Julie McEnery is NASA's Project Scientist for the Fermi Gamma-ray Space Telescope. When she checked her email on March 29, 2012, she was startled to find an automatically generated message stating that in six days, her half-billion-plus dollar satellite was going to cross paths with Cosmos 1805, a Soviet-era spy satellite. The predicted encounter had the two satellites occupying the same coordinates only 30 milliseconds apart. Not only that, but Cosmos was in an orbit moving nearly perpendicular to Fermi such that their collision would be equivalent to tons of high explosives. Essentially total destruction.
Read the full article: We nearly lost Fermi: The problem of orbital debris