Happy Anniversary to the Hubble Space Telescope, launched 20 years ago today. Since a start-up marred by a flawed mirror, Hubble scientists and engineers have overcome every challenge the telescope tossed them, making Hubble arguably the best-known, most productive engine of scientific discovery in history. The final upgrades made by spacewalking astronauts last May have left the telescope better equipped than ever to advance our understanding of the universe during the observatory's final years.