Netting a derelict satellite

Mar 24 2014, 03:58 IST
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SummaryDecades of satellite launches have left Earth surrounded by a halo of space junk. To tackle the problem, various clean space initiatives are underway to remove the space debris

If you are a frequent space odyssey movie watcher, this scene will not come as a surprise to you: a Roman gladiator-style array of nets and harpoons floating in space to first trap rogue satellites and then drag them downwards until they burn up in the atmosphere. Fact is that the visual described is not from a science fiction movie, but a European Space Agency clean space initiative taking concrete shape to capture derelict satellites adrift in orbit. How big is the problem, read on to find out.

More than $300 billion worth of satellites are drifting through space in geosynchronous orbit (GEO)—about 22,000 miles from Earth’s surface—but many of these have been “retired” due to normal end of useful life, obsolescence or failure. Some 20,000 objects larger than a mobile phone that are currently tracked and an estimated half-a-million objects no bigger than a British pound coin that can’t be surveyed may turn lethal as they hurtle through space at a speed of more than 8 kilometres (5 miles) a second, says London-based Royal Aeronautical Society. Not only can space debris affect critical equipment such as communications satellites, but it can also

endanger manned space flights.

Most of those are useless fragments of once-useful objects, which were created by explosions, collisions or missile tests. For instance, an accidental collision between the Iridium-33 and Kosmos-2251 satellites in 2009 caused them to shatter into 2,200 (recorded) fragments. Smaller space debris is much harder to track, but National Aeronautics and Space Administration (NASA) estimates that up to 500,000 objects larger than 1 cm, and 135 million particles over 1 mm in size may now be orbiting the Earth.

But how can mission controllers on the ground remove those troublesome pieces of space junk—including defunct satellites, spent rocket stages and other pieces of man made debris—from their dangerous orbits? Technology readily available today could mitigate the space junk threat. By taking only five satellites out of orbit each year for the next 100 years, while adhering to an international understanding called the 25-year rule, space agencies could stabilise the orbital environment, according to a NASA study.

Space debris is becoming a serious issue, and many space agencies have started working on solutions. Retired satellites are typically put into a GEO-disposal or “graveyard” orbit, but the growing number of man-made objects and debris in this low-orbit graveyard is leading to an increased risk of collisions, which in turn

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