Astronaut Michael Good, STS-125 mission specialist, participates in the mission's fourth session of extravehicular activity (EVA) as work continues to refurbish and upgrade the Hubble Space Telescope. During the eight-hour, two-minute spacewalk, Good and astronaut Mike Massimino (out of frame), mission specialist, continued repairs and improvements to the Space Telescope Imaging Spectrograph (STIS) that will extend the Hubble's life into the next decade.