Two U.S. astronauts ventured outside the shuttle Columbia Monday to begin a week of spacewalks aimed at improving the Hubble Space Telescope. The astronauts replaced the first of two new solar wings that will give more power to the observatory.
Astronauts John Grunsfeld and Rick Linnehan floated outside Columbia for seven hours to exchange one Hubble solar array for a new one. An alternate pair of spacewalking astronauts will repeat the task with the other array during a second spacewalk Tuesday.
Unlike the old, flexible ones, the new arrays are rigid and smaller, causing less drag. "That makes an easier ride for the telescope," said U.S. space agency's astronomy director, Anne Kinney. "These new solar arrays will give a cleaner ride to the telescope. The telescope will be able to dwell more quietly. We really hope they will give us a nice long science lifetime on the Hubble Space Telescope."
Though smaller, the new solar wings will generate 20 per cent more power than the old ones, which had been degrading in output because of the effects of space radiation. Ms. Kinney says the replacements will assure simultaneous operation of all instruments when new, more power hungry components are installed on the next servicing mission. "That allows you to maximize your scientific return," she said. "If we didn't have this increase in power, the old solar arrays would continue to decrease and we'd eventually be stuck operating just one instrument at a time."
Later in the week, the astronauts will install a new generator to distribute the power from the new solar wings. This is the most risky task of the mission because flight directors must shut down the telescope's entire electrical system for the first time, raising the specter of freezing delicate components and ruining them. But mission officials say if all goes well, 6.5 hour outing will not last long enough for this to happen.
Other tasks facing the spacewalkers this week are installing a new gyroscope to aim Hubble and a new camera to boost the observatory's visual strength by 10 times. The vision improvement will let the observatory see closer to the edge of the universe and, in effect, further back in time.
The crew also hopes to revive a long dormant infrared camera that sees celestial objects through the dust of space.