Iridium 33 × Cosmos 2251
2009-02-10 · LEO ~789 kmThe first accidental hypervelocity collision of two intact satellites: an active Iridium communications satellite and a defunct Russian Cosmos satellite, near 789 km. It created thousands of tracked fragments still on orbit today.
Coordination: No effective coordination. The defunct object had no operator to maneuver it, and no shared warning was acted on.