One of the attractive things about using a satellite is that it doesn’t
require a revolutionary breakthrough in technical knowledge. It can
employ a satisfactory means of communicating that is already available:
the microwave radio relay. Today, this kind of transmission is used on a
routine basis to send thousands of telephone calls and television
programs across long distances. It gives high-quality performance and
has a large message capacity. But there has always been one difficulty
keeping us from using it for overseas communications: Extremely high
frequency waves can travel almost unlimited distances, but they can go
only in straight lines. This means that the curvature of the earth
limits a microwave’s line-of-sight path to about 30 miles; so we must
build a series of transmission relay towers spaced every 30 miles or so.
Obviously, this isn’t possible when you send messages across an ocean.
But, if we could find a way to send a signal high up into the sky and
then bounce it from there back again to a far-off spot, we could send
microwave messages great distances.
[Illustration: _Curvature of the earth requires microwave towers to
be about 30 miles apart_]
[Illustration: _Microwaves sent via an orbiting satellite can travel
vast distances_]
As long ago as 1945, Arthur C. Clarke, an English writer and scientist,
proposed that a man-made satellite orbiting in space might be used to
relay signals in this way. In 1945, of course, the very idea of getting
a satellite out into space seemed utterly fantastic, and satellite
communications could only be classified as science fiction. Ten years
later, although Sputnik I had not yet been launched, artificial
satellites were close to reality. At that time, John R. Pierce of Bell
Telephone Laboratories made the first serious study of what would have
to be done to build a working satellite communication system—assuming it
ever became possible to put satellites into orbit. And Bell Laboratories
has been interested in satellite communications ever since.