ICESat-2 ATLAS telescope testing

Many lessons were learned in the comprehensive testing of the one meter Beryllium flight telescope for the ICESat-2 mission. This paper will focus on testing areas of encircled energy analysis, plate scale measurements, and boresight alignment for alignment of fiber optic cables. The Optical Development System Lab (ODSL) at NASA's Goddard Space Flight Center (GSFC) was developed to build up experience using engineering test units. This experience was applied to testing the flight telescope. Several tests were able to be performed on the telescope itself, helping drive down risk, cost, and schedule during the integration phase of the telescope onto the instrument and box structure. The main ICESat-2 instrument is the Advanced Topographic Laser Altimeter System (ATLAS). It measures ice elevation by transmitting laser pulses, and collecting the reflection in a telescope. Because so few photons return from each pulse, the alignment of each receiver channel fiber is critical as well as minimizing the distortion.