卫星定位精度对在轨甚低频干涉测量影响分析

由于地球电离层的阻挡以及其他干扰,在地面难以进行有效的甚低频天文观测,而使用搭载于绕地或绕月轨道卫星上的甚低频天线进行干涉观测会大大提高观测灵敏度和角分辨率.卫星定位精度会影响观测数据的处理结果,进而影响成图质量,并且会大幅影响飞行项目的复杂度和总成本.首先分析卫星姿态控制精度和星间基线测量精度对绕地轨道甚低频干涉观测的影响,之后对干涉观测中信号延时误差进行仿真,研究延时误差与数据相关处理中条纹搜索范围之间的关系,并对数据计算速度需求进行估算.分析和仿真结果可以辅助相关空间甚低频观测项目总体方案的制定和工程指标的优化.

An Analysis of Influences of Satellite Positioning Accuracies on Earth-Orbital Ultra-Long Wavelength Interferometry

Being free from constraints on ground-based observations such as those due to the ionosphere and artificial/natural interferences, astronomical observations in ULW （Ultra-Long Wavelength） bands are more easily carried out in space. Antennas deployed on an Earth orbit can detect signals of frequencies well below 10MHz, and space interferometry can have baselines many times longer than the Earth diameter. Space interferometry can thus reach higher angnlar resolutions and sensitivities at ULW bands than interferometry. During interferometric observation antennas are synchronized to receive The observation data are then transmitted to ground stations for signals subsequent processing, ground-based simultaneously. including fringe search, signal correlation, and inverse Fast Fourier Transformations. For interferometric observation accuarcies of satellite attitudes and baselines between satellites will affect image quality and data-processing speeds. Using the fringe-search method in data processing can reduce the influences of signal-delay errors on result data correlation and images. Although some instruments for high-accuracy inter-satellite ranging can be carried on- board satellites to achieve highly accurate measurements for the purpose, this would increase the complexities and costs of relevant missions. In this paper we first analyze effects of control accuracies of satellite attitudes and measurement accuracies of baselines on Earth-orbital ULW interferometry. We then simulate a particular array configuration by taking into account satellite positioning errors in the direction toward the interference phase center. The simulations reveal the relations between signal-delay errors and fringe-search ranges as appearing in data processing. We also estimate data-processing speeds needed to achieve a common level of image quality for different fringe-search ranges. The simulation results show that for the adopted parameter set an increase of 6 times in the satellite positioning accuracies leads to a reduction of