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(CNN) -- When space shuttle Discovery blasted off, it joined thousands and thousands of manmade objects orbiting Earth.
But should one of those objects hit the craft as it orbits at 16,000 mph, it could cause severe damage and a scuttled mission.
The shuttle crew is too busy to watch out for objects in Discovery's orbit, and because no traffic cops patrol space, tracking is the responsibility of the 1st Space Control Squadron (SPCS) of the U.S. Air Force Space Command, which operates the Space Control Center (SCC) inside Cheyenne Mountain Operations Center in Colorado Springs, Colorado.
The squadron is charged with detecting, tracking, identifying and cataloging all manmade objects orbiting Earth larger than 10 centimeters (4 inches) long.
"We kind-of liken it to working on the world's largest jigsaw puzzle," said Robin Thurston, a historical data analyst employed by the 1st SPCS.
There are plenty of pieces to the puzzle. Thurston said the squadron is tracking 13,400 objects, of which 8,800 are cataloged, meaning that the squadron has associated them with a specific launch. The other 4,600 are awaiting identification.
'Floating around up there'
When the space shuttle is flying, the squadron performs "collision avoidance analysis" for NASA.
To do this, the squadron plots "a theoretical box around the shuttle" that measures 10- by-10-by-40 kilometers (6.2-by-6.6-by-24.8 miles). If any of the objects intersects this theoretical box, the squadron sends its analysis to NASA, which determines whether to change the shuttle's flight path.
NASA has changed the shuttle's flight path 12 times since the SCC began performing its analysis in 1981. The center also works for the international space station (ISS). NASA has moved the ISS six times based on SCC analysis.
To track the objects, the squadron uses data captured by the Space Surveillance Network, a worldwide collection of 19 space surveillance sensors -- radar and optical telescopes, both military and civilian. Inside Cheyenne Mountain, the squadron correlates the sensor data to the orbiting objects and updates the position of each one.
According to Thurston, the sensors can track satellites in a low-earth orbit down to a size of 10 centimeters. In high-earth orbit, Thurston said the ground-based Electro-Optical Deep Space Surveillance (GEODSS) sites, which use 40-inch telescopes, can track a satellite the size of a basketball at 35,000 kilometers.
As a historical data analyst, it is Thurston's job to use the data captured by radar sites to match up objects in space with their launches. For example, last December the center used data to match an object with an experimental satellite launched in June 1966.
The satellite, which measures 28 inches in diameter, stopped working in 1967. Tracking facilities were limited then, Thurston said, so once it stopped sending data, the Air Force had no way to track it.
"It had been floating around up there," Thurston said.
The oldest object tracked by the 1st SPCS is Vanguard 1, a 6-inch sphere launched from the Air Force Eastern Test Range (AFETR) on March 17, 1958. The largest object is the international space station.
The lost screwdriver
The objects aren't always satellites. One was a screwdriver that was lost during a 1985 space shuttle mission.
The space shuttle Discovery launched in August 1985 to deploy three communications satellites and to make repairs on LEASAT-3, which had been deployed from an earlier shuttle mission but was stranded in a low-earth orbit. After repairs, LEASAT-3 was successfully boosted into the proper orbit, and the sailing screwdriver burned up as it re-entered the atmosphere in February of 1986.
The squadron is composed of roughly 120 military, civilian and contractor personnel assigned to the unit. Thurston is a civilian employee, but he started working at the SCC when he was an active-duty airman. He retired from the Air Force eight years ago with the rank of technical sergeant.
Five crews, staffed by six active-duty military personnel and two contractors, work in the Space Control Center 24 hours a day. The squadron also has 32 personnel in its Space Analysis Center, where Thurston works.
According to the Air Force, only a small amount of debris exists where the shuttle orbits and the likelihood of a "significant collision" between a piece of debris and the shuttle is extremely remote.
However, if it did happen, the impact would not be good. According to Thurston, satellites in orbit at 350 kilometers altitude, the altitude at which the ISS and most shuttle missions orbit, travel at 7.7 kilometers a second, or more than 16,000 mph.
Thurston said his job is very interesting and he enjoys working in Cheyenne Mountain -- and he is truly inside. The center is located deep in the mountain and is protected by 25-ton blast doors. Constructed during the Cold War, it was built to withstand a limited nuclear strike and rests on more than 1,300 three-foot high steel springs, which are supposed to help dampen an explosion. And despite the location, there are no lovely mountain views.
"I brought my wife in and she said, 'I don't know how you can work in here,'" he said.
http://www.cnn.com/2005/TECH/space/08/02/space.junk/index.html
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