http://www.newscientist.com/article/dn16584-satellite-collision-creates-copious-space-junk.html
'Two space satellites smashed into each other on Tuesday in an unprecedented orbital accident. Government agencies are still assessing the aftermath, but early radar measurements have detected hundreds of pieces of debris that could pose a risk to other spacecraft. As first reported by CBS News, a defunct Russian Cosmos satellite and a communication satellite owned by the US firm Iridium collided some 790 kilometres above northern Siberia on Tuesday. "This is the first time that two intact spacecraft have accidentally run into each other," says Nicholas Johnson, chief scientist of NASA's Orbital Debris Program Office <http://orbitaldebris.jsc.nasa.gov/> in Houston, Texas. Danger to satellites The NASA office, which detects and tracks debris measuring less than 10 centimetres across, has just begun its assessment of the damage, Johnson told *New Scientist*. But the US military, which tracks objects spanning 10 centimetres or more, has already detected more than 500 pieces of debris from the collision, Julie Ziegenhorn, a spokesperson for the military's Strategic Air Command<http://www.stratcom.mil/>, told *New Scientist*. The destruction<http://www.newscientist.com/article/dn10990-china-dismisses-space-arms-race-fears.html>of the Chinese weather satellite Fengyun-1C in 2007 generated more than 2000 pieces of orbital debris<http://www.newscientist.com/article/dn14207-weak-solar-cycle-may-keep-more-space-junk-in-orbit.html>of that size. Until now, fragments of that satellite accounted for more than 25% of all catalogued debris in low-Earth orbit. The chance the debris will collide with other spacecraft is still unclear. The International Space Station, which orbits at an altitude of some 350 kilometres, does not seem to be at immediate risk of colliding with the debris, Johnson says. But the detritus could potentially hit a number of Earth observation, communication, and scientific satellites. If that happened, the satellite it struck could itself break up, creating ever more space junk in a cascade effect. Decades to decay The two craft were moving in almost perpendicular directions when they collided, and the extent of the damage will become clearer as the debris from the two satellites spreads out, Johnson says. According to Iridium documents, such satellites orbit at speeds of more than 25,000 kilometres per hour. Most of the debris is expected to stay in orbit for years. "The majority is right there around 790 kilometres, and those will take a long time to fall back to Earth," Johnson told *New Scientist*. "The majority will take decades at least." It is unclear whether the risk of the collision was predicted in advance. The US defense department monitors some 18,000 objects in orbit around the Earth, Johnson says, and this data is publicly available for most satellites. "The satellite was in the position it was supposed to be," Iridium spokesperson Liz DeCastro told *New Scientist*. DeCastro added that the firm subcontracts the maintenance of its network of 66 satellites, which included the lost spacecraft, to aerospace firm Boeing <http://www.boeing.com/> and could not confirm whether that company calculated the risk of an impact' --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Cosmology, Mathematics and Philosophy" group. To post to this group, send email to cosmology-mathematics-and-philosophy@googlegroups.com To unsubscribe from this group, send email to cosmology-mathematics-and-philosophy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/cosmology-mathematics-and-philosophy?hl=en -~----------~----~----~----~------~----~------~--~---
