[Illustration: 38. Ground inflation test on _Echo 1_, the world’s
first passive communications satellite.]
Communications satellites can be grouped into two broad categories.
Passive vehicles reflect signals from one ground station to another.
Active satellites accept ground signals and either amplify and
rebroadcast them immediately or record messages for later transmission.
The Echo satellite balloons typified the passive category of
communications spacecraft. These satellites “bounced” radio signals from
one ground station to another. Uninflated Echo payloads were carried
into orbit packed in special storage containers. When released in space,
the balloon was inflated by chemicals packed inside which subliminated
to produce inflating gas. The mylar plastic skin of the satellite was
sandwiched between two layers of aluminum foil. _Echo 2_—on
display—included a system for releasing gas over a long period of time
to maintain the satellite’s spherical shape. Launched January 25, 1964,
_Echo 2_ was the first satellite used for communication experiments
between the United States and the Soviet Union.
Project West Ford, launched May 9, 1963, was a unique experiment in
passive satellite communications. It was not a solid vehicle, but a
series of 400-million tiny individual copper filaments called dipoles.
The dipoles formed a reflective layer some 64,300 kilometers (40,000
miles) long, 32 kilometers (20 miles) thick, and 32 kilometers (20
miles) wide. The distance between the individual dipoles averaged 536
meters (one-third mile). The West Ford experiment proved disappointing,
and advances in the design of active communications satellites made
further experiments of this nature unnecessary.
_Oscar 1_ (Orbital Satellite Carrying Amateur Radio) was conceived,
designed, and constructed by American amateur radio “hams.” Launched as
a “piggyback” satellite on December 12, 1963, Oscar transmitted a series
of Morse code dots spelling “hi.” The message was picked up by 5000
operators in 28 nations during the 18 days of transmission. Oscar
investigated radio propagation phenomena in space on that portion of the
radio frequency spectrum allocated to amateur radio (144-146 megaherz).
Testing the use of a “delayed-repeater” satellite in global military
communications, _Courier 1-B_ was placed in a high-altitude orbit on
October 4, 1960. The craft accepted and stored messages as it passed
over one ground station, then replayed them on command.
_Relay_, another active repeater satellite, was placed in orbit on
December 13, 1962. _Relay_ carried communications experiments to test a
variety of relay equipment—including that for photofacsimile,
teleprinter, and data transmission. During its 25-month lifespan, _Relay
1_ introduced the nations of the world to satellite communication. A
second, improved _Relay_ was launched in 1964.
[Illustration: 39. The exterior of eight-sided _Relay_ is composed
of honeycomb aluminum panels studded with 8215 solar cells.]
The world’s first commercial communications satellite was called “Early
Bird,” or INTELSAT 1. Built a decade ago by Hughes Aircraft Company for
Communications Satellite Corporation (COMSAT), Early Bird could transmit
simultaneously on 240 two-way channels for telephone, telegraph, or data
transmission. Transatlantic telephone circuit capability increased by 50
percent once Early Bird went into orbit on April 6, 1965. Although the
craft had a life expectancy of 18 months, it operated satisfactorily in
full-time service for more than three and one-half years.
INTELSAT 2 introduced multipoint communications between earth stations
in the Northern and Southern hemispheres. With almost twice the power of
Early Bird, INTELSAT 2 proved particularly important as communications
support for the Apollo missions to the Moon.
INTELSAT 2 established a global network of three satellites that was
effective in linking two-thirds of the world’s people in one
communications chain. The first of the series was launched on January
11, 1967. These spacecraft were designed and manufactured by the Hughes
Aircraft Company for Intelsat, Inc., and had a design lifetime of three
years.
INTELSAT 3 was a series of five communications satellites which provided
global coverage for the first time. This INTELSAT had a capacity of 2400
voice, data, facsimile, and telegraph circuits, plus four television
channels and had a design lifetime of five years.
The satellite featured a de-spun antenna which remained pointed at a
particular area of the globe, while the body of the satellite spun
around it. It was the first commercial satellite capable of transmitting
voice and television broadcasts simultaneously.
INTELSAT 3 satellites were manufactured by TRW Systems, Inc., for
Intelsat, Inc.
_Echo 2_, _Courier 1-B_, and _Relay_ are from the National Aeronautics
and Space Administration; _OSCAR 1_ is from Project Oscar, Inc.;
INTELSAT 1, INTELSAT 2, and INTELSAT 3 are from the International
Telecommunications Satellite Organization.