The Surprisingly Interesting Story Behind Why the Geosynchronous Region Around the Earth is Called the Clark Orbit

On August 19, 1964, a Delta D rocket blasted off from Cape Canaveral in Florida and soared into space, successfully delivering the Syncom 3 satellite into a 42,164 kilometre equatorial orbit. At this altitude, the satellite orbited at the same rate as the earth’s surface, making it appear to stand still high over the Pacific Ocean. Anchored in the sky, Syncom 3 relayed television coverage of the 1964 Tokyo Olympics from Japan to North America, launching a new era of global telecommunications. Today, over 500 geostationary satellites orbit the earth, providing television, radio, telephone and other services to nearly every square centimeter on Earth. But while today we largely take this technology for granted, back in 1964 it must have seemed like the stuff of science fiction. And indeed, it was a science fiction writer who first proposed the idea some two decades before this, at a time when launching anything into orbit still seemed like a distant dream. This is the story of how Sir Arthur C. Clarke came up with the idea of the communications satellite.

Sir Arthur Charles Clarke is a legend in the science fiction community, having authored more than 80 books and 500 articles and short stories over his 60-year career. Among his most well-known and influential works are Childhood’s End, Rendezvous With Rama, and 2001: a Space Odyssey, which he wrote concurrently with the famous 1968 Stanley Kubrick film. Born on December 16, 1917 in Minehead, Somerset, from an early age Clarke displayed a passion for science – especially fossil collecting and astronomy. He avidly read American science fiction pulp magazines, and was a member of the British Interplanetary Society. However, Clark lacked the means to attend university, and so in 1936 at the age of 19 he joined the UK Board of Education as a pensions auditor. The outbreak of the Second World War, however, gave Clarke a second chance at an education, and in 1941 he joined the Royal Air Force and became a radar technician and instructor. During the war, Clarke worked on the development of Ground-Controlled Approach or GCA radar, which allowed ground controllers to track approaching aircraft and guide them to a safe landing in all kinds of weather. This technology, which formed the basis for Clarke’s 1963 book Glide Path – his only non-science fiction novel – was developed too late to have any impact on the War, but is now used in nearly every major airport around the world.

In October 1945, just a month after the end of the Second World War, Clarke published an astonishingly prophetic letter in the British magazine Wireless World titled Extra-Terrestrial Relays – Can Rocket Stations Give World-Wide Radio Coverage? in which he laid out a detailed proposal for a space-based global telecommunications system. Clarke opens the letter by laying out the practical limitations of conventional ground-based communications:

“Although it is possible… to provide telephony circuits between any two points or regions of the earth for a large part of the time, long-distance communication is greatly hampered by the peculiarities of the ionosphere, and there are even occasions when it may be impossible. A true broadcast service, giving constant field strength at all times would be invaluable, not to say indispensable, in a world society.

Unsatisfactory though the telephony and telegraph position is, that of television is far worse…the service area of a television station…is only about a hundred miles across. To cover a small country such as Great Britain would require a network of transmitters…at intervals of fifty miles or less. A system of this kind could provide television coverage at a very considerable cost, over the whole of a small country.”

Clarke’s solution to this problem is to place the relays in orbit high above the earth’s surface, pointing out that:

“…one orbit, with a radius of 42,000 km, has a period of exactly 24 hours. A body in such an orbit, if its plane coincided with that of the earth’s equator, would revolve with the earth and would thus be stationary above the same spot on the planet.

…let us now suppose that [a space station] was built in this orbit. It could be provided with receiving and transmitting equipment and could act as a repeater to relay transmissions between any two points on the hemisphere beneath, using any frequency which will penetrate the ionosphere…a single station could only provide coverage to half the globe, and for a world service three would be required, though more could really be utilized…the stations would be arrange approximately equidistantly around the earth…[and] would be linked by radio or optical beams, and thus any conceivable beam or broadcast service could be provided.”

Clarke then goes on to calculate the theoretical power requirements for such space stations, concluding that even with the radio technology of the time, these would be considerably less expensive than a conventional ground-based relay system.

The sheer prescience of this letter is difficult to overstate. Commercial television had only just been introduced experimentally a few years before the war, yet Clarke foresaw the central place the technology would have in post-war society, and the need for a global network to carry television signals. Furthermore, by 1945 only one manmade object – a German V-2 ballistic missile – had even touched the edge of space; launching anything into orbit – let alone a practical communications relay – seemed to many like a far-off dream. Indeed, while Clarke’s October letter laid out his idea in greater detail, he had first proposed the concept of the geostationary communications satellite in a February 1945 letter to Wireless World in which he wrote:

“I would like to close by mentioning a possibility of the more remote future- perhaps half a century ahead. An “artificial satellite” at the correct distance from the earth would make one revolution every 24 hours i.e. it would remain stationary above the same spot and would be within optical range of half the earth’s surface. Three repeater stations, 120 degrees apart in the correct orbit, could give television and microwave coverage to the entire planet. I’m afraid this isn’t going to be of the slightest use to our post-war planners, but I think it is the ultimate solution to the problem.”

But while Clarke had predicted nearly every technical detail of communications satellites, he turned out to be dead wrong about the timeline of their development. On October 4, 1957, nearly 12 years to the day from the publication of Clarke’s letter, the Soviet Union launched Sputnik 1, the world’s first artificial satellite, into orbit, kicking off the Space Age far earlier than anyone had predicted. From here, development of satellites for all manner of practical purposes – military, scientific, and commercial – proceeded at a rapid pace. On December 18, 1958, the United States Army launched Signal Communications by Orbital Relay Equipment or SCORE, an SM-65 Atlas intercontinental ballistic missile fitted with radio transmission equipment and a wire recorded. SCORE was not a proper communications satellite, being incapable of relaying signals to and from the ground. Instead, it broadcast a pre-recorded holiday greeting from U.S. President Dwight D. Eisenhower to the world. It was also not geosynchronous, orbiting at an altitude of just a few hundred kilometres. After only five weeks, this orbit decayed, causing SCORE to reenter the atmosphere and burn up. Nonetheless, the experiment proved the practicality of orbital-based communications and paved the way for future, more sophisticated satellites.

