Continued eyewitness coverage of the final mission to completely overhaul and update the Hubble Space Telescope continues to stream in from Dr. Ed Cheung, Principle Engineer of the Hubble Service Project, who was born and raised in Aruba.
Sunday’s spacewalk, EVA 4, was performed by astronauts Mike Massimino and Michael “Bueno” Good. The walk took an additional 2 hours longer than the original 6 ½ hours planned. The goal was to repair one of two redundant channels in the Space Telescope Imaging Spectrograph (STIS), a state-of-the-art instrument that broke down in 2004 when its low-voltage power supply failed. Removal of a handrail blocking access held up the work. Three bolts holding the central bar of the handrail unscrewed easily, but the forth was stripped by attempts at removal. The final solution was the use of brute force, as Astronaut Massimo pulled the handrail away once the anticipated breaking points were protected with tape to prevent debris from flying about. The time wasted forced the astronauts to return to the shuttle to top off their air supply and recharge the batteries on their power tools to be able to continue with the purpose of EVA 4.
Dr. Cheung’s latest update on Sunday’s events:
“Today we performed the repair of the STIS. I did not work on this hardware. We were also intending to install a replacement shell on one of the small doors. These are called NOBLs (”nobels”). When we repaired ACS, it included the removal of 32 little screws. Today, we repaired STIS, which required the removal of 111 screws of three types! Doing these repairs were considered a crazy idea when these instruments failed, but we gradually found that “yes” we can do this little job, then that little job, and before you knew it, we realized we could do the whole thing.”
“However, before we could get to the lid, we had to remove a handle bar on the outside shell of the instrument. Recall that this science instrument was never intended to be repaired in space. Well, the crew removed three of the four screws, but….the fourth one was damaged and would not turn! After one and a half hours of various attempts at removal, the crew considered just pulling the bar off, and breaking the screw. By then, several of our colleagues had replicated this condition on the ground in one of our machine shops and found that it took 60 lbs of pull force to snap the bolt by pulling the long handle. Here in Houston, we saw the video of the team doing this back home in Maryland, and the spectacular result of the bar flying around the machine shop once it was loose. We all wondered if crew safety would allow us to perform this procedure in space.”
“We had Mike Massimino doing the task (nicknamed “Mass”). He is a very tall and strong guy, so he was up to it. Unfortunately, we did not have a video link, so we never got the video. He pulled the handle off, and we were able to proceed. That was another one of those unbelievable moments of this mission were they just did what had to be done. He then placed a special plate on top of the cover of the instrument. This plate is extra thick with little Lexan compartments. A thin tool can be used to loosen the screws of the lid, but they would be captured in this Lexan shell.”
“Once all those screws and the lid was removed, Mass brought it close to his helmet camera, and it was breathtaking to see all those tiny screws and washers floating around in each of their little Lexan cells. They looked like little fish swimming around in their little bowls. Ordinarily such a sight in space would be a nightmare were it not for them being contained. One of my coworkers describes it best. He said that they looked like a bunch of angry bees. OMG, if they ever got out!”
“In a previous update, I described the voice ‘loops’ that we use to communicate with each other. The most exclusive of these is A/G, or Air-to-Ground. This is what Houston uses to talk to the crew in space. The only person that is normally permitted to talk from the ground is called “Capcom” (captain of communications). This person is always an astronaut. He represents the crew’s interest on the ground, and he sits right next to the Flight Director (”Flight” from Apollo 13). Any of us is allowed to listen to monitor this loop. Well tonight, we were privy to an unusual event. Flight talked directly to the astronaut crew in a strategy session for tomorrow, the final space walk day at Hubble. It was a very candid talk, and we felt the great relationship they have with each other.”
“So far, all of our space walks have been very successful. It is a testament to my coworkers that all the hardware has electrically and mechanically fit and functioned without problems. Of course, the astronaut crew deserves credit too, but there are thousands of unseen people on the ground that designed, built, tested and prepared the hardware over the course of years to get to this point. We now have two amazing imaging instruments, half a set of new batteries, new gyros, a new spectrograph, and other smaller items installed and tested. Soon (tonight) we will find out about the second spectrograph repaired today. Hubble is already the most powerful it has ever, ever been, and we have one more day to go.”
As equipment is installed and repaired, the Hubble team at Goddard Space Center in Maryland begins running tests to insure all is working properly before the shuttle departs the HST for good. One more day of repairs, with no more missions to HST planned, as a new telescope platform is already designed to eventually replace Hubble. Astronauts’ lives are at stake every day in space, a calculated risk, but one NASA does take arbitrarily. Turing the final day of STS-125, they must be sure they have successfully accomplished all they set out to do to insure HST is performing at top efficiently while delivering high quality information to scientists exploring our universe.