Home >> July 2008 Edition >> Feature: The History of Satellites — Part 4 (Relay)
Feature: The History of Satellites — Part 4 (Relay)

by Donald Martin, Paul Anderson, and Lucy Bartamian


The Relay program [1–9] was undertaken by 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.

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 (WB) signals or two-way transmission of narrowband (NB) signals. The communication subsystem block diagram is shown; the satellite details follow. 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

  • Two double-conversion repeaters (one on, one standby), each with one WB and two NB channels

  • WB: 300 one-way voice circuits or one TV channel
  • NB: 12 two-way telephone circuits (limited by ground equipment, not satellite bandwidth)

  • 4164.7, 4174.7 MHz (NB), 4169.7 MHz (WB)
  • All solid state except TWT
  • 10 W output

  • 1723.3, 1726.7 MHz (NB), 1725 MHz (WB)
  • All solid state
  • 14 dB noise figure

  • Two biconical horns (one transmit, one receive)
  • Approximately 0 dB gain normal to spin axis
  • Circular polarization

  • One year

  • Relay 1: 712 x 4012 nmi, 47.5 deg inclination
  • Relay 2: 1130 x 4000 nmi, 46 deg inclination
Orbital history
  • Relay 1: launched 13 December 1962, operated until February 1965
  • Relay 2: launched 21 January 1964, operated until May 1965
  • Delta launch vehicle

Developed by RCA for NASA Goddard Space Flight Center, 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.

Select the book graphic to order this book from The Aerospace Company

* * * * * *

  1. Space Communications and Navigation 1958–1964, NASA SP-93 (1966).
  2. K. W. Gatland, Telecommunication Satellites, Prentice Hall, New York (1964).
  3. Final Report on the Relay 1 Program, NASA SP-76, Goddard Space Flight Center (1965).
  4. L. Jaffe, "The NASA Communications Satellite Program Results and Status," Proceedings of the 15th International Astronautical Congress (1964), Vol. 2: Satellite Systems (1965).
  5. S. Metzger and R. H. Pickard, "Relay," Astronautics and Aerospace Engineering, Vol. 1, No. 8 (September 1963).
  6. Publications of Goddard Space Flight Center 1963, Vol. II:
  7.   a. S. Metzger and R. H. Pickard, "Relay" (See Ref. 5).
  8.   b. R. H. Pickard, "Relay 1 Spacecraft Performance."
  9.   c. R. Pickard, S. Roth, and J. Kiesling, "Relay, An Experimental Satellite for TV and Multichannel Telephony."
  10. "Development of the Relay Communications Satellite," Interavia, Vol. 17 (June 1962).
  11. D. R. Glover, "NASA Experimental Communications Satellites," http//sulu.lerc.nasa.gov/dglover/satcom2. html (10 June 1999).
  12. D. R. Glover, "NASA Experimental Communications Satellites, 1958–1995," in Beyond the Ionosphere: Fifty Years of Satellite Communication, A. J. Butrica, ed., NASA History Office, Washington, D.C. (1997), ch. 2.