Late tomorrow night, NASA's Kepler spacecraft will—conditions permitting—lift off from Cape Canaveral Air Force Station in Florida on its unprecedented mission to find habitable, Earth-like planets around distant stars.

The $600-million venture will train Kepler's photometer on a group of 100,000 stars several hundred to a few thousand light-years away and track them for more than three years. As the planets believed to reside there pass between their stars and Kepler's detector, the spacecraft will register a slight dip in stellar brightness. Over time these dips can be used to compile a profile of the planetary systems in Kepler's view, which, according to prevailing models of planetary formation, should include several Earth-like planets. Once astronomers know how common Earths are and where in the galaxy they can be found, follow-up missions will be able to refine their searches for extraterrestrial life.

Astronomers are hopeful that Kepler's launch will be more successful than that of NASA's Orbiting Carbon Observatory, which crashed into the Indian Ocean off Antarctica after failing to reach orbit aboard its Taurus launch vehicle last week. Kepler will blast off on board the well-tested Delta 2 rocket, which boasts a 98.5 percent reliability record according its operator, United Launch Alliance. If all goes well, a scant 62 minutes will pass between liftoff and Kepler settling into an orbit trailing Earth in a loop around the sun.

NASA will stream the launch, which is scheduled to take place between 10:49 P.M. and 11:16 P.M. (Eastern Standard Time), live on NASA TV, and Twitterers can monitor the developments by following the Kepler mission's tweets.

For more on Kepler and its prospects for turning up planets similar to our known, see last week's Q&A with planetary scientist and Kepler team member Alan Boss, author of The Crowded Universe.

Image credit: NASA