Earth in the third dimension

The German satellite TanDEM-X was launch into orbit on a mission to map more accurate to be made available to the surface of the Earth. The satellite will fly radar technology with identical platform called TerraSAR-X launched in 2007. Both measured variations in the height of the globe with an accuracy of better than two meters.

Its digital elevation model will have many uses, from helping military jets fly ultra low height to show where rescue workers was worse the damage caused by an earthquake.

"Our goal is to build a model at a resolution and quality as it exists today," he told the BBC Dr Vark Helfritz, the processing company Infoterra GmbH satellite images.

"It will be a truly global product, not a patchwork of datasets that have been put together," he adds. The TanDEM-X was placed in a polar orbit slightly steeper than that occupied by the TerraSAR-X, about 514 miles above the planet. "This is the first time that two satellites have been placed in a formation so close," said Brigadier General Thomas Reiter, a former astronaut and now a member of the executive board of the German Aerospace Center (DLR).

"Their orbits closer to the minimum distance of about 200 meters, which, as you think it will be a huge challenge for mission controllers." The TerraSAR-X was able to see through the plume of ash from the volcano Eyjafjallajoekull.

Variations terrestrial

The pair of radar works constantly active microwave pulses at the planet surface. Because they keep track of how long it takes the signal to make the return trip, the instruments can determine variations in height. The compact "dance" orbital satellites give a "stereo vision" allowing them to operate in interferometric mode, which acts as a satellite transmitter / receivers and the other as a second receiver.

To draw with the level of detail of the TanDEM-X all 150 million square kilometers of the Earth's land surface will require three years. Radar observations already have very extensive applications in military camps, civilians and scientists. Recent examples include the Eyjafjallajoekull volcano eruption in Iceland and the oil spill in the Gulf of Mexico.

In the first event, the vision of the TerraSAR-X microwave was able to look through the ash plume, which allowed scientists to analyze the status of the volcano. And in the Gulf of Mexico spill, the satellite has allowed to follow the progression of the layer of oil during day and night by the way radar signals are reflected in contaminated water. This is possible because the spread of oil tends to flatten the sea surface and this effect can be detected from space.

More Apps

The elevation model outlined by the TanDEM-X will have many applications. Now, improved data that will emerge from the TanDEM mission may extend the range of applications of radar technology. For example, mobile operators can use the elevation model to identify the best places where they can locate their antennas.

Also, the aviation sector may use the information to plan better routes flight planners need this data to analyze the risks of flooding in urban areas and maritime officials may even use the information to track vessels weighs pirates or illegal. The project is operated TerraSAR-X/TanDEM-X publicly and privately.

The German space agency owns the hardware, the European consortium of services and space projects, EADS Astrium, the company built and Infoterra GbmH has exclusive rights to market data.