An optical sensor for the drag-free satellite

An optical sensor for drag-free satellites is described. It is based on using fluorescent re-emission from the proof mass excited by a pulsed ultraviolet source, a technique that separates the frequencies of the excited and excitant light fluxes. A theoretical analysis of the performance and linearity of the sensor was verified by the results on a laboratory prototype. The sensor provided a measure of the position of a 4 cm radius proof mass in a 10 cm cavity to an accuracy of 1 mm. Null drift and thermal gradients caused errors less than 0.05 mm.