L and VHF Band Airborne SAR. System Features and Comparative Image Analysis

To provide an opportunity to perform multichannel low-frequency radar experiments, airborne SAR “Compact” was designed to operate in L and VHF band. Both channels were mounted on board of Mi-8 helicopter without the need of any platform modification. The SAR system gives the possibility to obtain VHF data in VV and HH polarizations. L and VHF band observations were performed simultaneously, under the same conditions, for the several test sites equipped with calibrated corner reflectors. Reflectors were specially calibrated for both L and VHF bands and for VV and HH polarization (in both bands). The comparative analysis of backscattering properties for some natural surfaces was performed using generated SAR images. Backscatter coefficients for surfaces for L and VHF band were calculated. These measurements are in good fit with the results obtained by other SAR under similar observation conditions. Several examples of L and VHF SAR images containing clearly seen frequency- and polarization-dependent differences are demonstrated. The joint use of VHF band VV and HH images seems to be an interesting instrument in SAR image analysis.