The use of small drone platform has become a popular topic in these days but its application for SAR operation has been little known due to the burden of the payload implementation. Drone platforms are distinguished from the conventional UAV system by the increased vulnerability to the turbulences, control-errors and poor motion stability. Consequently, sophisticated motion compensation may be required to guarantee the successful acquisition of high quality SAR imagery. Extremely limited power and mass budgets may prevent the use of additional hardwares for motion compensation and the difficulty of SAR focusing is further aggravated. In this paper, we have carried out a feasibility study of mico-SAR drone operation. We present the image acquisition results from the preliminary flight tests and a quality assessment is followed on the experimental SAR images. The in-flight motion errors derived from the unique drone movements are investigated and attempts have been made to compensate for the geometrical and phase errors caused by motions against the nominal trajectory. Finally, the successful operation of drone SAR system is validated through the focussed SAR images taken over test sites.

Airborne synthetic aperture radars(SARs) are vulnerable to geometric distortion when operated in the squinted mode. The polar format algorithm(PFA) is preferred owing to its convenient motion compensation, good image quality, and efficient computational performance. As a major drawback of the conventional PFA, the increase in data distortion under the forward-looking mode results in interpolation errors, thereby deteriorating image quality. In this paper, we propose a high-resolution SAR processing method based on the sub-aperture division PFA. In this approach, multiple antenna beams are imposed on extended areas divided by sub-aperture regions. Antenna beam steering is implemented from multiple platforms to simultaneously collect raw data from the sub-apertures. Thereafter, multiple sub-data images, each featuring low-resolution qualities, are processed in parallel to compensate for phase distortion and further merged to obtain a complete SAR image over an extended area. The results show that the synthesized SAR image yields an improved quality with enhanced resolution.

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