The time tag bias estimation of HY-2 satellite radar altimeter

A satellite radar altimeter is one of the important sensors for an ocean remote sensing. An altimetry system and an orbit determination system are the most important components of the altimeter. If these two systems use different system clocks, there will be a time tag between the satellite altitude and the range which is the distance between the satellite and the sea surface in the nadir-looking direction of an antenna. The time tag can reduce the sea surface height measurement accuracy of the satellite radar altimeter. In this study, for the time tag bias problem of HY-2 satellite radar altimeter, the contribution of the time tag bias is analyzed to the sea surface height measurement accuracy, and a method is introduced to estimate the time tag bias value using self-crossover data. Based on the 21st cycle IGDR (Interim Geophysical Data Record) data of HY-2 satellite radar altimeter, experiments are carried out to correct the time tag bias. After correcting the time tag bias, the degree of convergence for the difference distribution of HY-2 self-crossover sea surface height is improved obviously, and the RMS of the HY-2 self-crossover sea surface height differences is reduced from 24.7 to 7.0 cm, and the RMS of the co-crossover sea surface height differences between HY-2 and Jason-2 is reduced from 16.6 to 7.3 cm. This suggests that the method for correcting the time tag bias can improve the sea surface height measurement accuracy of HY-2 satellite radar altimeter effectively.