Development of the reconstructive transponder for in-orbit calibration of HY-2 altimeter

HY-2 satellite, the first ocean dynamic satellite of China, was launched in August 2011, carrying a dual frequency (Ku band and C band) altimeter, to measure the global mean sea level [1]. To provide truly sea level measurements, in-orbit calibration is essential. This paper concerns the transponder in-orbit calibration method. A signal reconstructive transponder for HY-2 altimeter in-orbit calibration is presented. Different from the existing bent-pipe ones, this kind of transponder can capture and track altimeter pulses, record them, and reconstruct the chirp pulses, transmit them back to the altimeter. It is carried on a SUV, reduces requirement for a permanent installation site. With the characteristics of capture and record altimeter signals, the HY-2 altimeter inner path delay and clock drift could be derived from the calibration data.