Mapping Terrestrial Impact Craters with the TanDEM-X Digital Elevation Model

The TanDEM-X mission generates a global digital elevation model (DEM) with unprecedented properties. We use it for mapping confirmed terrestrial impact craters as listed in the Earth Impact Database. Both for simple and complex craters detailed investigations of the morphology of the particular structure and of the surrounding terrain can be performed

First TerraSAR-X interferometry evaluation

The German radar satellite TerraSAR-X was launched in June 2007 [1] and is currently ending its commissioning phase. We anticipate quite different interferometric application scenarios compared to ERS- 1/2 and ASAR due to the X-band frequency, the short orbital repeat cycles of 11 days, the high range resolution and the spotlight mode of this sensor. During the commissioning phase we have scheduled a number of acquisitions over selected test sites with different characteristics to get an early quick look of TerraSAR-X's interferometric capabilities and to assess the phase quality of the sensor and DLR’s processor system [2]. Our first results are quite encouraging and the technical parameters of the system are as specified. Many spectacular image details let us expect that the high resolution will demand a different view on SAR interferometry and allow new applications in urban environments. In our paper we show interferograms and images of different test sites, coherence measurements and a first assessment of the interferometric properties. We will give hints to future scientific users on data selection and data processing. The results are of high relevance for the TanDEM-X mission scheduled for 2009, when a second compatible SAR-sensor will be launched for a joint 3 year bistatic interferometric formation flight

TerraSAR-X SAR Data Processing

The TerraSAR-X Mission started operational provision of SAR image products to the scientific and commercial user community in January 2008. An essential prerequisite for the excellent quality of the SAR products was the successful execution of a comprehensive commissioning phase (CP) in 2007. Here, the complete SAR system which comprises instrument commanding, instrument SAR data acquisition as well as SAR processing has been characterized, calibrated and verified. Finally SAR image product verification ensured that the product performance parameters are within the specification. Besides the versatile high-resolution X-Band SAR instrument in space, featuring Stripmap, ScanSAR and Spotlight imaging modes in different polarizations, the TerraSAR Multi-Mode SAR Processor (TMSP) is the central part of the ground segment. Most instrument and SAR calibration parameters have been derived on basis of SAR image products generated by the TMSP. Therefore, already in the beginning of the CP the products had to be relatively radiometric calibrated and geometrical undistorted. An indispensable prerequisite for this was the imaging mode independent normalization of the processor gain as well as the incorporation of external information, i.e. a digital elevation model for the projection of the elevation gain antenna pattern onto the terrain surface and a model of the atmosphere accounting for additional propagation delays. During the CP the TMSP has been adjusted to the in-orbit characteristics of the SAR data and instrument internal calibration. This includes adaptations of calibration pulse processing to a modified internal calibration strategy, accounting for duty cycle dependent pulse energy and temperature dependent gain levels as well as a fine tuning of the signal and geometry based Doppler centroid estimation algorithm. Furthermore, the determination of the reference function for range focusing has been optimized. Finally, the spectral weighting of the SAR data has been adjusted in order to obtain well balanced impulse response function properties in terms of resolution, side lobe ratios and azimuth ambiguities. The presentation reviews the essential features of the TMSP, summarizes the TMSP adjustments and presents results of the SAR product verification

ASAR Level 0 Product Analysis for Image, Wide-Swath and Wave Mode

ENVISAT/ASAR data for all five operational modes (Image, Wave, Alternating Polarisation, Wide-Swath and Global Monitoring) are archived in raw format as level 0 products. These products consist mainly of the ASAR instrument source packets and are accompanied with a minimum set of characterizing parameters. The generation of any ASAR level 1 user product starts from the level 0 product as input. The integrity of the long-term ASAR level 0 data archive has to be ensured, i.e. the level 0 products have to be in line with their specification and they should not show any systematic deficiencies. This is the major task of the level 0 product validation activity. This paper focuses on the level 0 product analysis for the Image, Wide-Swath and Wave mode in VV polarization

ASAR Level 0 Product Analysis for Alternating Polarisation and Global Monitoring Mode

ENVISAT/ASAR data for all five operational modes (Image, Wave, Alternating Polarisation, Wide-Swath and Global Monitoring) are archived in raw format as level 0 products. These products consist mainly of the ASAR instrument source packets and are accompanied with a minimum set of characterizing parameters. The generation of any ASAR level 1 user product starts from the level 0 product as input. The integrity of the long-term ASAR level 0 data archive has to be ensured, i.e. the level 0 products have to be in line with their specification and they should not show any systematic deficiencies. This is the major task of the level 0 product validation activity. The level 0 product analysis results for the Image, Wide-Swath and Wave Mode have been already presented at the ENVISAT Calibration Review. This paper supplements the results obtained for Alternating Polarisation and Global Monitoring Mode

TerraSAR-X Data Acquired in Pursuit Monostatic Mode during TanDEM-X Commissioning Phase

The successful launch of the second national German radar satellite TDX-1 in June 2010 marked the beginning of the challenging TerraSAR-X add-on for Digital Elevation Measurement mission. Major TanDEM-X mission goal is the consistent generation of a worldwide global digital elevation model with high accuracy. Therefore the two satellites TSX-1 and TDX-1 are flown in close configuration to form a single-pass space-borne SAR interferometer. To counterbalance the interferometric usage of the TSX-1 satellite, data for the ongoing TerraSAR-X mission have to be acquired by both satellites TSX-1 and TDX-1. Commissioning of the joint TerraSAR-X/TanDEM-X system was done in well-defined stages. TDX-1 was launched at June 21, 2010, and started its drift towards TSX-1. At July 22, 2010, it had reached a distance of 20 km and started its helix formation flight. This pursuit monostatic configuration was kept for 77 days to allow not only a thorough TDX-1 system verification, but also to qualify the overall system e.g. for the close formation flight with its zero-mean along track distance which started mid of October 2010. The good performance of both the TDX-1 satellite and the joint TerraSAR-X/TanDEM-X ground segment allowed to acquire a significant amount of TerraSAR-X data from the TDX-1 satellite in addition to the planned commissioning data set. These data represent nominal TerraSAR-X acquisitions and their processing thus leads to TerraSAR-X basic products showing a nominal product performance. This lead to the decision, that – after a careful inspection – these TDX-1 data will be made available to users for catalogue ordering despite their commissioning phase character. Of specific user interest among them are those scenes which were acquired with both the TSX-1 satellite and the TDX-1 satellite following each other in less than 3 seconds distance. This paper gives an overview of the different types of TerraSAR-X data acquired by both TSX-1 and TDX-1 in this unique pursuit monostatic flight configuration. It furthermore provides exemplary evaluations, e.g. in the area of ship detection

Extending the TerraSAR-X Ground Segment for TanDEM-X

This paper describes selected areas in which the TerraSAR-X ground segment had to be extended in order to incorporate the TanDEM-X mission, namely flight dynamics, instrument operations and receiving stations and addresses their testing