PARIS — Germany’s TanDEM-X radar Earth observation satellite was successfully launched June 21 aboard a Russian-Ukrainian Dnepr rocket and is expected to enter service in early 2011 alongside the TerraSAR-X satellite already in orbit to provide 3-D digital terrain models of the Earth’s entire landmass.
Officials from the German Aerospace Center, DLR, which webcast the launch from the Russian-run Baikonur Cosmodrome in Kazakhstan, said the satellite had sent its first signals and was healthy in orbit.
The 1,340-kilogram TanDEM-X, like the TerraSAR-X spacecraft launched in June 2007, is the result of a partnership between DLR and Astrium of Germany, whose Infoterra division has the rights to sell the satellites’ imagery products.
TanDEM-X is about a year late in being launched following delays related to the satellite’s construction and to the availability of the Dnepr rocket. But DLR officials said TerraSAR-X, whose contracted service life was five years in orbit, is healthy enough to operate until 2014, providing three years of tandem operations with TanDEM-X.
DLR officials expect to spend about six months calibrating TanDEM-X. After that, it will join TerraSAR-X in a three-year mission to map the Earth’s entire landmass with a ground resolution of 12 meters and a vertical precision of 2 meters or better.
The resulting product — some 15 terabytes of data covering 150 million square kilometers of territory — will provide what DLR bills as the first global digital elevation model.
The two X-band radar satellites are the latest manifestations of Germany’s long interest in radar Earth observation. A German radar was placed aboard the U.S. space shuttle in 2000 as part of the Shuttle Radar Topography mission that mapped much of the Earth’s area between 60 degrees north and 60 degrees south latitude. Two data sets were produced — one at 90-meter spatial resolution, one at 30 meters — with a vertical precision of between 5 meters and 10 meters.
TerraSAR-X was built for 185 million euros, or $226 million at current exchange rates, with DLR paying 80 percent of the costs and Astrium financing the remaining 20 percent. TanDEM-X, which uses much of the same hardware as TerraSAR-X but is not an exact duplicate, was built for 165 million euros, with DLR paying 75 percent and Astrium the rest. The figures include the launch and operations.
TanDEM-X will operate in the same 514-kilometer polar low Earth orbit as TerraSAR-X, with the two satellites separated by a distance of between 200 meters and several kilometers.
The global digital elevation model data are expected to take about three years to collect and another year to render into usable form, according to DLR. DLR will use the data for scientific and other research purposes, while making the global set available to Friedrichshafen, Germany-based Infoterra.
Infoterra spokeswoman Mareike Doepke said June 21 that because both satellites will be involved in creating the global digital terrain model, Infoterra will not have more conventional radar imagery available to it.
Doepke said Infoterra, part of the Astrium Services company that includes Spot Image of France, which specializes in optical satellite imagery, anticipates a commercial market for the 3-D models once they become available in about four years.
“The commercial potential of the TanDEM-X data set is very promising, even if current forecasts project that only one-third of the data set, or about 50 million square kilometers, is of a true commercial interest,” Doepke said in an e-mailed response to questions. “Infoterra does not expect revenues from elevation models in remote, scarcely populated areas, or areas for which up-to-date elevation models are already available from airborne campaigns. Nevertheless, from the availability of the elevation model in 2013-14, we expect a promising revenue growth potential in the following years.”
Infoterra has not determined how the elevation model data will be priced, choosing to wait to determine the level of quality the market demands.
TanDEM-X’s X-band synthetic aperture radar has three imaging modes. The ScanSAR mode has a 100-kilometer swath width and a 16-meter ground resolution. In StripMap mode, the satellite takes images with a 3-meter ground resolution and a 30-kilometer swath width. The highest-resolution mode, SpotLight, has a 10-kilometer swath width and is capable of distinguishing objects or features as small as 1 meter in diameter.
