From its launch in 1990 until its first servicing in 1993, the Hubble Space Telescope was a $1.6 billion embarrassment, nearly useless because of a misshapen mirror. Sixteen years and thousands of awe-inspiring images later, the fixed Hubble is an invaluable tool for astronomers. In May, astronauts latched on to the tractor-trailer-size satellite for the fifth and final time to make repairs and add instruments that effectively turn it into a new telescope all over again.