HOUSTON - The Hubble Space Telescope will get its final tune-up Monday by a pair of spacewalking astronauts, the last two people who will ever touch the aging observatory.
The spacewalkers are Atlantis astronauts John Grunsfeld and Andrew Feustel, who plan to float out into their shuttle?s cargo bay and add new batteries, insulation and a guidance sensor to the 19-year-old Hubble.
Today?s orbital work is slated to begin around 9:16 a.m. EDT (1216 GMT) but could start early since the crew is ahead of schedule, NASA officials said. It will mark the last of five ambitious spacewalks in five days by the Atlantis crew to add upgrades and make repairs aimed at extending Hubble?s mission life to at least 2014, if not beyond.
The 11-day mission is NASA?s fifth and final service call on the observatory before the space agency retires its shuttle fleet next year, so there?s a push among Atlantis? crew to get everything done. After this mission, Hubble will never see humans again.
?It?s kind of like being in a horse race, we?re in the homestretch,? Hubble program manager Preston Burch told reporters here at NASA?s Johnson Space Center late Sunday. ?We?ve done just about everything we set out to accomplish.?
Final upgrades on tap
Today, Grunsfeld and Feustel plan to replace a second set of batteries and one of Hubble?s old fine guidance sensors.
About the size of a baby grand piano, the sensor is one of three that help the space telescope keep its camera eye steady. They can also be used for astrometry, the ultra-precise science of star positions and their motions.
The spacewalkers also plan to install new thermal insulation panels to ward off Hubble?s deterioration from the harsh space environment. Grunsfeld and Feustel plan to add at least one new insulation panel, and may add a second one that a different team of spacewalkers were unable to install on Sunday when they ran out o time.
Over the course of their back-to-back spacewalks, the seven Atlantis astronauts have installed a new camera for deep-space viewing, a super-sensitive spectrograph to study the composition of the universe, and resuscitated two other instruments - Hubble?s advanced camera and an older spectrograph - both of which were never built to be fixed in space.
The vital maintenance, like today?s spacewalk, has added new batteries, gyroscopes and a science data computer. The astronauts also added a docking ring so a robotic spacecraft can latch onto Hubble years from now and send it into the Pacific Ocean when its science mission is over.
The $1.1 billion mission caps a $10 billion investment in Hubble since its inception. The Atlantis crew will release Hubble back into its 350-mile (563-km) orbit on Tuesday.
Hubble hugger?s last chance
That Grunsfeld, an astrophysicist-turned-astronaut, is part of Hubble?s last spacewalking crew is fitting in a way. He?s making his third trip to the iconic observatory and has a reputation as being Hubble?s biggest fan.
?He is the chief Hubble hugger of the astronaut corps,? Burch told SPACE.com late Sunday.
Like fellow Atlantis spacewalker Michael Massimino and the shuttle?s skipper Scott Altman, Grunsfeld was on NASA?s 2002 service call on Hubble. But he also visited the observatory in 1999.
On this flight, where Grunsfeld has served as the spacewalking chief, he is performing three out of the five spacewalks alongside Feustel. He told SPACE.com before launch that while he expect to stay focused on his orbital work, there will be some time to reflect on today?s last-ever spacewalk on the Hubble Space Telescope.
?Every time we climb on the telescope, you know grabbing a handrail, it?s giving Hubble a hug,? Grunsfeld said. ?At the very end, we?re going to take one last look at the Hubble and just go, ?wow,? you know. This has been quite an experience.?
SPACE.com is providing continuous coverage of NASA's last mission to the Hubble Space Telescope with senior editor Tariq Malik in Houston and reporter Clara Moskowitz in New York. Click here for mission updates, live spacewalk coverage and SPACE.com's live NASA TV video feed.
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