SYMPHONIE SATELLITES – FACT SHEET

Mission

French German experimental telecommunication mission in geostationary orbit
using C-band broadband transponders, a global receive coverage (up-link at 6
GHz band) and two transmit coverage (down-link at 4 GHz band), over
Europe-Africa and Eastern Americas zones respectively.

In-orbit service

Overall service of SYMPHONIE A and SYMPHONIE B satellites was performed in
the period 1975 – 1984 under French German co-operation. Mission was
specified for 5 years and achieved over 10 years; spacecraft lifetime lasted
about 9 years for each flight model in specified orbital position.

SPACECRAFT FEATURES

Spacecraft mass

: Mass at launch 402 kg, injected into synchronous orbit 242 kg, dry 215 kg

Spacecraft power

: 303 W BOL (beginning of life) down to 187 W EOL (end of life) generated from

unfolded solar panels
30 Ah energy available from two Ni-Cd batteries over eclipse time

Station keeping

Capacity to maintain orbit inclination over 5 years and on station longitude
over 10 years

Pointing accuracy

: Accuracy better than

5 degree in all body-stabilised attitude control modes

PAYLOAD FEATURES



One global receive antenna, two transmit antennas on dedicated coverage zones



Frequency band of 500 MHz subdivided in four sub-bands, two of them dedicated per satellite



Two double frequency conversion transponders of 90 MHz bandwidth each



Receive sensitivity G/T = -15 dB/°K



Transmit radiated power EIRP of 30 dBW on edge of covered transmit zones



Two 13 W travelling wave tube TWT power amplifiers in the 4 GHz transmit bands



Intelligible crosstalk level better than –60 dB

BUS SUBSYSTEMS FEATURES

Structure



Six-sided equipment case, 1

7 m diameter and

5 m in height, braced with a aluminium

central tube through three suspended webs



Webs, plates and panels made of aluminium
honeycomb core sandwich type technology



Solar array panels and antenna dishes made of
aluminium honeycomb with glass epoxy sheets

Thermal control



« insulated core » thermal control type with
trimming heaters in cold locations



super-insulation blankets combining multi-
layer aluminised Mylar and Kapton cover sheet



external radiating surfaces covered with optical

solar reflectors (OSR) cells

Power supply



Fixed solar generator after deployment



22000 2-by-2 cm silicium solar cells



27 Volts regulated bus voltage



300 W shunt dissipator capacity



Two 14 Ni-Cd elements batteries



4 DC-DC power converters

Telemetry- Tracking and Command (TTC)



Main mode in VHF frequency bands



Auxiliary mode in C-band coupled with payload
operation



Telemetry modulation PCM/PSK/PM



Telemetry rate of 8 bps in low mode with 198
quantities and 64 bps with 24 quantities



Command modulation PDM/AM on TDCS
standards



127 on-off type commands plus 8 bits memory
registers

Propulsion



Bi-propellant apogee motor, 400 Newton
thrust with Isp of 305 s



7 bi-propellant 10 Newton thrusters for orbit
control with Isp of 285 s



8 nitrogen 1 Newton thrusters, for attitude
control and East-West station keeping back-
up, with Isp of 68 s

Attitude control



Spin stabilised mode with tilting capacity until
synchronous orbit acquisition phase



3-axis body stabilised modes all over
communication mission, thanks to momentum
(20 Nms) flywheel permanent control loop and
periodical thrusters control operations



Infrared Earth sensors and sun sensors
attitude measurement (no gyros set on-board)



Attitude control electronics with memory
registers and download checking capability