On March 26, a Japanese satellite named Hitomi stopped communicating, except in sporadic bursts, with the Japan Aerospace Exploration Agency (JAXA). Some 40 minutes after it went silent, the US Joint Space Operations Center detected five unidentified objects around the satellite – thought to be debris. Tracking data also revealed that the satellite had veered off its orbit and was tumbling. While the cause for the mishap remains unclear, many think it’s the result of some kind of internal malfunction. Go Cher Hiang, a satellite project director at the National University of Singapore however thinks, “It could also be from a collision with something in space, either from outer space or a man-made object already in space.” If Go Cher’s conjecture is proven, then the Hitomi mishap will be an unfortunate case highlighting the dangers of space debris.
A seminal paper co-authored by NASA astrophysicist Donald Kessler, published in 1978, outlined that all the junk in space – together with obsolete crafts – accumulated over the years will increase the density of space debris to such an extent that one crash would not only be inevitable but also ultimately deadly. He projected that a single collisions would be able to kick of a chain of further collisions, each singularly catastrophic, exacerbated by the high speeds obtained by debris in orbit around Earth. The end result: a ring of space debris continuously circling the planet, dense and energetic, rendering future satellite launches completely infeasible.
This event, dubbed the Kessler syndrome, was ignored until 2009. Then, two satellites called Iridium 33 and Kosmos-2251 collided at a height of 789 km over Siberia, prompting Kessler himself to admit, “… it’s building up as I expected. The cascade is happening right now”. The collision destroyed both satellites and, by July 2011, had resulted in over 2,000 pieces of debris floating around. The attention paid to such events has since become more keen, with scientists recalling that both the International Space Station and the Hubble Space Telescope have been threatened by space-junk. The threat in the latter case was from a Chinese satellite that had been obliterated by a Chinese rocket, in a demonstration of capabilities that also turned out to be the single largest contribution to space-junk in its history.
And thus the Kessler syndrome has moved on from its humble origins as a radical theory to a real problem with far-reaching consequences. Its practical realisation refuted NASA’s big-sky theory, which holds that the vastness of space allows it to act as a dumping ground for mission debris. The space agency has since acknowledged the problem that now lies at the doorstep of that vastness. So, what have agencies been doing to keep the problem under control?
In December 2009, NASA and the Defence Advanced Research Project Agency organised the International Conference on Orbital Debris Removal, hoping to draw the attention of scientists and engineers to the space-junk problem and get them to invent new solutions. Studies were commissioned from around the world to investigate which patches and types of debris should be tackled first and how. One concluded that the greatest danger came from medium-sized debris (0.5-10 cm long) even as the smaller objects could be shielded against while the larger ones could be tracked. And how these objects can be removed continues to be a challenge. Jer Chyi Liou, NASA’s chief scientist for orbital debris, has said, “As of today, there is no economically viable or technically feasible method to allow us to do it.” At the same time, he thinks that debris removal is not an immediate problem and can be put off for 10 or 20 years. Obviously, Kessler doesn’t echo this sentiment, and has claimed, “The longer you wait to do this the more expensive it’s going to be … This scenario of increasing space debris will play out even if we don’t put anything else in orbit.”
There are also a few bright spots like the European Space Agency’s CleanSpaceOne project, which aims to ‘capture’ a satellite and bring it into atmospheric reentry, where it will burn up. Another project is DARPA’s Phoenix, which will deploy smaller satellites to raid the larger, defunct ones in orbit for parts.
In an update on March 29, the US military confirmed that Hitomi’s ‘breakage’ debris was not the result of a collision with an external object but most likely due to an internal part failure. Nonetheless, the threat posed by space debris is real and we shouldn’t need another collision to be reminded of it. If it seems difficult to consider the problem on a personal level, get this: in the visually stunning accelerated Kessler syndrome depiction in the 2013 film Gravity, a character quips, “Half of North America just lost their Facebook.” The consequences of the syndrome realised in full glory are far greater – imagine a world without critical weather and climate data, military intelligence and global communication systems, a superset that includes mobile and wireless Internet. Personal enough?