Of course, Hubble’s history has not been without glitches. The most critical appeared within weeks of its deployment. Early images revealed that the telescope’s 2.4-meter mirror was flawed — its edges were too flat by 2 micrometers, or roughly 1/50 the width of a human hair — and could not focus light sharply. For a telescope whose whole raison d’être was to deliver crystal-clear views of the cosmos from above the distorting effects of Earth’s atmosphere, the imperfection was more than disheartening.

Fortunately, NASA designed Hubble to be serviced regularly. On December 3, 1993, a team of seven astronauts rocketed into orbit aboard the space shuttle Endeavour. Their most important task: Install two new instruments that would serve as “eyeglasses” and transform fuzzy images into crystal clarity.

Four subsequent servicing missions — the final one in May 2009 — have completely revamped the observatory and made it into a 21st-century science machine. It has captured more than 1 million images of the cosmos, exploring objects as near as the Moon and as distant as some of the first galaxies to form in the early universe. And it has studied myriad examples of almost every type of target that lies between.