Estimating the Time Tag Bias of HY-2A Radar Altimeter and Its Application to Dual-frequency Ionosphere Correction |
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| Authors: | Maofei Jiang Ke Xu Yalong Liu Lei Wang |
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| Institution: | 1. Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese Academy of Sciences, Beijing, China;2. University of Chinese Academy of Sciences, Beijing, China;3. Yantai Marine Environmental Monitoring Center Station, State Oceanic Administration, Yantai, China |
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| Abstract: | The sea surface height (SSH) derived from radar altimetry is determined by the distance from the satellite to the sea surface and the altitude of the satellite above a reference ellipsoid. The former is measured by the radar altimeter, while the latter is determined by the precision orbit determination (POD). The clock for the POD equipment is independent from that of the radar altimeter onboard the HY-2A satellite. The time tag bias, which is the bias between the time tags provided by the two independent clocks, can greatly affect the SSH measurement accuracy of HY-2A altimeter. This paper estimates the time tag bias of HY-2A radar altimeter using the crossover differences obtained from the sensor geophysical dataset records (SGDR) from February 2014. We obtained a ?0.61-ms Ku-band time tag bias and a ?5.61-ms C-band time tag bias. After we added the time tag bias corrections to the SSH measurements from Ku and C bands, respectively, the means and standard deviations of the global crossover differences can be significantly reduced. We then applied the SSH measurements with the time tag biases corrected to calculate the HY-2A dual-frequency ionosphere correction, significantly improving the accuracy of the HY-2A dual-frequency ionosphere correction. |
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| Keywords: | Dual-frequency ionosphere correction HY-2A radar altimeter time tag bias |
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