When Atlantis was on its way to Hubble, space shuttle Endeavour was prepared as a backup vehicle for Atlantis. Endeavour will also be launched if in the unlikely event that it's needed for a rescue flight.
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| Space shuttle Atlantis lifts off on a mission to NASA's Hubble Telescope from its launch pad at the Kennedy Space Center in Cape Canaveral, Florida May 11, 2009.(Xinhua/AFP Photo) |
That's because Atlantis' 11-day mission comes with a higher risk than usual. Atlantis will be flying in an unusually high orbit for a space shuttle -- 350 miles up. Space is more littered there with spacecraft parts, and the odds of a catastrophic strike are greater.
If Atlantis is irreparably damaged during flight, its crew won't be able to reach the safe haven of the International Space Station to seek refuge for the months required to ready an unprepared shuttle for a rescue. Hubble flies higher than the space station (about 350 miles up, while the station sits at 220 miles) and in a different orbital inclination -- or tilt with respect to Earth's equator.
Without access to the space station, Atlantis would only have enough food and air to keep its crew alive for 25 days, even less time if serious damage is discovered late in the mission.
Scientists estimated that there's a slightly higher risk of damage from the orbital debris -- about a 1-in-229 chance of a critical strike. To offset that, NASA plans to fly Atlantis down to a safer orbit just after releasing Hubble back into space near the end of the flight.
Hubble, launched by NASA in 1990, was named after U.S. astronomer Edwin Hubble whose work revolutionized our understanding of the size and structure of the universe. After its first two months of tests in 1990, the initial images from Hubble were a blurry disappointment. A slight flaw in the telescope's main mirror -- barely the width of a human hair -- fouled the observatory's vision.
In 1993, NASA sent a shuttle up to Hubble, where astronauts added corrective lenses -- essentially glasses -- to sharpen its vision. The result was crystal clear: 16 years of stunning cosmic photos followed.
Since that first orbital fix, astronauts returned to Hubble three more times; in 1997, 1999 and 2002.
Hubble has given the world amazing insight into the origins of our universe. Among its greatest discoveries are determining the age of the universe (13.7 billion years); finding that virtually all major galaxies have black holes at their center; discovering that the process of planetary formation is relatively common; detecting first ever organic molecule in the atmosphere of a planet orbiting another star; and providing evidence that the speed at which the universe is expanding is accelerating – caused by an unknown force that makes up more than 75 percent of the universe.
