2009 satellite collision

A replica of an Iridium satellite

The 2009 satellite collision was the first major collision between two intact artificial satellites in Earth orbit. The collision occurred at 16:56 UTC on February 10, 2009, at 789 kilometres (490 mi)^[1] above the Taymyr Peninsula in Siberia, when Iridium 33 and Kosmos-2251 collided.^[2][3][4] The satellites collided at a speed of 11.7 kilometres per second (7.3 mi/s), or approximately 42,120 kilometres per hour (26,170 mph).^[5][6]

Collision

Collision diagram

The collision destroyed both Iridium 33 (owned by Iridium Satellite LLC) and Kosmos 2251 (owned by the Russian Space Forces). While the Iridium satellite was operational at the time of the collision, the Russian satellite had been out of service since at least 1995 and was no longer actively controlled.^[7][8] Kosmos-2251 was launched on June 16, 1993, and went out of service two years later, in 1995, according to Gen. Yakushin^[9].

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U.S. space agency NASA reported that a large amount of debris was produced by the collision. Currently the U.S. Space Surveillance Network tracks more than 500 pieces of debris, but it will take more time to estimate the full extent of the collision debris.^[3] NASA says the risk to the International Space Station, which orbits about 430 kilometres (270 mi) below the collision course, is low,^[10][11] as is any threat to a shuttle launch planned for later February 2009.^[11] However, Chinese scientists have said that the debris does pose a threat to Chinese satellites in Sun-synchronous orbits.^[12]

Several smaller collisions had occurred previously, often during rendezvous attempts or the intentional destruction of a satellite, including the DART satellite colliding with MUBLCOM,^[13] and three collisions involving the manned Mir space station, during docking attempts by Progress M-24, Progress M-34, and Soyuz TM-17.^[14] In 1996, the Cerise satellite collided with space debris.^[15] There have been eight known high-speed collisions in all, most of which were only noticed well after the fact.^[16]

Spacecraft

Kosmos-2251 was a 950-kilogram (2,094 lb) Strela communications satellite.^[17] It was launched on a Kosmos-3M carrier rocket on June 16, 1993.^[3] It had been deactivated prior to the collision, and remained in orbit as space debris. Iridium 33, a 560-kilogram (1,235 lb) satellite that was part of the Iridium satellite constellation of 66 communications satellites,^[3] was launched on September 14, 1997 atop a Proton rocket.

Fallout

On February 13, witnesses in Kentucky began hearing sonic booms.^[18] The National Weather Service issued an information statement alerting residents of "explosions and or earthquakes" due to the falling satellite debris.^[19] Similar reports from as far west as New Mexico were all attributed to falling debris from the collided satellites.^[20] The Federal Aviation Administration also released a notice warning pilots of the re-entering debris.^[21]

However, in contradiction to these government agencies' reports, the United States Strategic Command, which tracks satellites and orbital debris, denied that the reports of booms and flashes of light in the sky were related to the satellite collision.^[22]

A bolide ("fireball") over Texas on February 15 was mistaken for reentering debris.^[23]

Nicholas L. Johnson, NASA's chief scientist for orbital debris, estimated that the satellite collision created approximately 1,000 pieces of debris larger than 10 centimeters (4 inches), in addition to many smaller ones.^[24]

Cause

Events where two satellites approach within several kilometers of each other occur numerous times each day. Sorting through the large number of potential collisions to identify those that are high risk presents a challenge. Precise, up-to-date information regarding current satellite positions is difficult to obtain. Calculations made by CelesTrak had expected these two satellites to miss by 584 meters.^[25]

Planning an avoidance maneuver with due consideration of the risk, the fuel consumption required for the maneuver, and impacts on the satellite's normal functioning can also be challenging. John Campbell of Iridium spoke at a June 2007 forum discussing these tradeoffs and the difficulty of handling all the notifications they were getting regarding close approaches, which numbered 400 per week (for approaches within 5 km) for the entire Iridium constellation. He estimated the risk of collision per conjunction as one in 50 million.^[16]

This collision and numerous near-misses have renewed calls for mandatory disposal of defunct satellites (typically by deorbiting them), but no such international law as yet exists.^[26]

See also

• Kessler Syndrome (Ablation cascade)
• Laser broom
• Liability Convention

References

External links

	Wikinews has news coverage of the 2009 satellite collision Russian and US satellites collide Burning debris from satellites spotted over several US cities:

• Rachel Courtland. "Satellite crash prediction is plagued with uncertainty". New Scientist. http://www.newscientist.com/article/dn16592-satellite-crash-prediction-is-plagued-with-uncertainty.html. Retrieved 2009-02-13. 
• Animations and graphic renderings of the collision
• Satellite Crash video
• Satellite Crash Animation in 3D with Google Earth