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First communications satellite
“Balloon satellite in orbit; delayed message heralds new communications era”. This was the headline of the New York Times newspaper for Aug 13, 1960 — the day following the one on which the first communications satellite in history was launched. The story below the headline discussed how a message from the then president of the United States, Dwight D. Eisenhower, had been relayed back to Earth by an object in space known as satellite.
Exactly 46 years on, the satellite is still considered to be an important technological tool for communications. It is the communication satellite which enables us to view sports events, cultural functions and political programmes taking place around the world. It allows us to hear voices and see images generated in far-flung areas.
Sir Arthur Charles Clarke, a writer of science fiction, was a Briton who served as a radar instructor during World War II. He is credited with formulating the idea of satellite communications in the fall of 1945.
He was the one who proposed the location of objects in the Geosynchronous Earth Orbit (GEO). Such objects, or satellites, were to travel in GEO over the equator, from west to east, at an elevation of approximately 35,900 kilometres and at a speed matching that of Earth’s rotation. As a consequence of their speed and location, they were to look stationary in relation to the Earth. That’s why they were called “Geostationary”.
It may seem astonishing to many, but it’s a fact that work on satellites had begun as early as the late 1940s. By the 1950s, satellite communications had become a fundamental part of the military prowess of the United States.
American navy became active in the discipline in 1954. In all their experiments, the moon served as a “reflector”. By 1959, they had developed an operational communication link between Hawaii and Washington DC, with the moon continuing to act as a reflector in their experiments.
John Robinson Pierce (1910 to 2002) — an American engineer and author — was perhaps the first person who carefully assessed the various technical options and financial prospects vis-à-vis satellite communications. He developed projects designed to test various concepts involving the communications satellite. During a speech in 1954 and in an article published in 1955, he emphasised the utility of a communications “mirror” in space, a medium-orbit “repeater” and a 24-hour-orbit “repeater”.
Then came the rivalry between the US and what was then the USSR, as they both wanted to make inroads into the space. However, on Oct 4, 1957 — that is, almost half a century ago — a breakthrough was achieved by the Soviet Union when it successfully launched Sputnik.
This was the first artificial satellite in history, which weighed only 183 pounds and equalled a football in size. It took just 98 minutes to revolve around the planet on its elliptical path. This in turn opened a new era, with the US and the USSR doing their best to beat the other to the new frontiers.
The US military’s Satellite Communications Repeater (Score) was launched on Dec 18, 1958 into the Low Earth Orbit (LEO). It was sent with the program to record on tape a received transmission from one ground station and then to relay the communication to another point on Earth within hours.
It was then that the newly created National Aeronautics and Space Administration (Nasa) wanted to send an inflatable sphere into space for scientific research. However, John Pierce had different ideas, as he wanted to utilise the opportunity to have signals reflected from the metallic surface of the balloon.
The sphere — the artificial satellite called “Echo 1” — was successfully launched on Aug 12, 1960. Echo 1, based on the ideas proposed by Pierce, is regarded as the first communications satellite in history as it successfully bounced back to the Earth the signals it received.
Because this “artificial moon” didn’t have any sort of electronic hardware, and yet it safely worked as a reflector, it was dubbed a “passive satellite”. Pierce felt that active satellites were essential for better communications.
One major problem with the satellite placed in orbits lower than the GEO is that you need a number of them to keep the transmissions going. A single GEO satellite, due to its higher elevation, offers better coverage as it can cover more than one-thirds of the total Earth surface. On the other hand, satellites in LEO and MEO can only cover from a mere 2 per cent to a maximum range of 20 per cent of the entire surface.
So, if we were to switch to LEO and MEO, we would need a fleet of satellites for forming a communications network in order to provide complete coverage. An important merit of the LEO and MEO communication options, however, is minimised latency, which is the period of apparent inactivity between the time a stimulus is presented and the moment a response occurs. This may also be seen as the time delay between a transmitted signal and a response, often described the “echo effect”.
Despite the reality that radio signals travel at the same velocity as light, a time delay of 0.24 seconds occurs for a round-trip signal to a GEO satellite and back, which would definitely be problematic in phone calls. Despite this drawback, placing satellites in GEO was seen as a cost efficient option.
As we have already learnt, the Echo satellite was Nasa’s first experimental communications satellite project. It was designed to serve as a passive communications reflector to bounce communications signals transmitted from one end of the Earth to another.
The success of Echo 1 was important because it opened avenues for further communications through satellites. Probably due to its size and the fact that it was brighter than many stars, Echo 1 was visible even to the naked eye. It was 30.5 metres in diameter and was shaped like a balloon. Its exterior was used to mirror 960 and 2390Mhz signals.
The writer is a senior instructor at a technical college in Karachi
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