ALOS-Next/Tandem-L is a proposal for a highly innovative L-band SAR satellite mission for the global observation of dynamic processes on the Earth's surface with hitherto unparalleled quality and resolution. It is based on a collaboration between DLR and JAXA which started with a pre-phase A study in 2013 and is currently undergoing a phase A study. Thanks to the novel imaging techniques and the vast recording capacity with up to 8 Tbytes/day, it will provide vital information for solving pressing scientific questions in the biosphere, geosphere, cryosphere, and hydrosphere. By this, the new L-band SAR mission will make an essential contribution for a better understanding of the Earth system and its dynamics. ALOS-Next/Tandem-L will, moreover, open new opportunities for risk analysis, disaster management and environmental monitoring by employing especially designed acquisition modes and techniques in combination with a reconfigurable tandem satellite configuration and an L-band SAR instrument with advanced digital beamforming techniques.

In this paper the science requirements for the mapping of dynamic processes on the Earth surfaces is presented. From the science requirements and the need of a regular and continuous global surface cover for most of the applications a dedicated mission concept has been developed. The presented results are a summary of pre-phase A mission study that is performed in a bilateral cooperation between the Japan Aerospace Exploration Agency (JAXA) and the German Aerospace Center (DLR). Tandem-L is an innovative mission proposal that will provide a unique, world-wide database for a better understanding of the Earth system dynamics in important research and societal relevant fields, as well as enabling a multitude of innovative applications.