The Research For Evaluations And Corrections Of HY-2Satellite Altimeter Instrument Error

Satellite radar altimeter is an important technology for ocean remote sensingobservations in current. It has the characteristics of all-day, all-weather, globalobservations and accurately reproducible, which makes a fundamental breakthroughfor ocean observing in real time and in large space scales, and provides a large amountof research data for oceanography, geodesy, geophysics and other fields.For the application of altimetry data in the oceanography, it needs to providecentimeter-level accuracy of the data. So there is a high demand for the high-precisionof satellite radar altimeter measurements and it must be carried out on the impactcentimeter accuracy error correction. The instrumental error is an important class oferror sources, and different types of instrument errors have a different order ofmagnitude of the error. But it is true that many of these error sources can reach theorder of centimeters and they must be corrected in the processing.Relying on the National Oceanic and Welfare Industry Funding for Research andSpecial Projects of the First Institute of Oceanography, SOA, this paper carried out theDoppler error and acceleration error, time tag bias and the error caused by theinconsistent of the height direction of the satellite orbit and the satellite antennapointing. At first, this paper introduces the basic principles of satellite altimetry andthen the experimental data used in this article. In this paper, a method of calculating theintersection of altimetry data and another method for benchmark unified used betweendifferent satellites in order to get as much as possible high-precision altimetry data forassessment. Then, the basic principles which produce the errors talked above aredescribed. And it also describes the detailed method for error correction processingbased on these principles. In which, the Doppler error and acceleration error can becorrected by the method of fitting continuous altimetry data using the method of leastsquares and using the first-order and second-order derivative independently tocalculate the errors with the corresponding equation. The time tag bias can also use the method of least squares to get a formula related to the rate of change of the heightmeasurement to estimate the error. For the mispointing error, this paper uses a methodof simulating the mean return power waveform. Through getting the differencebetween the retracking parameter in relate to the range and the simulation “true value”,it evaluates the measure accuracy of HY-2satellite radar altimeter. Finally, this papercompares the Histogram Distribution and Global Distribution between theself-interaction difference of HY-2’s sea surface height data before and after correctingthe error individually for the qualitative comparison and compares the RMS betweenthe self-interaction(or the cross-interaction) difference of HY-2sea surface height databefore and after correcting the error individually for the quantitative comparison. Theresult of the quantitative comparison is that the RMS of the self-interaction differenceof HY-2SSH is9.6cm, and the cross-interaction difference of HY-2SSH is10.7cmbefore correcting the Doppler error and Acceleration error. The two RMSs are26.6cmand16.6cm respectively before correcting time tag bias. Then the RMSs decrease to7.0cm and7.3cm respectively after correcting the errors of which we have talked to do.The results indicate that the processing methods discussed in this paper can improvethe measure accuracy of HY-2satellite radar altimeter effectively.