TerraSAR-X and TanDEM-X Tackle the Final Stretch of WorldDEM™ Data Collection
The WorldDEM™ program has accomplished another major project milestone: the second complete coverage of the Earth’s entire landmass has recently been finalised. For the final phase of the acquisition campaign the satellites have now swapped formation.
Following the successful first coverage of the Earth’s entire land surface delivered in early 2012, WorldDEMTM data collection has now advanced another key step with the completion of the second coverage. A slight adjustment to the acquisition angles of the satellites was used during the second coverage to eliminate any remaining height ambiguities in the first coverage data takes.
While the first coverage already generated quality levels close to the final dataset specifications, with the second coverage now dual baseline processing techniques are applied to increase the homogeneity of the global coverage.
Mountain High and Valley Low
The two twin satellites are now focussing their full attention on the Earth’s challenging terrain areas. They are taking a third and sometimes even fourth look at the high-altitude mountain ranges of the globe, like the Himalaya, the Alps and the Cordilleras in North and South America. The purpose of this additional data take is to ensure that details even in steep terrain, valleys, canyons or gorges are made visible that might otherwise be hidden due to shadow areas. The combined processing of these various data takes will ensure the globally consistent high quality and level of accuracy for the final WorldDEM™ product.
Satellite Formation Swapping
The control room at the German Space Operations Center (GSOC) during the formation swap of TerraSAR-X and TanDEM-X © DLR/Edith Maurer
For the final stretch of the acquisition campaign the formation of TerraSAR-X and TanDEM-X was revised in early August: at the start of the mission TanDEM-X circled around TerraSAR-X in an anti-clockwise direction, after the satellite swap it is now clockwise. This change of formation was necessary to view complex mountainous terrain from a different viewing angle to eliminate missing information due to radar effects. For the safe performance of this complicated manoeuvre the distance between the satellites was first increased to appr. 10km. Following the performance of the flight path adjustments, the satellites then converged again to their nominal distance of a few hundred metres. The complex manoeuvre took in total three days and was successfully concluded by the experts at DLR on August 9th.