Navigation satellite system Galileo

摘要

We now switch from communications to navigation. This talk will be about the European Galileo program. We all hope that it, together with GPS, will be as successful in the future as telecommunications is today. Furthermore, we believe that can be done best in combination with telecommunications. I would like to bring you up to speed on the Galileo program. It is all about worldwide users, who want to use its features wherever they are in cars, in planes, in ships, or anywhere. Galileo (Fig. 1) is pretty much like GPS. It comprises a satellite constellation of 30 satellites in three circular orbits at 23, 600 km with inclination of 56°. At a given time, each of these satellites transmits its position down to users on the ground. There are two control centers that are always in touch with the spacecraft, and five Telemetry and Telecommand stations which take care of the health of the spacecraft, checking various parameters of the satellite platform and ensuring that it is working well. There are 30 sensor stations for orbit determination, satellite clock synchronization, and integrity monitoring. Since the positions of the stations are known, the orbits of the satellites and clocks in the satellite can be estimated from the received user signals. For integrity, it is checked in near real time whether estimate and reality coincide. If there is a significant error, they can feed this back into the control center, which can get in touch, so to speak, with the payloads of the satellites concerned and make adjustments, such as correcting their clocks.