With the first launching of a satellite into orbit by the Soviet Union
in 1957, the real development work on satellite communications began. By
1960 Project Echo had proved that signals could be reflected off a
man-made satellite and received several thousand miles away. And, in
1962, Project Telstar demonstrated to the whole world that an active
repeater satellite could send telephone calls, data, and television
across the ocean.
Bringing satellite communications almost to reality has required more
than putting a man-made satellite into orbit around the earth. Just as
important have been the invention and development of many remarkable new
devices: the transistor, the solar cell, the traveling wave tube, the
horn-reflector antenna, the waveguide, the solid-state maser, and the
electronic computer—to mention only some of the more important. Without
them it would still be impossible to find a tiny speeding object miles
out in space, send signals to it, amplify them billions of times, and
then return them to distant points on the earth.
Some of the new devices that help make satellite communications
possible
[Illustration: horn-reflector antenna]
[Illustration: traveling-wave tube]
[Illustration: transistor]
[Illustration: solar cell]
[Illustration: solid-state maser]
_When you look back at it, we have seen remarkable progress in satellite
communications—and work is still continuing at a fast pace. Some of the
milestones have been these:_
OCTOBER 1945 Arthur C. Clarke publishes “Extra-Terrestrial Relays—Can
Rocket Stations Give World-Wide Radio Coverage?” in _Wireless World_,
suggesting the use of satellites for communications.
JANUARY 11, 1946 Project Diana of the U. S. Army Signal Corps bounces
microwave radar signals off the moon and back to the earth, proving that
relatively low power can transmit signals over very long distances.
APRIL 1955 John R. Pierce publishes “Orbital Radio Relays” in _Jet
Propulsion_, pointing out the requirements for a satellite
communications system.
JULY 29, 1958 Congress passes the National Aeronautics and Space Act,
setting up the National Aeronautics and Space Administration (NASA),
with satellite communications experimentation as one of its interests.
DECEMBER 18, 1958 Score, the first communications satellite, is launched
by the U. S. Air Force. It is equipped with tape recorder units that
transmit prerecorded messages back to the earth upon receipt of signals.
On December 19 a Christmas greeting to the world recorded by President
Eisenhower—the first message from a satellite to the earth—is
transmitted. Score continues to transmit for 12 days before its
batteries become too weak for further use.
[Illustration: {uncaptioned}]
NOVEMBER 23, 1959 Live voice transmission is accomplished from Bell
Telephone Laboratories in Holmdel, New Jersey, via the moon to Jet
Propulsion Laboratories in Goldstone, California. This is the first of
17 tests in Project Moonbounce, all using the moon as a reflector.
JULY 8, 1960 The Bell System proposes to the Federal Communications
Commission a detailed plan for a world-wide communications system using
active repeater satellites to provide telephone circuits and facilities
for transmitting television to various parts of the world.
AUGUST 12, 1960 Echo I is launched into orbit by NASA. Project Echo
carries on a large number of communications experiments and, most
important, proves that it is practical to use a man-made satellite to
reflect two-way telephone conversations across the United States. Echo
also dramatizes the possibilities of satellites for communications.
Since it is a 100-foot inflated balloon made from aluminum-coated Mylar,
it is large enough to be seen by the naked eye. People throughout the
world see Echo I sail on schedule across the sky in its 1000-mile-high
circular orbit. Three years later, although it is now wrinkled and
deflated, the balloon is still in orbit.
[Illustration: {uncaptioned}]
Project Echo provided valuable data for future work in satellite
communications. It demonstrated that a passive satellite—that is, one
that simply reflects the microwave signals it receives from an earth
station back to another point—would work. Two-way conversations of good
quality were sent between the Bell Laboratories Holmdel station and Jet
Propulsion Laboratories in Goldstone, and successful transmission was
made to other points in the United States and Europe. A scaled-up
horn-reflector antenna proved itself. A method of receiving microwave
signals that had been little used until then, known as frequency
modulation with feedback (FMFB), performed very well. New types of
low-noise amplifiers using solid-state masers gave excellent results.
And tracking of the satellite by electronic computers, by radar, and by
telescope proved to be extremely reliable.
[Illustration: {uncaptioned}]
OCTOBER 4, 1960 Courier I-B is launched by the Army Signal Corps into a
500- to 650-mile-high orbit. A sphere weighing 500 pounds and measuring
51 inches in diameter, the Courier satellite is powered by 20,000 solar
cells and contains four receivers, four transmitters, and five tape
recorders. It is designed to demonstrate the possibility of using active
repeaters for delayed transmission of messages. Signals are received,
stored on the tapes, and then retransmitted back to earth when the
satellite has moved on. After 18 days in orbit, technical difficulties
ended Courier’s ability to send signals, but it received and
retransmitted 118 million words during its active life.
