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About this Article
Written by: Jordan Olliges
Written on: July 17th, 2009
Tags: aerospace engineering
Thumbnail by: NASA Orbital Debris Program Office
About the Author
In summer 2009, Jordan Olliges was a senior majoring in Aerospace Engineering at the University of Southern California. He plans to continue his education at USC with a Master’s Degree in Aerospace Design before pursuing a career in launch vehicle development.
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Volume XI Issue I > The Impact of Orbital Debris
On January 11, 2007, the People's Republic of China tested an anti-satellite (ASAT) weapon and destroyed its own Fengyun-1C meteorological satellite [5]. A ballistic interceptor was launched from a Chinese launch site and impacted the 960 kg satellite in orbit. The incident was the largest fragmentation event in the history of manned space operations and the debris from it accounts for more than 25% of all cataloged objects in Low Earth Orbit (LEO) [6]. Large fragmentation events have a significant impact on the total number of orbiting debris and have been on the rise for the last 50 years [7]. The Fengyun-1C fragmentation event created a dramatic increase in total orbital objects during 2007, and as of January 2009, there were 2,378 Fengyun-1C fragments larger than 5 cm being tracked by the U.S. Space Surveillance Network. The total number of fragments larger than 1 cm created by the ASAT test was estimated to be greater than 150,000 [8].
Even with China creating massive debris clouds, the U.S. Space Surveillance Network (SSN) has historically held the responsibility of tracking all objects larger than 10 cm orbiting the Earth [9]. A combination of ground-based radar and optical equipment is used to track more than 17,000 of these larger diameter particles while more focused radar systems with higher spatial resolutions can make estimates of the amount of smaller debris [10] [2]. During NASA’s Space Shuttle missions, the U.S. Space Surveillance Network studies the trajectories of the larger objects and determines if anything will endanger the astronauts. If there is greater than a 1 in 10,000 chance of collision, the shuttle will maneuver away from the incoming object [9]. Similarly to NASA, mission planners for the International Space Station (ISS) rely heavily on the Space Surveillance Network to continually monitor orbital debris and determine if there is a threat to the human inhabitants on board. Like the Shuttle, the ISS can maneuver away from objects larger than 10 cm. To protect the astronauts from smaller debris, the station is the heaviest shielded vehicle ever launched into orbit and can withstand particle impacts of up to 1 cm in diameter [11]. However, the gap between survivable 1 cm objects and tracked 10 cm objects is of big concern to manned missions. With an average relative velocity of 10 km/s between two objects in LEO, an impact with anything larger than 1 cm would be catastrophic to a manned space mission [9]. With no way to avoid these intermediate-sized objects, an international focus on debris mitigation is vital to keeping space safe for future manned missions.