基于有源定标器的HY-2B卫星雷达高度计时钟频率偏差在轨测试

In-Orbit Test of Clock Frequency Deviation of HY-2B Satellite Radar Altimeter based on Transponder

雷达高度计的主要功能是测量全球平均海平面高度(SSH:Sea Surface Height),它通过准确测量收发脉冲之间的时间间隔来实现精准的星地距离测量,时间测量的准确度取决于高度计时钟的准确性。卫星在轨运行期间,雷达高度计时钟频率会产生缓慢漂移,时钟频率漂移会影响星地距离的测量准确度,造成对海面高程的测量偏差。在基于重建型有源定标器对HY-2A卫星高度计时钟偏差在轨测试方法的基础上,提出了从星地斜距函数曲线时间偏移量中提取高度计时钟偏差的估计方法,应用于HY-2B卫星雷达高度计在轨定标测试中,测量了雷达高度计时钟频率漂移量,精度优于0.001 Hz。结果表明:HY-2B高度计原子钟性能稳定,时钟频率偏差造成的测距偏差为毫米量级,平均测距漂移率为2.95×10^(-7)m/d。

The main function of radar altimeter is to measure the global average Sea Surface Height(SSH). It can accurately measure the satellite ground distance by measuring the time interval between sending and receiving pulses. The accuracy of time measurement depends on the accuracy of altimeter clock. During the operation of satellite in-orbit,the frequency of radar altitude clock will drift slowly,which will affect the accuracy of satellite ground distance measurement and result in the measurement deviation of sea surface elevation. Based on the in-orbit test method of altimeter clock deviation of HY-2 A satellite based on reconstruction transponder,this paper proposes an estimation method of altimeter clock deviation extracted from the time offset of satellite ground offset function curve,which is applied to the in-orbit calibration test of HY-2B satellite radar altimeter.The frequency drift of radar altimeter is measured,and the accuracy is better than 0.001 Hz. The results show that the performance of the atomic clock of HY-2B altimeter is stable,the range error caused by clock frequency deviation is millimeter magnitude,and the average range drift rate is 2.95×10^(-7) m/d.