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月基合成孔径雷达(SAR)与传统低轨SAR相比,成像几何上存在成像距离长的特点,其多普勒参数估计方法也不同于常规的机载和星载SAR.基于喷气推进实验室(JPL)高精度星历,可以通过插值获取月心在地心惯性坐标系下的位置、速度和加速度以及月球天平动,然后经由坐标转换得到月面任意位置在地心惯性坐标系下的位置、速度和加速度.在此基础上,建立了两个二次方程组,第1个方程组的解表示任意星下点离线角和斜视角情况下的波束矢量,第2个方程组求得波束矢量的模值,以此解算地面波束中心的坐标.结果表明,月基SAR的波束角需沿轨不断调整,而且天线放置的位置也会对多普勒参数产生明显影响.
Compared with the conventional low-orbit SAR, moon-based SAR has the feature of long imaging distance and its Doppler parameter estimation method is also different from the conventional airborne and spaceborne SAR.According to the Jet Propulsion Laboratory (JPL) high-precision ephemeris, the position, velocity and acceleration of the moon’s heart in the geocentric inertial coordinate system can be obtained through interpolation, and the lunar day can be translated, and then the position of any lunar surface under the geocentric inertial coordinate system can be obtained through coordinate transformation , Velocity and acceleration.On the basis of this, two quadratic equations are established, the solution of the first system of equations shows the beam vector under the condition of off-line and off-angle under any star point, the second equation obtains the beam The results show that the beam angle of the moon-based SAR needs to be adjusted along the track, and the location of the antenna will also have a significant impact on the Doppler parameters.