By Andrew Robinson
Connecting you now: LEASAT satellite orbits the Atlantic in 1984
Granger Historical Picture Archive / Alamy Stock Photo
Satellite: Innovation in orbit by Doug Millard, Reaktion Books
IN 2002, two NASA satellites nicknamed “Tom” and “Jerry” were charting Earth’s gravitational field, as part of the Gravity Recovery and Climate Experiment. As they moved in the same polar orbit, the distance between them was monitored to an accuracy of 10 micrometres, a tenth of the width of a human hair. When either satellite flew over an area of increased gravity, it would speed up slightly and the distance would increase or decrease.
The experiment’s vital result is recounted in Satellite, Doug Millard’s accessible and superbly illustrated book, which tracks the history of this amazing extension to our lives. By combining the changes in distance between the satellites with their respective positions – measured by GPS – it was possible to build a detailed map of Earth’s gravity field, writes Millard, deputy keeper of technologies and engineering at London’s Science Museum.
Satellites have a long history, with Isaac Newton the first to imagine one in Principia Mathematica (1687). He envisioned a cannon projecting a ball from a mountaintop with ever more force. In the end, noted Newton, the ball would reach beyond Earth’s circumference, retain its velocity and “describe the same curve over and over”.
But Newton had no concept of a satellite’s usefulness. That came in 1869, when Edward Everett Hale suggested in his story, The Brick Moon, that they could be used as an orbiting reference point for measuring longitude.
By the early 20th century, rocket pioneers like Robert Goddard, Hermann Oberth and Konstantin Tsiolkovsky were showing how satellites could be launched, and in 1944, a German military team led by Wernher von Braun fired a V2 missile to an altitude of some 180 kilometres. Inspired by the V2, in 1945 Arthur C. Clarke, then a Royal Air Force radar engineer, predicted that it would take only three satellites in geostationary orbit, 36,000 kilometres above the equator, to handle Earth’s communications.
In the 1950s, the US and Soviet Union raced to launch a satellite. The Soviets won in 1957, marking the start of the space age. The name of their satellite, Sputnik, translated into “fellow traveller”, or companion to Earth. Fellow traveller was also cold-war speak for Communist sympathiser.
The triumph humiliated the US, provoking the country to set up NASA, launch Explorer (its first satellite) in 1958, establish the Apollo space programme in 1961, and Telstar, the first commercial communications satellite, in 1962.
Millard, who curated the Science Museum’s 2015 hit Cosmonauts show, mixes technology with Russian, US and European politics to great effect. For example, his book includes an early 1960s photo of a US aircraft that could capture a capsule dropped by a US satellite, containing film of Earth’s surface. He quotes an off-the-record comment by President Lyndon Johnson about the secret film’s value: “We were building things we didn’t need to build… Because of satellites I know how many missiles the enemy has.”
“Isaac Newton imagined satellites in Principia Mathematica, but had no concept of their usefulness”
Today, everyone has access to detailed images of Earth’s surface. More than 1400 satellites, some 500 in geostationary orbit, predict weather and handle navigation, communications and TV broadcasting. But, says Millard, we must not depend on them completely. In 2009, a retired Russian satellite crashed spectacularly into a working US communications satellite. Indeed, tonnes of space junk threaten to degrade all satellite services.
Then there are solar flares, which caused electrical disruption in 1859 and 1921. In 2012, one just missed Earth. The price of our connected world is that the next big flare will produce chaos.
This article appeared in print under the headline “Connecting the world”
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