Some good news after the ISS was recently forced to dodge a piece of orbital debris:  As the sun moves into its active phase, the upper layers of the Earth’s atmosphere heat up and expand, causing a tiny amount of drag on orbiting satellites, to the eternal frustration of their operators. But space junk, which tends to be small, slows down and begins spiraling downwards till it eventually re-enters the atmosphere and burns up.  A report from NASA’s Orbital Debris Program Office shows that the effect is strong enough that, over the course of 2011, the number of debris in Low Earth Orbit (LEO) actually decreased, despite increasing launch activity.  As a specific example, they refer to the Fengyun-1C anti-satellite test of January 2007, when the People’s Republic of China demonstrated an anti-satellite rocket by blasting one of their defunct weather satellites into shrapnel.  The result of the test was to scatter thousands of scraps of metal across the orbit.  As radar tracking stations monitored the debris (in order to be able to alert the ISS and satellite operators of impending collisions), they noted that by the beginning of 2011 only 6% of the debris had re-entered the Earth’s atmosphere, yet less than a year later fully half had since fallen to Earth.

As the world’s space-faring governments gradually wake up to the problem of debris in Earth orbit, it’s good to know that natural phenomena will provide some assistance in dealing with the problem.