Timing precision of active Q-switched mode-locked laser and fire control system for the synchronous satellite laser ranging

We have developed a laser fire synchronization system which controls the firing time of the laser so that each laser pulse reaches a target satellite exactly within 100 ns at a specified epoch. A conventional Nd:YAG active-passive laser has been modified to an active Q-switched mode-locked laser to reduce the laser delay jitters with respect to commanded time. An epoch-triggered fire control system has also been introduced to ensure commanded time to take account of the target range prediction, station clock error, and other fixed delays. Timing jitters of 70 ns RMS have been demonstrated on a geodetic satellite after evaluating laser delay offset, predicted range error, and station clock drift. Improvements to the 10 ns level by further laser control upgrades are possible