The synthetic aperture radar (SAR) is a type of active radar that can obtain polarization scattering information of ground objects, which is an important supplement to optical remote sensing. This paper designs a high-precision quantitative SAR system that combines radiation and polarization calibration processing to achieve a subtle perception of the changes in soil moisture and straw coverage. In Yushu, Jilin, we conducted the first S-band agricultural remote sensing application experiment. The backscattering coefficient was measured under different water content and straw coverage conditions, and the results showed that the backscattering coefficient increased by about 2 dB and 6 dB, respectively. We estimated that the soil water content increased by about 0.01 cm³/cm³, which was consistent with the theoretical analysis. The polarization scattering characteristics also showed significant differences under different straw coverage. The results indicated that S-band quantitative SAR had an excellent response ability to water content and straw coverage, which provided a technical basis for further radar agricultural applications in the future.

For the challenges of high-precision mapping in complex terrain, a novel airborne Interferometric Synthetic Aperture Radar (InSAR) system is designed. This system, named ASMIS (Airborne Short-Baseline Millimeter-Wave InSAR System), adopts the coplanar antenna and a pod-type structure. This design makes the system lightweight and highly integrated. It can be compatible with small general aviation flight platforms. The baseline is millimeters in size, which greatly simplifies the unwrapping process. The coplanar antennas have two advantages: they maximize the baseline utilization and minimize the Doppler decorrelation and the motion error inconsistency. Acquisition campaigns of the system have been carried out in Boao, Bayannur, and Chengde, China. In the Chengde experimental area, we designed an antiparallel flight experiment to account for the topographic relief. High-precision Digital Orthophoto Maps (DOMs) and Digital Surface Models (DSMs) at a scale of 1:5000 were obtained. The coordinate Root Mean Square Error (RMSE) of the checkpoints within the obtained DSM is less than 0.82 m in altitude and 3 m horizontally. The RMSE of the Sparse Ground Control Points (GCPs) within the obtained DSM is less than 0.3 m in altitude. Experimental results from different areas, including plains, mountains, and coastlines, demonstrate the system’s performance.

Based on the high-precision quantitative measurement ability, the S-band subsystem of China's high- resolution aviation system carried out the agricultural application test for the first time in Jilin elm, China. The experiment is mainly carried out in combination with vegetation growth, soil moisture content inversion, wheat straw returning and ground feature classification. Through the design of quantitative measurement scheme, the results of different straw coverage and observation at different times are compared, which shows the prospect of S-band full polarization synthetic aperture radar system in the field of agricultural application.

Single-pass dual-antenna airborne millimeter-wave interferometric synthetic aperture radar (InSAR) provides high spatial accuracy, yet is highly sensitive to minor baseline deviations, owing to its the narrow beamwidth, short wavelength and short baseline configuration. Based on the airborne shortbaseline millimeter-wave InSAR system (ASMIS), this study proposes a framework for dynamic baseline calculation and motion compensation, combining with real-time onboard attitude guidance, to achieve high accuracy elevation surveying. Firstly, we model- the spatial relationships among aircraft, POS, rotating mechanism and antenna phase centers, and derived center position of two antennas from IMU to calculate the dynamic baseline. And then, the motion compensation is executed in two steps: real-time onboard attitude guidance and ground-based post-processing. Onboard, we adopt a mechanical range scanning and electronic azimuth scanning scheme, which concurrently suppresses inclination error and corrects beam steering. In the subsequent ground-processing stage, a compensation strategy combined with attitude residual adjustment is proposed to achieve precise height reconstruction. Experimental results demonstrate that the vertical error of the generated Digital Surface Models (DSMs) is less than 0.5 m in terrain with 100 m relief, as validated by ground control points. In high-relief mountainous regions, the system achieved an elevation root-mean-square error (RMSE) of 2.65 m relative to SRTM data, confirming the high precision of the ASMIS in complex environments.