RSL ground campaign on the Aletsch glacier
The Aletsch glacier is the longest in the Alps at 23 km long. With an altitude difference of about 1 km between its upper and lower "tongues", it is in constant motion - a motion that is additionally modulated by the changing seasons and an increasingly warm climate. The surface of the glacier flows downhill like a river in slow motion. In conjuction with other observations, this motion can therefore serve as an indirect indicator of climate change. Because such observations are ideally repeated at regular intervals, for the whole glacier at a time, and in a reliable and inexpensive way, satellite remote sensing is the ideal tool for such observations. TerraSAR-X is a radar satellite operated by the German Aerospace Center (DLR) and Infoterra GmbH, providing the highest-resolution civilian SAR image products available today. Its resolution makes it possible to see glacier features such as ridges and crevasses as small as ~1 metre in size. Since SAR can "see" at night, through clouds and even rain, the glacier can be imaged at any time and under any weather conditions. By tracking glacier features over time using multiple images, it is possible to estimate the glacier flow velocity at its surface. In the context of a wider TerraSAR-X calibration/validation campaign, RSL has marked several reference points on the glacier’s central area (Konkordiaplatz) and measured their positions using differential GPS. These reference points will therefore have known velocities, and will serve as calibration/validation points for automated tracking. If successful, such a method could be used operationally for regular glacier tracking, providing useful data to glaciologists and climatologists, and helping us better understand glacier dynamics and their role as climate-change indicators. The ground campaign on the glacier is being coordinated in conjuction with the High-Altitude Research Station at Jungfraujoch, stationed at the top of the glacier.