On-Orbit Performance of the GF-7 Satellite Laser Altimetry System from 2020 to 2024

Abstract. The Gaofen-7 (GF-7) satellite represents China's first civil satellite equipped with a full waveform laser altimeter. This study aims to evaluate its on-orbit performance by analyzing the transmitting and receiving systems through the examination of waveform parameter and laser energy. The results indicate that the transmitting waveform of Beam 1 exhibits a little instability compared to that of Beam 2. It is supposed that the extreme solar activity on March 31st, 2022, affected the stability of the receiving waveform of Beam 1 in April 2022, while simultaneously impacting the stability of transmitting waveform and the receiving waveform of Beam 2’s transmitting and receiving. As a result, the pulse width of the receiving waveform for both Beams has been extended by approximately 1.5 ns and 2.4 ns, respectively after April 2022. Both beams have experienced a decline in ability to emit laser energy, with Beam 1 decreasing by 0.4 mJ per month and Beam 2 by 0.08 mJ per month. Notably, following the extreme solar activity, the rate of decline became more pronounced, escalating to 0.5 mJ per month for Beam 2. Overall, Beam 1 demonstrated superior transmitting and receiving radiation capacity compared with Beam 2, while the receiving radiation performance of both beams remained relatively stable. Nevertheless, there were some changes in the full waveform data transmitted and received by the altimetry system during the four years on-orbit peroid of the GF-7 satellite, the changes were very small, highlighting the overall stability of the laser altimetry system.