The Clarke Belt was named after him, but how much of the visionary writer's invention came to fruition?
The satellite communications age started in 1945, when Arthur C Clarke published a visionary scientific paper entitled The Space Station – Its Radio Applications.
Sir Arthur not only invented the idea of a geostationary satellite orbiting over a fixed point on the Equator, he also predicted it would be extremely useful for international communications.
The paper contains dozens of other sci-fi predictions, but 62 years later, how many are now science fact?
The provision of worldwide ultra-high-frequency radio services, including television: Spot-on, although the range of frequencies used for different applications are wider than expected.
It is probable that TV may be among the least important [service]…Other examples are frequency modulation, facsimile (100,000 pages an hour) specialised scientific and business services and navigational aids: Sir Arthur couldn’t have seen how TV would dominate all other forms of entertainment, but FM is still in use. Fax has become today’s data and email networks. Science and business rely on satellite communications and data collected from orbit. Navigational aids use both geostationary and low-Earth orbit satellites.
Use of 12,000 megacycles (what we’d call 12GHz): Spot-on again, along with FM line-of-sight, but TV started out in the 4-8GHz C-band range, and today’s satellites also use frequencies from the 2GHz S-band to 30GHz Ka-band.
Terrestrial networks of TV transmitters will be needed. Only highly populated communities will be able to have TV: Despite the cost of terrestrial networks they still cover most of the planet, although satellite is now an equal competitor, reaching even isolated communities as Sir Arthur foresaw.
Large airliners which will fly...over oceans and uninhabited regions...will require TV and allied services: It took a while, but in-flight satellite links are now being introduced by major airlines for TV, phone and internet access.
All these problems can be solved by the use of a chain of space stations with an orbital period of 24 hours: This single sentence created the satellite TV industry.
Only using three satellites to cover the globe: He was theoretically correct, but the reality saw hundreds of small automated satellites instead of three huge manned stations.
Use of 3GHz: Lower-frequency services like C-band and S-band are both operated around this region.
A reflector only a few feet across [to concentrate power on the earth]: Yes, although lower-power antennas in orbit meant that truly small dishes on the ground didn’t arrive until the early 1990s.
Arrays a metre or so in diameter...to illuminate single countries if a more restrictive service was required: So-called spot-beams like the UK beam on Astra 2D are becoming ever more common to make efficient use of the most popular Ku-band frequencies.
Satellites connected to each other by narrow-beam, possibly optical, links: He was really far ahead on this one. The ESA has been testing laser links between satellites on its Envisat spacecraft but they haven’t gone into commercial use yet.
Simultaneous TV to the entire globe, including to aircraft: Yes, direct news reports from distant locations are so common they’re spoofed on programmes like The Daily Show.
Relaying of programmes between distant parts of the globe: Absolutely yes. The technology prompted the Eurovision Song Contest to publicise the European Broadcasting Union, and created unforgettable events like the Live Aid and Live8 worldwide concerts.
Satellites will make redundant the network of [TV] relays: Theoretically correct, but with entire populations committed to their TV aerials it’s very unlikely. It could save many Megawatts of electricity, so maybe global warming will bring this back to the agenda.
The receiving equipment...would consist of small parabolas perhaps a foot in diameter with dipole pickup: Sir Arthur was half-right, but today’s LNBs are very much more complex and sensitive than a simple dipole.
These would be sufficiently directive to prevent interference [between different satellites]: Yes, and even small receive-only dishes can typically distinguish between satellites as little as three degrees apart.
...once adjusted, [antennas] need never be touched again: True in most cases, unless mis-aligned by severe weather.
Mobile equipment would require automatic following, which presents slight mechanical complications but no technical difficulties: Today’s mobile antennas can track satellites while moving at motorway speeds, and many ships are equipped with triple-axis stabilised dishes that maintain their alignment while at sea.
...almost all the power would fall on the service area: Yes, with operators able to publish very accurate footprint maps even before the satellites launch.
...world broadcast would require about 10kW while beam relay would require only fractions of a kilowatt: Half right – thanks to advances in electronics, a transponder uses about 100W and can do both broadcast and relay.
These powers are very small compared with present-day broadcasting stations some of which radiate hundreds of kilowatts: Spot-on again. Maybe the ecological benefits of using solar power to transmit thousands of TV channels to replace the Megawatts used terrestrially will get noticed soon.
All the power required…could be obtained from solar generators...with mirrors about 10m in diameter: The right power, but photovoltaic cells are able to produce all the electricity a satellite needs without mirrors to focus the sunlight.
Use of valves (there’s a lot of vacuum up there) and the need for a crew to change them: Valves were replaced by transistors and then microchips, which rarely malfunction, so there was no need for human crews to maintain them.
No communication development which can be imagined will render the chain of stations [satellites] obsolete and since it fills what will eventually be an urgent need, its economic value will be enormous: Pretty solid – unless someone makes an instantaneous quantum communication device, satellites will be busy for centuries to come.
He also mentions in passing several other areas such as scientific research, meteorology and space traffic control. The first two are major geostationary satellite users, and we’re long overdue for some way of managing the increasingly busy and hazardous orbital thoroughfares.
By my reckoning, out of 38 predictions in this paper, Sir Arthur scores 24 positive, seven negative, five debatable and two that were theoretically correct but didn’t actually happen the way he foresaw. Not bad! Congratulations, Sir Arthur – and thanks for the geostationary satellite
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