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

Abstract

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.