Crossover Adjustment of ICESat-2 Satellite Altimetry for the Arctic Region

The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) mission, operated by NASA, was launched in September 2018. The mission aims to obtain height measurements that create a global portrait of Earth’s radial dimension, gathering data to monitor changes of terrain including glaciers, sea ice, forests and more. It is important to understand the error budget of the observations, one component of which is radial orbit error. Apart from the altimetric ranging errors, radial orbit errors directly influence the accuracy of the measurement of sea surface height (SSH). These errors can be assessed by analyzing the difference of SSHs at ground track intersections, so-called crossover differences (XO differences). An effective approach is to model the orbit error by minimizing the residual XO difference by the least-squares method. XO differences are assumed to be caused by the difference of radial orbit errors between ascending and descending arcs, the sea surface variation, mispointing, and measurement errors. Since the sea surface variation in a short time interval and measurement errors can be considered as random variable, these residuals can be reduced by the method of XO adjustment. In our study, the RMS XO differences of ICESat-2 is significantly reduced from 17.2 cm to 8.7 cm in the Arctic region.