关于X射线脉冲星自主导航的位置观测方程

摘要

在X射线脉冲星自主导航(XNAV)中,位置观测方程表达了X光子到达航天器的时刻(TOA)和航天器位置的关系.具体讨论时,一般用TOA和“时间基准”的差值代替TOA,用太阳系质心系中的位置矢量表示航天器的位置.“时间基准”可以取X光子到达太阳系质心(SSB)的真实时间,也可以取X光子到达SSB的“等效时间”.讨论了基于这两种时间基准的位置观测方程,给出了时间精度为0.1 ns的位置观测方程,分析了其中各项的物理意义.%The position measurement equation of XNAV (X-ray pulsar-based autonomous navigation) reveals the relation between the TOA and receiving position of X-ray signal. For navigation , TOA is often rewritten in the form of difference between TOA and some preset "time reference". The "time reference" may be the true TOA at SSB, or some "equivalent TOA" at SSB. Because the true TOA at SSB is difficult to obtain, the "equivalent TOA" is more convenient for navigation. From the expression of "true TOA", the expression of the "equivalent TOA" is derived, and the physical origin of each item is analyzed. The "equivalent TOA" consists of those items irrelevant to the craft, but relevant to the background. Then in the new measurement equation, the time difference concentrates on the items directly relevant to the position of the craft. The new equations has the time accuracy of 0.1 ns.