Laser Ranging and Metrology Test Facility (LRMT)
This large-scale facility of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) provides the infrastructure required for the verification of high-resolution laser ranging instruments. These are used when satellites are flying in formation or in constellations. The system has successfully been used for the on-site verification and testing of the laser metrology systems of the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission.
Precise distance measuring between satellites
The LRMT comprises high-precision optical metrology to verify the set-ups of lasers that are used to measure the distances between satellites (laser interferometry, set-ups for the simulation of laser beams from distant satellites). It also comprises a test rig that can be used to thermally and mechanically characterise the highly stable materials used in such optical instruments and verify them for use. Determining the coefficients of thermal expansion of tubular samples is possible with a precision in the range of 10 parts per billion across a temperature range of 150–350 Kelvin.
In addition, the LRMT includes the development of high-precision optical frequency references, both as a laser source for highly sensitive laser interferometry, and as a reference for the verification of other laser sources.