A particular challenge for the Tandem-L mission is the development of two powerful but economic SAR satellites able to meet the user demands. In addition to the innovative mission concept, a new technology for the SAR instruments is implemented to fulfill the requirements for a wide swath, short revisit time, high resolution, and fully polarimetric operation. The decisive innovation with Tandem-L is the use of a large, deployable reflector antenna fed by an array with several parallel digital channels. This technological revolution combines the advantages of digital beam-forming with high sensitivity due to the large aperture area of the deployable reflector, which is huge compared to the aperture of conventional SAR instruments. Digital antenna synthesis using digital beam-forming technology vastly improves the radar imaging flexibility and allows the implementation of extremely powerful operating modes, which can be optimally adjusted to meet the different requirements of the 3-D Structure Mode and the Deformation Mode. For instance, the implementation of the latest SAR operating modes, whereby images are generated in parallel with variable pulse repetition frequencies and several antenna patterns, allows the imaging of extremely large swaths with hitherto unknown spatial resolution without compromising other imaging parameters. In contrast, with conventional radar systems, the resolution worsens proportional to the swath width (or, conversely, the swath width reduces with an improvement in resolution). On top of this, the use of the large reflector increases the sensitivity and allows a considerable reduction in transmit power. In this way, the SAR instruments can be operated quasi-continuously.
The combination of a reflector antenna and digital beam-forming allows the imaging of wide swaths with high resolution