CHAMP (Challenging Minisatellite Payload) is a small German satellite mission for geoscientific and atmospheric research and applications, managed by GFZ Potsdam. Using an advanced GPS (global positioning system) CHAMP measures how its orbit changes in response to Earth's gravitational pull, enabling researchers to map indirectly the density of Earth's crust. By mapping the density to a high precision over many years, scientists can detect changes in variables such as seawater level, the thickness of the polar ice caps, and even the density of the atmosphere.