热层氦激光雷达系统参数设计和性能分析

Parameter Design and Performance Analysis of Lidar System for Thermospheric Helium

为满足氦(He)激光雷达系统的探测指标,实现200~1000km大气中He原子密度的测量,对He密度探测激光雷达系统的参数和性能进行设计(主要包括激光发射部分、光学接收部分、数据采集和控制部分),对比在不同亚稳态He密度、不同积分时间、不同距离分辨条件下系统接收光子数与距离的关系,其中亚稳态He的密度对信号强度的影响最大。用较低高度的瑞利散射信号标定共振荧光信号,获得相对数密度曲线和信噪比(SNR)曲线。仿真结果显示,在积分时间为30min,距离分辨为50km,亚稳态He原子[He(2~3S)]密度最低的情况下,在250~530km高度范围内,相对误差小于2%,SNR大于40。结果证明系统设计的参数可以满足高层大气He原子密度的探测要求,对将来系统的实现有一定参考价值。

To achieve the detection targets of the helium （He） lidar system and to measure the density of He atoms of the atmosphere at altitude of 200-1000 km, the parameters and performance of the He-density detection lidar system are designed, which mainly includes laser emitting part, optical receiving part, data acquisition and control part. According to the parameters of the He lidar, the relationship between the expected number of photons received and the distance under the conditions of different metastable He ~He（23 S）] densities, integration time and range bin is compared, in which it is found that the density of metastable He（23 S） has the greatest influence on the signal intensity. The resonance fluorescence signals by Rayleigh scattering signals is calibrated at a common lower altitude to obtain a relative number density curve and signal-to-noise ratio （SNR） curve. The simulation results show that in the height range of 250~530 km, the relative error is less than 2% and SNR is more than 40 when the integration time is 30 min, the range bin is 50 km, and the density of He（2^3S） reaches the minimum. These results prove that the designed parameters of the system meet the detection requirement of He atom density in upper atmosphere and have certain reference value for the system implementation in the future.