Recently, researchers use data analysis or simulation to validate algorithm of "X-ray pulsar autonomous navigation". Concerning the error estimation methods, the error magnitude and the various affecting factors of spacecraft autonomous positioning, a conclusion has not given based on the specific initial conditions. In this paper, Astrometry method is used to estimate errors of spacecraft autonomous positioning based on pulsar timing. Obviously, uncertainty of a timing measurement has direct influence on autonomous positioning; this uncertainty has difference and relation between timing noise. Given pulsars with different distance, we discuss whether or not to replace expression of spherical wave with plane wave, whether or not to ignore pulsar distance uncertainty even distance related term under recent arrival-time precision. We make analysis of how to build pulsar clock model when lack of radial velocity. At last, we analyze affecting features of pulsars spatial distribution on positioning coordinate components of a spacecraft.%目前很多学者希望从"X射线脉冲星自主导航"的导航算法研究入手,利用数据分析或仿真进行验证.其中关于航天器自主定位的误差估计方法、误差量级和各种影响因素的讨论,并没有在给定详细初始条件的基础上系统性地说明问题.为了分析上述问题,需从天体测量学的角度出发,对自主定位的各种误差源及其影响因素进行探讨和误差量级的估计.首先,由脉冲到达时间测量精度的定义出发,在对比了其特征及其与计时噪声的区别和联系的基础上,在现有观测精度条件下,分析了对于不同距离的脉冲星是否可以用平面波代替球面波的表达,是否可以在时延表达式中忽略脉冲星距离的不确定性以及是否可以忽略脉冲星距离相关项.其次,在缺少脉冲星视向速度资料的情况下,分析了对脉冲星计时数据处理和建立脉冲星自转模型的影响.最后,从原理上分析了脉冲星空间分布对自主定位精度的影响.
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