Geostationary satellites positioned by GSOC

An important function of GSOC is the positioning and routine control of communications satellites. Since 1974, twelve satellites of this type have been successfully positioned in geostationary orbit.

GSOC's first geostationary communications satellites were the Franco-German projects Symphonie A and B. From 1987 to 1992 five national communication satellite missions were carried out for the Deutsche Bundespost Telekom: TV-SAT 1 & 2, and DFS Kopernikus 1, 2 & 3. For the European Telecommunications Satellite Organization (EUTELSAT), five satellites of the EUTELSAT II series were positioned in the geostationary orbit from 1990 to 1995. Again GSOC was selected to perform the Launch and Early Orbit Phase (LEOP) services for the new generation of EUTELSAT's telecommunication satellites EUTELSAT W24 with a first launch early 1998. In the time between mid 1989 and the end of 1992 a positioning was executed, on average, every five months.

The satellites were launched by different launch vehicles, such as the European ARIANE and the American launchers ATLAS and DELTA.

A globe-spanning ground station network is needed during the first part of the of the positioning phase. For telemetry data reception, telecommand transmission and tracking data collection a network of S-Band (2 GHz) ground stations is used:

the DLR ground stations at Weilheim (Germany); the NASA ground stations at Goldstone (California), Madrid (Spain) and Canberra (Australia); the ISRO ground stations at Bangalore (India). Before and during the launch GSOC is connected to the specific launch site to receive the latest satellite telemetry. Voice lines are established to ensure direct contact with the launch site. the Ariane Space Center at Kourou (French Guyana) for an Ariane launch; the U.S.A.F. Air Station at Cape Canaveral (Florida) the Russian Space Center at Baikonur (Kazakhstan) for a Proton launch.

This network ensures a near continuous monitoring of the satellite during LEOP operations. During critical phases dual site visibility may be available for redundancy purposes. The NASA ground station network is operated by the Jet Propulsion Laboratory (JPL) in Pasadena (California), the ground station at Bangalore by the Indian Space Research Organization ISRO.

At the German Space Operations Center all the activities for the positioning of the satellites are prepared and coordinated. After the separation of the satellite from the launcher GSOC's task comprises all operations starting with the first acquisition of the satellite. Depending on the launcher injection orbit three or four main boost maneuvers are performed to inject the satellite into the geostationary orbit (approx. 36.000 km above earth). During the following drift phase the satellite is maneuvered into its designated on-station position. Before the satellite is ready to go into service (approx.3 weeks after launch) the on-station configuration is established and In-Orbit-Tests are performed.

All the activities are carried out by fully trained teams of specialists for satellite operations, flight dynamics and facility operations. The Satellite Operations Team is supported by experts of the customer and of the satellite manufacturer who follow the operations at GSOC during the first days after launch.

GSOC can provide the following accommodation for the monitoring of the spacecraft operations:

a main control room which comprises consoles for 17 persons. A standard console consists of two display work stations, one X-terminal, one TV monitor, two printers and two voice (intercom) stations; a second control room with consoles for 15 persons is available for the satellite specialists from the customer and industry; a separate area (the navigation room) for attitude and orbit activities. a system control area from which the operation of the ground data system, the network and the GSOC computer system are coordinated and controlled.