2009 satellite collision

A replica of an Iridium satellite.

The 2009 satellite collision was the first accidental hypervelocity collision between two intact artificial satellites in Earth orbit.^[1] The collision occurred at 16:56 UTC on February 10, 2009, at 789 kilometres (490 mi)^[2] above the Taymyr Peninsula in Siberia, when Iridium 33 and Kosmos-2251 collided.^[3][4][5] The satellites collided at a speed of 42,120 km/h (26,170 mi/h).^[6][7]

Collision

Collision diagram.

The collision destroyed both Iridium 33 (owned by Iridium Communications Inc.) 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.^[8][9] Kosmos-2251 was launched on June 16, 1993, and went out of service two years later, in 1995, according to Gen. Yakushin.^[10]

Several smaller collisions had occurred previously, during rendezvous attempts or the intentional destruction of a satellite, including the DART satellite colliding with MUBLCOM,^[11] and three collisions involving the manned Mir space station, during docking attempts by Progress M-24, Progress M-34, and Soyuz TM-17,^[12] but these were all low-velocity collisions. In 1996, the Cerise satellite collided with space debris.^[13] There have been eight known high-speed collisions in all, most of which were only noticed well after the fact.^[14]

Spacecraft

Kosmos-2251 was a 950-kilogram (2,094 lb) Strela military communications satellite.^[15] It was launched on a Kosmos-3M carrier rocket on June 16, 1993.^[4] It had been deactivated prior to the collision, and remained in orbit as space debris. Iridium 33 was a 560-kilogram (1,235 lb) satellite and was part of the commercial satellite phone Iridium constellation of 66 communications satellites.^[4] It was launched on September 14, 1997 atop a Proton rocket.

Fallout

Flashes created by the tumbling main body of the Iridium 33 wreckage.

The collision resulted in significant debris in Low Earth Orbit

U.S. space agency NASA estimated that the satellite collision created approximately 1,000 pieces of debris larger than 10 centimeters (4 inches), in addition to many smaller ones.^[16] By July 2011, the U.S. Space Surveillance Network had cataloged over 2000 large debris fragments.^[17] NASA determined the risk to the International Space Station, which orbits about 430 kilometres (270 mi) below the collision course, to be low,^[15][18] as was any threat to the shuttle launch (STS-119) then planned for late February 2009.^[15] However, Chinese scientists have said that the debris does pose a threat to Chinese satellites in Sun-synchronous orbits,^[19] and the ISS did have to perform an avoidance maneuver due to collision debris in March 2011.^[17]

By December 2011, many pieces of debris were in a steady decay towards Earth, and expected to burn up in the atmosphere within one or two years.

A small piece of Kosmos 2251 satellite debris safely passed by the International Space Station at 2:38 a.m. EDT, Saturday, March 24, 2012. As a precaution, the six crew members on board the orbiting complex took refuge inside the two docked Soyuz rendezvous spacecraft until the debris had passed.^[20]

A number of reports of phenomena in Texas, Kentucky, and New Mexico were attributed to debris from the collision in the days immediately following the first reports of the incident in 2009.^[21] On February 13, 2009, witnesses in Kentucky heard sonic booms.^[22] The National Weather Service issued an information statement alerting residents of sonic booms due to the falling satellite debris.^[23] The Federal Aviation Administration also released a notice warning pilots of the re-entering debris.^[24] A bolide ("fireball") over Texas on February 15 was mistaken for reentering debris.^[25]

NASA and the United States Strategic Command, which tracks satellites and orbital debris, did not announce any reentries of debris at the time^[26] and reported that these phenomena were unrelated to the collision.^[27] Some reports include details that point to these phenomena being caused by a meteoroid shower.^[26]

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.^[28]

Planning an avoidance maneuver with due consideration of the risk, the fuel consumption required for the maneuver, and its effects 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.^[14]

This collision and numerous near-misses have renewed calls for mandatory disposal of defunct satellites (typically by deorbiting them), but no such international law exists yet. Nevertheless, some countries have adopted such a law, such as France in December 2010.^[29]

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:

• Courtland, Rachel (February 13, 2009). "Satellite crash prediction is plagued with uncertainty". New Scientist. Archived from the original on 16 February 2009. Retrieved 2009-02-13. 
• Animations and graphic renderings of the collision
• Satellite Crash video
• Satellite Crash Animation in 3D with Google Earth