基于X射线脉冲星的最小误差熵定姿态方法

Autonomous attitude estimation method for spacecraft based on X-ray pulsars and minimum error entropy

提出一种基于X射线脉冲星能量观测信息和最小误差熵算法的航天器自主定姿方法.首先建立了圆形准直器差分测量模型,观测两颗脉冲星的辐射光子能量.然后引入信息熵概念来充分表征脉冲星辐射信号的随机性,用最小误差熵原理进行参数拟合,解出脉冲星在航天器坐标架下的方向矢量,通过矢量定姿法解算出航天器在参考坐标系中的完整姿态.最后结合美国国家宇航局HEACARC数据库提供的脉冲星观测数据进行了仿真试验,结果表明:在所给试验条件下,基于最小误差熵方法的参数估计精度要优于常用的最小二乘法,相比于后者,俯仰、滚动和偏航三轴精度分别提高了31.4%,27.1%和32.5%.

Aiming .at autonomously determining the attitude of spacecraft, a method only using X-ray pulsars was proposed. The method established a difference measurement model firstly. The model employed two cylindrical collimators and one X-ray detector to observe the radiation photon energy of pulsars. Then the light curve was obtained according to the characteristics of response function and the mathematical model. To fully represent the randomness of pulsar radiation signals, the concept of information entropy was introduced. The principle of minimum error entropy was employed to fit attitude parameters and work out aspect solution of pulsar in the spacecraft coordinate system. According to the known position of pulsars in the celestial coordinate system, the spacecraft attitude with respect to the celestial coordinates could be calculated. At last, combined with the observation data from NASA＇s HEASARC database, numerical experiments were given to verify the effectiveness of the method. The simulation results indicate that the precision of attitude determination using only X-ray pulsars can meet tile requirements of spacecraft attitude determination mission. With the given conditions, the accuracy of parameters fitting by the algorithm of minimum error entropy is superior to least square method and increases 31.4% ,27.1% and 32.5% in direction of pitch, roll and yaw, respectively.