Oh, this made me worried about JWST (as it can't be serviced once the gyroscopes break), but I found this: > To detect changes in direction JWST uses hemispher

Oh, this made me worried about JWST (as it can't be serviced once the gyroscopes break), but I found this: > To detect changes in direction JWST uses hemispherical resonator gyroscopes (HRG). HRGs are expected to be more reliable than the gas-bearing gyroscopes that were a reliability issue on Hubble Space Telescope. They cannot point as finely, however, which is overcome by the JWST fine guidance mirror.[18] https://en.wikipedia.org/wiki/Spacecraft_bus_(James_Webb_Space_Telescope) https://en.wikipedia.org/wiki/Spacecraft_bus_(James_Webb_Spa... So Hubble uses gyroscopes that are more precise but less reliable than the HRGs used in JWST.