The other three characterize the gyro rotor. The satellite orbit is polar, circular, at 400-mile altitude and coplanar with the line to the guide star, Rigel. The gyroscopes are aligned parallel to the telescope axis, two spinning clockwise and two counterclockwise, each gyroscope measuring both relativity effects. Pugh, in his independent proposal for a gyroscope experiment, suggested a means for removing these accelerations, which was subsequently developed at Stanford and demonstrated in 1972 on the U.S.Navy's Triad transit navigation satellite. Another powerful aid is roll.
Liquid helium is unusually hard to store.
Helium oozes through the pores, and provides refrigeration by instantly evaporating, just like sweating in a desert climate. Slosh baffles help suppress tidal motions in the liquid. The dewar operates at low pressures, making the helium superfluid. Superfluidity is a peculiar state of liquid helium at temperatures below 2.16K where, under certain conditions, it flows without viscous resistance and transports heat far better than any metal.