geostationary telecommunications satellites electronic telephone set ...

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HAROLD A. ROSEN
Vice President
Hughes Aircraft Company, USA
In contrast to all other orbits, the geostationary
orbit permits continuous
communications over vast areas via a
single satellite and requires little, if
any, tracking capability in the associated
earth terminals. Thus, potentially
large cost savings in both the orbiting
and earthbased elements of a
satellite communications system would
accrue when geostationary satellites
were available. However, in 1959 the
prospects of early achievement of this
goal were bleak. Many problems resulted
from the size and complexity of
the designs then being considered.
The large size precluded the use of
launch vehicles available at that time;
but, even if launchable, these designs
were too complex to have an economically
attractive life expectancy.
While pondering these matters, it occurred
to me that the satellite's size
and complexity could be greatly reduced
if a spinning configuration were
adopted. This would provide stabilization
of a toroidal antenna beam which
continuously encompassed the earth,
simplifying the attitude control, while
permitting orbital period control by use
of spin phased impulses, thus simplifying
the orbit control system. Additional
savings in weight could be
achieved by the use of a solid state
receiver for the communications receiver
and a traveling wave tube amplifier
for the transmitter, an invention
of Kompfner's perfected by Pierce.
These design concepts provided the
basis for a lightweight geostationary
communications satellite design; and,
starting in the fall of 1959, I led a small
team charged with perfecting and reducing
it to practice. My late colleaugue,
Donald Williams, was responsible
for the orbit and attitude control
system design and analysis, and,
among many other contributions, invented
a method of attitude control
using a single thruster, which he demonstrated
with a dynamic model in
1960. The entire attitude and orbit control
of the satellite could now be accomplished
with only two thrusters,
using spin phased impulses when necessary.
My friend and coworker, Thomas
Hudspeth, was responsible for the
receiver and antenna development and
designed efficient, lightweight elements
years ahead of their time. John
Mendel adapted the traveling wave
tube transmitter to space applications
by perfecting a rugged, lightweight
design featuring metal-ceramic construction
and periodic permanent magnet
focusing. With these elements, we
proceeded to construct and test a prototype
geostationary satellite during
the year 1960, an effort supported by
Hughes Aircraft Company, and also
began a campaign to get it launched.
Our initial proposals were turned down
by all U.S. Government agencies and
every communications company that
was approached. An unsuccessful attempt
to interest European agencies
and communications companies in the
idea centered on the Paris Air Show of
1961 and a subsequent demonstration
on the Eiffel Tower, where it was alleged
that "this is as high as it will ever
get". The general feeling of skepticism
expressed both in the United States
and Europe involved doubts about the
technical approach as well as the quality
of voice communications via a geostationary
satellite. The latter objection
was raised because of the propagation
time delay associated with the
high altitude orbit, and its adverse interaction
with the echo suppressors
used in the ground networks. However,
continued tests on this question showed
that the time delay could be acceptable
when the voice circuits were
equipped with properly designed echo
suppressors, and was of no consequence
for television and telegraphic
communications.
After additional persuasion, late in
1961 the U.S. Space Agency, NASA,
with cooperation from the Department
of Defense, sponsored a program to
test the concept—this became known
as the Syncom program, for Synchronous
Communications. While the flight
models of Syncom were being constructed
and tested in the summer of
1962, Telstar, which was constructed
by Bell Telephone Laboratories of
AT&T, was launched by NASA into a
low altitude orbit and first demonstrated
the feasibility of wideband transoceanic
communications via satellite.
The first Syncom satellite was launched
in February 1963 but exploded when
injected into final orbit and became