Sensing the Position and Vibration of Spacecraft Structures

The authors are involved in the development of a family of laser heterodyne sensors for use in the active control of spacecraft structures. These sensors include a HeNe distance measuring system for structures requiring accuracies to 0.1 mm, and a CO2 distance measuring system which will measure unambiguously down to 0.01 Atm. Vibration sensors based on both HeNe and CO2 lasers are also being developed. These systems will measure fractions of a /im displacement from dc to kHz. This paper discusses the design theory and tradeoffs required for instrument selection.