We hope the last few pages haven’t given you a wrong impression of
satellite communications. It is easy to assume, when we list the
orderly, step-by-step progress from purely theoretical ideas to a
working satellite such as Telstar, that everything has gone like
clockwork. That isn’t the case at all—and in the rest of this book we
are going to show you why it isn’t. Many problems had to be solved; many
scientific and technological advances had to be made.
We touched on a number of the problems of satellite communications in
our detailed account of Project Telstar. Most of them are not confined
to that project—they are the sorts of questions that any complex advance
in satellite communications will run into. We will list some of the more
important ones here. Then, in Part II, we will talk about some general
methods of solving scientific and technological problems. All this is a
rather roundabout—but necessary—way of leading up to our main interest:
the accounts by six Bell Laboratories engineers and scientists of their
work to solve some typical problems in satellite communications.
The many complications of satellite communications can be divided into
several groups. First of all, there are the problems involved in
_fitting satellite communications into an already established world
communications system_. There are, next, many problems, both small and
large, in _designing the right kind of satellite_. There are the
problems of _launching a satellite and getting it into the proper
orbit_. There are the problems in _making sure it stays in the right
orbit once it gets there_. And, finally there are the problems in
_seeing that it continues to do its job reliably_.
In these five categories there are a lot of specific questions that must
be answered to plan a working satellite communications system. A list of
some of them follows. We haven’t attempted to cover everything, but
these should give you some idea of the tasks and questions involved in
planning an immense project like this.
General Problems of a Satellite Communications System
_What jobs could a communications satellite do best?_
_Should it be used for television?_
_Should it carry telephone messages? How many?_
_Would it be more valuable for data transmission? Facsimile?_
_What parts of the world should be covered?_
_Can all the problems of international cooperation be solved?_
_Would a satellite that could broadcast directly to home receivers be
possible?_
_What military uses could a communications satellite system serve?_
_Would a passive satellite—one that reflects signals without
amplifying them—be worth developing?_
_Or should the emphasis be on active repeaters, which can receive,
amplify, and retransmit signals?_
_What kind of technical standards should be set as the minimums?_
_How detrimental is time delay in sending communications to a
satellite and back?_
_What kind of ground transmitters and receivers would be needed?_
_How powerful or sensitive should they be?_
_Where should they be located?_
_How many satellites would be needed?_
_How much would all this cost?_
Satellite Design Problems
_How big should a satellite be?_
_What should it be made of?_
_What color should it be?_
_What kind of power supply should it use?_
_How powerful should its electronic equipment be?_
_What should be its message-handling capacity?_
_What are the best receiving and transmitting antennas to use?_
_What frequencies ought to be employed?_
_What kind of modulation should be used?_
_How should signals be amplified?_
_What kind of telemetry equipment will be needed?_
_How can radiation in space be measured?_
Launching and Tracking Problems
_How big a rocket booster would be needed?_
_From what part of the world should a satellite be launched?_
_What kind of orbit should it go into? (See table below)_
_How far up should the satellite go?_
_How can a satellite be tracked once it is in orbit?_
_How do we predict future orbits of a satellite?_
Orientation and Control Problems
_How can orders be given to a satellite while it is in orbit?_
_If it is to stay in a fixed attitude, how can it be kept there?_
_What can be done to keep a satellite properly stabilized?_
_Can optical measurements be made on a satellite?_
_What will be the effects of sunlight and gravity on its position in
space?_
Problems of Reliability
_How long will the satellite remain active?_
_What factors will affect its service life?_
_Should its equipment be made redundant?_
_What kinds of components will be most reliable in space?_
_What is the best way to test its equipment before the satellite is
launched?_
_What effects will radiation in space have on the satellite?_
_How can its components be protected from these radiation effects?_
_How can it be insulated from extremes of temperature?_
_What can be done to protect the satellite from the shock and
vibration of launching?_
_Will it be possible to repair an orbiting satellite?_
_Could a satellite be brought back from orbit to be repaired or
salvaged?_