Tandem-L: A Highly Innovative Bistatic SAR Mission for Monitoring Earth's Dynamic Processes

Abstract

Tandem-L is a proposal for a highly innovative L-band SAR mission for the systematic observation of dynamic processes on the Earth's surface with hitherto unparalleled quality and resolution. Thanks to the novel imaging techniques and the vast recording capacity of up to eight terabytes/day, it will provide vital information for solving pressing scientific questions in the biosphere, geosphere, cryosphere, and hydrosphere and will make an essential contribution for a better understanding of the Earth system and its dynamics. The Tandem-L mission concept is based on the use of two SAR satellites operating in L-band with variable formation flight configurations and is distinguished by its high degree of innovation. Examples are the polarimetric SAR interferometry (PolinSAR) for measuring forest height, multi-pass coherence tomography for determining the vertical structure of vegetation and ice, the utilization of the latest digital beamforming techniques in combination with a large deployable reflector for increasing the swath width and imaging resolution, as well as the formation flight of two cooperative radar satellites with adjustable baselines for single-pass interferometry. The systematic acquisition concept is based on two imaging modes: 1) 3-D structure mode with a bistatic radar operation and 2) Deformation imaging mode with differential SAR interferometry (DinSAR), both allowing the following mission objectives to be achieved: (i) global measurement and monitoring of 3-D forest structure and biomass for a better understanding of ecosystem dynamics and the carbon cycle, (ii) systematic recording of small and large scale deformations of the Earth's surface with millimeter accuracy for earthquake, volcano and landslides research as well as risk analysis and mitigation, (iii) quantification of glacier movements, 3-D ice structure and melting processes in the polar regions for improved predictions of future sea level rise, (iv) fine scale measurements of soil moisture and its variations close to the surface for a better understanding of the water cycle and its dynamics, (v) systematic observation of coastal zones and sea ice for environmental monitoring and ship routing, (vi) monitoring of agricultural fields for crop yield forecasts, as well as, (vii) generation of highly accurate global digital terrain and surface models which form the basis for a wide range of further remote sensing applications. In this presentation, we provide an overview of the current status of this innovative mission and its main application areas and discuss challenges for calibrating such a versatile radar instrument featuring digital beamforming with a large reflector antenna.