Astronauts Michael Good (bottom) and Mike Massimino participate in the STS-125 mission's fourth spacewalk on May 17, 2009, as work continued to refurbish and upgrade the Hubble Space Telescope. During more than 8 hours of work, Massimino and Good conducted repairs and improvements to the Space Telescope Imaging Spectrograph that will extend Hubble's life into the next decade.
Image Credit: NASA
