天宫二号紫外前向光谱仪大气临边高度计算

High precision limb height calculation of ultraviolet forward spectrometer of TianGong-2

天宫二号紫外前向光谱仪是一种对全球中层大气进行大气痕量气体垂直分布探测的新型光谱仪,在对大气痕量气体进行反演中,需要高精度地计算观测大气的高度参数等几何位置参数。本文针对该光谱仪的几何成像特点,设计并提出了一种高精度的大气高度的计算方法。首先,计算传感器坐标系下的观测矢量;其次,利用平台的轨道参数、姿态及成像时间等成像几何参数,推导出传感器坐标系到地心固定坐标系的转换矩阵,同时将观测矢量转换到地心固定坐标系下;再次,以标准地球椭球体为基准,建立经过临边切点的虚拟椭球体模型,并计算切点的地理坐标;最后,依据切点坐标推导出切点的临边高度。与理论值对比分析,在相同地球临边高度对应的散射光谱幅亮度分布保持一致,并且与美国OMPS载荷反演的O3结果进行定位误差分析,高度误差小于1pixel,在2km范围内,从而验证了本文所提算法的可行性和正确性。

TianGong-2 ultraviolet forward spectrometer is a new type of spectrometer to detect the vertical distribution of atmospheric trace gases in the middle atmosphere of the world. In view of the geometric imaging characteristics of the spectrometer, a high precision calculation method of atmospheric altitude was proposed in this paper. Firstly, the observation vector in the sensor coordinate system was calculated. Secondly, the transformation matrix of the sensor coordinate system to the geocentric fixed coordinate system was derived by using the geometrical parameters such as orbital parameters, attitude and imaging time of the platform, and the observation vector was transformed into the geocentric fixed coordinate system. Thirdly, based on the standard earth ellipsoid, the virtual ellipsoid model through the tangent point was established and the geometric coordinates of the tangent point were calculated. Finally, the limb height was derived according to the tangent point coordinates. The luminance distribution of the scattered spectral spectrum is consistent with the theoretical value at the same limb height, and compared with the O 3 results of OMPS inversion in the United States, the height error is within 2 km, which verifies the feasibility and correctness of the proposed algorithm.