地球反照对星敏感器的影响分析

Analysis of influence of earth albedo on star tracker

利用光度学的概念和点源辐射传输率(PST),提出了一种分析地球反照对星敏感器的影响的几何光学模型。该模型对地球表面按照经纬度划分了网格,为已知的TOMS反射数据的应用提供了接口,具有一定的通用性和实用性,可简要分析卫星上的星敏感器在一定输入条件下,包括轨道高度、星敏感器的安装方位、太阳入射角度等,地球反照到达遮光罩入口、出口的照度,以及不同离轴角下像面接收的地球反照的照度值。借助此模型,可以为星敏感器在卫星上的安装方位提出建议,并估算出星敏感器遮光罩的抗地球反照干扰性能。仿真分析表明,对于中低轨道而言,地球反照到达星敏感器遮光罩入口的辐照度变化不大,地球反照到达星敏感器遮光罩出口的辐照度主要与遮光罩自身的PST和遮光罩的安装仰角有关;当遮光罩的安装仰角φ=32.5°时,出口的辐照度下降到10-7W/m2,满足遮光罩消杂光的要求。

A geometry optical model for analyzing the influence of earth albedo on star tracker is presented. Based on the principle of photometry and Point Source Transmittance （PST）, this model has a certain generality and practicability by means of dividing earth surfaces into 2D cells with longitude and attitude and providing application interface of available TOMS reflectance data. It can be used to analyze the magnitude of irradiance of entrance and exit of a sunshade and corresponding imaging surface at different off-axis angles, where earth albedo pours on within some conditions, including altitude of orbit, installing position of star tracker, incident angle of sun, etc. Based on this model, we can make proposal of installing orientation of star tracker on satellites and estimate anti-earth albedo performance of sunshade of star tracker. Simulation indicates that for MEO and LEO, the irradiance of earth albedo reaching the entrance of sunshade of star tracker changes little, the magnitude of irradiance of earth albedo received by the exit of sunshade is mainly related to its PST and installation elevation;When this angle is equal to 32.5°, the irradiance of the exit of sunshade declines to 10-7 W/m2 ,thus satisfying sunshade＇s requirement of suppressing stray light.