Symphonie Satellites
Symphonie Satellites |
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Symphonie ALaunch: 12 December, 1974 on THOR DELTA;
Symphonie BLaunch: 27 August, 1975 on THOR DELTA;Position: 11.5°W, de-orbitted: 19 December, 1984 |
Symphonie was a joint German-French telecommunications satellite programme. In June 1967, the governments of the French Republic and the Federal Republic of Germany signed an agreement on the definition, development, manufacture, launch and utilization of two experimental direct broadcasting telecommunications satellites as well as on the design and construction of two earth stations. On this basis, a bilateral organization was established on a governmental level, which awarded a contract for the development of the satellites to a German-French industrial consortium, financed in equal parts by France and Germany.
The Symphonie ground segment comprised of a series of
earth stations which allowed a large spectrum of utilization such as transmission of
television and radio programmes, telephone calls, telexes and data.
The Symphonie space segment consisted of two 3-axis-stabilized geostationary satellites, which allowed simultaneous communication between several earth stations in the 4 and 6 GHz frequency ranges.
The two satellites were positioned in close co-operation with the French Space Organization CNES and successfully put into operation. During their life time both satellites were controlled jointly by the German-French control centres on a time-shared basis.
At the beginning of 1977, Symphonie A was moved to a position over the Indian Ocean (49°E) where it stayed for approximately two years.
After a project duration of ten years the satellites were switched off and removed from the geostationary orbit into the so-called "grave-yard-orbit".
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The Symphonie satellites were injected from the US Cape Canaveral launch site with THOR-DELTA launchers. In a first step a circular parking orbit with 400 km altitude and 28.3 deg inclination was reached. After a tilt maneuver and a second firing of the upper stage the spacecraft was injected into the eccentric transfer orbit with an oversynchronous apogee height of 38.000 km and a reduced inclination of 13.2 degrees. After separation from the launcher the satellite was put into the PRIMARY ORBIT by an apogee boost maneuver at the sixth apogee of the transfer orbit. The 19 min 50 sec lasting burn of the satellite's 400N engine raised the perigee to 34.000 km and reduced the inclination from 13.2 deg to zero. |
Positioning of the Symphonie satellites
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Throughout the injection and the orbit coarse correction maneuvers the satellite was spin-stabilized around its thrust axis. The first coarse orbit correction lifted the primary orbit perigee form 34.000 km to almost geostationary height thus leading to the SECONDARY ORBIT. The second coarse orbit correction brought the spacecraft into the DRIFT ORBIT by reducing the supersynchronous apogee height to 36.000 km. During the drift phase to the designated orbital position the satellite was configured to its on-station configuration by despin- and three-axis stabilization maneuvers. Three additional east/west maneuvers were carried out to reach the geostationary point and to eliminate the residual orbit eccentricity and inclination. |
On-station control of the Symphonie satellites
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The routine operations for the Symphonie satellites were performed on a time-shared basis from the
German DLR space control center at Oberpfaffenhofen and the French CNES center at Toulouse.
Every 6 months the responsibility for the two flight models was swapped between the centers.
The main tasks for the on-station control were:
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The designed lifetime for the Symphonie satellites was five years each; nevertheless despite of some technical (ageing-) problems the satellites could be operated for ten years. Both satellites were de-orbitted successfully by DLR at the end of mission using up the remaining fuel of the attitude control system.
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