EVA 3 - replacement of the Power Control Unit

STS109-322-029 (6 March 2002) --- Astronaut John M. Grunsfeld, STS-109 payload commander, participates in the third of five space walks to perform work on the Hubble Space Telescope (HST). The third overall STS-109 extravehicular activity (EVA) marked the second of three for Grunsfeld, who was joined by astronaut Richard M. Linnehan on them all. On this particular walk, astronauts Grunsfeld and Linnehan turned off the telescope in order to replace its power control unit or PCU, the heart of the HST�s power system.