大气临边观测中视轴临边指向精度的在轨补偿

为提高大气臭氧观测中的临边大气反演精度,克服臭氧探测仪在轨热变形和卫星姿态误差对临边指向精度的影响,建立了在轨视轴临边指向的精度补偿方法。通过分析低星等恒星的能量和观测时机,设计合适的恒星观测窗口和积分时间;采用平板玻璃获取星点像的弥散斑,用阈值距心法计算恒星像在像面上的位置;然后根据卫星轨道和探测仪的几何结构,设计临边指向精度的在轨补偿方法并分析了补偿后的临边指向精度。地面对星观测实验的结果表明:采用恒星定位补偿法,可使星点像的定位误差小于1.83″,当前视轴的指向误差控制在±3.08″以内;在编码器的位置重复精度为±2.47″的条件下,使临边观测光轴位置上的扫描镜定位误差控制在±3.95″以内,臭氧探测仪临边指向精度达到±7.9″以上,完全满足反演所需的指向精度优于±12.4″的要求。

Correction Method On-Orbit for Limb Pointing Error of Ozone Detector

To improve the accuracy of the atmospheric inversion of an ozone observation instrument and to overcome the effects of thermal distortion and satellite attitude error on the orbit for the accuracy of limb pointing, an error correction method for the limb pointing of an ozone detector on the orbit was established. First, through the analysis of low-magnitude star energy and based on observations, an appropriate star observation window and integration time were designed. The blur spot of a star was obtained using flat glass. An image motion compensation technique was then used to ensure the blur spot was stable. The position of the star in the image plane was calculated using a threshold centroid. Subsequently, based on the satellite orbit and detector geometry, a pointing correction method was designed and the pointing accuracy was analyzed after being modified. The results of star observation experiments on the ground show that with this method, the error of stellar positioning is less than ±1.83″ and the pointing error of the visual axe is less than ±3.08″. When the encoder repeats accuracy is ±2.47″, the positioning error of the scanning mirror in the limb observation axis is within ±3.95″, and the accuracy of limb pointing of the ozone detector is better than ±7.9″, which fully meets the inversion accuracy requirement of ±12.4″.