NASA’s ICESat-2 mission launched in September 2018 carrying a single instrument, the Advanced Topographic Laser Altimeter System (ATLAS). ATLAS uses a high-repetition-rate, low-pulse-energy laser with its output split into six beams and a photon-counting receiver to measure Earth surface elevation with centimeter-level precision, repeating its ground track every 91 days. During more than four years of on-orbit operation, ATLAS has met or exceeded its lifetime and performance requirements. We present performance measurements, trends and projections for several instrument parameter, including transmitted laser pulse energy, receiver sensitivity, the instrument’s impulse response, transmitter/receiver alignment, dead-time behavior, and elevation measurement performance. The laser energy setting was increased in September 2023, for the first time, to maintain ranging performance at its earlymission level. The trends in instrument parameters indicate capability to continue on-orbit operation of ATLAS for many years into the future.

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Anthony J. Martino, John Cavanaugh, Aimee Gibbons, James E. Golder, Alvaro Ivanoff, Peggy Jester, Nathan Kurtz, Thomas Neumann, Almut Pingel, and Craig Swenson, "ICESat-2/ATLAS at 4 years: instrument performance and projected life," Proc. SPIE 12512, Advanced Photon Counting Techniques XVII, 125120A (Presented at SPIE Defense + Commercial Sensing: May 03, 2023; Published: 15 June 2023); https://doi.org/10.1117/12.2665113.