As a space telescope scientist or satellite operator, the last thing you want to hear is that your expensive and possibly one-of-a kind — maybe irreplaceable — spacecraft is in danger of colliding with a piece of space junk. On March 29, 2012, scientists from the Fermi Gamma-ray Space Telescope were notified that their spacecraft was at risk from a collision. And the object heading towards the Fermi spacecraft at a relative speed of 44,000 km/h (27,000 mph) wasn’t just a fleck of paint or tiny bolt.
Fermi was facing a possible direct hit by a 1,400 kg (3,100-pound) defunct Russian spy satellite dating back to the Cold War, named Cosmos 1805. If the two satellites met in orbit, the collision would release as much energy as two and a half tons of high explosives, destroying both spacecraft and creating more pieces of space junk in the process.
But this story has a happy ending, with the Fermi telescope still operating and continuing its mission to map the highest-energy light in the universe, all thanks to a little orbital traffic control.
You can watch the video here for the complete story, or read more at the Fermi website about how the Fermi Space Telescope dodged a speeding bullet.