The imaging method of the non-uniform movement for GEOSAR

Synthetic aperture radar on geosynchronous orbit (GEOSAR) can realize the continuous image on the larger coverage area in the short revisit period of nearly 24h. However, the problems with the variable velocity along the geosynchronous orbit and the path delay effect for the higher altitude of about 36000km, make the classical imaging methods are not suitable for the signal processing of GEOSAR. Hence, in this paper, we infers the satellite-object-satellite range model considering the path delay, and the new imaging method based the above range model is also provided in detail. The new approach firstly implements the delay processing and the motion compression eliminating the effect of the curve track. In the following, we carry out the conversion from the uniform sampling to the non-uniform sampling in the azimuth time domain. Then, through the non-uniform discrete Fourier transform, the non-uniform sampling in the azimuth time domain is transformed to the uniform sampling in the azimuth frequency domain. After the series of the processing steps of the new approach, the focused imaging results are obtained. Finally, the imaging simulation further verifies the effectiveness of this method.