In the News this month... and finally
At four minutes to five in the morning on February 10th, an active communications satellite operated by Iridium and a retired Russian military satellite collided 800km above Siberia. Moving at a relative speed of 10 km/s, the collision released an estimated 50 kilojoules of energy per gram, according to researchers at the University of Southampton in the UK who simulated the incident. The collision took place in a busy part of Earth orbit and created more than 600 pieces of debris large enough to be tracked from the ground. The space around Earth is already home to many hundreds of satellites, including 66 satellites operated by Iridium, and the amount of debris is increasing every year, raising the risk of further damaging collisions between objects.
Simulation of the collision Credit: Southampton University
While astronauts on the International Space Station use a much lower orbit and so are not likely to be at risk from debris from this particular incident, it has increased the chances of a collision during the planned shuttle mission to fix the Hubble Space Telescope. Even before this particular incident, a previous test of a Chinese anti-satellite weapon in 2007 had increased the chances of a catastrophic collision during a Hubble servicing mission to close to NASA's acceptable level of risk for a manned mission. This incident has further increased that risk and could mean the mission is scrapped.
The problem of space debris is only going to get worse as more satellites are launched into increasingly busy orbits filled with older satellites which are often left in orbit once they reach the end of their operational lifetimes. While both NASA and ESA track many thousands of pieces of space debris, there are many more fragments of space junk orbiting Earth which are far too small to be detected from the ground, but which could cause serious damage to other orbiting spacecraft if another collision were to occur.