Absolute distance interferometrie measurement for on board satellite metrology

We present an absolute interferometer based on a synthetic wavelength generated by mixing two fiber coupled extended cavity diode lasers. The synthetic wavelength scheme is simple and compact and based on fiber components. The measurement capability has been demonstrated up to 500 m in air and the accuracy is limited by the refractive index of air. The ultimate estimated accuracy in vacuum is of the order of few micrometers. The interferometer, originally designed for Synthetic Aperture Radar missions can be used whenever the distance between two or more parts of a satellite (e.g. an antenna fixed to a boom) or even the distance between satellites flying in formation has to be monitored or controlled.