Communication Satellites (4th Ed.)
Donald Martin
Chapter 1: Experimental Satellites (cont.)
Relay
The Relay program [1–9] was undertaken by the National Aeronautics and Space Administration (NASA) to perform active satellite communications and to measure Van Allen belt radiation and its effect on satellite electronics. Basic objectives were to transmit telephone and television signals across the Atlantic and to transmit telephone signals between North and South America. During the time the satellite was being developed, foreign governments were invited to participate in communications experiments. Primary ground stations were in Maine, England, and France—the same stations that conducted demonstrations with Telstar 1. Other ground stations were in California, New Jersey, Germany, Italy, Brazil, and Japan.
|
Relay Satellite |
The Relay satellite had a more complex communication subsystem than Telstar, with two identical redundant repeaters. Either repeater could be connected to the common antennas by ground command. Each repeater had one 25-MHz channel and two 2-MHz channels. These channels allowed either one-way transmission of wideband signals or two-way transmission of narrowband signals. The communication subsystem block diagram is shown; the satellite details are as follows:
Satellite
Octagonal prism, 35 in. long, 29-in. diam (53 in. overall length)
172 lb in orbit
Solar cells and NiCd batteries, 45 W
Spin-stabilized, 150 rpm
Configuration
Two double-conversion repeaters (one on, one standby), each with one wideband and two narrowband channels
Capacity
Wideband (WB): 300 one-way voice circuits or one TV channel
Narrowband (NB): 12 two-way telephone circuits (limited by ground equipment, not satellite bandwidth)
Transmitter
4164.7, 4174.7 MHz (NB), 4169.7 MHz (WB)
All solid state except TWT
10-W output
Receiver
1723.3, 1726.7 MHz (NB), 1725 MHz (WB)
All solid state
14-dB noise figure
Antenna
Two biconical horns (one transmit, one receive)
Approximately 0 dB gain normal to spin axis
Circular polarization
Relay Communication Subsystem |
Telemetry and command
Telemetry: 136.05 MHz, 200-mW transmitter
Command: approximately 123 MHz
Four-element helical antenna
Design life
Two-year goal
Orbit
1: 514 X 3051 nmi, 45-deg inclination
2: 525 X 5830 nmi, 43-deg inclination
Orbital history
1: launched 10 July 1962, operated until 23 November 1962, and 4 January to 21 February 1963
2: launched 7 May 1963, operated until May 1965
Delta launch vehicle
Management
Developed by Bell Telephone Laboratories for AT&T
Relay 1 was launched in December 1962. Radiation experiment data were obtained on the first day. That same day, difficulties with communications transponder No. 1 that caused excessive power consumption were noticed. The problem could not be fully corrected, and from January 1963 transponder No. 2 was used for almost all the communication experiments. Relay 1 operated until February 1965.
During 1963, several tests and demonstrations were conducted including telephone and television transmissions. Network TV broadcasts were transmitted from the United States to Europe and to Japan. Several times, both television and telephone transmissions were used for international medical consultations. In October 1964, television coverage of the Olympic Games was relayed from Japan to the United States by Syncom 3 and then from the United States to Europe by Relay 1.
Relay 2 was modified slightly to provide increased reliability and radiation resistance. Relay 2 was launched in January 1964 and was used in a variety of communications tests similar to those done with Relay 1. By July 1964, Relays 1 and 2 had been used for 112 public demonstrations of telephone and television transmission. Relay 2 was used until May 1965.
The Telstar and Relay programs were both considered successful. They demonstrated that the technology at that time could produce a useful, medium-altitude communication satellite. In addition, ground station technology was proven, and routine operation of ground stations was demonstrated. Measurements of communications parameters indicated no significant deviations from theoretically expected values. Finally, it was shown that satellite communication systems could share frequencies with terrestrial microwave systems without mutual interference.
******
- Space Communications and Navigation 1958–1964, NASA SP-93 (1966).
- K. W. Gatland, Telecommunication Satellites, Prentice Hall, New York (1964).
- Final Report on the Relay 1 Program, NASA SP-76, Goddard Space Flight Center (1965).
- L. Jaffe, "The NASA Communications Satellite Program Results and Status," Proceedings of the 15th International Astronautical Congress (1964), Vol. 2: Satellite Systems (1965).
- S. Metzger and R. H. Pickard, "Relay," Astronautics and Aerospace Engineering, Vol. 1, No. 8 (September 1963).
- Publications of Goddard Space Flight Center 1963, Vol. II:
a. S. Metzger and R. H. Pickard, "Relay" (reprint of Ref. 5).
b. R. H. Pickard, "Relay 1 Spacecraft Performance."
c. R. Pickard, S. Roth, and J. Kiesling, "Relay, An Experimental Satellite for TV and Multichannel Telephony." - "Development of the Relay Communications Satellite," Interavia, Vol. 17 (June 1962).
- D. R. Glover, NASA Experimental Communications Satellites, (10 June 1999).
- D. R. Glover, "NASA Experimental Communications Satellites, 1958–1995," chapter 6 in Beyond the Ionosphere: Fifty Years of Satellite Communication, A. J. Butrica, ed., NASA History Office, Washington, D.C. (1997).
Next: Syncom 1 to 3
