Once a satellite is launched, the success of its mission often depends on the ability to communicate with it and to follow its progress. Since May 1968, most of the satellites launched for ESA have been under the control of the European Space Operations Centre (ESOC) in Darmstadt, Germany.
The centre includes a Main Control Room, which is the hub of activity during the first stages of a mission. Once the satellite is up-and-running, operations are switched to smaller, Dedicated Control Rooms. The work of ESOC begins as soon as a mission is pencilled in for study. As the mission evolves and develops, ESOC studies all aspects of flight control, satellite operations and communications.
Once a satellite is launched, the centre has to track and control the satellite. This includes sending commands to change the spacecraft’s attitude or orbit, and keeping a watch to see that it is working properly. ESOC also monitors the onboard instruments and sends new instructions when necessary.
A number of missions that seemed to be lost have been saved by experts at ESOC. They include Hipparcos, which was able to complete its three-year star-mapping mission, despite being stranded in the wrong orbit.