[Illustration: {uncaptioned}]
JANUARY 19, 1961 The American Telephone and Telegraph Company is
authorized by the Federal Communications Commission to establish an
experimental satellite communications link across the Atlantic. Two
170-pound satellites are to be launched by NASA but will be designed,
built, and paid for by AT&T. This project is later given the name
“Telstar.”
MAY 18, 1961 NASA selects the Radio Corporation of America to design and
build the Relay satellite, which will be used to test the feasibility of
transoceanic telephone, telegraph, and television communications.
AUGUST 11, 1961 NASA awards the Hughes Aircraft Corporation a contract
to build Syncom, an experimental active satellite to be placed into a
22,300-mile-high orbit that will be synchronous with the rotation of the
earth. (See page 37 for definitions of various kinds of satellite
orbits.)
DECEMBER 20, 1961 The United Nations adopts a resolution on the peaceful
uses of outer space that includes a request for world cooperation in
developing a system of communications satellites. Both the United States
and the Soviet Union sign the resolution.
FEBRUARY 7, 1962 President Kennedy asked Congress to pass a bill setting
up a corporation to operate a satellite communications system. The
proposed corporation would be owned jointly by the public at large and
the country’s communications common carriers.
JULY 10, 1962 Project Telstar is successful. For the first time, voice
communications and live television are transmitted across the Atlantic
via a man-made satellite that picks up signals sent from one continent,
amplifies them, and retransmits them to another continent. (On pages 21
to 33 we talk at further length about Project Telstar.)
[Illustration: {uncaptioned}]
AUGUST 31, 1962 President Kennedy signs the Communications Satellite
Act, establishing a private corporation under government regulation—the
Communications Satellite Corporation—which will plan, own, and operate a
commercial satellite communications system.
[Illustration: {uncaptioned}]
DECEMBER 13, 1962 Relay I is launched by NASA. Similar in many ways to
the Telstar satellite, it is an active repeater device that picks up
telephone, television, and other electronic signals and retransmits them
to a distant point. Relay also provides the first satellite
communications link between North and South America. The satellite is a
tapered cylinder 33 inches long weighing 172 pounds. A mast-like antenna
at one end is used to receive and transmit a single television broadcast
or 12 simultaneous two-way telephone conversations. Four whip antennas
at the other end of the cylinder handle control, tracking, and
telemetry—turning experiments on and off and sending information on the
behavior of its components and on the amount of radiation it encounters
in space. Relay is powered by nickel-cadmium storage batteries that are
charged by more than 8,000 solar cells mounted on its eight sides. It
contains two identical receiving, amplifying, and transmitting systems
called transponders, each with an output of 10 watts.
Relay I is traveling in an orbit that ranges from 820 to 4,612 miles
high, and circles the earth about every 185 minutes. Soon after it is
launched, Relay’s telemetry reports trouble in the voltage regulator of
one of the transponders, which causes excessive power drain. On January
3, 1963, the alternate transponder is switched on, and a successful
series of tests—including live television broadcasts between the United
States and Europe—begins.
JANUARY 4, 1963 The Telstar I satellite, which for almost two months
could not be turned on to transmit communications signals, is
reactivated by Bell Laboratories engineers. (The story of this ingenious
electronic detective work is told in detail on pages 78 to 85.)
FEBRUARY 14, 1963 The first Syncom satellite is launched by NASA, but
its communications systems do not operate. It is the first satellite to
try for a synchronous path, revolving around the earth once every 24
hours and thus appearing to hover continuously over the same longitude.
Syncom is a short cylinder 28 inches in diameter and 15½ inches long,
and weighs 86 pounds. Like Telstar and Relay, it is powered by a
combination of solar cells and nickel-cadmium batteries, but it is
designed to handle only one two-way telephone conversation and cannot
transmit television.
[Illustration: {uncaptioned}]
MAY 7,1963 The Telstar II satellite is launched for the Bell System by
NASA. (See page 31.)
What About the Future?
As this is written (June 1963), second Relay and Syncom launchings are
in the offing. And there are plans for more experimentation with passive
satellites, including a new, more nearly rigid Echo balloon.
Further in the future, studies are going on of a proposed Intermediate
Altitude Communications Satellite for military use in the 6,000- to
10,000-mile-high range (beyond that of Telstar and Relay) and Advanced
Syncom, a synchronous satellite of increased capacity. Work is also
continuing to acquire new technical knowledge that will be needed in the
future—such as various methods of keeping satellites stabilized in space
and new ways of supplying power, including improved solar cells and the
use of radioisotopes.
The ultimate goal, of course, is a working commercial communications
satellite system. Exactly when this will be a reality—and what form it
will take—are questions whose answers still lie ahead of us.
[Illustration: _The orbits of four communications satellites vary in
size and shape_]
Echo I 1000 miles 1000 miles
Relay I 4612 Miles 820 miles
Telstar I 3531 miles 592 miles
Telstar II 6697 miles 604 miles