On 10 December, seven weeks after the start of the first two Galileo navigation satellites, scientists at the GFZ German Research Centre for Geosciences received the first signals from one of the two satellites (GSAT101). By analysing these first observational data, the GFZ scientists were able to determine the orbit of the satellites, which are flying at an altitude of 23222 km, for the first time to a few decimetres.