Salute to the Kepler space telescope

Kepler was retired today, after control problems made it untenable to keep the mission running. Since its launch in 2009, Kepler has discovered 2,600 planets and looked at half a million stars, giving us a far better (and more enthralling) view of the galaxy than any previous mission.  NASA estimates "that 20 to 50 percent of the stars visible in the night sky are likely to have small, possibly rocky, planets similar in size to Earth, and located within the habitable zone of their parent stars." An enormous archive of data (the spacecraft sent 678 gigabits) is yet to be analyzed. Approved in 2001 (the 9-year development is not too unusual for complex science missions), it was seemingly done in 2013 when a reaction wheel failed, but engineers were able to work around it.  In 2016, news reports claimed it had discovered an "alien megastructure" (now identified as a dust cloud moving around a star, important but not admittedly not as much fun.  In 2013, the Transiting Exoplanet Survey Satellite was launched and has taken over the planet-hunting mission. Congratulations to NASA Ames, JPL, Ball Aerospace, and all others involved.