This event, which was one of the most momentous in
the history communication, demonstrated the feasibility of the science
fiction writer A.C. Clarke's prediction in Wireless World (October 1945)
of the use of satellites for world-wide transmission.
It was brought to fruition by the work of ATT/Bell Telephone Laboratories
scientists in the USA, who designed and built the 'Telstar' satellite
launched from Cape Canaveral by the American National Aeronautics and
Space Administration on 10 July 1962.
ATT/Bell had built a ground station at Andover, Maine with a huge
horizontal steerable horn aerial inside a 200ft diameter radome; the
French PTT constructed , with ATT/Bell help, a similar station at Pleumer
Bodou, Brittany.
The British Post Office Engineering Department was very much alive to the
potential of satellites for world-wide communication and had set up at
POED HQ, London a 'Space Comunication Systems' Branch, of which the writer
of this note was the first head . It took part in a UK Government
Civil/Military Mission to NASA in 1960 which agreed a basis for ATT/Bell,
French PTT and British Post Office TransAtlantic communication satellite
tests.
The POED ground station was built at Goonhilly on the Lizard Peninsula, Cornwall. It incorporated an 800 ton, 85ft diameter steerable
parabolic reflector aerial, unprotected by a radome; the mechanical design
of this massive aerial - which had to withstand gale force winds - was due
to the civil engineer Tom Husband who had designed the 240ft diameter
radio astronomy aerial at Jodrell Bank.
The Telstar satellite, which contained a microwave receiver and
transmitter, was launched into an elliptical orbit varying in height
from 600 to 3,500 miles and circling the earth every 2.5 hours. This meant
that each period of transmission between American and European ground
stations was limited to about 30 minutes; it also required that the ground
station aerials, which had beamwidths of less than a degree had to track
the moving satellite with great precision. This is in contrast with
present-day equatorial orbit satellites at 22,300 miles height which are
virtually stationary as seen from the earth.
The construction of the British ground station was a daunting task - at a
virgin site on the Lizard roads, buildings and the massive aerial had to
be erected and power supplies provided. Complex microwave receiving and
high-power transmitting equipment had to be designed and constructed.
Computer-controlled precision tracking equipment for the aerial had to be
created. With excellent co-operation from British industry, the Government
Services Electronics Research Laboratory and the POED Radio Experimental
Branch at Dollis Hill, this task was completed in the remarkably short
period of 18 months in readiness for the Telstar launch.
On the 10th of July the first test transmissions from Andover were received at Goonhilly - after an initial problem due to an aerial polarization
reversal, excellent quality TV pictures were received from and transmitted
to Andover on 11 July. It was a time of considerable tension - none of the
complex equipment could be fully tested before Telstar first appeared over
the horizon and all this had to be done with millions of viewers waiting
on both sides of the Atlantic and broadcasting commentators Raymond Baxter
and Ian Trethowan on site, reporting every move. On the night of 11 July,
after success had been achieved after months of strenuous effort, the ITA
kindly provided a crate of the best champagne and Goonhilly nearly became
an airborne satellite ground station!
The television transmissions were followed by extensive multi-channel
telephony and high-speed data transmission tests that demonstrated the
high quality of the satellite link. And HM the Queen spoke of 'the thrill
of communicating through a dot in space'.
The design of the British ground station, with its massive open parabolic
dish aerial, was outstandingly successful. Not only was the cost a
fraction of the Andover and Pleumer Bodou radome covered horn aerials, but
it performed well even under rain conditions when a radome could reflect
radio noise into the horn aerial from the 'hot' earth and interfere with
the weak signals from the satellite.
It is significant that ongoing development of satellite communication throughout the world followed essentially the British
precedent. Today the BT ground station at Goonhilly has fifteen large
open-dish aerials providing world-wide communication for a variety of
services and is the busiest station in the world. These aerials have been
named after the Knights of the Round Table and it is fitting that the 1962
aerial, which is still in service after 38 years, has been named 'Arthur'!
*W.J.Bray CBE, F.REng.,FIEE,FCGI
Director of Research POED 1969 - 1975
Author of 'The Communications Miracle', pub. Plenum,New York 1995 A
revised and up-dated version of the above book, 'Innovation and the
Communication Revolution' is to be published by the Instn.Electrical
Engineers, London.2002. These books contain a detailed account of the
Telstar story from the UK standpoint.
John Bray's autobiography appears in 'The Autobiography of a
Communications Engineer', Book Guild, London, 1999
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