Eyes in the sky
How all-seeing satellites watch the world from the safety of space.
Ever since the launch of the first satellite, Sputnik, by the USSR in October 1957, thousands more have orbited – and remain orbiting – the Earth. We don’t tend to hear about reconnaissance, or spy satellites though, and as their missions are classified, their equipment and capabilities are often not disclosed. Hundreds of these secretive spies in the sky have been launched since the 1960s.
Spy satellites are used for both military and intelligence purposes, including detecting troop movements, monitoring the dismantling of nuclear weapons and radio signals, spotting missile launches and providing precise positional information. Flying high above the surface of Earth, these eyes are free to scan the ground below with their most important asset – their onboard camera. It’s estimated that these satellites can see objects on the ground that are just ten centimetres across – enough to see an individual person in a crowd. These use the same technology that’s in your smartphone – a charge-coupled device (CCD) – a sensor that converts light into electrical signals. These are stored on the satellite’s onboard computer until it can send the encrypted information back to the ground. Satellites must also have a
source of power, in many cases either solar or nuclear, and a means of controlling their altitude, such as via thrusters. There are also radio-listening spy satellites that can listen to radio signals that are being transmitted by another satellite.
During the height of the Cold War, the US felt threatened by a nuclear attack from the Soviet Union. The US used aircraft and balloons to spy on the Soviets, but after one of the US’ U-2 spy planes was shot down, the country needed other ways to gather intelligence, so space-based photo reconnaissance satellites were developed. The programme was called Corona and was approved months after the Soviets launched Sputnik.
These early spy satellites, however, were nothing like modern-day reconnaissance satellites; they used photographic film to store photos that were then returned to Earth in a ‘film bucket’ that was caught by an aeroplane in mid-air at about 4,572 metres. Modern-day satellites can stay in orbit for years, while the Corona satellites were limited by the amount of photographic film they had on board – at most they could only stay in orbit for a few weeks. Over its 12-year lifetime the Corona programme collected more than 800,000 images, each of which had to be carefully scrutinised by humans working on the project.
Recently the National Reconnaissance Office (NRO) has been working on an elusive project named Sentient, an AI spy system that’s like an all-knowing, all-seeing brain in the sky. The programme can process vast amounts of information and combines this with satellite data to learn about the world below and respond in real time. Given its classified nature, however, its true capabilities will never be known, and it could be used without us ever knowing.