https://techcrunch.com/2018/10/30/nasas-prolific-planet-hunter-kepler-has-finally-earned-its-retirement/

After nine years of service, half a million stars surveyed, and thousands of planets discovered around those stars, NASA’s astonishingly successful Kepler space telescope is finally taking a well-earned rest. Out of fuel but in a safe orbit, the spacecraft will drift through the solar system looking at nothing in particular as its immense trove of data continues to drive discoveries here on Earth.

Kepler launched in 2009 after, as is so often the case, decades of preparation, studies, and delays. Its mission, slated to last three and a half years, was to stare unblinkingly at one small patch of sky, watching each star for the minute changes that could indicate a planet briefly blocking its light.