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  • Anniversary of an Orbital Space Collision

    Reggie Jones
    15 Years ago this month on 10 February 2009, the 2094 pound deactivated Russian satellite Kosmos-2251, and the 1235 pound Iridium 33, smashed into each other in orbit, with a collision speed of 26,170 miles/hour. The collision generated over 2000 debris fragments, which are still in orbit.
    These debris fragments pose a serious risk to other orbiting satellites, and to the International Space Station (ISS). Since launching in 1998, the ISS has performed 27 debris avoidance maneuvers (as of August 2022), 2014 being the record year with 5 debris avoidance maneuvers in that year alone. And on 4 occasions there was not enough time even for that, and the astronauts in the ISS evacuated to the Soyuz emergency escape capsule until the danger had passed.
    According to the NASA Orbital Debris Program Office (FAQ 3): “More than 25,000 objects larger than 10 cm are known to exist. The estimated population of particles between 1 and 10 cm in diameter is approximately 500,000. The number of particles larger than 1 mm exceeds 100 million. As of January 2022, the amount of material orbiting the Earth exceeded 9,000 metric tons.”
    For reference, 1 inch = 2.54 centimeters (exactly). So, 10 cm = about 3.94 inches, and 1 cm = about 0.394 inches. Objects as small as 3 millimeters (about 0.118 inches) can be detected by ground based radar.
    The pictures show the evolution of the debris field in orbit, within an hour after the collision. The first image shows the point of collision, the 2nd image shows the debris field 20 minutes after the collision, and the 3rd image shows the debris field 50 minutes after the collision.
    As the 3rd image illustrates, the collision fragments retain the vector velocity of the original satellites, and spread out along the parent orbits. So, in the 3rd image, the debris fields are colliding near Antarctica. And in that way, even more smaller debris fragments can be generated. For the most part, the debris fragments continue along the same orbits as the original satellites.
    It’s much the same dynamics that keeps meteor showers in much the same orbit as the parent comet. And just as the solar system hosts a lot of comet debris field, so does near-Earth space hold a lot of satellite debris fields, as well as non-collision related debris.
    Add to that, at least several hundred thousand tiny communication satellites (i.e., SpaceX Starlink), that are now fashionable, and Earth orbital space is getting pretty crowded. At some point, someday, nearly everything that launches will have to risk one or more debris or satellite collisions, before it gets away from Earth. This is known as the Kessler Syndrome, named after Donald Kessler [b. 1940], astrophysicist & NASA scientist, who first proposed the idea seriously, in 1978. So it’s not exactly a new idea, but it’s a lot more realistic now.
    https://ntrs.nasa.gov/citations/20100002023 (NASA Technical Report Server)
    https://en.wikipedia.org/wiki/2009_satellite_collision (2009 Satellite Collision - Wikipedia; images source)
    https://en.wikipedia.org/.../Collision_avoidance... (Spacecraft collision avoidance - Wikipedia)
    https://scienceandglobalsecurity.org/.../analysis_of... (“Analysis of Debris from the Collision of the Cosmos 2251 and the Iridium 33 Satellites” - Science & Global Security, 2010)
    https://swfound.org/.../swf_iridium_cosmos_collision_fact... (Collision fact sheet , 3-page PDF - Secure World Foundation)
    https://www.researchgate.net/.../242543407_Analysis_of... (“Analysis of the Iridium 33 Cosmos 2251 Collision” - T.S. Kelso, Center for Space Standards and Innovation, September 2009)
    https://en.wikipedia.org/wiki/Kessler_syndrome (Kessler Syndrome - Wikipedia)
    https://orbitaldebris.jsc.nasa.gov/ (NASA Orbital Debris Program Office)
    Originally posted by Tim Thompson, NASA Senior Astronomer (Retired)




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