Kepler is scheduled for launch atop a Delta II rocket from Cape Canaveral Air Force Station, in Florida, on March 5 at 10:48 pm (0348 GMT, March 6).
It will be the National Aeronautics and Space Administration's first mission in search of Earth-like planets orbiting suns similar to ours, at just the right distance and temperature for life-sustaining water to exist.
"Kepler will push back the boundaries of the unknown in our patch of the Milky Way galaxy. And its discoveries may fundamentally alter humanity's view of itself," Jon Morse, astrophysics division director at the US space agency's Washington headquarters, told a press conference Thursday.
"The planetary census Kepler takes will be very important for understanding the frequency of Earth-size planets in our galaxy and planning future missions that directly detect and characterize such worlds around nearby stars," he added.
Equipped with the largest camera ever launched into space -- a 95-megapixel array of charged couple devices, known as CCDs -- the Kepler telescope is able to detect the faint, periodic dimming of stars that planets cause as they pass by.
At a cost of close to 600 million dollars, the Kepler mission will last three years and examine more than 100,000 sun-like stars in the regions of the Swan and Lyre constellations in the Milky Way.
William Borucki, Kepler's principal investigator based at NASA's Ames Research Center in California, said the project was about finding places where conditions are perfect for sustaining life.
"What we're interested in finding are planets that are not too hot and not to cold, but just right," he said.
"We're looking for planets where the temperature is just about right for liquid water on the surface of the planet."
The telescope, set to stare at a single patch of sky throughout its mission, can watch for the stars that are affected by planets.
"Earth-size planets in habitable zones would theoretically take about a year to complete one orbit," so Kepler's three-year lifespan enables the project to confirm a planet's presence by observing its subtle impact on the star it orbits, NASA said in a statement.
"If we find that many, it certainly will mean that life may well be common throughout our galaxy, that there is an opportunity for life to have a place to evolve," noted Borucki.
"If none or only a few of these planets are found, it might suggest that habitable planets like Earth are very rare and Earth may be a lonely outpost for life," he said.