Metastable helium He (23S) is a potential tracer for lidar detection of thermosphere and even exosphere. The lidar group in University of Science and Technology of China has been developing a large metastable helium lidar system since 2019. In the summer of 2023, the lidar system was initially assembled in Danzhou, Hainan Province of China. This system consists of 3 1083nm pulsed lasers with energy of more than 70 mJ and an array of 6 telescopes with diameter of 1m. The detector is a superconducting nanowire single photon detector (SNSPD). Observations are performed in case of clear night since November and more than 30 days of valid data was collected. More data processing and retrieval methods will be conducted in the future.
Zhao et al. (Thu,) studied this question.