U.S. astronauts have successfully performed risky repairs to prevent an electrical disaster to the Hubble Space Telescope. They replaced a dangerous faulty power control unit that distributes electricity throughout the observatory.
Crewmen John Grunsfeld and Rick Linnehan floated in space outside the shuttle Columbia to take on the cumbersome task of replacing a problem power control unit (PCU).
A loose screw inside the unit had been causing higher resistance to electricity flow to Hubble instruments. U.S. space agency astronomy director Anne Kinney says a worsening of the condition could have reduced or cut off all power. "If the PCU does not work, Hubble telescope does not work," she said.
The crucial spacewalk was delayed two-hours when a water leak developed in the cooling circuit of John Grunsfeld's spacesuit, forcing him to switch outfits. Hubble project manager Preston Burch says the wait caused his team anxious moments, wondering if the critical repair would take place. "I can tell you that our feeling in the Hubble area was that it was like going to a football game and watching your favorite team come on the field and suddenly be told that they had a 40-point disadvantage, and that they had to still try to win the game. It was a tough act to pull off," he said.
Once the astronauts finally went out in space, they raced against time to replace the equipment. The observatory's electrical system and heaters had to be turned off for the operation, subjecting delicate instruments to frigid space temperatures.
Despite unwiring and rewiring dozens of closely spaced connectors, the crewmen exchanged the unit in a little over four hours and power was restored well before the cold could damage components.
Anne Kinney compared their work to an award winning movie performance. "This dramatic and masterful performance caused us to laugh, caused us to gasp occasionally, and finally caused us to sigh," she said. "The room erupted in applause as the last of 36 plugs was connected."
With the successful repair of the power control unit, the Hubble's electrical system has been overhauled. On two previous spacewalks this week, astronauts replaced aging solar wings with a more powerful new pair. Preston Burch says it will boost the telescope's power generating capabilities for the observations to come. There is no doubt in my mind that we will be able to run all of the instruments in the manner in which we would like to, following this servicing mission, as well as servicing mission four, when we will be adding two scientific instruments," he said.
The last two spacewalks of the week are aimed at improving Hubble's vision. On Thursday, astronauts install a powerful new camera that allows Hubble to see further into space. On Friday, they will try to revive a dormant infrared camera that allows astronomers to see light from celestial objects shrouded in dust.