In Satellite Laser Ranging (SLR) a global network of stations measures the instantaneous round trip time of flight of ultrashort laser pulses to satellites equipped with special reflectors. The few returning photons are detected at the SLR station and time tagged, allowing range measurements with millimeter precision, which can be accumulated to provide accurate orbits and a host of important science products.
left: SLR station Graz (Austria); right: LAGEOS (Laser Geodynamics Satellite, NASA)
SLR is the most accurate technique currently available to determine the geocentric position of an Earth satellite, allowing for the precise calibration of radar altimeters and separation of long-term instrumentation drift from secular changes in ocean topography.
SLR‘s ability to measure the temporal variations in the Earth‘s gravity field and to monitor motion of the station network with respect to the geo-center, together with the capability to monitor vertical motion in an absolute system, makes it unique for modeling and evaluating long-term climate changes.
Additional, SLR provides a unique capability for verification of the predictions of the Theory of General Relativity.
One of the SLR stations is located in Austria/Graz. It was the first station world wide using a 2 kHz ultrashort pulsed laser (High Q Laser); the Graz system allows additional side products: Satellite Spin Determination, Atmospheric Seeing measurements, Data Transmission etc.
