spacetoday.net: Shuttle astronauts complete third critical Hubble EVA

Posted: Wed, Mar 6, 2002, 2:43 PM ET (1943 GMT)
STS-109 EVA #3 (NASA)

Shuttle astronauts successfully performed the equivalent of a “heart transplant” on the Hubble Space Telescope Wednesday morning, swapping out a power control unit on the orbiting observatory. Astronauts John Grunsfeld and Richard Linnehan started their EVA, the third of the STS-109 mission and the second by those two, about two hours late after they discovered a water leak in Grunsfeld’s suit, forcing him to switch suits. Once the spacewalk started, though, the two experienced few problems as they removed the old power control unit and replaced it with a new one. The power control unit serves as a switching station, distributing electricity to the telescope’s instruments and other systems. The change required the telescope to be complete powered down for the first time since its launch in 1990. The telescope was without power for four and a half hours during the replacement, and after it was completed power was slowly but successfully restored. The fourth spacewalk of the mission is scheduled for early Thursday, when Mike Massimino and Jim Newman will remove Hubble’s Faint Object Camera and replace it with a new instrument, the Advanced Camera for Surveys.