The potential for processing bistatic SAR data using a monostatic airborne SAR processor with adapted motion and antenna pattern compensation algorithms

Kurzfassung

Synthetic Aperture Radar (SAR) is an active microwave imaging technique that achieves high spatial resolution by synthesising a long antenna aperture through platform motion. SAR imagery is obtained from the acquired raw data in a complex and computationally intensive image formation process. SAR data can be acquired in a monostatic configuration, where the transmit and the receive antennas are mounted on the same platform, or in a bistatic configuration, where the antennas operate on separate platforms. Bistatic SAR offers enhanced scattering characteristics, forward-looking capabilities, and reduced platform detectability. With the upcoming DuoLIM mission, DLR’s airborne SAR signal processing group will process bistatic SAR data for the first time. However, the groups operational SAR processor CARAMBA was designed with monostatic imaging geometries in mind. This thesis investigates the feasibility of modifying existing algorithms for Motion Compensation (MoCo) and Antenna Pattern Correction (APC) to enable efficient bistatic processing. The core methodology generalises the monostatic range calculation to the bistatic case, effectively transforming bistatic raw data into an equivalent monostatic representation. The approach is first validated in a simplified one-dimensional simulation, then integrated into CARAMBA’s processing workflow and evaluated on simulated two dimensional SAR data for various across-track and along-track configurations. While the original monostatic implementations proved unsuitable for the processing of bistatic SAR data, even for moderate baselines, results demonstrate that the modified algorithms maintain high imaging quality for across-track baselines exceeding 800 m and along-track baselines up to 1600 m. In many configurations, the results meet the quality criteria required for interferometric processing. The modified workflow is therefore well suited for both initial system validation activities and a broad range of subsequent scientific measurements. By demonstrating that geometric generalisation within the MoCo algorithm can extend the capabilities of a monostatic processors to bistatic scenarios, this work provides a robust, interim processing strategy ahead of the DuoLIM maiden flight. Moreover, the results obtained with this processing chain will be vital for verifying the outputs of dedicated bistatic image formation algorithms to be developed in the future.