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X射线脉冲星导航(X-ray pulsar-based NAVigation,XNAV)的原始导航信息是航天器接收的X光子时间序列,在折叠过程中估计出观测脉冲轮廓与相应标准轮廓的时延、频偏和频偏变率等参量,是XNAV的关键问题。首先给出光子数序列等相位点的时间关系,利用Larsson周期折叠法和相干函数法求初步近似;然后采用最小二乘法求高级近似,并利用循环迭代得到较为精确的频偏和时延估计值。初步仿真试验结果表明:即使不进行消噪和平滑处理,该方法也可以获得高精度的估计参数。虽然这一算法较为复杂,但它证明了XNAV的导航方法是完全可行的。
The original navigation information of X-ray pulsar-based navigation (XNAV) is the X-ray time series received by the spacecraft. During the folding process, the delay and frequency offset of the observed pulse profile and the corresponding standard profile are estimated Frequency deviation rate and other parameters, is the key issue XNAV. Firstly, the temporal relationships of phase points such as photon number sequences are given. The Larsson periodic fold method and the coherence function method are used to obtain the initial approximation. Then the high-order approximation is obtained by the least square method, and the more accurate frequency offset and delay estimation . The preliminary simulation results show that this method can obtain high-precision estimation parameters even without de-noising and smoothing. Although this algorithm is more complicated, it proves that XNAV navigation method is completely feasible.