A Helium Lidar system, which is being developed for measurements of metastable helium density in the thermosphere and exosphere, employs a CW 1083nm laser with power of 60W, a telescope array consisting of six 1m-diameter telescope and an area-array ICCD. To realize range-resolved remote sensing, the laser is located separately from the location of telescope with a distance of D and the laser beamed is leaned towards the Field-of-view (FOV) of the telescope array with an zenith angle of θ. The signal in a specific height is finally imaged onto a corresponding pixel of the ICCD. Before the retrieval of metastable helium density, the first procedure is to decide the relation between the pixels and corresponding heights. Based on the FOV of the telescope, the divergence angle of the laser beam, the geometry of the laser and telescope, and the size of the pixels, every pixel corresponds to a specific height range, as shown in Fig. 1. The darkest shade corresponds to one pixel of the ICCD. Therefore, the second procedure is to correct the height range overlap of the signal from adjacent pixels to decrease the smoothness of the signal profile caused by the height overlap of adjacent pixels. The signal received by the ICCD is simulated based on a metastable helium density model developed by Waldrop et. al. The results show that these two signal correcting procedures can improve the precision of each pixel’s signal by 5% in average.

Since the first space-borne Doppler wind lidar, Aeolus, was launched, global wind field observations from space have been possible. Several ground- and air-based validations followed, although most of these comparisons remained below 10 km in the troposphere, with rare validation work for the stratosphere. The Rayleigh Doppler lidar developed by the University of Science and Technology of China (USTC) was deployed in Xinjiang, China in 2017. It can observe wind speed and temperature in the stratosphere and mesosphere. By setting two geographical ranges centered on the USTC lidar, the Aeolus Rayleigh winds within these ranges can be compared with ground-based lidar wind data. Furthermore, after eliminating the effect of particulate backscatter on the USTC lidar, the lower limit of the detection range was extended to 10 km to obtain more samples. The mean biases between the Aeolus winds and the USTC lidar winds were 1.05±5.98 (-0.35±4.78) m/s, 1.80±6.30 (-1.88±4.97) m/s, and 0.17±5.45 (0.51±4.44) m/s for all data, ascending orbits, and descending orbits, respectively, in a large (small) geographical range. The results for descending orbits have a higher degree of consistency with those for ascending orbits, and the farther the distance between Aeolus observation swaths and the USTC lidar, the greater the bias. Overall, the Aeolus winds are consistent with the USTC lidar winds in the stratosphere.