Spacewalkers Overcome Obstacles To Repair
Frank Morring, Jr./Johnson Space Center
Further mission updates are being posted at the On Space blog, where this file also appeared.
Spacewalkers managed to repair a defunct instrument on the Hubble Space Telescope today, but it seemed that everything that could go wrong went wrong.
The job wouldn't have been easy even if everything had worked as advertised, because some 111 unattached screws stood between astronaut Mike Massimino and the circuit board he needed to change out in the Space Telescope Imaging Spectrograph (STIS).
One of the first four of them got stuck, its head apparently stripped so Massimino's power tool head couldn't grip it. After trying another tool head without success, controllers here and at Goddard Space Flight Center concluded it would be safe just to break it off to get a handhold out of they way that was blocking access to the STIS cover.
Once Massimino had done that - a task that required an estimated 60 pounds of pressure on the handhold to break the stuck screw - he had to install a green capture plate on the STIS cover. The plate was designed to hold the remaining screws so they wouldn't get loose and foul the inside of the telescope.
That job was a little tricky too, because a gasket apparently was out of place and Massinimo had to straighten it. He did, and the plate slipped into place.
Murphy wasn't done yet. With the capture plate in place, Massimino pulled out a special "mini" power tool to crank the screws out. It wouldn't start.
"Oh for Pete's sake," he exclaimed.
Ultimately Massinimo was sent back to the airlock for a spare tool, and to recharge the oxygen in his spacesuit because it was clear the extravehicular activity (EVA) would run longer than the planned six and a half hours. The backup tool worked, and the veteran Hubble repairman made fairly short work of unscrewing the fasteners and pulling off the cover with the capture plate. The loose screws could be seen rattling around inside their plastic enclosures.
Next on the agenda was replacing the power supply circuit board in the STIS that failed in 2004. That job went well, but it took a little wrestling match for Massinimo and EVA partner Mike Good to get the capture plate and STIS cover into a stowage box securely. After that Massinimo was able to install a replacement cover that substituted two simple latches for all the screws, finishing the job more than two hours late. The task took so long that controllers here decided not to tackle the second job of the spacewalk -- replacing some degraded thermal blankets on one of the telescope's doors - and ordered the two spacewalkers to wrap it up.
Photo credit: NASA TV
