Satellite Laser Ranging (SLR) is a method to measure the distance to satellites or space debris by using very short laser pulses down to a single shot precision of 3 millimeter. As one of the world-leading Satellite Laser Ranging (SLR) stations the observatory located at Lustbühel in Graz has been measuring continuously since 1982.

Currently, more than 150 “cooperative” targets (satellites with retroreflectors) are routinely measured up to an orbital height of 36,000 kilometers. The precision of the measurement is independent of the orbital height. SLR data is continuously uploaded to various analysis centers within the International Laser Ranging Service (ILRS) where highly accurate orbit predictions are calculated. The measurements to geodetic satellites provide a crucial input defining the center of mass, the gravitation field of our planet and uniquely contribute to the Earth-fixed coordinate system - the International Terrestrial Reference Frame (ITRF). Scientific satellite missions connected to oceanic and tectonic motions, Earth topography or relativistic effects also rely on precise SLR measurements.

Graz SLR station is the pioneer station performing highly accurate range measurements to space debris targets. By using a higher power laser, the diffuse reflection of “uncooperative” objects - targets without a retroreflector - can be measured as well. Such measurements deliver valuable data to improve orbit predictions to space debris, which could significantly reduce collision avoidance maneuvers. Recently Graz SLR station for the first time showed that space debris laser ranging during daylight is possible. In parallel to satellite and space debris laser ranging, Graz SLR station is also measuring light curves (the sunlight reflected from satellites or space debris) from which individual surfaces can be identified. Due to the high temporal resolution of the datasets (up to repetition rates of 1 MHz), range and light curves variations of rotating targets can be resolved allowing to determine the spin period and spin axis of space debris.

In 2017 Graz SLR station participated in a unique experiment together with the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences led by Nobel-Prize winner Anton Zeilinger. Graz SLR station was acting as one of the three ground stations realizing quantum key distribution via the Micius satellite.