The synthetic aperture radar (SAR) satellite TerraSAR-X is capable to cover offshore areas of hundreds of square kilometres and to obtain wind data spatially distributed with some tens of metres. Images can be taken up to twice a day when the satellite passes the measurement site.
The German Aerospace Center developed the TerraSAR-X satellite for launch in late 2006 or early 2007 on a Russian-Ukrainian Dnepr rocket. TerraSAR-X features an X-band SAR that will be capable of producing imagery with 1-meter resolution. TerraSAR-X also carries a laser terminal that would be used to test high-bandwidth satellite-to-satellite communications. The German Aerospace Center plans to launch a nearly identical second satellite, dubbed TanDem-X, in 2009.
Infoterra, a subsidiary of EADS-Astrium, believed that their next generation digital synthetic aperture radar (SAR) technology provided them with a competitive edge in securing the SAR-Lupe follow-on contract with the German MOD and actively pursued entry into the USG defense intelligence market. The plans for the next generation TerraSAR-X2 (TSX-2) was scheduled for deployment in 2013.
Infoterra, created in 2001 to prepare and commercially exploit the TerraSAR-X (TSX-1) mission under a PPP financial structure, finds itself in a strengthened financial position without the need for government funding for future commercial satellite projects. For the first time in Infoterra's seven-year history, Infoterra will turn a modest profit in 2008. Infoterra's improved financial resources gave them greater control of their data products and satellite tasking. Under the PPP agreement with DLR, DLR had rights to 50 percent of all TSX-1 data leaving the other 50 percent available for Infoterra commercial exploitation.
The company hoped to submit the superior proposal for the SAR-Lupe follow-on contract and said "Infoterra will not lose out to OHB again." OHB-System AG is located in Northern Germany and has successfully deployed and operated Germany's first satellite-based radar reconnaissance system. Infoterra was in the advanced stages of its advanced TSX-2 design and expressed confidence that OHB did not possess comparable technology. The current SAR-Lupe system (contract awarded to OHB in August 2005 and first satellite launched in December 2006) had a life expectancy of 10 years. This implies that the follow-on system will likely need to be deployed by 2017 with the contract awarded in the 2013-2015 timeframe.
The next generation TSX-2 would aim for better imaging resolution, increased coverage area, and larger data throughput volumes. Current TSX-1 performance parameters are given below:
RESOLUTION COVERAGE AREA ---------- ------------- -- spotlight mode: 1 m 5 km x 10 km scene -- stripmap mode: 3 m 30 km swath width -- scanSAR mode: 16 m 100 km swath width
Infoterra's next SAR generation would achieve resolutions on the order of 0.5 m in spotlight mode and 1 m with a 70 km scene width in stripmap mode, the workhorse mode. It was projected that this technology would be deployable by 2013. DLR efforts were to develop a High Resolution Wide Swath (HRWS) imaging capabilities using digital "beamforming" techniques. The desired goal is to collect 1-meter resolution radar imagery over an area of approximately 100 km (equivalent to the TSX-1 scanSAR mode). This ambitious plan was closely coordinated with Infoterra and could possibly be implemented with Infoterra's next generation SAR satellites.
The penalty for imaging larger areas with greater resolution is the need for increased data transmission bandwidth to the ground station. DLR's innovative approach to this problem is to create a space-based optical Laser Communication Technology (LCT) data network (Germany awarded the first LCD contracts to Tesat-Spacecom GmbH at the end of the 1990s). Infoterra's TSX-1 bus is equipped with a experimental LCT payload intended to demonstrate high bandwidth satellite-to-satellite optical communications. In February 2008, the LCT aboard TSX-1 and NFIRE (a U.S. experimental satellite) successfully exchanged data covering a distance of more than 5000 km without any errors, at a bandwidth of 5.5 Gbit/s (a data equivalence to roughly 400 DVDs per hour). The next step will be to relay TSX-1 data via LCT from a geosynchronous relay (GEO-Relay) satellite to a ground station. The first GEO-relay satellite was scheduled to launch in 2012.
Between September and December of 2009, Infoterra in a PPP cooperation with DLR would launch TanDEM-X, a nearly identical twin of TSX-1 with a three-year interferrometry mission to acquire high quality Digital Elevation Models (DEM) of the entire Earth. TanDEM-X will operate in conjunction with TSX-1 to form a tandem constellation, separated by only 200 m. DLR's stated goal with this program is to acquire HRTI-3 level data with the following parameters:
Spatial Resolution: 12 m X 12 m Absolute Horizontal Accuracy: < 10 m Absolute Vertical Accuracy: < 5 m Relative Vertical Accuracy: < 0.8 m
This accuracy, if achievable, would likely represent the highest fidelity global DEM data available and would likely be of interest to U.S. defense customers.
Foreign satellite data providers had been unable to break into the U.S. defense market, but an unclassified July 2008 USAF Space Radar Acquisition Decision Memorandum (ADM) calling for potential use of international entities to fill future Warfighter needs may change this. Specifically, the July ADM calls for action to "Quantify the performance, capability, and utility of the near-term available sources of radar data from commercial and international space systems." In response to this, Infoterra was prepared to sell data directly to the USG to fill this need and would even be prepared to offer a complete spacecraft capability, including ownership of the data. It is believed that Infoterra has already submitted a proposal in response to this ADM.
Infoterra was clearly advancing its SAR technology at a rapid pace and their technical cooperation with DLR had certainty paid dividends fostering this advancement. As Infoterra's economic position improves, so does its ability to embark on projects independently without obligations to the German government. Given the U.S. need for alternative sources for space-based radar data detailed in the USAF Space Radar ADM and Infoterra's emergence as a world leader in SAR technology, Infoterra believes it is well-positioned to break into the U.S. defense market.
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