Since its launch in March 2009, more than 2,600 planets orbiting other stars (exoplanets) have been discovered, sparking a fundamentally new field of scientific research.
95MP cameraThomas Zurbuchen from NASA's Science Mission Directorate said in an administration release that Kepler had "wildly exceeded" expectations, and paved the way for the future search for extra-terrestrial life.
Now orbiting the sun 156 million kilometres from Earth, the spacecraft will drift further from our planet when mission engineers turn off its radio transmitters, the USA space agency said.
Kepler made the first major survey of planets within the Milky Way.
The most common size of planet Kepler found doesn't exist in our solar system - a world between the size of Earth and Neptune - and we have much to learn about these planets.
Kepler searched for alien worlds by looking out for their transits, which are dips in the brightness of stars that could indicate orbiting planets.
"When we started conceiving this mission 35 years ago, we didn't know of a single planet outside our solar system", said the Kepler mission's founding principal investigator, William Borucki, now retired.
Kepler showed us that "we live in a galaxy that's teeming with planets, and we're ready to take the next step to explore those planets", she said.
The $700 million mission even helped to uncover previous year a solar system with eight planets, just like ours.
Kepler's more powerful follow-on mission, the Transiting Exoplanet Survey Satellite, is already in operation. Kepler's transmitter and other instruments will be shut down in the coming days.
Kepler also surprised scientists four years into its mission after its primary objectives were met, by lasting much longer.
The observation of so many stars has allowed scientists to better understand stellar behaviors and properties, which is critical information in studying the planets that orbit them.
Scientists are expected to spend at least another decade searching for more discoveries buried in the pile of photometric data that Kepler has captured.
Bottom line: NASA has now officially retired the highly successful Kepler planet-hunter, after nine years in space. "I'm excited about the diverse discoveries that are yet to come from our data and how future missions will build upon Kepler's results".
Before retiring Kepler, NASA pushed the telescope to its fullest potential, and successfully completed many observations and downloaded the valuable data, after initial low fuel warnings.