Fast Response, Medium Resolution Digital Event Timer and Range Gate Generator for Satellite Laser Ranging

For our kHz Satellite Laser Ranging (SLR) system in Graz, we developed a fast response, medium resolution Event Timer to determine laser firing times; and a digital Range Gate Generator to activate the Single Photon Avalanche Detector (C-SPAD). The Event Timer has a resolution of about 500 ps, and determines the Event Times within 20 ns; the Range Gate Generator produces a range gate pulse with about 500 ps resolution, and with an accuracy of better than 1 ns. Both devices are fully digital, and are implemented within an FPGA circuit. These devices can be used in the present 2 kHz SLR system, as well as in future higher repetition rate SLR systems.