Laser Ranging Signal Detection in Harsh EMC Environment

Based on lessons learnt with the BepiColombo Laser Altimeter (BELA) [1], electronics design improvements have been implemented for the Ganymede Laser Altimeter (GALA), to be launched on ESA's JUICE spacecraft in 2022 [2]. Improvements include multi-point grounding and separation of “aggressor” printed circuit boards (PCBs) for the high-voltage Q-switch electronics and the pulsed high-power current source of the diode-laser pumped Nd:YAG laser from “victim” PCBs for the sensitive Si avalanche photodiode detector (APD) operating at a noise floor of about 300 fA/sqrt(Hz) in a bandwidth of 100 MHz. Most importantly, the detector amplifier has increased phase margin to avoid feedback of undamped filter resonances, and its output is digitized as differential signal very close to the APD.