The spacecraft is named Kepler after the German 17th-century astrophysicist and it will be on the lookout for possible Earths in one faraway corner of the galaxy.
It's scheduled to rocket away from Cape Canaveral late Friday night. Excellent launch weather is forecast.
Kepler will spend more than three years staring at 100,000 stars, measuring their brightness and any winks in the light that might signify orbiting planets. The mission will cost $600 million, from start to finish.
The launch comes on the heels of a failed flight of a NASA science satellite from California, just over a week ago.
Copyright Associated Press