HIGH on the crest of Mount Haleakala, an extinct volcano on the Hawaiian island of Maui, stands a large, shiny cylinder that glints silver in the sun. Known as AEOS, it is the US defence department's largest telescope, America's most powerful "eye" on the heavens.
When the clouds drift into the crater, visitors who have climbed or driven to the volcano's lofty rim 10,030ft above sea level, can see little more than a few hundred feet below them at times, with the land obscured by the white haze.
Yet AEOS –
the Advanced Electro Optical System – can peer upwards into space and pick out a tennis-ball sized scrap from a discarded satellite, or any other of the 14,000-odd items of detectable "space junk" that are circling close to Earth.
This is part of the US space surveillance network, a system of radars and optical sensors located at 25 sites worldwide, including in Greenland, Alaska and the Indian Ocean, that detect, track, catalogue and identify man-made objects measuring 10cm or more in Low Earth Orbit – an area defined as between 100 and 1,240 miles above the surface of our planet.
Between them, they can predict where and when a defunct space object will fall through our atmosphere, determine which country owns it and assess whether there is any risk either to people and places on the ground, to the manned International Space Station, or to Nasa's space shuttle if it is aloft on a mission.
Crucially, the system guards against any falling space object – which on radar screens resembles a missile – from triggering a false alarm on global attack warning systems. It has been operating since the start of the space age in 1957, when the Soviet Union launched the first satellite, Sputnik I. Since then, a further 4,500 craft have been propelled into orbit.
Yesterday, the network detected at least 600 more fragments to worry about, following Wednesday's collision between an operational Iridium 33 satellite, owned by a commercial US communications company, and a defunct Cosmos 2251 Russian relay station at an altitude of 491 miles.
But over the coming days and weeks, there will be hundreds, if not thousands, more pieces of wreckage turning up on AEOS's radar.
Mind-boggling figures released to The Scotsman last night by the Union of Concerned Scientists estimate that if the satellites collided head-on, which is believed likely, more than three million shards of debris have been scattered in space. "The figure of 600 is only the big stuff they can see so far," reveals David Wright, the co-director and senior scientist at the UCS's global security programme. "The debris cloud created by this collision was like a shotgun blast."
Only an estimated 1,200 pieces will ever reveal themselves to the space surveillance network. The rest, measuring less than a millimetre (0.4in) apiece, are too small to focus on, joining 150 million other tiny bits of man-made flotsam that have formed a cloud around our planet over the past five decades.
Space, it seems, has become the ultimate junkyard where, instead of derelict cars, old sofas and broken-down refrigerators, a perpetual parade of dead satellites, spent rockets, empty fuel tanks – some of which have exploded and fractured into thousands of pieces – nuts, bolts and other decaying hardware from human space exploits now spin around orbit.
Mr Wright says: "The analogy I like to use is that it's a little like when people went to settle the Wild West. The whole concept brings up this notion of a vast expanse of nothingness, so people think no laws are needed because you don't run into anyone there. No need to worry where you dump the garbage, because there's no neighbours to bother… and that's what's happened in space.
"People thought about putting satellites in space – but no-one thought about how to bring them back down again safely once they've run their course, so the debris accumulates. For a while that didn't matter, but now certain regions of space are so heavily used by satellites, plus the dead satellites and junk, that in the long term we are getting to the point where it's difficult to use those useful parts of space any more, because it's too risky and crowded."
Periodically, items that are dragged back into Earth's gravity field fail to burn up entirely. In Oklahoma in 1997, Lottie Williams was strolling through a park when she was struck on the head by a 6in fragment of charred material that was later identified as coming from a defunct Delta 2 rocket-booster used by the US military to launch an infrared satellite.
And in 2001, part of a Delta 2 weighing about 154lb slammed down in Saudi Arabia, while a titanium tank from the same craft landed in Texas.
As the extra-terrestrial rubbish tip grows, so does the risk of collisions for the 905 working satellites, owned by 115 countries, that are up in orbit with a job to do – providing telecommunications services, assisting with astrophysical studies, monitoring agricultural crops, assessing the effects of environmental changes, providing weather forecasts and an early warning system for natural disasters, such as hurricanes. Around 150 are military-owned, some on secret spy missions.
Nasa's robotic Aqua spacecraft, which helps scientists to fathom climate change, and Aura, which measures trace gases in the atmosphere to assist in the understanding of global warming and ozone depletion, are currently travelling at an altitude of 438 miles – just a few miles below the shower of wreckage from the six-miles-per-second Iridium/Cosmos smash.
Even before China scattered another 2,000 large oddments – and likely millions more minor particles – into orbit last year by shooting apart one of its own satellites, Nasa's orbital debris office warned in a startling 2006 report that parts of space had already reached "super-critical debris densities".
And the problem is set to get worse. Over the next 200 years, the report predicted, the amount of trash sized at 10cm or more will triple in the 500-600-mile altitude band – the heaviest area for satellite traffic – as junk from GEO cascades downwards, further threatening traffic below.
There is, as Nasa's chief orbital debris scientist, Nicholas Johnson, terms it, "no universal space traffic control", making collisions inevitable and, over time, more frequent.
"There was no doubt this was going to happen," he lamented yesterday as his department scurried to get a handle on the extent of the space traffic accident.
In the 1990s, the issue of space junk received attention from world governments, who agreed international "debris mitigation" guidelines that were adopted by the United Nations – but they hold no legal authority and there is no mechanism to oversee their enforcement.
Scientists want to see tough regulations – with teeth.
"There has to be an understanding that if you have a satellite that's dying, especially in a heavily used part of space, you are obliged to get it out of that region before it ceases to operate," said Mr Wright.
Mr Johnson added: "If that had been done with this Russian satellite, this collision would never have occurred."
Fears grow of radioactive debris going into orbitRUSSIAN military scientists have added another worrying possibility to the consequences of the collision between the defunct Soviet satellite and an operational American one – the threat the debris poses to other old Russian nuclear-powered satellites.
Debris could hit Soviet-era satellites with nuclear reactors, the semi-official Interfax news agency reported, quoting an unnamed Russian military space expert.
"The debris got scattered in all directions, including upwards, where old Soviet satellites are 'buried', those which were intended for surveillance over the navy of a potential enemy … (and are) equipped with nuclear reactors," Interfax quoted the expert as saying. "There is a threat of collision with these spacecraft and therefore of the appearance of radioactive debris in orbit."
Others still wondered how the collision had occurred. Igor Lisov, another prominent Russian space expert, said he did not understand why Nasa's debris experts and Iridium, the owner of the American communications satellite, had failed to prevent it, since the Iridium satellite was active and its orbit could be adjusted.
"It could have been a computer failure or a human error," he said. "It also could be that they only were paying attention to smaller debris and ignoring the defunct satellites."
Nicholas Johnson, an orbital debris expert at the Houston Space Centre, said the speeding junk could reach the orbit of the Hubble Space Telescope.
Iridium said the loss of the satellite was causing brief, occasional outages in its service and it expected to fix the problem by today. The company said it expected to replace the lost satellite with one of its eight in-orbit spares within 30 days.
"The Iridium constellation is healthy, and this event is not the result of a failure on the part of Iridium or its technology," the statement said.
No-one has any idea yet how many pieces of space junk were generated by the crash or how big they might be.
Iridium satellites are unusual because their orbit is so low and they move so fast. Most communications satellites are in much higher orbits and do not move relative to each other, which means collisions are rare.
The full article contains 1563 words and appears in The Scotsman newspaper.
