The Kepler spacecraft operates a single instrument
The Kepler spacecraft operates a single instrument, a photometer, which continually monitors the brightness of over 145,000 specifically selected stars in a fixed field of view. The selected stars may have been mostly the larger F-Class stars for their brightness, which would likely be less affected by weakening conditions in the space around their solar systems. All this means that it cannot be said that the Kepler mission has delivered absolute proof that no sun anywhere has ever gone inactive, as has been suggested. When the inactivation of a sun occurs, which should typically be rare and occur quickly, the result would likely be missed unless one specifically looks for such events.The Kepler mission, officially, detected no such events, nor was it designed to do so. It operated for a brief span from December 2009 till May 11, 2013. While it operated, a greater-than-expected noise to data ratio was experienced, from both the stars and the spacecraft itself, which means that the results were not as clean as expected and open to errors.