But the innovative spacecraft enjoyed an illustrious career, discovering as many as 2,600 planets and inspiring new fields of research, NASA said. "We're confident that TESS is going to find thousands more planets, just like Kepler did".
The far more advanced James Webb Space Telescope, scheduled to lift off in 2021, should be able to reveal more about planets' mass, density and the makeup of their atmosphere - all clues to habitability. These exoplanets are also located within the habitable zone, also called the Goldilocks Zone, of their parent stars.
He said Kepler showed mankind how many planets might be out there.
NASA announced on Tuesday that the Kepler mission - which has transformed how we understand planets outside of our solar system - is officially over.
"Before we launched Kepler, we didn't know if planets were common or rare in our galaxy", he said. It was packed with cutting-edge technology, including the largest digital camera for outer space observations at the time and the latest techniques for measuring stellar brightness.
The telescope laid bare the diversity of planets that reside in our Milky Way galaxy, with findings indicating that distant star systems are populated with billions of planets, and even helped pinpoint the first moon known outside our solar system.
Kepler is at the verge and waiting for the command which would come in the next two weeks that will deactivate its transmitter and instruments after which it will drift in a safe orbit trailing the Earth. "It was an extremely clever approach to doing this kind of science", said Leslie Livesay, director for astronomy and physics at NASA's Jet Propulsion Laboratory, who served as Kepler project manager during mission development.
"He put together a like-minded team of scientists and engineers", Hertz said of Borucki.
There was a lot of malfunction that happened with steering and dwindling hydrazine fuel levels costing $600 million spacecraft which stayed in action nearly for nine years and with 19 observation campaigns which are longer than its original four-year mission. The data from the extended mission were also made available to the public and science community immediately, allowing discoveries to be made at an incredible pace and setting a high bar for other missions. Scientists are expected to spend over a decade making new discoveries in the treasure trove of data Kepler provided.
Jessie Dotson, Kepler project scientist at NASA's Ames Research Center, said, "I guess I feel like it was the little spacecraft that could".
"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". In the lead-up to its impending retirement, "scientists pushed Kepler to its full potential" by preemptively powering down the spacecraft several times to extend its lifespan.
NASA's Transiting Exoplanet Survey Satellite (TESS) is already in space and embarking on its own planetary hunt using a similar method to Kepler, keeping an eye on dips in starlight as planets move between the satellite and its host star. Launched in April, TESS will build on Kepler's planet-hunting legacy by searching for exoplanets around almost 200,000 of the brightest and nearest stars to Earth. It is created to cover an area 400 times larger than Kepler could manage and is expected to find some 20,000 or more exoplanets during the course of its mission.