The National Aeronautics and Space Administration test simulates the vacuum of space, and the extreme temperatures Kepler will face. The spacecraft is placed into a vacuum chamber and surrounded by a cold shroud, the space agency said. Then one side of the spacecraft -- the side with solar panels -- is baked as if it were being heated by the sun.

"The goal is to make sure the spacecraft and its detectors operate properly in the space-like environment," NASA said, noting an electromagnetic compatibility test, to ensure Kepler's electronics are sound, will soon begin.

The spacecraft is designed to monitor 100,000 stars, searching for signs of planets, including ones as small as, or smaller than, Earth, NASA said. To date, no Earth-sized planet has been discovered.