Ocean Surface Observations Using the TanDEM-X Satellite Formation

The TanDEM-X SAR satellite formation permits improved ocean surface observations by means of bistatic along-track interferometry (ATI) when compared to single-satellite systems. The flexible imaging geometry of its two cooperating SAR sensors forms an interferometer that can achieve very high sensitivity to motions of objects on ground. This way, radar imaging of surface currents with unprecedented accuracy, high spatial resolution and wide coverage at the same time becomes possible. We demonstrate the capabilities of the sensor in the contexts of tidal current mapping, measurement of thermohaline and wind-driven ocean currents as well as detection of areas with surface films. We have developed a dedicated postprocessing system for TanDEM-X image products that allows extracting surface current information from the data. By this paper, we address bistatic data acquisition and processing aspects for sea surface imaging with TanDEM-X like interferometric baseline geometry, temporal decorrelation, and phase calibration. We present a variety of examples of data evaluation that clearly demonstrate the application potential of the methodology

River Run Off Measurement With SAR Along Track Interferometry

The paper summarizes the need for global space borne river run-off measurements. It reports about an airborne SAR experiment aimed to measure the surface velocity of the river Isar in Bavaria / Germany. The results from two different SAR techniques, including Along Track Interferometry (ATI) show good correspondence. Finally suggestions for further studies are given

First Results Of TanDEM-X Along-Track Interferometry

The interferometric imaging modes of the TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) satellite formation offer improved along-track interferometric capabilities e.g. through longer and multiple baselines. While the first provide high sensitivities to ground motions, the latter enable to resolve ambiguities. The extraction of motion information from TanDEM-X data by means of ATI is challenging due to the hybrid nature of the interferometric baseline. This is generally composed of an across-track (XTI) and an along-track interferometric (ATI) component BATI and requires a separation of the respective interferometric phase contributions

Schiffsdetektion in Interferometrie-Radardaten

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zur Ermittlung je einer Position und einer Fahrtrichtung für ein oder mehrere im Wasser fahrende Wasserfahrzeuge aus Interferometrie-Radardaten, in denen die Wasserfahrzeuge und die Wasserfahrzeuge umgebende Wasseroberflächen abgebildet sind. Das vorgeschlagene Verfahren umfassend folgende Schritte: Bereitstellen (101) der Radardaten als 2D-Interferogrammdaten INT1(x, y); Segmentieren (104) der 2D Interferogrammdaten INT1(x, y) zur Ermittlung von segmentierten 2D-Interferogrammdaten INT2(x, y), wobei die segmentierten 2D-Interferogrammdaten INT2(x, y) nur 2D-Datenbereiche Bn der 2DInterferogrammdaten INT1(x, y) umfassen, die jeweils ein zusammenhängendes Streifenmuster, sogenanntes Fringe-Pattern, wiedergeben, mit n = 1, 2, ...; Ermitteln (106) einer Kontur für jeden der 2D-Datenbereiche Bn; Ermitteln (108) eines Schwerpunktes für jeden der 2D-Datenbereiche Bn, wobei weiterhin für jeden der 2D-Datenbereiche Bn die Position eines Wasserfahrzeugs auf Basis des Schwerpunktes ermittelt wird; Ermitteln (109) einer geometrischen Ausrichtung des in den Daten jedes 2D-Datenbereichs Bi abgebildeten Streifenmusters relativ zu einer Bildachse der 2D-Interferogrammdaten INT1(x, y); und für jeden der 2D-Datenbereiche Bn abhängig von der ermittelten Ausrichtung des Streifenmusters, und der ermittelten Form der Kontur des jeweiligen 2D-Datenbereichs Bn Ermitteln (110) der Fahrtrichtung des jeweiligen Wasserfahrzeugs

An Interferometric SAR Satellite Mission

The paper provides a critical review of the achievements in SAR interferometry from the ERS mission as well as from the Shuttle Radar Topography Mission SRTM. It describes the development from the original idea of the Interferometric Cartwheel to the concept of a formation flight of identical and active SAR satellites. From the experience gained from ERS and SRTM interferometric data processing as well as from the analysis of the Cartwheel concept a list of mission requirements has been set up. The most demanding one is the autonomous configuration flight of a tight x-band constellation, where the satellites fly as close as up to 30 m with a dead-band of +/- 10 m. The guidance, navigation and control considerations come to the conclusion that such a mission is feasible

The TerraSAR-X Traffic Monitoring System

The presentation gives an overview about the TerraSAR-X traffic monitoring project at DLR. The tasks of the "traffic processor" and the overall ground segment are described. Results from first airborne campaigns are presented including the monitoring of a traffic jam on a motorway near Munich / Germany. Furthermore radar cross sections of passenger cars are presented

The Extended Timing Annotation Dataset for Sentinel-1 - Product Description and First Evaluation Results

This article introduces the extended timing annotation dataset (ETAD) product for Sentinel-1 (S-1) which was developed in a joint effort of German Aerospace Center (DLR) and European Space Agency (ESA). It allows to correct range and azimuth timing of S-1 images for geophysical effects and for inaccuracies in synthetic aperture radar (SAR) image focusing. In combination with the precise orbit solution, these effects determine the absolute geolocation accuracy of S-1 SAR images and the relative collocation accuracy of repeat pass image stacks. ETAD contains the gridded timing corrections for the tropospheric and ionospheric path delays, the tidal-based surface displacements, and the SAR processing effects, all of which are computed for each data taken using standard models from geodesy and auxiliary atmospheric data. The ETAD product helps S-1 users to significantly improve the geolocation accuracy of the S-1 SAR products to better than 0.2 m and offers a potential solution for correcting large-scale interferometric phase variations. The product layout and product generation are described schematically. This article also reports first the results for different SAR techniques: first, the improvement in geolocation accuracy down to a few centimeters by verification of accurately surveyed corner reflector positions in the range–azimuth plane; second, the well-established offset-tracking technique, which is used for systematic ice velocity monitoring of ice sheets and glaciers, where ETAD can reduce velocity biases down to subcentimetric values; and third, the correction of atmospheric phase contributions in wide-area interferograms used for national and European ground motion services. These early results proof the added value of the ETAD corrections and that the product design is well-suited to be integrated into the processing flows of established SAR applications such as absolute ranging of targets, speckle/feature tracking, and interferometry

Evaluation of ESA's Extended Timing Annotation Dataset (ETAD) for Sentinel-1 - First Results for Ice Velocity Monitoring and InSAR Applications in Greenland, Iceland and Norway

SAR images benefit from excellent geometric accuracy due to accurate time measurements in range and precise orbit determination in azimuth. Moreover, the interferometric phase of each single pixel can be exploited to achieve differential range measurements for the reconstruction of topography and the observation of earth surface deformation and surface motions. But these measurements are influenced by the spatial and temporal variability of the atmospheric conditions, by Earth dynamics, and by SAR processor approximations, which may lead to overall displacements shifts of up to several meters. These effects become visible in various SAR applications including the retrieval of ice velocity applying offset tracking and various InSAR applications, which might require several post-processing steps and external information for correction. In this paper we present the Extended Timing Annotation Dataset (ETAD) for Sentinel-1 recently developed in a joint effort by ESA and DLR based on research results and processor prototypes available at DLR