— The space shuttle Discovery appears to have survived its lift-off on Saturday with no critical damage to its all-important heat shield from falling foam or ice, preliminary observations suggest.
As the shuttle tried to catch up to the International Space Station on Sunday, the seven astronauts onboard scanned the leading edges of the orbiter's wings and its nosecap with a device mounted on the end of an extension to its robotic arm.
The inspections have become standard since the 2003 Columbia accident, in which foam pierced the orbiter's wing during launch. Columbia was not outfitted with a sophisticated inspection system.
Back on the ground, flight controllers were busy analysing photos, videos and data from Discovery's launch to make sure there was no damage inflicted to the orbiter.
"All the reports that came in were that we had a very typical ascent," says NASA's Mission Management Team chairman John Shannon. "There were no surprises as of yet and we're just waiting for the inspection data to come down."
Accelerometers embedded in Discovery's wing did, however, show four small blips about 110 seconds into the flight. These devices measure vibrations that could be caused by something hitting the wing.
The accelerometers have given similar readings on past flights. The four separate vibrations measured were just 10% as strong as what is required to even scuff the wing and only 5% as strong as what is necessary to crack it.
The readings show up at about the same time as tiny bits of foam insulation are known to come off a ridged section mid-way up the external tank, known as the "intertank" region because it lies between the hydrogen and oxygen tanks.
But NASA says this "popcorning" phenomenon may not be the cause of the accelerometers' signals. "I wouldn't go so far as to say strikes," says Shannon. The readings could instead be due to thermal insulation panels covering the front edge of the wing settling during the launch.
The shuttle is expected to dock with the ISS at 1705 EST (2205 GMT) on Monday. As the shuttle approaches the ISS, it will do a backflip to let the three ISS astronauts photograph the heat shield tiles on its belly to look for damage or any unusual material that may be sticking out.
By mid-day on Tuesday, mission managers expect to know whether they will ask the crew to make focused inspections of specific areas on the heat shield.
Discovery's Saturday night launch was the last planned shuttle lift-off from Launch Pad 39B. The rest of the shuttles will take off from neighbouring Pad 39A.
This is to make room for NASA's Constellation project, the successor to the shuttle programme. The planned Ares I and V rockets would take astronauts and cargo to the ISS, the Moon and perhaps even Mars.
"It's evolution," says NASA's launch director Mike Leinbach. "It's what this country wants us to do, and we can't just keep doing what we're doing. We have to move on."
There is a slim chance that Pad 39B could yet be used again for a shuttle launch. If something goes wrong during an upcoming shuttle mission to service the Hubble Space Telescope, a rescue shuttle will have to be launched quickly to get the crew back safely, bringing pad B out of retirement.
Although changes will be made to the pad to get it ready for the Ares rockets, it will remain a shuttle pad until the Hubble mission returns safely.
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