EVA 3 - newly installed PCU unit

STS109-322-025 (1-12 March 2002) --- A close-up view of the power control unit or PCU, which is the heart of the Hubble Space Telescope (HST) power system. Astronauts John M. Grunsfeld and Richard M. Linnehan, STS-109 payload commander and mission specialist, respectively, replaced the PCU on March 6, 2002, during the third space walk of the mission.