Exploring the Unknown - NASA's History Office

Chapter One
The History of Satellite
Communications
by Joseph N. Pelton
Although the idea of using artificial Earth satellites to relay messages from one point
on the Earth to another had been discussed in several places prior to 1945, 1 most accounts
of the development of satellite communications begin by discussing Arthur Clarke’s landmark
works on the topic during that year. In two 1945 papers—one privately circulated
and one published in Wireless World—Clarke discussed the special characteristics of geosynchronous
orbit that would enable three satellites in that orbit to provide global communications.
2 [I-1, I-2] Clarke noted that in an orbit of 22,300 miles above the Earth, the
velocity of a satellite exactly matched the velocity of the Earth’s surface as the planet rotated
about its axis; thus from the Earth, a satellite would appear to remain in a fixed position
in the sky. In such an orbit, a satellite could “see” 40 percent of the equatorial plane.
Clarke noted the benefits of such an orbital perspective, especially for telecommunications,
because the curvature of the Earth’s surface and atmospheric interference placed
limits on ground-based transmissions. In addition, the use of satellites in geosynchronous
orbit would make the design of a ground antenna simpler in terms of tracking and pointing
mechanisms.
For these insights, Arthur C. Clarke is frequently called the “Father of Satellite
Communications,” and there have been ongoing efforts to officially designate the geosynchronous
orbit as the “Clarke Orbit.” Ironically, however, while a visionary in many
respects, Clarke did not foresee how quickly communications satellites would become a
reality. This is because he did not anticipate the invention of the transistor, which greatly
reduced the necessary weight of a communications satellite and dramatically increased its
reliability and lifetime. From the pre-transistor perspective of 1945, Clarke envisioned that
communicating via satellite would in effect require a space station—an orbital platform
weighing many tons with an on-board crew to replace burned-out vacuum tubes. 3 And
while Clarke may not have been totally prescient, he can be credited with identifying a line
of technological development that bore fruit in less than twenty years.
1. Delbert D. Smith, Communication via Satellite: A Vision in Retrospect (Boston: A.W. Sijthoff, 1976),
pp. 15–19.
2. The more frequently cited of Clarke’s semi-annual papers is Arthur C. Clarke, “Extra-Terrestrial
Relays: Can Rocket Stations Give World-Wide Radio Coverage?,” Wireless World 51 (October 1945): 305–08. A May
25, 1945, typed paper about geosynchronous satellites, “The Space Station: Its Radio Applications,” was sent to
members of the British Interplanetary Society and other addressees some five months before the more famous
Wireless World article. This earlier paper was finally published in Spaceflight 10 (March 3, 1968): 85–86.
3. Personal interview by the author with Arthur C. Clarke, Sri Lanka, May 1984.
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