This story was updated at 12:51 p.m. EDT.
CAPE CANAVERAL, Fla. - Astronauts aboard the space shuttle Atlantis inspected their spacecraft?s vital heat shield for damage Tuesday while en route to the Hubble Space Telescope to perform one last service call.
The spaceflyers used an inspection pole tipped with laser sensors and cameras to seek out any dings in the heat-resistant panels lining the spacecraft?s wing edges and nose.
The shuttle?s heat shield health will be a key concern for NASA throughout the risky mission to overhaul Hubble. The space agency has put the shuttle Endeavour on standby to fly a rescue mission to retrieve the Atlantis astronauts if their spacecraft is damaged beyond repair.
Atlantis and its crew of seven astronauts launched toward Hubble on Monday to begin NASA?s fifth and final mission to the 19-year-old space telescope. After the successful liftoff, NASA technicians were surprised to find damage at the launch pad from the fiery blast of the shuttle?s rocket engines, agency officials said.
Atlantis is due to arrive at Hubble on Wednesday and is about 8,000 miles (12,874 km) and closing on the telescope. The astronauts plan to perform five consecutive spacewalks to add two new cameras, repair two other instruments never designed to be repaired in space and perform other maintenance.
Shuttle looks good
Some pieces of debris were spotted falling from the shuttle?s external tank and boosters during launch, but none of the pieces appeared to cause any damage, NASA officials said.
?They?re very minor from what we could observe,? NASA?s space operations chief Bill Gerstenmaier said after launch.
NASA has kept a close watch on shuttle heat shield health since 2003, when a piece of fuel tank foam struck the Columbia orbiter?s wing and led to its destruction and the loss of seven astronauts. Now, astronauts inspect their shuttle heat shield twice on every mission.
Today, Atlantis commander Scott Altman and his crew conducted extended version of heat shield scans used on missions bound for the International Space Station. The scan is one of two to make sure Atlantis is not damaged by launch debris or space junk.
The area around Hubble?s 350-mile (563-km) orbit is littered with space trash, giving Atlantis a slightly higher chance of being struck by debris or micrometeorites, NASA officials have said. But the risk is still within NASA?s acceptable limits, they added.
Back on Earth, NASA technicians are evaluating the damage to Atlantis? launch pad caused when the shuttle blasted off Monday. The damage was spotted in the pad?s flame trench, which funnels rocket engine exhaust away from a shuttle during liftoff.
Some nitrogen and pressure lines were damaged, as well as a 25-square-foot section of the heat-resistant coating that covers the bricks beneath the launch pad, NASA spokesperson Allard Beutel told SPACE.com. The damage is less severe than that seen during a launch last year, and can be repaired in time for NASA?s next mission in June, he added.
Today?s shuttle survey will take nearly 10 hours to complete - about twice as long as normal - because the Atlantis crew must inspect the thousands of black, heat-resistant tiles covering the spacecraft?s underbelly. On missions to the space station, the same area is covered in photographs taken by astronauts inside the orbiting laboratory while the shuttle performs an orbital back flip nearby.
?What we?ve added for this flight is a belly tile survey,? said shuttle flight director Tony Ceccacci, adding that Atlantis astronauts will go nearly nine hours without a break to cram the extended survey into an already tight schedule. ?Usually, in a station flight, you break that up with a meal, we don?t have that luxury with the timeline.?
Atlantis astronauts used the shuttle?s robotic arm to inspect the outside of the crew cabin and cargo bay. To see the hard-to-reach spots on Atlantis? belly, astronauts will reach under the spacecraft with the 50-foot (15-meter) inspection pole, which double?s the length of the shuttle?s robotic arm.
Mission specialist Megan McArthur, Atlantis? robotic arm expert, will lead the inspection work, but the long job will be shared among the entire crew. The chore, she said, is not too different than those used on station-bound shuttle missions, just longer.
?They?re very similar, so it?s a very well understood operation,? McArthur said.
SPACE.com is providing continuous coverage of NASA?s last mission to the Hubble Space Telescope with senior editor Tariq Malik at Cape Canaveral and reporter Clara Moskowitz in New York. Click here for mission updates and SPACE.com's live NASA TV video feed.
- New Video Show - Hubble's Final Shuttle Service Call
- New Video - The Hubble Rescue Mission Revealed
- Image Gallery - Hubble?s Latest Views of the Universe: Part 1, Part 2