Final spacewalk leaves like-new Hubble ready for its final bow
Astronauts made all the needed repairs, giving the telescope five to 10 more years of life.
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Five successful spacewalks on five consecutive days have repaired and refurbished one of the most revolutionary observatories in the history of astronomy.
It's a bittersweet moment for those on the ground as well as those on orbit. A successful release of Hubble tomorrow marks the beginning of the end for the venerable telescope – its final five to 10 year period of research before it is sent plummeting into the Pacific Ocean.
But what a five to 10 years it is expected to be.
Targets range from galaxies in the very young universe billions of light-years away to planets orbiting other stars in the Milky Way.
When it was launched in 1990, Hubble had five instruments. But embarrassing vision problems forced its architects to replace one instrument with a box of optics designed to correct the problem. Successive upgrades to the other instruments has rendered the box obsolete. It was removed on this flight and replaced with a cosmic-origins spectrograph – once again returning Hubble to five operating instruments.
In what experienced Hubble-repair hands have called true Hubble fashion, tasks that were easy in training turned out to be harder on orbit. By contrast, some of the tougher training tasks in NASA's oversized training pool, designed to simulate moving in weightlessness, were easier in space.
Still, spacewalkers had to handle the unexpected.
In wrapping up today's 8 hour, 2 minute outing, mission specialist John Grunsfeld bumped into one of the telescope's low-gain antennas while he was retrieving a piece of tape floating near Hubble during after-work clean-up. Clearly crestfallen, Dr. Grunsfeld was relieved to hear that the antenna was still working. As Grunsfeld wrapped up his work, a crewmember inside Atlantis's cabin radioed out: "Consider it a goodbye kiss, John."
Yesterday, mission specialist Mike Massimino had his own challenges repairing the Space Telescope Imaging Spectrograph – an instrument never designed for on-orbit repairs. Before he could get to the electronics card he had to replace, he had to remove a handrail, as well as a cover plate that was fastened with 111 tiny screws. One reluctant bolt on the handrail failed to yield to successively more powerful twists from the power tool Dr. Massimino was using – a tactic that had worked on a similarly balky bolt during the previous day's spacewalk. In the end, one final tug from Massimino himself freed the handrail.
In the process, the power tool's battery had failed, forcing him to go back to the air lock for a fresh battery and some additional oxygen for his space suit to ensure he'd have enough to finish the work.
By the end of Sunday's spacewalk, every task on the crew's long Hubble to-do list had been completed. And every test that engineers on the ground have given the newly installed or repaired instruments have returned the message: I'm OK.
"They accomplished more than we actually expected them to accomplish," says Dr. Burch Of Goddard Space Flight Center. It will now take weeks to perform setup tasks, such as aligning and focusing the instruments, he adds. The first "early observation" images should be ready in early September, he says.
Back on Atlantis, the fact that this would be astronauts' final house call on the telescope wasn't lost on the crew. From his perch on the work platform fastened to the shuttle's robotic arm, Grunsfeld snapped pictures for posterity as he and partner Drew Feustel tidied up the payload bay in preparation for releasing Hubble tomorrow.
This was Grunsfeld's third Hubble repair mission. As he eased his way to the air lock to join Dr. Feustel, the Earth slowly turned beneath the upside-down orbiter. Dan Burbank, the spacecraft communicator in mission control, called out: "John, take a moment more, you've earned it."