星载光学敏感器受天体干扰的可能性分析

各种用途的星载光学敏感器均可能受到日、月、地等天体进入敏感区所形成的干扰.对光轴固定于星体的星敏感器,以及光轴在空间中保持方位不变的天文望远镜两类星载光学敏感器,根据敏感锥面和天体锥面之间的空间位置关系,导出了天体干扰的发生条件,给出了预测干扰发生时间的实用计算公式.      

视场内导航星分布的预测

给出理想情况下视场内导航星分布模型的基础上,根据敏感器的星等门限和测量精度,进一步实现了存在星等误差情况下导航星分布的预测,使得该模型更为接近真实的情况.实验表明,采用该模型获得的分布与用MonteCarlo方法获得的统计分布极为接近,证明了该模型的正确性和有效性,从而得到了一种事先对视场内导航星分布作出较为准确估计的新的方法.      

一种采用行列聚类并行的星像坐标提取方法

为了提高星敏感器的数据更新率,必须减少星像坐标的提取时间.在提取星像坐标的过程中,现有基于FPGA的方法虽然避免了星图保存和读取过程,然而需要高性能的FPGA才能实现.为此提出了一种采用行列聚类并行的星像坐标提取方法,将逐个像素聚类的方式优化成像素队列聚类的方式,实现了对恒星星像坐标的实时提取,可以解决现有的实时提取星...     

GOCE star tracker attitude quaternion calibration and combination

We analyse the inter-boresight angles (IBA) measured by the star trackers on board the GOCE satellite and find that they exhibit small offsets of 7–9″ with respect to the ones calculated from the rotation of the star tracker reference frames to the satellite reference frame. Further, we find small variations in the offsets with a peak-to-peak amplitude of up to 8″, which correlate with variations of the star trackers’ temperatures. Motivated by these findings, we present a method for combining the attitude quaternions measured by two or more star trackers that includes an estimation of relative attitude offsets between star trackers as a linear function of temperature. The method was used to correct and combine the star tracker attitude quaternions within the reprocessing of GOCE data performed in 2018. We demonstrate that the IBA calculated from the corrected star tracker attitude quaternions show no significant offsets with respect to the reference frame information. Finally, we show that neglecting the star tracker attitude offsets in the processing would result in perturbations in the gravity gradients that are visible at frequencies below 2?mHz and have a magnitude of up to 90?mE. The presented method avoids such perturbations to a large extent.     

A triangle voting algorithm based on double feature constraints for star sensors

A novel autonomous star identification algorithm is presented in this study. In the proposed algorithm, each sensor star constructs multi-triangle with its bright neighbor stars and obtains its candidates by triangle voting process, in which the triangle is considered as the basic voting element. In order to accelerate the speed of this algorithm and reduce the required memory for star database, feature extraction is carried out to reduce the dimension of triangles and each triangle is described by its base and height. During the identification period, the voting scheme based on double feature constraints is proposed to implement triangle voting. This scheme guarantees that only the catalog star satisfying two features can vote for the sensor star, which improves the robustness towards false stars. The simulation and real star image test demonstrate that compared with the other two algorithms, the proposed algorithm is more robust towards position noise, magnitude noise and false stars.     

低温红外镜头星点检测数据处理方法研究

在实验室模拟低温真空环境对红外镜头进行星点检测时，不能在像面处直接测得星点光源的像，而是通过在焦面处放置反射镜使系统二次成像的方法测得二次成像的弥散斑大小。二次像斑尺寸的变化将能反映出由温度变化引起的被测镜头焦面处像斑尺寸的变化。通过理论推导得出一次像与二次像弥散斑大小的数学关系，并通过对不同尺寸星点光源、不同像质光学系统的仿真分析，得出星点检测法的检测精度与星点孔直径有关，而与镜头本身成像品质无关。     

基于星敏感器的卫星姿态估计方法研究

以星敏感器姿态信息作为测量数据,结合卫星姿态动力学方程组,采用增广卡尔曼滤波方法对无陀螺卫星姿态进行估计。研究发现,干扰力矩的变化会降低卫星姿态估计结果的精度,为此提出两种改进的姿态估计算法:增广自适应卡尔曼滤波方法和增广强跟踪卡尔曼滤波方法;仿真表明,两种算法都能很好地克服干扰力矩变化导致的精度下降现象。     

空天飞行器星敏感器安装误差在线标定方法

空天飞行器高动态、长航时的运动特性可能导致一体化安装的惯性/天文组合导航系统中星敏感器与惯导间产生安装误差角。设计了一种星敏感器安装误差角动态辨识方法,建立了星敏感器安装误差角模型,设计了基于天文角度观测的星敏感器安装误差角动态辨识方案,分析了不同机动飞行方式下星敏感器安装误差角的可观测度。仿真结果表明,所设计的基于卡尔曼滤波的动态辨识方法能够在飞行器机动过程中快速地对星敏感器安装误差角进行在线标定,对安装误差角的标定值可以达到实际误差值的85%以上,有效地提高了组合导航系统的精度。     

星相数据的姿态确定

本文给出了利用卫星拍摄的星相数据计算卫星姿态的数学关系式和计算方法。经实际使用证明这种方法是正确的。