Muscle power saves the day for Hubble camera
Applying elbow grease to free a stuck bolt, a shuttle spacewalker saved the day and freed an aging camera, clearing the way for installation of a $132 million replacement.
In a make-or-break attempt to free a stuck bolt holding an old camera in place on the Hubble Space Telescope, spacewalker Andrew Feustel, anchored to the end of the shuttle Atlantis' robot arm, used old-fashioned elbow grease to save the day, releasing the bolt and clearing the way for installation of a powerful new camera.
If the bolt had snapped--and that was a possibility--the astronauts would have been unable to remove the 16-year-old Wide Field Planetary Camera 2. In that case, the new $132 million Wide Field Camera 3 would have been returned to Earth aboard Atlantis in a major disappointment for the science community.
"I don't normally reveal my age and I'm not going to here, but I can tell you, I'm five years older now than I was when I came to work this morning," Hubble Project Scientist Dave Leckrone told reporters after the spacewalk was over. "We were concerned we might not end up with our highest priority instrument in."
But after removing a torque limiter from his wrench and applying more muscle power, Feustel was able to loosen the stuck bolt to the relief of concerned scientists, engineers, and flight controllers. He and partner John Grunsfeld then removed the old camera without incident.
Dubbed "the camera that saved Hubble" by project scientists, WFPC 2 took most of the spectacular photos that have made Hubble a national icon since it was installed in the telescope during the first servicing mission in 1993.
"It's been in there for 16 years, Drew, and it didn't want to come out," Grunsfeld said.
The spacewalkers had no problems installing the new camera and a science instrument command and data-handling system computer to replace a unit that failed last September, triggering a seven-month delay for the Atlantis servicing mission.
Grunsfeld also installed a grapple fixture on the base of the space telescope that will help a future crew, or a robotic spacecraft, lock onto the observatory to drive it safely out of orbit when its useful life ends.
Finally, the astronauts installed special latches on critical access doors to make it easier to reach telescope components later in the mission. Two of four latches could not be fully engaged, but the astronauts worked around that by installing alternate devices.
"Well, we got to Hubble and gave Hubble a hug," Grunsfeld said from the airlock when the day's work was done. "In traditional Hubble fashion, Hubble threw us a few curves. But I think it's really a testament to the whole team on board here and of course, on the ground...that we were able to overcome them."
The spacewalk began at 8:52 a.m. and ended with airlock re-pressurization at 4:12 p.m. for a duration of seven hours and 20 minutes. It was the 19th extravehicular activity (EVA) devoted to servicing the Hubble Space Telescope, the first of five planned by the Atlantis astronauts, the sixth for Grunsfeld and the first for Feustel.
The first item on the agenda was installation of the new Wide Field Camera 3. Attempting to remove the old camera, Feustel initially was unable to loosen a critical bolt holding the instrument in place. Grunsfeld returned to the airlock and retrieved a torque limiter and Feustel tried again, exerting more force. The bolt refused to budge.
"Drew, do you have any other suggestions before I check with Houston?" astronaut Mike Massimino called from inside the shuttle.
"No, I'm afraid I don't. I'm out," Feustel said.
Working through a contingency checklist, Feustel then removed the torque limiter from his wrench--a device that was limiting the applied torque to 45 inch pounds--before trying to apply more elbow grease directly to the stuck bolt.
"I just want to understand how far can we go with this and what are the implications if I over-torque and break the bolt?" Feustel asked.
"Are you sure you want to know?" Massimino quipped. He then called Houston: "We know the failure torque on this bolt is 57.1 foot pounds," Massimino radioed. "He had the MTL (multi-setting torque limiter) set at 45. What the crib sheet says is if we don't get it to break (loose) here, we're going to reconnect the ground strap and blind mate connector. So I guess Drew's just wondering how hard he should try on this A latch? If you have any words for us, we'd appreciate it."
"Atlantis, Houston, we copy that. And thanks for asking," replied Dan Burbank in mission control. "There's actually no issue with having the latch taken all the way to the failure point. The instrument should still function. So Drew can have at it, and you're correct, if we get to that point, we will need to reconnect the ground strap blind mate connector and we'll just leave it as is."
"So in other words, he can use what he needs from his strength to try to break the torque, is that what you're telling us?" Massimino asked.
"That's exactly right," Burbank said. "And as soon as he does, if he's successful, starts to have some motion in the latch, we'd like to go ahead and stop at that point."
"OK, thanks, Dan."
"OK, but I think we understand if it breaks, then Wide Field (Planetary Camera 2) stays in," Grunsfeld chimed in, verifying the make-or-break nature of the next step.
"What John said is correct," Burbank confirmed.
"OK, here we go," Feustel said, attaching the socket, sans torque limiter, to the attach bolt. Then, a moment later: "I think I got it! It turned, it definitely turned. And it's turning easily now."
"OK, Atlantis, Houston, for EVA, we copy, that's great news," Burbank said.
A few minutes later, Feustel attached a power wrench and backed the bolt out all the way to free the camera.
"Woo hoo, it's moving out," he said.
"That's great news," Massimino said. "That's awesome."
From that point, the camera replacement work went smoothly and the Wide Field Camera 3 was installed without incident. Engineers at the Goddard Space Flight Center in Greenbelt, Md., then sent commands to verify the new camera was hooked up properly and functioning as expected.
"Good news," Burbank called. "Aliveness test on Wide Field 3 is good."
"That's awesome news, Dan, thanks," Massimino replied. "These guys did a great job and we appreciate all the great support we got from the ground getting Wide Field in to unlock the secrets of the universe."
"More of the secrets," chimed in astronomer-astronaut Grunsfeld.
"More of the secrets of the universe," agreed Massimino.
Initial checkout of the replacement science data computer also went well.
Total Hubble EVA servicing time now stands at 136 hours and 30 minutes. Grunsfeld's total EVA time through six spacewalks stands at 44 hours and 52 minutes, putting him eighth on the list of most experienced spacewalkers.