RapidScat is a Ku-band scatterometer that was launched September 2014 and is currently operating on the International Space Station. It estimates ocean vector winds through accurate measurement of the normalized radar coefficient (σ0) of the ocean surface. In order to ensure the accuracy of σ0 measurements and consistency with previous Ku-band scatterometers, post-launch calibration and validation is necessary. Calibration and validation is performed using natural land targets, namely the Amazon and Congo rainforests, to complement calibration efforts over the ocean. The σ0 response of the targets is estimated with respect to viewing angle and time of year using previous Ku-band scatterometers. Taking advantage of the ISS orbit, the diurnal response of each target is estimated using RapidScat. Normalizing factors for incidence angle, azimuth angle, local time of day, and time of year are derived from these measured responses. RapidScat σ0 measurements are found to be consistent throughout its mission life with instrumental drift less than 0.3 dB. The effectiveness of slice balancing is evaluated and found to be highly dependent on the pitch of the ISS. Understanding of the diurnal backscatter response and incidence response allow comparison of RapidScat measurements with measurements from the QuikSCAT, NSCAT, and Oceansat-II scatterometers. RapidScat σ0 is found to be biased low compared to QuikSCAT by 0.1--0.3 dB.



College and Department

Ira A. Fulton College of Engineering and Technology; Electrical and Computer Engineering



Date Submitted


Document Type





RapidScat, QuikSCAT, scatterometer, calibration