PMT gain changing measurement for airborne laser depth sounding

The return signals from airborne laser depth sounding have dynamic ranges that exceed the capabilities of the sequential measurement equipments.The study on gain controlling of photomutiplier tubes(PMT) GDB-333,GDB-49 and R1333 have been carried out.The results show that the signal dynamic range can be compressed to 2.5×104orders by controlling the electric potential of grid and eletromutiplier electrode.The method of changing PMT gain to detect signals from sea bottom is very compatible to airborne laser depth sounding.