Proof of concept demonstration of a metastable helium fluorescence lidar for thermospheric wind and temperature measurements

We report on the first, to the best of our knowledge, spectral measurements of terrestrial thermospheric metastable helium using ground-based lidar. By stimulating fluorescence of He(2 S) at four closely spaced wavelengths within the He line around 1083 nm and measuring the lidar returns, we measured the He(2 S) spectrum at 600 km, providing coarse constraints on the He(2 S) temperature and vertical wind speed. This work serves as a proof of concept and precursor experiment for future, more powerful helium lidar systems capable of measuring vertical profiles of neutral wind and temperature in the upper terrestrial thermosphere.