三视场红外地球敏感器导航算法分析及研究

Numerical analysis and experiment study of navigation algorithm with triple-FOV infrared earth sensor

红外地球敏感器广泛运用于空间飞行器，尤其是在地球轨道附近。目前最新的静态地球敏感器使用焦平面探测器来覆盖整个地球红外辐射圆。若面向飞行在70—100km处的临近空间飞行器，地球敏感器就需要有很大的视场（〉120°）且相对分辨率很低。针对临近空间飞行器的天文导航运用，采用线阵CCD作为探测器，设计了一个三视场红外地球敏感器。地球敏感器的3个视场按照二维角度均匀分布以确保每个光学头能够均匀地指向地球红外辐射圆上。每个CCD覆盖20°以便能够精确地分辨地球辐射和空间的边界点。综合考虑地球辐射模型和地球扁率等因素，利用地球敏感器观测的向量可以获得地球水平、地心矢量和飞行高度。以70—100km飞行高度为示例，建立相应的数学模型，同时提出了相应的姿态和高度确定算法并进行了仿真。综合上述分析，研制了一套三视场地球敏感器原理样机并进行相关测试。仿真和实验结果表明：高度测量精度优于200m，姿态测量精度优于0．002°。

Infrared earth sensors are widely used in spacecraft, especially the ones around earth orbit. Nowadays the state-of-art static earth sensor employs a focal plane infrared detector to cover the entire earth infrared irradiation circle. As a result, aiming at the near space vehicles at the height of 70 - 100 km, the earth sensor needs to have a very large field of view （FOV） （ 〉 120°） and the relative accuracy is poor. In this paper, aiming at the near space vehicle astronomical navigation application, a triple-FOV （field of view） infrared earth sensor is designed using line CCDs as the detectors. Three FOVs of the earth sensor are uniformly distributed in 2- dimensional angle in space, which guarantees that each optical head is uniformly pointing to the spots on the earth infrared irradiation circle. Each CCD only covers an FOV of 20°, therefore the boundary points between earth irradiation and space are accurately distinguished. Comprehensively considering the earth irradiation model, the earth oblateness and etc. , from the observation vectors obtained by the earth sensor, the earth horizon, geocentric vector and flying altitude could be simultaneously obtained in the near space vehicle coordinate system. Taking the flight altitude of 70 - 100 km as an example, the related mathematic model was established, and the algorithm for determining the flying attitude and altitude was proposed, and the simulation was conducted. Upon this analysis, a prototype of triple-FOV earth sensor was built and related tests were conducted. The simulation and experiment results show that the altitude measurement accuracy is better than 200 m, and the altitude measurement accuracy is better than 0.002°.