A military spacecraft launched 55 years ago was moved from its orbit – and nobody is quite sure who did it, or why.
In 1969 the UK launched Skynet-1A, a military communications satellite placed in orbit above the east coast of Africa in order to relay information to British armed forces. It stopped working due to hardware issues around 18 months after it started operating, and the spacecraft was left to the laws of physics to orbit the Earth – it is now the oldest UK spacecraft still in space.
It’s a good idea to check on defunct satellites, to make sure the space debris is not on course to collide with any working satellites or populated areas of the Earth below. In the 1970s, when the satellite was closely tracked, it was in a geostationary arc at a longitude of around 40 East, where it remained when it was decommissioned. Such orbits are subject to gravitational perturbations by the Sun, Earth and Moon.
“If Skynet-1A had failed at its operational location of around 40 East, we would now expect it to be oscillating by +/- 35 degrees either side of 75 East,” satellite-system engineer Dr Stuart Eves explains in a blog post for The Global Network on Sustainability in Space.
“Except that it isn’t. According to the UK Registry , Skynet-1A is currently sitting very close to the bottom of the other well at 105 West, oscillating by just a couple of degrees.”
The spacecraft is not where it is supposed to be according to what we know about orbits, now some 36,000 kilometers (22,369 miles) above the Americas. At some point in the intervening years, the satellite has likely been moved – but nobody appears to know when, who, or why. Tracking of the satellite has been patchy, particularly in the mid-1970s when the maneuver appears to have taken place, and any records of what happened appear to have been lost.
The satellite, though the UK’s first, was built and partly operated by the USA, with both countries sending commands to it.
“A Skynet team from Oakhanger would go to the USAF satellite facility in Sunnyvale (colloquially known as the Blue Cube) and operate Skynet during ‘Oakout’,” Rachel Hill, a PhD student from University College London searching the National Archives for clues, told the BBC. “This was when control was temporarily transferred to the US while Oakhanger was down for essential maintenance. Perhaps the move could have happened then?”
While an interesting mystery as to who fired it and why, it could become more pressing in the future. In its current orbit, the satellite could pose problems for other nearby satellites in geostationary orbit. Should it collide with another, the question of who issued the order to fire the satellite’s thrusters could decide which country is held liable for the damage.
