星载激光测高仪大气干项延迟校正

Hydrostatic delay correction for satellite laser altimeter

星载激光测高仪发射的激光脉冲在通过地球大气层时发生折射,导致激光路径的延长,为了获得高精度的测距结果,必须对大气延迟进行修正;而大气干项延迟在大气延迟中占主导作用,仅由测量位置的地表大气压力决定。通过推导静态大气在非理想气体条件下的流体静力学方程,得出地表气压与位势高度有关的大气压力模型,结合NCEP基于标准大气压层的气象数据和GLAS测量的时间经纬度和高程数据,对位势高度使用4阶Runge-Kutta算法进行数值积分得出地表气压,进而计算大气干项延迟。通过该方法和NCEP地表气压估计得出的干项延迟分别与GLAS官方公布的干项延迟对比,该方法计算结果的趋势与准确程度均占优,且最大干项延迟误差小于2 cm。证明通过流体静力学方程数值积分计算地表气压的方法能够得出对星载激光测高仪较为准确的大气干项延迟。

The laser pulse transmitted by satellite laser altimeter bends for atmospheric refraction and extends the ray paths, and it is necessary to correct the atmospheric delay to get accurate ranging results. The hydrostatic delay is the major component of total zenith delay, which is only decided by surface pressure. The hydrostatic equation of static atmosphere was deduced under the condition of non-ideal gas, and surface pressure model was established relevant to geopotential height. Combined with the meteorological data of NCEP and position and elevation data of GLAS, the surface pressure was calculated by numerical integration of 4 order Runge-Kutta algorithm, and then the hydrostatic delay was obtained. Through the respective comparisons between the hydrostatic delays got by this method and the NCEP estimated surface pressure with the GLAS official results, the trend and accuracy of this method are both better with the maximum error less than 2cm. It is concluded that the hydrostaticdelay of satellite laser altimeter can be corrected effectively and accurately by the method based on hydrostatic equation and numerical integration.