Satellite and Microwave Technology

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Timeline of telecommunication history

Bose’s microwave demonstration (1895)

Up to 1900 the focus of invention had been on sending and receiving communication signals. As the 20th century progressed scientists worked with longer radio wavelengths (lower frequency signals) to achieve ever-greater distances. But some scientists were going the other way, looking at the properties of very short wavelengths. The theory was that by shortening the wave, you could pack more electromagnetic energy into the signal. One of the pioneers was J.C. Bose in India. In 1895 he gave his first public demonstration of very short wavelengths, ranging from 2.5cm down to 5mm - equivalent to a frequency of 60 Gigahertz (GHz). He used these transmissions to ring a bell remotely and to explode a charge of gunpowder.

The first microwave links (1930) 

Microwave links first came into practical use during the 1930s. In 1931 Britain's Standard  Telephone & Cable Ltd (STC) demonstrated its 'Micro-Ray' microwave communications link across the Channel between Dover and Calais. The following year, Britain's first ultra short wave radio telephone link was set up by The Post Office across the Bristol Channel, spanning a distance of 13 miles.

The first radar (1935)

In 1932 Sir Robert Watson-Watt figured out a way to harness the power of very short waves to detect objects far away. He came up with the idea of pulsing energy out on very short wavelengths in order to 'bounce' it off a target and detect the reflected signals. He wrote a paper (with A.F. Wilkins) describing this new technique in 1935 and the idea was taken up rapidly.

By the autumn of 1938 his Radio Direction Finding (RDF) systems were in place along the south and east coasts of Britain. During the Battle of Britain in 1940, the British were able to detect enemy aircraft at any time of day and night and in any weather conditions, proving the defensive value of RDF or, as it would soon come to be called, 'radar' - short for Radio Detection And Ranging.

Arthur C. Clerk’s proposal for communication satellites

Once Werner von Braun's V2 missiles ceased raining destruction on London and other cities, a young RAF technician called Arthur C. Clarke conceived a vision for the post-war future in a magazine called Wireless World. In a letter headed 'V2 for Ionospheric Research', Clarke explained how a network of satellites could be placed in stationary orbit, 22,300 miles above the Earth's surface. Later, in an article titled 'Extra-Terrestrial Relays' published in October 1945, Clarke explained how these satellites could be used to transmit radio, TV and telephone signals around the world.

Geostationary orbits (1945)

The notion of the geostationary (or geosynchronous) orbit was first proposed in 1945 when the science fiction writer Arthur C. Clarke published his visionary concept of relaying communication signals from one ground station to another via artificial satellites circling the Earth. Keeping a steady flow of information between two ground stations and the satellite would need the satellite to remain in a fixed position in sight of both stations.

Clarke reasoned that if the satellite orbited in the same direction and the same orbital speed as the Earth's rotation, it would appear to remain in a fixed position in the sky. He correctly calculated that the satellite would exactly match the speed of the Earth's rotation and keep in constant orbit at an altitude of 35,800km (22,300 miles) above the equator.

NASA’s syncom programme (1963)

In July 1963 the Hughes Aircraft Corporation launched the experimental Syncom 2 for  NASA, the world's first geosynchronous communications satellite. Its earlier sister, Syncom 1, had been blown up on launch earlier that year, but version two was a huge success. It carried the first live two-way satellite call between heads of state when President John F. Kennedy in Washington, D.C., telephoned Nigerian Prime Minister Abubaker Balewa in Africa.