Accurate control and guidance of spacecraft require continuous high performance three-dimensional navigation solutions. Celestial sources that produce fixed radiation have demonstrated benefits for determining location near Earth and vehicle attitude. Many interplanetary navigation solutions have also relied on Earth-based radio telescope observations and substantial ground processing. This dissertation investigates the use of variable celestial sources to compute an accurate navigation solution for autonomous spacecraft operation and presents new methodologies for determining time, attitude, position, and velocity. A catalogue of X-ray emitting variable sources has been compiled to identify those that exhibit characteristics conducive to navigation. Many of these sources emit periodic signals that are stable and predictable, and all are located at vast distances such that the signal visibility is available throughout the solar system and beyond. An important subset of these sources is pulsar stars. Pulsars are rapidly rotating neutron stars, which generate pulsed radiation throughout the electromagnetic spectrum with periods ranging from milliseconds to thousands of seconds.A detailed analysis of several X-ray pulsars is presented to quantify expected spacecraft range accuracy based upon the source properties, observation times, and X-ray photon detector parameters. High accuracy time transformation equations are developed, which include important general relativistic corrections. Using methods that compare measured and predicted pulse time of arrival within an inertial frame, approaches are presented to determine absolute and relative position, as well as corrections to estimated solutions. A recursive extended Kalman filter design is developed to incorporate the spacecraft dynamics and pulsar-based range measurements. Simulation results demonstrate that absolute position determination depends on the accuracy of the pulse phase measurements and initial solutions within several tens of kilometers are achievable. The delta-correction method can improve this position solution to within 100 m MRSE and velocity to within 10 mm/s RMS using observations of 500 s and a 1-m2 detector. Comparisons to recorded flight data obtained from Earth-orbiting X-ray astrophysics missions are also presented.Results indicate that the pulsed radiation from variable celestial X-ray sources presents a significant opportunity for developing a new class of navigation system for autonomous spacecraft operation.
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机译:航天器的精确控制和引导需要连续的高性能三维导航解决方案。产生固定辐射的天体辐射源已证明对确定地球附近的位置和车辆姿态有好处。许多行星际导航解决方案还依赖于基于地球的射电望远镜观测和大量的地面处理。本文研究了使用可变天体源来计算自主航天器运行的精确导航解决方案,并提出了确定时间,姿态,位置和速度的新方法。已编制了X射线发射变量源目录,以识别那些具有有助于导航的特征的变量。这些源中的许多源都发出稳定且可预测的周期性信号,并且它们都位于很远的距离,因此整个太阳能系统及其他区域都可以看到信号。这些来源的重要子集是脉冲星。脉冲星是快速旋转的中子星,在整个电磁波谱中产生脉冲辐射,周期从毫秒到几千秒不等。根据源特性,观测时间,对几种X射线脉冲星进行了详细分析,以量化预期的航天器射程精度。和X射线光子探测器参数。开发了高精度的时间变换方程,其中包括重要的一般相对论校正。使用比较惯性框架内测得的和预测的脉冲到达时间的方法,介绍了确定绝对和相对位置以及对估计解的校正的方法。开发了递归扩展卡尔曼滤波器设计,以结合航天器动力学和基于脉冲星的距离测量。仿真结果表明,绝对位置确定取决于脉冲相位测量的精度,并且可以在几十公里之内获得初始解。使用500 s的观测值和1-m2的检测器,增量校正方法可以将此位置解提高到MRSE 100 m以内,将速度提高到RMS / mm 10s / s以内。还对与从地球轨道X射线天体物理学任务获得的记录的飞行数据进行了比较。结果表明,来自可变天体X射线源的脉冲辐射为开发用于自主航天器操作的新型导航系统提供了重要的机会。
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