X射线脉冲轮廓稳定性对导航精度的影响

X射线脉冲星具有广阔的导航应用前景,稳定的脉冲轮廓是自主导航的基础,然而在X射线脉冲轮廓的稳定性及其对导航精度的影响方面一直缺乏系统的研究.采用Pearson相关系数、标准偏差及功率谱熵三组指标量化脉冲轮廓的稳定性.利用罗西X射线计时探测器卫星X射线段(2—16 keV)11年的观测资料,统计了包括周期跃变在内的Crab脉冲轮廓稳定性.在此基础上,引入Cramer-Rao理论建立了脉冲轮廓稳定性对距离测量误差影响的数学模型,并通过分析各误差因素确定脉冲轮廓稳定性对距离测量误差的影响范围.实测数据处理表明,Crab脉冲星的X射线脉冲轮廓具有极高的稳定性,跃变期间脉冲轮廓无明显变化,脉冲轮廓的稳定性导致沿脉冲星方向上产生34 m±25 m的距离测量误差.

Effect of stability of X-ray pulsar profiles on range measurement accuracy in X-ray pulsar navigation

The Crab pulsar is an isolated rotation-powered pulsar which emits large X-ray fluxes, making it a candidate source for carrying out the X-ray pulsar navigation (XNAV). The long-term stable profiles are considered as the foundation of XNAV. However, systematic studies of the long-term stability of the X-ray pulsar profile and its effect on range accuracy in XNAV are lacking. In this paper, we use the X-ray band (2–16 keV) data monitored by Rossi X-ray timing explorer (RXTE) spacecraft over the latest 11 years, to first investigate the stability of the Crab pulsar including the profiles after the glitches. Furthermore, some measurements of the long-term profile shape, including Pearson correlation coefficient, standard deviation and spectral entropy, are presented both in the time domain and in the frequency domain. In the data processing, the Fourier analysis and cross-correlation are used to deal with the 191 RXTE data sets. With the help of the Cramer-Rao theory, the effect of the profile variation on the error of the range determination in XNAV is studied. Furthermore, after analyzing those errors, the effect of the stability of the Crab pulsar on range determination is confined to more narrow limits. The results demonstrate that the 2–16 keV profiles are almost constant during the period 2001–2012. The profiles after the glitches show no significant discrepancy. The variation of Crab profile inevitably has an influence on the navigation precision to a certain extent. The calculated range error along the pulsar line-of-sight due to the stability of the pulsar profile is 34 m±25 m.
Keywords： profile stability Rossi X-ray timing explorer spacecraft Crab pulsar glitches