This paper introduces a SAR mission concept uniquely designed for sub-daily interferometric-compatible revisits, essential for the timely monitoring of ecosystem water status in regions of significant scientific, ecological, societal, and economic value. The key concept is based on the strategic deployment of a constellation of several small satellites in short-revisit low-Earth orbits, equipped with low complexity SAR payloads to enhance efficiency and minimize overall costs. In particular, L-band SARs with decametric spatial resolution and sub-daily revisit will be considered. The paper provides an overview of the mission requirements, technical concept, scientific relevance, and acquisition potential. The analysis is based on a study conducted in the frame of an ESA Earth Explorer 12 mission proposal titled "SLAINTE" [1].

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.

The German Tandem-L mission is devoted to provide an overall observation of the dynamic processes within the Eart system at different spatial and temporal scales. Among the mission objectives, the measurement of the 3-D fores structure by means of multi-pass coherence SAR tomography (TomoSAR) has particular relevance. Up to now, th potential of TomoSAR for the characterization of the forest volume has been proved with airborne data, but Tandem-will allow for the first time to map the vertical forest structure and monitor seasonal and annual variations globall with a high spatial resolution. Recently, a performance model for the characterization of the structure information o multibaseline (MB) data stacks has been presented, and the primarily objective of this paper is to examine in dept such model for global performance analysis and investigate the required acquisition trade-offs in the framework of th Tandem-L mission design and acquisition plan.

The capabilities of the current concept for a post-Sentinel-1 High ResolutionWide Swath (HRWS)C-band SAR system as discussed. Product-level performance analysis are given for two example applications (large scale deformation and ship detection), showing the clear improvement with respect to Sentinel-1 and exposing some of the trade-offs associated to the choice of operating mode.

Tandem-L is a highly innovative SAR satellite mission for the global observation of dynamic processes on the Earth's surface with hitherto unknown quality and resolution. Thanks to its novel imaging techniques and its unprecedented acquisition capacity, Tandem-L will deliver urgently needed information for the solution of pressing scientific questions in the areas of the biosphere, geosphere, cryosphere and hydrosphere. The feasibility of Tandem-L has been analyzed and confirmed in the scope of a phase A study, which has been conducted in close cooperation between the German Aerospace Center (DLR) and the German space industry. This paper provides an overview of the Tandem-L mission concept and summarizes the actual development status.