Future spaceborne synthetic aperture radar (SAR) systems are expected to deliver enormous quantity of data. Accordingly, the observation plan becomes crucial for a proper allocation of the mission resources. A central challenge is to reduce the number of acquisitions by making the same image available for more applications. Here, a relevant restriction is the interferometric incompatibility between fully polarimetric (QP) and single polarimetric (SP) SAR images, which typically occurs when the acquisitions are performed in burst mode, as in case of SAR products with wide coverage acquired by means of ScanSAR or terrain observation by progressive scanning (TOPS) technique. In order to overcome this limitation, a new operational mode, denoted as beam-switch wide-swath (BSWS), was conceived. The BSWS mode exploits the operational flexibility of future SAR systems to generate SP images, interferometrically compatible with the QP ones, keeping the wide coverage characteristic of the SP products. This letter presents in detail the BSWS mode, analyzing its functional principle, and imaging performance, based on a realistic future SAR system, the high-resolution wide-swath (HRWS) SAR, considered for the next generation of the Sentinel-1 mission.@en

The High Resolution Wide Swath (HRWS) system opens up new horizons for spaceborne synthetic aperture radar (SAR) imaging. In order to best exploit the HRWS capabilities as successor of the current Sentinel-1 mission, a study focused on the HRWS applications was recently founded by the European Space Agency. Within this study, a new operational mode, denoted as Beam-Switch Wide Swath (BSWS), was proposed by the German Aerospace Centre to provide a better answer to specific final user needs. In fact, the BSWS exploits the operational flexibility associated with the HRWS multi-channels architecture and digital beamforming capability to generate single/dual-polarimetric (SP/DP) images, interferometrically compatible with the fully polarimetric ones, while keeping the wide coverage of the SP products. This paper presents the BSWS mode, explains its functional principle and analyses its imaging performance, based on a realistic HRWS reference system.

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SAR instruments with multiple transmit/receive channels allow for a variety of operation modes. The trade-space includes the instrument and antenna parameters designed to enable various operation modes. These are utilized to achieve a required SAR performance derived from the mission and user requirements. Finding a solution in this multi-dimensional trade space is not trivial and often involves the compromise of parameters. This paper addresses the topic of SAR instrument design tailored to a set of operation modes. It explains and compares the SAR techniques and gives the performance.

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SAOCOM-CS denotes a satellite formation based on SAOCOM, Argentina's L-band SAR satellite, and a small passive companion satellite (CS) of the European Space Agency (ESA). The realization of this mission is currently under evaluation by ESA. A possible acquisition geometry of particular interest for its scientific and innovative value is a large baseline bistatic (LBB) configuration. This paper discusses the impact of the LBB geometry on the SAR imaging performance computation and presents the expected performance results in a reference scenario based on a stripmap, full polarization operational mode.

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The term MIMO SAR is used for Synthetic Aperture Radar (SAR) systems utilizingmultiple-receive andmultiple-transmit channels (Multiple-Input Multiple Output: MIMO). The trade-space for such SAR systems includes the instrument and antenna parameters taking into consideration the techniques, i.e. the operation modes of the radar. The purpose of exploring this trade-space is to improve and optimize the performance of the system, described through the performance parameters. The aim of this paper is to show examples of how MIMO SAR offers new and unexpected ways of trading the system and performance parameters versus each other. Adequately exploring the trade-space yields a high flexibility and allows to simultaneously improve multiple performance parameters; a feature not available in conventional single channel SAR systems. The content of this paper is considered novel in the sense that it deals with highly advance SAR techniques.

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This paper reviews radar architectures that employ multiple transmit and multiple receive channels to improve the performance of synthetic aperture radar (SAR) systems. These advanced architectures have been dubbed multiple-input multiple-output SAR (MIMO-SAR) in analogy to MIMO communication systems. Considerable confusion arose, however, with regard to the selection of suitable waveforms for the simultaneous transmission via multiple antennas. In this paper, it is shown that the mere use of orthogonal waveforms is insufficient for the desired performance improvement in view of most SAR applications. As a solution to this fundamental MIMO-SAR problem we had previously suggested to exploit the special data acquisition geometry of a side-looking imaging radar equipped with multiple receiver channels in addition to appropriately designed waveforms transmitted by multiple antennas. Here, we extend this approach to a more general set of radar waveforms with special correlation properties that satisfy a short-term shift-orthogonality condition. We show that the echoes from simultaneously transmitted pulses can be separated if the short-term shift orthogonality is combined with digital beamforming on receive in elevation. This enables the implementation of a fully functional MIMO-SAR without correlation noise leakage for extended scattering scenarios.

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