Method for determining the footprint center of a satellite laser altimeter based on marked waveforms by CCRs.

Abstract

To evaluate the data accuracy of a satellite laser altimeter, in situ verification should be performed periodically, and the laser footprint center should be precisely extracted and positioned. To date, two methods have been derived to determine the center of the laser footprint: using waveform matching when a laser is illuminated on complex surfaces or using an energy detector array to capture the laser footprint when illuminating a flat calibration site. A corner cube retroreflector (CCR) array is never used to calculate the footprint center. In this study, a new method is derived to determine the laser center by analyzing the return waveforms, which are marked with a designed CCR array above ground. First, the parameters of a single CCR are designed to compensate for the velocity aberration of a satellite. The footprint center is positioned based on a damped steepest decent method when at least four CCRs are hit, and the corresponding return waveforms are marked. Next, the layout scheme of the CCRs is designed, and the positioning accuracy is evaluated using this new method. The simulated results indicate that the positioning accuracy of the laser footprint centers will be approximately 2m horizontal. In the future, this method will be used to determine laser footprint centers and will be integrated with the current method of energy detector array in the calibration site to provide basic data to accomplish in situ verification work for the China GF-7 satellite laser altimeter.