suspension system must not interfere with these sensors during ground and on-orbit operation.4. Minimize electrostatic torques during science data collection. The suspension system must meetcentering requirements with minimal control effort and thus with minimal residual torques on therotors.5. Apply controlled torques to the rotor for calibration and initial rotor spin axis alignment.6. Act as an accelerometer as part of the “drag-free” translation control system to further minimize classicaltorques on the rotors.All of these requirements were met during the GP-B mission, and the suspension systems continue to operatewell following the depletion of helium from the dewar since they do not require cryogenic electronics tofunction.Figure 9-1. Block diagram of the payload electronics package showing the interconnect of the GSS unitsGravity Probe B — Post Flight Analysis • Final Report March 2007 257