Before the digital age, early spy satellites took images using photographic film. The film was then ejected in capsules and collected in mid-air or floated down to earth by parachute.
Eyes in the Sky
Did you know that right now a spy satellite might be passing overhead about 300 kilometres above you? While Australia doesn’t have any of its own, countries such as Japan, Russia, Israel and the US all have specially equipped reconnaissance satellites snooping in the skies above.
Spy satellites have been used for about 50 years by governments, originally mainly to see images of buildings and roads. However, now they can also listen in to secret conversations far below.
In fact, in November 2010 the US launched the largest spy satellite ever known. A huge Delta IV rocket carried the satellite known only as USA-223 into a high orbit. NASA won’t say much about it but it’s thought to have an antenna diameter of 100 metres for listening in on important electronic signals.
Spy satellites are mainly used to collect military information, such as whether or not the enemy is making secret weapons. Other spy satellites are used for industrial espionage by companies that want to find out what their competitors are doing.
Spying from Space
Spy satellites are really just space telescopes pointing towards the earth. They are usually launched into space by a rocket before being released. Once in space, their solar panels turn on to provide power for communications. The satellites then orbit the earth at a distance of somewhere between 200 and 600 kilometres.
They travel at a speed of 27 400 kilometres per second and circle the earth every 90 minutes. They gather information that is then sent back to secret defence tracking stations for analysis.
A famous spy satellite is the Lacrosse. Five Lacrosse satellites belonging to the USA have been launched since 1988. They use radar imaging to see through clouds and even into the soil. The data is put together to make very accurate 3D images and pictures for specialist intelligence officers to inspect.
Silent Spies
Look into the night sky just after sunset on a cloudless night and you might see small lights moving silently high above. These are usually satellites. They make no flicker or noise like an aeroplane does and they range from very bright to very dim as the sun glints off them.
You can do your own satellite spying by visiting the website http://heavens-above.com, which tracks most satellites. There you can enter where you live to find out which satellites are going over your town each night.
If, like most of us you don’t get to see secret spy images, then why not try the next best thing. Both Google Earth and Google Maps allow you to zoom into an area using colour pictures. Try locating your home or school and see what interesting buildings, rivers or roads you can identify. The images on these sites were taken by satellites orbiting the earth, just like spy satellites!
Based on the article by Neil Bramsen