NASA was forced to consider a sixth spacewalk to replace a critical steering component of the Hubble Space Telescope that malfunctioned early today.
Mark Lee and Steven Smith had just finished fixing Hubble’s torn insulating cover in the cargo bay of space shuttle Discovery when Mission Control notified them that one of four reaction wheels had developed “a glitch.”
After an hour, Mission Control told the astronauts to end their spacewalk and be prepared to go back out again tonight if engineers determine the part needs to be replaced.
The crew has a spare flywheel on board, as a backup to one installed over the weekend.
The sluggish reaction wheel - one of four - was rotating much too slowly and engineers feared it might fail altogether. It was not the new one.
During the fifth and what should have been the final spacewalk of the servicing mission Monday night, Lee and Smith used bits of foil, wire, clips, plastic twists and parachute cord to repair Hubble’s peeling insulation.
The spacewalkers hung quiltlike patches over splits in Hubble’s thin, reflective insulation, apparently damaged by sun exposure during seven years in orbit. They clipped the six 9-inch-by-16-inch pieces of material to rails and knobs on the telescope.
In a spot where the insulation was cracked but not yet ripped, the Discovery crewmen stretched two wires to prevent the material from tearing.
It was frustrating work. Twice, Lee cursed. The spacewalkers had to work by the light of their helmets; most of the 2-hour job took place in the blackness of space.
Mission Control added the spacewalk to Discovery’s flight so Lee and Smith could finish the insulation repairs begun by two colleagues the night before.
The astronauts discovered the damage last week while installing state-of-the-art scientific gear that will allow the telescope to look deeper into the universe.
With the sort of ingenuity used on Apollo 13, the crew cobbled together the patches early Monday as Gregory Harbaugh and Joe Tanner installed the last of Hubble’s replacement parts, and did a little mending, too.
Harbaugh and Tanner were proud of their handiwork. They spent 1-1/2 hours attaching two blankets and adjusting them just so.
“What do you think?” Harbaugh asked, backing away.
“Like it. Looks good from here,” Tanner replied.
Mission Control put it this way: “A masterpiece.”
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