So glad I stumbled over this edition of Catalyst.
The website is great:-
"Following is a list of some of the extraordinary accomplishments achieved by GP-B during the 17 months of its flight mission.
- Over the course of the 17.3-month mission, we communicated with the spacecraft over 4,000 times, and the Mission Planning team successfully transmitted over 106,000 commands to the spacecraft.
- GP-B is the first spacecraft ever to achieve nine degrees of freedom in control. The spacecraft itself maintained three degrees of freedom in attitude control (pitch, yaw, and roll), plus three degrees of freedom in translational drag-free control (front-to-back, side-to-side, and up-down). In addition, the Gyro Suspension System (GSS) for each gyro maintained three degrees of freedom in controlling the location of its spherical rotor within the gyro housing.
- The GP-B gyros, which performed extraordinarily well in orbit, have been listed in the Guinness Database of World Records as being the roundest objects ever manufactured.
- The spin-down rates of all four gyros were considerably better than expected. GP-B’s conservative requirement was a characteristic spin-down period (time required to slow down to ~37% of its initial speed) of 2,300 years. Measurements during IOC showed that the average characteristic spin-down period of the GP-B gyros was approximately 15,000 years—well beyond the requirement.
- The magnetic field surrounding the gyros and SQUIDs (Super-conducting QUantum Interference Device) was reduced to 10-7 gauss, less than one millionth of the Earth’s magnetic field—the lowest ever achieved in space.
- The gyro readout measurements from the SQUID magnetometers had unprecedented precision, detecting fields to 10-13 gauss, less than one trillionth of the strength of Earth’s magnetic field.
- The gyro suspension system operated magnificently. It had to be able to operate both on the ground for testing purposes prior to launch, as well as in space. This meant that the suspension system had to operate over 11 orders of magnitude—an enormous dynamic control range—and its performance throughout the mission was outstanding.
- The science telescope on board the spacecraft tracked the guide star, IM Pegasi (HR 8703), to superb accuracy, and it also collected a year’s worth of brightness data on that star. The brightness data we collected on IM Pegasi represents the most continuous data ever collected on any star in the universe."