Optical Metrology Terminal for Satellite-to-Satellite Laser Ranging

Interferometric laser ranging is a powerful enabling technology for high-precision satellite-to-satellite tracking within the context of Earth observation, gravitational wave detection, and formation flying. Since the launch of the gravity field mission GRACE Follow-On in 2018, the onboard Laser Ranging Interferometer has successfully been operating as a technology demonstrator in a low-Earth orbit and has significantly enhanced the measurement accuracy compared to the former microwave instrument.
Within the framework of this work, a new design concept for an optical instrument of this type is derived, allowing the location of the reference point and the external beam offset to be tuned independently of the integrated retroreflector. On this basis, optical design and construction of the "Optical Metrology Terminal" are carried out, resulting in a basically flight-representative instrument as it could be used in future gravity field missions. Experimental evaluation on elegant breadboard level demonstrated excellent tolerance against variations of the angle of incidence.