“ It would, we admit, take a little more experience to solve problems like these on your own—and to deal with all the other complications of satellite communications. But we hope our brief glimpses into the laboratory have shown what this experience might be like. Our six case histories have only scratched the surface, but they should give you a good idea of the fascinating work that goes into practical science and engineering. They should show that something like Project Telstar doesn’t succeed only because of far-sighted, imaginative thinking—nor only because of ingenious engineering. ”

“ Now you, who have in your own homes seen pictures transmitted across the ocean by satellite, can learn first hand from the men who worked on hard and varied technical problems just what these problems were and how they were solved. And, by reading you can find out what sort of knowledge, training, and habits you yourself will need if you wish some day to adventure into those undiscovered or unexplored fields of technology which will be new and exciting when Telstar has become old hat. ”

“ Space had become an adventure, not just for lonely astronauts, but for everyone right in his living room.
Project Telstar, of course, had more serious objectives:
to prove that a broadband communications satellite could transmit telephone messages, data, and television; to test, under the stresses of an actual launch and the hazards of space, some of the electronic equipment that had been developed for satellite communications; to measure the radiation that a satellite would meet in space; to find out the best ways to track a moving satellite accurately ”

“ But perhaps more important than the prestige it would give our country is a second reason for our great interest in satellite communications: We need it. The world today is going through one of its great periods of change. This has caused many complications, and one of the most important is the need for much better communications between nations and peoples. By “communications” we mean all the various ways of sending information from one place to another: mail, telephone calls, business data, radio, television. ”

“ Within the white aluminum-oxide outer shell of the satellite is crammed a complicated array of electronic equipment. Surprisingly, most of this gear has to do not with Telstar’s prime function—communications—but with its command and telemetry systems. The reason is that the satellite is an experimental device, not just a spectacular way to relay television programs. Altogether, the satellite’s various electronic circuits contain more than a thousand transistors and almost 1500 semiconductor diodes, plus a single electron tube—a traveling-wave tube used in the communications amplifier. ”

“ We can also calculate the heat from the sun that will be absorbed by a body. If we let S be the total amount of solar energy that would be absorbed by a perfect black body, αS will be the amount that is actually absorbed by a body with an absorptivity of α for solar radiation. If our body is a spherical satellite, the sun’s rays will only strike it from a single direction. Thus only an area equivalent to the sphere’s cross-section (largest inscribed circle) will receive energy at any one time. ”

“ Fortunately, modern technology—given a boost by the world’s interest in rockets, missiles, and the exploration of space—has shown us one answer to this problem: the communications satellite. The conventional pathways for long-distance communication have led along the earth’s surface, under the oceans, and through the lower atmosphere. ”

“ It isn’t possible to build an antenna that radiates at exactly the same power in all directions. Telstar’s antennas work very well, but they operate better in the direction of the satellite’s equator than they do towards its poles. This means that if the spin axis is constantly changing transmission will fade in and out—even at times passing through “null” where no transmission at all is possible. No single fixed orientation is perfect for the spin axis, but we decided that the best average position would be to keep it always perpendicular to the plane of the earth’s orbit. ”

“ A man-made satellite’s position relative to the earth is very like that of the earth in relation to the sun; the earth, after all, is itself a satellite of the sun. And during most of its useful life a satellite will be in thermal equilibrium—it will be losing just as much heat energy by its own radiation into space as it will be gaining from other sources, primarily the sun. Since the total amount of energy it absorbs is equal to the amount of energy it emits, Qbody is equal to Qsun. ”

“ In the transfer of heat by radiation, the surface of the heated body—such as a satellite—is very important. All energy gained must be absorbed at the surface; all energy leaving must be emitted at the surface. So the physical properties of this surface control how energy is absorbed and how it is emitted. The origin of the radiant energy is vitally important; most surfaces, for instance, will behave differently when exposed to solar radiation from the sun’s temperature of 10,000° Fahrenheit than when exposed to radiation from nearby objects at room temperature. ”

“ They tell us how fast we must move a precision tracker to follow the satellite through the sky, how much time a satellite will spend above the horizon, and how long will be the time from one chance of seeing it to the next. However, in the Echo project we were not merely concerned with planning our experiments from hour to hour; we also needed to know how the satellite would move for weeks and perhaps months in advance. When you study the motion of a satellite over such a length of time, you discover that its circular orbit will not remain the same as it was at launch. ”

“ 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? ”

“ Although we can communicate at speeds close to that of light—186,000 miles per second—we cannot go any faster than that. You might think that 186,000 miles a second was fast enough for us, and most of the time it is. However, if you send signals 22,300 miles up into the sky, transmit them back to earth, perhaps send them up again to a second satellite, and finally bring them 22,300 miles back down to earth, even the speed of light may not be fast enough. The delay will be only about a second or so, but it may—for some kinds of communications—be long enough to cause trouble. ”

“ 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 14 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. ”

“ The electric field across the p-n junction causes the holes to flow to the p-side and the electrons to the n-side of the barrier. This flow tends to make the p-side positive and the n-side negative, so that, when a load is connected between them, a useful external voltage (amounting to about six-tenths of a volt) is produced, and electric current will flow. Thus, we have converted light energy into electrical energy.
Only part of the energy in light can be used to generate an electrical output, since a good deal of the light striking a cell is absorbed as heat or is reflected from its surface. ”