SCORE was followed by Echo 1, a 30-metre diameter spherical balloon made of aluminized mylar plastic, which could bounce radio waves from one part of the earth to the other. Developed by Bell Telephone Laboratories engineers John R. Pierce and Rudolf Kompfner, Echo 1 was launched into orbit on August 12, 1960, reaching an altitude of 1,500 kilometres. Over the next nine years, Echo 1 and its sister, Echo 2, were used in dozens of experiments, contributing to countless advances in telecommunications technology, satellite tracking, and our understanding of the upper atmosphere.

Being completely passive reflectors, the Echo satellites were unsuited for commercial use, and it would not be until July 10, 1962, that NASA and AT&T launched the world’s first practical telecommunication satellite, Telstar-1. Two weeks later on July 23, Telstar-1 carried the world’s first commercial transatlantic television broadcast, which featured remarks by US president John F Kennedy, part of a baseball game, and segments filmed at Cape Canaveral, Washington, D.C, Quebec City and Stratford in Canada, and the Century 21 Exposition in Seattle. Later that evening, Telstar-1 also relayed the first satellite telephone call between US vice-president Lyndon B. Johnson and Frederick Kappel, chairman AT&T. Yet despite this promising start, the satellite’s pioneering mission would be short-lived, for seven weeks later on July 9 it – along with many other satellites – was permanently knocked out by the Starfish Prime high-altitude nuclear test. Though no longer broadcasting, Telstar-1 is still orbiting the earth, and is expected to continue doing so for another 300 years.

Though it launched a telecommunications revolution, Telstar-1 was not a complete realization of Clarke’s 1945 proposal, for it was not launched into a 42,000 kilometre geostationary orbit. Instead, it flew in an extremely elliptical 6,000 kilometre orbit, requiring complex and expensive tracking antennas to follow it and relay its signals. But just 7 months later on February 14, 1964, NASA launched Syncom 1, the first purpose-built geosynchronous satellite. While Syncom 2 stopped transmitting shortly after orbital insertion, its follow-up, Syncom 2, was more successful, reaching an altitude of 36,440 kilometres on July 26, 1964. In August of that year, Syncom 2 relayed carried a voice conversation between President Kennedy and Nigerian Prime Minister Abubakar Tafawa – the first satellite phone call between sitting heads of state – while in September it transmitted the first experimental satellite television signals between Fort Dix, New Jersey, and Andover, Maine. But while Syncom 2’s orbit was geosynchronous, it was inclined 33 degrees to the equator, meaning it was not geostationary – instead tracing an elongated figure-8 across the sky. But finally, on August 19, 1964, Syncom 3 entered geostationary orbit, while on April 6, 1965, the Communications Satellite Corporation or Comsat launched Early Bird, the first commercial geostationary communications satellite. Early Bird – later renamed Intelsat-1, could carry 240 simultaneous telephone calls, for which users paid $4,200 – $23,000 in today’s money – per month. It could also carry one television signal, which cost $2,400 per half-hour. While limited and expensive by today’s standards, Early Bird pointed to the shape of things to come. Today there are nearly 10,000 artificial satellites orbiting the earth – more than 500 of which reside in geosynchronous or geostationary orbit.

Though often hailed as the father of the telecommunications satellite, Clarke saw himself merely its godfather, pointing to others who put forward similar ideas long before him. In 1923, for example, German theoretician Hermann Oberth proposed communicating with orbiting satellites using mirrors and lights; while in 1928, Austrian army officer Herman Potocnick – better known by his pen name Hermann Noordung – laid out the basic concept of geostationary relay satellites in his book The Problem of Spaceflight. Clarke was not even the first science fiction author to envision a communications satellite. That distinction instead belongs to American clergyman and author Edward Everett Hale, whose 1869 short story The Brick Moon describes the construction and launch of a giant artificial moon made of bricks, whose inhabitants communicated with people on the ground via Morse Code by jumping up and down on the satellite’ surface.

Nonetheless, Clarke is credited with popularizing the concept of geostationary communications satellites, and for this reason the 42,000-kilometre geosynchronous region around the earth is now known as the “Clarke orbit” or “Clarke Belt.” But Clarke’s influence goes far beyond this groundbreaking prediction. He also predicted that satellites would someday be used for weather prediction, and in his 1979 novel The Fountains of Paradise he popularized the idea of the space elevator – a long tether connecting a geostationary orbiting platform to the earth’s surface. But perhaps his most influential work was his 1951 non-fiction book The Exploration of Space, which was used by German rocket engineer Wernher von Braun to convince US president John F. Kennedy to launch the Apollo moon landing project.

In 1956, Clarke moved to Colombo, Sri Lanka, where he lived until his death on March 19, 2008 at the age of 90. Reflecting on the shockingly rapid progress made in satellite communications since his landmark 1945 letter, he opined:

“Sometimes I’m afraid that you people down on Earth take the space stations for granted, forgetting the skill and science and courage that went into making them. How often do you stop to think that all your long-distance phone calls, and most of your TV programmes are routed through one or the other of the satellites?”

In addition to his hundreds of stories, articles, and novels, Clarke – true to his reputation as a technological prophet – also left behind three principles for accurately predicting the future, known as Clarke’s Laws:

1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.

2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.

And finally, the eternal classic:

3. Any sufficiently advanced technology is indistinguishable from magic.

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