Towards absolute all optical satellite range finding by photon counting

The accuracy of the measured distances in Satellite Laser Ranging is currently limited by 3 major error sources. These are associated with intensity variation of the detected echo, the satellite target structure and last but not least the electronic delay stability of the high resolution event timer. We have developed a continuous photon counting concept, where we can obtain accurate distances by timing the satellite return signals directly against a train of fs-clock pulses, derived from a delay compensated mode-locked laser. Conservative simulations suggest a practically achievable accuracy of less than 10 ps with respect to the time scale of the ranging station on the ground. In this contribution we outline the measurement concept and compare the obtained laboratory test results against the expectation of the theoretical simulations.