Autofocusing synthetic aperture radar images , by C. Prati

Correct focusing of Synthetic Aperture Radar data depends upon knowing both the geometric and transmission parameters of the system precisely. Transmission parameters (i.e. transmitted wavelengths, pulse repetition frequencies, sampling rate, etc.) are generally defined specifically, whereas geometric parameters such as sensor- target relative positions, satellite velocities, attitude etc. can be derived from the satellite effemerides or data. Referring to the focusing technique described by Rocca (1987), the only two geometric parameters involved in the focusing process are the sensor-target relative velocity and the sensor-target closest approach distance. In this paper, we suggest a technique to extract these two geometric parameters from the data themselves (autofocusing) in order to achieve the best possible focusing of SAR images. This technique has been tested both on synthetic and on real SEASAT and SIR-B data. The achieved precision of the parameters value has been estimated to be better than one part over ten thousand.


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