Research on Calculation Method of Doppler Centroid Shift from Airborne Synthetic Aperture Radar for Ocean Feature Retrieval

Abstract

Doppler center shift is an important parameter for Synthetic Aperture Radar(SAR) to retrieve ocean surface wind field and ocean surface current field. We present a calculation method of Doppler centroid shift for airborne side-looking SAR. We compute Doppler centroid frequency by aircraft motion status data and ocean detection echo data respectively, and make difference to solve the Doppler centroid shift. In order to remove the influence of noise, we add wavelet analysis in Doppler spectrum analysis method to improve Doppler centroid frequency accuracy from ocean detection echo data. We carry out flight detection experiment by airborne SAR to obtain the Doppler centroid shift, while put buoy wind direction and wind speed in detection area into CDOP geophysical model function to simulate the Doppler centroid shift as compared to the validation true value. Flight detection results of 9 group data show that the calculation error absolute value of Doppler centroid shift are less than 2 Hz, and the RMS error is 1.4 Hz. It is meets the accuracy requirements of marine environmental factors retrieval, and proves the effective of Doppler centroid shift calculation method. In practical applications, the accuracy of Doppler centroid shift calculation is the key to the application of marine environment research, which requires high-precision platform motion data and sounding echo data to ensure application value.

Keywords

• Airborne side-looking Synthetic Aperture Radar(SAR)
• Doppler centroid shift
• Calculation method
• Doppler centroid frequency