Roland points to this article about the upcoming Gravity Probe mission put together by Stanford University and NASA to test Einstein's general theory of relativity.
The equipment for this measurement is pretty amazing. At its heart are four precision cryogenic electrostatically suspended gyroscopes: nearly perfect quartz spheres, finely coated in a super-conducting material.
However, imperfections of the gyroscope rotor spheres such as asphericity and inhomogeneity also cause drifts due to classical torques. It is therefore essential that these unwanted drifts be small compared to the effects to be measured. From an analysis of the electrical torques on the rotors it was determined that in order to reduce the drift rate due to asphericity to less than 0.0001 arc sec per year, the rotor spheres have to be polished to 1 micro inch (25 nm) or to deviate no more than ± 0.5 micro inch (12 nm) from a perfect sphere. - Precision Spheres for Gravity Probe B Experiment
These Technical Papers cover the gyroscopes, SQUIDS, cryogenic telescopes, magnetic shielding, suspension mechanisms, and of course the spaceship which houses them.
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