Nuria Tous-Ramon

First Bistatic Spaceborne SAR Experiments With TanDEM-X

TanDEM-X (TerraSAR-X Add-on for Digital Elevation Measurements) is a high-resolution interferometric mission with the main goal of providing a global and unprecedentedly accurate digital elevation model of the Earth surface by means of single-pass X-band synthetic aperture radar (SAR) interferometry. Despite its usual quasi-monostatic configuration, TanDEM-X is the first genuinely bistatic SAR system in space. During its monostatic commissioning phase, the system has been mainly operated in pursuit monostatic mode. However, some pioneering bistatic SAR experiments with both satellites commanded in nonnominal modes have been conducted with the main purpose of validating the performance of both space and ground segments in very demanding scenarios. In particular, this letter reports about the first bistatic acquisition and the first single-pass interferometric (mono-/bistatic) acquisition with TanDEM-X, addressing their innovative aspects and focusing on the analysis of the experimental results. Even in the absence of essential synchronization and calibration information, bistatic images and interferograms with similar quality to pursuit monostatic have been obtained.

Fore and Aft Channel Reconstruction in the TerraSAR-X Dual Receive Antenna Mode

The TerraSAR-X satellite is a high-resolution synthetic aperture radar (SAR) system launched in June 2007 which provides the option to split the antenna in along-track direction and sample two physical channels separately. Modern SARs are equipped with active phased array antennas and multiple channels. In order to keep costs low, TerraSAR-X uses the redundant receiver unit for the second channel such that fore and aft channel signals are combined by a hybrid coupler to form sum and difference channel data. The dual receive antenna (DRA) mode can either be used to acquire along-track interferometric data or to acquire signals with different polarizations at the same time (Quad-Pol). Fore and aft channel reconstruction is necessary if ground moving target indication (GMTI) algorithms such as the displaced phase center antenna technique or along-track interferometry shall be applied, and in order to separate the horizontally and vertically polarized received signal components. The proposed approach uses internal calibration pulses from different calibration beams in order to estimate and compensate the hardware impact. The theoretical framework together with the results from the experimental data evaluation for the fore and aft channel reconstruction of the TerraSAR-X DRA mode are presented. The impact of the receive hardware transformation matrix estimation accuracy on errors in the reconstructed fore and aft channel image data is studied, and first examples on the GMTI capability of the TerraSAR-X DRA mode are given.

Taxi: A versatile processing chain for experimental TanDEM-X product evaluation

TanDEM-X is a high-resolution interferometric radar mission with the main goal of providing a global digital elevation model (DEM) of the Earth surface by means of single-pass X-band SAR interferometry. It is, moreover, the first genuinely bistatic spaceborne SAR mission, and, independently of its usual quasi-monostatic configuration, includes many of the peculiarities of bistatic SAR. An experimental, versatile, and flexible interferometric chain has been developed at DLR Microwaves and Radar Institute for the scientific exploitation of TanDEM-X data acquired in non-standard configurations. The paper describes the structure of the processing chain and focusses on some essential aspects of its bistatic part. Some experimental results performed with TerraSAR-X demonstrate the flexibility of the implemented processor.

TerraSAR-X Instrument, SAR System Performance & Command Generation

The paper presents selected results from the TerraSAR-X Commissioning Phase from instrument performance, SAR system performance and command generation.

First bistatic spaceborne SAR experiments with TanDEM-X

TanDEM-X is a high-resolution interferometric mission with the main goal of providing a global and unprecedentedly accurate digital elevation model (DEM) of the Earth surface by means of single-pass X-band SAR interferometry. Despite its usual quasi-monostatic configuration, TanDEM-X is the first genuinely bistatic SAR system in space. During its monostatic commissioning phase, the system has been mainly operated in pursuit monostatic mode. However, some pioneering bistatic SAR experiments with both satellites commanded in non-nominal modes have been conducted with the main purpose of testing the performance of both space and ground segments in very demanding scenarios. In particular, this paper reports about the first bistatic acquisition and the first single-pass interferometric (mono/bistatic) acquisition with TanDEM-X. Even in the absence of essential synchronisation and calibration information, bistatic images and interferogramswith similar quality to pursuit monostatic have been obtained.

Tidal current measurement with TerraSAR-X Along-Track Interferometry

In this paper we describe new achievements of surface current measurements obtained by space-borne Along-Track Interferometry (ATI). We show how tidal currents can be mapped using the TerraSAR-X satellite and adequate dual-channel SAR data processing techniques. We present results from tidal currents at the Orkney Islands that clearly demonstrate the potential and suitability of the method.

TerraSAR-X Dual Receive Antenna mode — Channel reconstruction and impact on the GMTI performance

TerraSAR-X is a high resolution synthetic aperture radar (SAR) satellite which provides the option to split the antenna in along-track direction and sample two physical channels separately. This so-called dual receive antenna (DRA) mode is implemented by use of a Magic-T hybrid junction which provides the sum and difference channel data instead of the fore and aft channel data. One way to exploit this spatial degree of freedom is to reconstruct the fore and aft channel data in the processing. The critical issue with the fore and aft channel reconstruction is the fact, that for space-based radar systems very high precision calibration is required. This is even more difficult since the wide bandwidth pulses employed by the radar makes the receive hardware transformation frequency dependent. In this paper a fore and aft channel reconstruction approach is described based on an estimation of the receive hardware transformation matrix by use of internal calibration pulses and calibration beams. The quality gain of the fore and aft channel reconstruction is demonstrated with experimental data and results on the ground moving target indication (GMTI) capability are shown.