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Syncom 1



Syncom 1 was designed to be the first test of a communication satellite in geosynchronous orbit. The objective of the mission was to put the satellite into a 24 hour orbit with an inclination of about 30 degrees over the Atlantic Ocean. After launch into a highly elliptical orbit on 14 February 1963, initial communication tests conducted from the USNS Kingsport off Nigeria were successful. About 5 hours after launch the apogee motor was commanded to fire to place the satellite into a near-synchronous orbit. At about the time the motor completed its 20 second burn all contact was lost. NASA officials assumed that "the satellite's spin axis was misaligned at the time of the apogee motor firing. Because of this they have been unable to determine whether the satellite is damaged." Attempts were made to communicate with the spacecraft but contact was never re-established. Using search patterns based on data from the Kingsport's range and range rate system, the Boyden Observatory at Bloemfontein, South Africa, sighted Syncom 1 on March 1. The spacecraft's initial orbit was computed to be 34,186 km to 37,021 km with a period of 23 hours, 46.5 minutes.

Spacecraft and Subsystems

The Syncom satellites were 71 cm diameter, 39 cm high cylinders. The fully fueled mass of the spacecraft was 68 kg. The nozzle of the solid propellant apogee motor (1000-lb-thrust designed to impart a velocity increase of 1431 meters/sec) extended from the bottom of the cylinder and a co-axial slotted array communications antenna from the top. The total height including the nozzle was 64 cm. The radial exterior was covered with 3840 P-on-n silicon solar cells which provided direct power of 29 watts the 99 percent of the time the spacecraft was in sunlight. Nickle-cadmium rechargeable batteries provided power when the spacecraft was in the Earth's shadow. No active thermal control was required. Most of the central interior of the spacecraft consisted of the tanks and combustion chamber for the apogee motor, around this were arranged two hydrogen peroxide and two nitrogen tanks and the electronics. Attitude and velocity control was provided by nitrogen jets to align the spin axis and hydrogen peroxide jets to position the satellite. Each system had two jets, one parallel and one perpendicular to the spin axis.

Syncom employed a redundant, frequency-translation, active repeater communication system designed to handle one two-way telephone or 16 one-way teletype channels. The dual transponders utilized 2-watt traveling wave tubes. Selection of receiver and transmitter was made by ground command. One receiver had a 13 megacycle bandwidth for TV transmission, the other a 5 megacycle bandwidth. The receiving gain was 2 dB through the slotted dipole antenna. Signals were received on two frequencies near 7360 megacycles and retransmitted on 1815 megacycles. The slotted dipole transmitting antenna radiated a pancake-shaped beam 25 degrees wide with its plane perpendicular to the spacecraft spin axis. There were also four whip antennas oriented normal to the spin axis for telemetry and command.

Alternate Names

  • 00553
  • A 25
  • Synchronous Communications Satellite 1
  • Syncom1

Facts in Brief

Launch Date: 1963-02-14
Launch Vehicle: Thor-Delta
Launch Site: Cape Canaveral, United States
Mass: 39 kg

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Communications

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Mr. R. J. DarceyProject ManagerNASA Goddard Space Flight Center
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