NASA is set to launch its Kepler telescope spacecraft atop a Delta II rocket at 10:48 p.m. ET March 5 from Cape Canaveral Air Force Station, Fla., to begin a multi-year hunt for Earth-like planets.

This is the first mission with the ability to find planets like Earth — rocky planets that orbit sun-like stars in a warm zone where liquid water could be maintained on the surface.

The mission will spend three and a half years surveying more than 100,000 sun-like stars in the Cygnus-Lyra region of the Milky Way galaxy.

It is expected to find hundreds of planets the size of Earth and larger orbiting at various distances from their stars.

If Earth-size planets are common in the habitable zone (where conditions favor liquid water), Kepler could find dozens of worlds like Earth. On the other hand, if those planets are rare, Kepler might find none.

The Kepler telescope is specially designed to detect the periodic dimming of stars caused by transiting planets. Some star systems are oriented in such a way that their planets cross in front of their stars, as seen from our Earthly point of view. As the planets transit, they cause their stars’ light to slightly dim, or wink. The telescope can register changes in brightness of only 20 parts per million.

"If Kepler were to look down at a small town on Earth at night from space, it would be able to detect the dimming of a porch light as somebody passed in front," said James Fanson, Kepler project manager at the Jet Propulsion Laboratory in Pasadena, Calif.

The mission will spend three and a half years surveying more than 100,000 sun-like stars To accomplish this feat, Kepler will use the largest camera ever launched into space, a 95-megapixel array of charged couple devices or CCDs.

By staring at one large patch of sky for the duration of its lifetime, Kepler will be able to watch planets periodically transit their stars over multiple cycles. This will allow astronomers to confirm the presence of planets. Earth-size planets in habitable zones would theoretically take about a year to complete one orbit, so Kepler will monitor those stars for at least three years to confirm their presence. Ground-based telescopes and the Hubble and Spitzer space telescopes will perform follow-up studies on the larger planets that they can see.

"Kepler is a critical cornerstone in understanding what types of planets are formed around other stars," said exoplanet hunter Debra Fischer of San Francisco State University. "The discoveries that emerge will be used immediately to study the atmospheres of large, gas exoplanets with Spitzer. And the statistics that are compiled will help us chart a course toward one day imaging a pale blue dot like our planet, orbiting another star in our galaxy."

This is part of a quest to see whether there might be intelligent life in the universe, a hunt that already has involved sending radio signals from Earth into space, in hopes that any intelligent beings that might be out there could hear the signals and realize that life exists on Earth.