Stefan Buckreuss

The TerraSAR-X Mission and System Design

This paper describes the TerraSAR-X mission concept within the context of a public-private partnership (PPP) agreement between the German Aerospace Center (DLR) and the industry. It briefly describes the PPP concept as well as the overall project organization. This paper then gives an overview of the satellite design and the corresponding ground segment, as well as the main mission parameters. After a short introduction to the scientific and commercial exploitation scheme, this paper finally focuses on the mission accomplishments achieved so far during the ongoing mission.

The terraSAR-X satellite project

The objective of TerraSAR-X is the setup of an operational space borne X-Band SAR system in order to produce remote sensing products for commercial and scientific use. The TerraSAR-X project is conducted under the aegis of the DLR Space Flight Management and comprises a space and a ground segment. The space segment is designed and built by ASTRIUM GmbH, the ground segment is set up by several institutions of DLR, namely the German Remote Sensing Data Center, the Remote Sensing Technology Institute, the German Space Operations Center and the Microwaves and Radar Institute.

The TerraSAR-X Ground Segment

TerraSAR-X, the first national German remote-sensing satellite, was launched on June 15, 2007. It carries an X-band high-resolution synthetic aperture radar (SAR) instrument featuring imaging modes like StripMap, ScanSAR, and, particularly, SpotLight in a variety of different polarization modes. Primary mission goal is the provision of both science and commercial users with a variety of products from advanced SAR modes. The TerraSAR-X Ground Segment, which is provided by the German Aerospace Center (DLR), constitutes the central element for controlling and operating the TerraSAR-X satellite, for calibrating its SAR instrument, and for archiving the SAR data, as well as generating and distributing the basic data products. This paper depicts the ground-segment layout and describes its major elements. The ordering and product-generation workflow is presented. It introduces the applied prelaunch integration, testing, verification, and validation approach, a major key to the completion not only of the SAR technical-verification program but also the operational qualification of the ground segment itself within the commissioning phase.

Overview of interferometric data acquisition and processing modes of the experimental airborne SAR system of DLR

This paper presents first the relevant parameters of the experimental E-SAR system for single- and repeat-pass SAR interferometry. The implementation of the different interferometric operation modes is described and special attention is paid to the problems posed by the unstable airborne platform. Each interferometric mode is described including the solution of its critical problems. The given examples prove the enormous information content one can obtain from the different imaging modes of airborne SAR interferometry. Finally, future developments concerning polarimetric SAR interferometry and tomography will be addressed.

Sector imaging radar for enhanced vision

SIREV (Sector Imaging Radar for Enhanced Vision) is an innovative airborne radar system which can supply high-quality images in any desired direction under almost every weather condition. In contrast to synthetic aperture radar (SAR) systems, no relative motion between sensor and targets is required in SIREV. The high frame repetition frequency in SIREV allows to detect even very rapid changes in the imaged scenes. Besides providing a map of the earths surface, the complex-valued radar images can be further processed to supply additional information about the topography and objects in the field of view. A fast processing algorithm has been developed for SIREV which allows a very accurate, phase preserving and efficient image formation. A prototype of a forward-looking SIREV system has been built up at the German Aerospace Center and raw data were obtained by a first demonstration flight using a helicopter as a moving platform. Motion errors of the platform could be extracted from the range compressed raw data avoiding the need of an inertial navigation system. The data processing results show good agreement with the theory. After image formation, coherent and incoherent image averaging processes have been applied to improve the image quality. The evaluation of the computational effort shows that a real-time hardware realization can be carried out using off-the-shelf digital components.

The German satellite mission TerraSAR-X

TerraSAR-X is Germanypsilas first national remote sensing satellite being implemented in a public-private partnership between the German Aerospace Centre (DLR) and EADS Astrium GmbH. TerraSAR-X was launched on June 15th, 2007 and will supply high-quality radar data for purposes of scientific observation of the Earth for a period of at least five years. At the same time it is designed to satisfy the steadily growing demand of the private sector for remote sensing data in the commercial market (Werninghaus et al., 2007)sigma.

TerraSAR-X: predicted performance

This paper reports about the status of the actual performance prediction and some selected investigations within the system engineering for the TerraSAR-X satellite, which will be implemented in a Public-Private-Partnership between the German Aerospace Center (DLR) and the ASTRIUM GmbH. The main sensor parameters and modes of operation are summarized. Image simulations based on X-band data from the E-SAR sensor of DLR give an impression on the expected image quality with respect to geometric and radiometric resolution. Different realization possibilities for the dual polarization mode are investigated and the actual baseline for this mode is described. The potential of two independent receiving channels is analyzed and the paper reports about possible additional features as investigated so far.

TerraSAR-X Mission Status

TerraSAR-X is Germanys first national remote sensing satellite being implemented in a public-private partnership between the German Aerospace Centre (DLR) and EADS Astrium GmbH, with a significant financial contribution from the industrial partner. This radar satellite, which is to be launched in June 2007 will supply high-quality radar data for purposes of scientific observation of the Earth for a period of at least five years. At the same time it is designed to satisfy the steadily growing demand of the private sector for remote sensing data in the commercial market. This contribution will describe first the public-private partnership scheme, the roles and responsibilities of the partners as well as the overall project organization. The mission and system design will then be described, followed by a brief overview of the satellite, the related Ground Segment and the applied data policy. The contribution will then focus on the actual mission status. Finally a brief outlook will be given on the activities to come.

Sector imaging radar for enhanced vision (SIREV): simulation and processing techniques

This paper presents a new formulation of the Extended Chirp Scaling algorithm (ECS)1+/, suitable for the processing of data from the forward looking SAR system SIREV (Sector Imaging Radar for Enhanced Vision. This system is presently under development at the German Aerospace Center (DLR). It is shown that the SIREV data acquisition has several similarities with the ScanSAR mode of operation. Also the differences between SIREV and ScanSAR mode are analyzed. According to these differences, the ECS for ScanSAR has been modified. The modified equations of the ECS are presented and several simulation results demonstrate the good performance of the ECS for SIREV processing. The SIREV project at DLR was partially funded by STN Atlas Elektronik, Bremen. This company also holds the SIREV license rights.

Sector Imaging Radar for Enhanced Vision (SIREV) : Theory and applications

The demand for supplementing existing airborne radar systems with enhanced forward looking abilities has considerably increased. Available radar systems are not able to accomplish the needed requirements for enhanced vision. Instead a new approach has to be taken to cover the forward lying sector with respect to the flight path. Presently a system called SIREV (Sector Imaging Radar for Enhanced Vision) is under development at DLR> Due to the all-weather capability of the system and its ability to present radar images very similar to optical images either as top view (mapping mode) or as pilot view (central perspective mode) the system is essentially qualified for navigation support, autonomous landing approaches or taxi support at the ground. IN this paper the authors will describe the idea the new SIREV system originates from and the relation of the SIREV principle to the SAR principle. Different modes of operation and thereby obtainable performance numbers will be discussed with regard to the special advantages of each sensor. Some potential applications of either sensor will be explained in detail. Finally a summarized overview of the system under development at DLR together with a description of a test field setup at Oberpfaffenhofen airfield will be given. The SIREV project at DLR was partially funded by STN Atlas Elektronik Bremen. This company also holds the SIREV license rights.