10 February 2009, 16:55:59.806 UTC

2009 Satellite Collision. Cosmos 2251, represented by the orange line, is orbiting from the upper left to lower right. Iridium 33, the blue line, is moving from the lower left to upper right. (Thomas S. Kelso, Ph.D., Analytical Graphics, Inc.)

10 February 2009, 16:55:59.806 UTC: Two artificial satellites orbiting Earth, Cosmos 2251 and Iridium 33, collided with each other at a closing speed of 26,170 miles per hour (42,117 kilometers per hour, 490 miles (789 kilometers) above Siberia. Because of the relative speeds of the satellites, this was termed a “hypervelocity collision.”

These satellites had been routinely tracked and estimates were that they would pass at a distance of 584 meters (1,916 feet).

Cosmos 2251 (Космос-2251) was a Strela 2M military communications satellite. It had been launched from Plesetsk, Russia, at 04:20:00 UTC, 16 July 1993, but was no longer active and was not controlled. The satellite weighed approximately 900 kilograms (1,984 pounds). It was in a 783 × 821 kilometers (486.5 × 510.1 miles) orbit, with an inclination, relative to Earth’s axis, of 74.0°.  It completed one orbit every 1 hour, 41 minutes.

Iridium 33 was commercial communications satellite which was launched from the Baikonur Cosmodrome, Kazakhstan, at 01:36:54 UTC, 14 September 1997. It was built by Lockheed Martin for Iridium Satellites LLC. weighed 1,234 pounds (560 kilograms). Iridium 33’s orbit was 522 × 541 kilometers (324.4 × 336.2 miles). It had an orbital inclination of 86.6° and orbited the Earth in 1 hour, 34.9 minutes.

According to a report by Thoman S. Kelso, Ph.D.,  of the Center for Space Standards & Innovation, light flashes captured on video “suggest that at least two MMAs (Main Mission Antennas. . . at the bottom of the satellite) on that object survived the collision relatively intact.”

Subsequently 406 pieces of Iridium 33 and 960 pieces of Cosmos 2251 were tracked as they spread in orbit. While some of the debris has re-entered the atmosphere, perhaps 50% of the total remains in Earth orbit.

© 2017, Bryan R. Swopes

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