Thisstory was updated at 7:43 p.m. EDT.
HOUSTON - Apair of spacewalking astronauts enhanced the Hubble Space Telescope?s sense ofdirection with some new gyroscopes Friday, but had trouble during the gruelingupgrade because of a stubborn part.
Atlantisastronauts Michael Massimino and Michael Good spent nearly eight hoursreplacing four of the 19-year-oldHubble?s old gyroscopes with new ones - a top priority task - but anelectronics box containing the last set refused to fit properly.
?No joy,?Good said when the balky box containing the last two new gyroscopes did notlock in place for the second time. ?It just doesn?t want to fit.?
Thespacewalkers were prepared, however, and installed a backup set of refurbishedgyroscopes that NASA packed aboard Atlantis just in case. The spare set were anolder design with parts rebuilt from earlier units removed from Hubble in 1999,NASA officials said. It will not hamper the telescope?s pointing skills, theyadded.
Theobservatory relies on six spinning gyroscopes to maintain its orientation inspace and keep its camera eye steady while catching its trademarkimages of the universe. Three of Hubble?s old gyroscopes have failed overthe years and the telescope was running on two, keeping a last one as a spare,until Friday?s successful fix.
?Mass andBueno, my friend Leonidas has a few words for you guys that are appropriateright now,? said Atlantis commander Scott Altman, using the spacewalkers?nicknames and referring to the Spartan king who died fighting against thePersians in the Battle of Thermopylae in 480 B.C. ?Remember this day men, forit will be yours for all time.?
Thegyroscope trouble pushed the astronauts nearly two hours behind schedule.Mission Control extended the spacewalk beyond its initial 6 1/2-hour durationto squeeze another vital task: replacing three of Hubble?ssix batteries, which had not been changed since the telescope launched in1990.
Massiminohad to top off his spacesuit?s oxygen supply so he didn?t run out of air duringthat final chore, which stretched the orbital work to eight hours and 56minutes. Good?s spacesuit batteries were his top consumable, but MissionControl told him he had enough for the extended work.
?I don'thave that much on internal battery," a tired Good replied. "I'm righton the edge now, but I?m willing to give it a try.?
Thegyroscope and battery tasks were NASA?s top priority for the Atlantis? entire11-day mission since the basic maintenance was crucial in order to keepHubble running. The flight is NASA?s fifth and final service call to theiconic space telescope.
It was thesecond of five consecutive excursions to extend the aging Hubble?s orbital lifethrough 2014. A different team of spacewalkers installed a powerful new camera,docking ring and fixed the computer data unit that beams the telescope?s imagesback to Earth.
?We?re along way already to greatly extending the longevity of the Hubble observatory,?Hubble?s senior project scientist Dave Leckrone at NASA?s Goddard Space FlightCenter told reporters late Friday.
OnSaturday, the astronauts will attempt an unprecedented repair for Hubble?smain imager, the Advanced Camera for Surveys, which has been offline since2007. Another set of batteries will be replaced in a Monday spacewalk.
Massiminohad to squeeze his tall frame inside Hubble to replace some of the gyroscopes.At times, both he and Good were wedged in and had to take great care not tobump each other or Hubble?s delicate star trackers near the gyroscopes.
Thespacewalk began at 8:49 a.m. EDT (1249 GMT) and ended up being the 8th longestin history.
Theastronauts had a brief scare early on when Massimino?s spacesuit radio wentout. But he quickly regained radio contact with Atlantis and Mission Control. ?Thatwas scary,? Good said.
?A littlebit,? Massimino replied.
Thespacewalk ran so long, Mission Control had to push back the Atlantis crew?sbedtime by an hour tonight and give them extra time to sleep in tomorrow. Itmarked the first spacewalk for Good and the third for Massimino, who ended theday with a total spacewalking time at 22 hours and 42 minutes.
?It wasreally great going out there today for the first time,? Good said as he thankedhis crewmates and Mission Control. ?An incredible effort.?
SPACE.comis providing continuous coverage of NASA's last mission to the Hubble SpaceTelescope with senior editor Tariq Malik in Houston and reporter ClaraMoskowitz in New York. Clickhere for mission updates, live spacewalk coverage and SPACE.com'slive NASA TV video feed.
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