Interferometric Synthetic Aperture Radar (SAR) Missions Employing Formation Flying

Microwaves & Radar Inst., German Aerosp. Center, Wessling, Germany
Proceedings of the IEEE (Impact Factor: 4.93). 06/2010; 98(5):816 - 843. DOI: 10.1109/JPROC.2009.2038948
Source: IEEE Xplore


This paper presents an overview of single-pass interferometric Synthetic Aperture Radar (SAR) missions employing two or more satellites flying in a close formation. The simultaneous reception of the scattered radar echoes from different viewing directions by multiple spatially distributed antennas enables the acquisition of unique Earth observation products for environmental and climate monitoring. After a short introduction to the basic principles and applications of SAR interferometry, designs for the twin satellite missions TanDEM-X and Tandem-L are presented. The primary objective of TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is the generation of a global Digital Elevation Model (DEM) with unprecedented accuracy as the basis for a wide range of scientific research as well as for commercial DEM production. This goal is achieved by enhancing the TerraSAR-X mission with a second TerraSAR-X like satellite that will be launched in spring 2010. Both satellites act then as a large single-pass SAR interferometer with the opportunity for flexible baseline selection. Building upon the experience gathered with the TanDEM-X mission design, the fully polarimetric L-band twin satellite formation Tandem-L is proposed. Important objectives of this highly capable interferometric SAR mission are the global acquisition of three-dimensional forest structure and biomass inventories, large-scale measurements of millimetric displacements due to tectonic shifts, and systematic observations of glacier movements. The sophisticated mission concept and the high data-acquisition capacity of Tandem-L will moreover provide a unique data source to systematically observe, analyze, and quantify the dynamics of a wide range of additional processes in the bio-, litho-, hydro-, and cryosphere. By this, Tandem-L will be an essential step to advance our understanding of the Earth system and its intricate dynamics. Enabling technologies and techniques are described in detail. An ou-
tlook on future interferometric and tomographic concepts and developments, including multistatic SAR systems with multiple receivers, is provided.

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Available from: Gerhard Krieger
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    • "Many of these processes are currently insufficiently understood and/or measured, primarily due to the lack of suitable observation data required. Existing remote sensing configurations are often inadequate in terms of imaging performance and/or measurement resolution and accuracy for drawing reliable conclusions on largescale processes and their dynamics [3], [5], [6], [7]. The measurement of dynamic processes requires a continuous, extended and systematically planned observation strategy in order to detect changes and quantify them with sufficient accuracy. "
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    ABSTRACT: 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 the results of a pre-phase A study which started 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 terabytes/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. 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.
    Full-text · Article · Jul 2015
    • "DIFFERENT receiver system paired with an existing or future X-Band SAR system (e.g. TanDEM-X [7], HRWS [4], or a custom satellite) provides a wide range of applications including glaciology, oceanography, imaging of urban areas, and moving target indication. "

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    • "The SAR data for this study were acquired during the TanDEM-X mission over Central Kalimantan on December 21, 2010. The mode used is called bistatic mode and is applied for the operational TanDEM-X mission acquisitions (Krieger et al., 2010). Both sensors are able to transmit the electromagnetic wave with a phased-array X-band antenna having a carrier frequency of 9.65 GHz (Pitz & Miller, 2010), corresponding to a wavelength of ~3.1 cm. "
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    ABSTRACT: Deforestation and forest degradation are one of the important sources for human induced carbon dioxide emissions and their rates are highest in tropical forests. For man-kind, it is of great importance to track land-use conversions like deforestation, e.g. for sustainable forest management and land use planning, for carbon balancing and to support the implementation of international initiatives like REDD + (Reducing Emissions from Deforestation and Degradation). SAR (synthetic aperture radar) sensors are suitable to reliably and frequently monitor tropical forests due to their weather independence. The TanDEM-X mission (which is mainly aimed to create a unique global high resolution digital elevation model) currently operates two X-band SAR satellites, acquiring interferometric SAR data for the Earth's entire land surface multiple times. The operational mission provides interferometric data as well as mono- and bistatic scattering coefficients. These datasets are homogenous, globally consistent and are acquired in high spatial resolution. Hence, they may offer a unique basic dataset which could be useful in land cover monitoring.
    Full-text · Article · Aug 2014 · Remote Sensing of Environment
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