In-orbit calibration of HY-2 altimeter using a signal reconstructive transponder

A reconstructive transponder for the internal path delay and backscattering coefficient calibration of the dual frequency radar altimeter onboard the HY-2 marine dynamic environment satellite is introduced. In comparion to the bent-pipe transoponder, which has been utilized for the in situ calibration of sereval satellite radar altimetry missions, the reconstructive transponder has real-time chirp tracking and response signal delay adjustment functions and provides a more flexible approach for radar altimeter in situ calibraton. The HY-2 calibration processure using reconstructive transponder and corresponding data post-processing are presented. Biases introduced by environment and instruments are corrected, and inner path delay, clock drift introduced delay and point target backscattering coefficient of the HY-2 altimeter can be obtained.