“ If a communications satellite is to go into regular commercial service, it must continue working for several years in space. The Telstar satellite, however, was designed as an experimental project, and we decided that two years would be a reasonable lifetime to plan for. When Project Telstar began, our problem was to develop solar cells that would operate in an environment subject to strong radiation effects—and keep on operating there for two years. ”

“ 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. ”

“ Satellite communications is one field in which, as far as we know, American engineering and science have been well in the lead—so we have an even greater incentive to press on in this direction as hard and as fast as we can. ”

“ Solar aspect cells on the satellite report via telemetry the amount of sunlight they receive; from these data we can calculate the angle θ between the satellite’s spin axis, OP, and the satellite-sun line, OS. This means that OP can be anywhere on the surface of cone OPP′.
2.
When sunlight is reflected to observing station T on the earth, we know that the angle of incidence i must be equal to the angle of reflection i′, and, if ORB is a line perpendicular to the reflector R, we know that the sun, the observer, and line ORB must all lie in one plane. ”

“ It is hard enough to fix a new piece of scientific equipment when it goes out of order in the laboratory. And when the equipment is sailing around the earth a couple of thousand miles up in the sky a repair job ought to be impossible. But during the last two months of 1962 we found this not to be true at all. That was when the Telstar I satellite began to misbehave and eventually would not obey the commands we sent it from the ground. ”

“ As you can imagine, making a solar cell to fit the very high requirements we had set for the Telstar satellite is not an easy job—and making these cells by the thousands is even more of a task. During October, November, and December of 1960 we carried on a crash program in which we made hundreds of experimental cells in our laboratories, using a variety of materials and many different manufacturing techniques. ”

“ As you can see, we have picked problems that offer a good deal of variety. Some of them have been satisfactorily solved; for others the solutions are not yet complete. Some deal with basic scientific research; others are much more concerned with the engineering applications of technical knowledge. Some were solved by careful, logical thinking; others were solved almost by accident. Some deal with a particular immediate task (in this case, Project Telstar) ; others are more concerned with general planning for satellite communications. ”

“ On May 7, 1963, the Telstar II satellite was launched into an elliptical orbit almost twice as large as that of Telstar I, ranging from an apogee of 6697 miles to a perigee of 604 miles. The new satellite circles the earth once every 225 minutes. The higher altitude provides Telstar II with longer periods when it is visible at both Andover and ground stations in Europe, and keeps it out of the high-radiation regions of space for a greater part of the time. The satellite itself is much the same as Telstar I, except for a few minor changes that make its weight 175 rather than 170 pounds. ”

“ One of the devices built into Telstar is a set of six solar aspect cells spaced at regular intervals around the satellite. These give a fairly accurate indication of the angle between the spin axis of the satellite and a line joining the satellite and the sun. When sunlight strikes these solar cells, they produce electric currents, and the value of the current from each cell is sent back to the ground via telemetry. ”

“ 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. ”

“ 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 151⁄2 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. ”

“ They found that, when radiation penetrates the outer shell of a transistor and ionizes the gases inside, electrically charged particles (ions) tend to collect on the surface and change the transistor’s electric properties. This effect is particularly noticeable when a transistor is operating under reverse bias voltage. We knew that some of the 37 transistors used in each Telstar I decoder circuit were operating under continuous reverse bias and that they also had less metal shielding than did those semiconductors in the telemetry and receiver circuits. ”

“ These case histories are examples of the things scientists and engineers are constantly faced with. To narrate them we have called on six experts—Bell Telephone Laboratories engineers and scientists who actually have been working on the problems. The second half of our book is taken up by their accounts of their own personal experiences. We hope that reading them will give you an insight into what it is really like to be a scientist or engineer working in a laboratory on an important new venture into the future. We hope you will see that what they do is not all excitement and glamour. ”

“ Of the 72 facets, 60 are used for the solar cells that are the satellite’s main power source. When Telstar is in sunlight, these cells convert solar energy into electrical power; at full capacity the 3600 solar cells will supply about 15 watts. As time goes by, this power slowly diminishes as the cells are gradually damaged by such hazards of space as radiation particles and micrometeorites. To reduce this damage, the satellite’s cells are covered with a thin layer of man-made sapphire. ”

“ 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. ”

“ After a week of intensive laboratory work, we had some pretty good evidence. The tests of individual transistors definitely showed that heavy radiation would cause them to deteriorate. Testing of the complete decoders also led to some failures, and, when we analyzed them, they turned out to be the kind that would be caused by faulty transistors. We also discovered that the most sensitive part of a decoder circuit was the zero gate, which recognizes the zeros in the one-and-zero code that commands the satellite. ”

“ Also, if their energy is reduced below a certain level (about 180 thousand electron volts) electrons will not be able to knock silicon atoms out of position, and thus cannot harm a solar cell. We experimented with a number of different kinds and thicknesses of cover plates, and found that transparent material with a mass of 0.3 gram per square centimeter would slow down electrons enough to make them no problem.
Another radiation study helped us take advantage of the fact that solar cells respond differently to light of different wave lengths. ”

“ Finding out how radiation would affect various kinds of solar cells; Making experimental cells and, when the best had been picked, determining the best ways to make them in the large quantities we would need; and Developing ways to mount the cells on the Telstar satellite so that they would withstand the stresses of being launched, the effects of radiation particles, and extreme changes in temperature. ”