Hey International Space Station Watch Out for that Satellite
Courtesy Lee Hutchinson, ArsTechnica
Orbiting about 250 miles (400-ish km) above our heads is one of the most complex and expensive engineering projects that the human race has ever put together: the International Space Station (ISS). The station masses around 450 tons (400 metric tons) and is a bit larger than an American football field. Its assembly required dozens and dozens of launches by Russia and the US (including 37 space shuttle flights), and it took astronauts and cosmonauts 155 spacewalks to get the whole thing bolted together—2.5 times more spacewalks than had previously occurred since the beginning of space flight.
Enlarge / The International Space Station compared to the size of an American football field.
The ISS has taken 13 years and as much as $150 billion to build and fly; to call it valuable real estate is an understatement. As we Americans are relaxing for the Fourth of July and drinking beers or lighting off fireworks, high above our heads, six human beings are working in space. But the station isn’t just sitting up there, static and unmoving. The ISS’ orbit decays due to atmospheric drag at the rate of about two kilometers per year; it must periodically be boosted in order to maintain its height. Moreover, the entire massive structure is mobile—it can be rolled and pitched and yawed, or even moved ("translated," in NASA parlance) in three dimensions to avoid a potential collision with debris.
Ars Senior Science Editor John Timmer wrote back in May about the complex process behind moving unmanned satellites around in orbit—specifically, what it took to move NASA’s Fermi Gamma-ray Space Telescope out of the way of some debris in its orbital path. But the ISS isn’t an unmanned satellite; its mass is much larger. More importantly, it has six living, breathing human beings on board. How does one move 400 tons of fragile space station when there’s an asteroid or something bearing down on it?
Ground control to Major Tom
To find out how to throttle-jockey the ISS around in orbit, I took a drive over to NASA’s Johnson Space Center and met up with Josh Parris, a NASA ISS flight controller. Parris is one of the people tasked with manning a console in the ISS flight control room—or "Mission Control" as it’s more commonly known. His station name is TOPO—Trajectory Operations Officer. As has been the case since the earliest days of manned space flight, the ISS flight controllers are all highly skilled individuals; Parris and his coworkers have all undergone years of specialized training to reach the point where they are trusted with "sitting a console."