One small (space) step for Hubble

Despite glitches that added nearly an hour to what should have been a 6-1/2 hour spacewalk, astronauts from the space shuttle Atlantis accomplished "99.9 percent" of their objectives Thursday in trying to restore the Hubble Space Telescope to health. It was the first of five planned spacewalks for the mission.

The astronauts added a potent new camera to the Hubble Space Telescope and replaced a critical system that serves as the observatory's "grand central station" for routing science and engineering data to and from Earth. The system failed last September, forcing NASA to reschedule this mission.

During their outing Thursday, mission specialists John Grunsfeld and Drew Feustel removed a grand-piano-sized camera designed to image wide swaths of sky and planets and replaced it with a more capable successor. They also replaced the data-handling system and performed other tasks to get Hubble ready for its final years of work.

Ground controllers reported that the camera had successfully undergone its "aliveness" tests – essentially, powering up properly. Engineers at the Goddard Space Flight Center in Greenbelt, Md., are still putting the camera through its system checks to ensure everything is functioning. As for the data system, that has cleared both types of tests.

Despite the overall thumbs-up that mission managers have given the day, "it's been a day of surprises," according to mission specialist Dr. Feustel, who radioed that observation to mission control as he and Dr. Grunsfeld wound down their workday.

Surprise No. 1 came when a key bolt linking the old camera to Hubble wouldn't budge. This led to some tense moments as the spacewalkers and engineers on the ground worked through a list of backup procedures to free the camera. The procedure that worked – essentially ramping up the twisting power of the tool Feustel was using to remove the bolt – was "near the bottom of the list," says David Leckrone, senior project scientist for Hubble. That approach ran the risk of shearing the bolt, which would have stopped the camera replacement dead in its tracks.

"I'm five years older now than when I came to work this morning," Dr. Leckrone quipped during a post-spacewalk briefing.

But with the installation of the camera and the data-handling center, "We can sleep pretty well tonight, knowing that's accomplished," he says.

In addition, the spacewalkers were asked to install three new latches on doors to the telescope's instrument bays. The latches are designed to make it easier to open and shut the bay doors on subsequent spacewalks and ensure that the doors close tight enough to keep light out of the instrument bays. But they could install only two because of complications at the third latch's location.

All in all, unexpected glitches turned a 6-1/2 hour spacewalk into a seven-hour, 20 minute excursion. "I'm ready for a hot shower and a good meal," Grunsfeld said as he headed into the air lock.

The spacewalk may have gone into overtime and required some seat-of-the-spacesuit changes, but astronauts still nabbed fleeting moments for some cosmic sightseeing.

As the team gathered up its tools and headed for the air lock at the end of its spacewalk, Feustel looked down to Earth and marveled at the view. "Is that California and Baja? Cool!" he said.

Mission specialists Mike Massimino and Michael Good head out for the second spacewalk at 8:16 a.m. Eastern Time. Friday. They are slated to replace batteries on the space telescope and sensors that help ensure the telescope changes its position properly for each new set of observations it is commanded to take.