Shuttle's Heat Shield Dings Appear to be Minor, NASA Says

This story was updated at 8:14 p.m. EDT.

HOUSTON - Astronauts discovered a trail of small dings in the vital heat shield of their space shuttle Atlantis on Tuesday, but NASA said the damage appears only minor and is not expected to be a concern.

The dings were caused by launch debris that fell from the shuttle?s external tank as Atlantis rocketed toward the Hubble Space Telescope on Monday afternoon. Astronauts spotted the damage while scanning Atlantis with an inspection pole tipped with cameras and laser sensors.

LeRoy Cain, NASA?s deputy shuttle program manager, said that even though the damage to Atlantis appears minor, a crack team of image analysis experts is hard at work evaluating the pictures beamed to Earth by shuttle astronauts during an in-depth inspection today.

?This is not something that we?re very concerned about but we want the team to do our normal assessment and evaluation of it,? Cain told reporters here at NASA?s Johnson Space Center. ?And we?ll do that overnight tonight.?

NASA has Atlantis' sister ship, the shuttle Endeavour, ready to launch as soon as Monday in the unlikely event that Atlantis is damaged beyond repair and its crew needs to be rescued in space. But Cain said that so far, nothing found on Atlantis has given NASA any reason to even consider a rescue mission.

?The chances of that being necessary are exceeding low,? Cain said.

Atlantis commander Scott Altman and his crew are flying an 11-day mission to overhaul the 19-year-old Hubble Space Telescope for the fifth and final time. They are due to arrive at the space telescope on Wednesday. Hubble closed its camera eye with a protective lid today to protect the delicate optics inside from debris during the service call.

Five consecutive spacewalks are planned to install two new cameras and repair two others that were never designed to be fixed in space among other upgrades.

Launch debris spotted

NASA believes the dings were scratched into the side of Atlantis about 106 seconds after the shuttle launched into space. A camera on the shuttle?s attached external fuel tank caught a piece of debris at that time, and wing-mounted sensors also recorded a slight impact then, too.

An image released by NASA shows the dings as white pockmarks in the black tiles caused by a piece of debris that appears to have scraped across a 21-inch (53-cm) section of the heat shield. The debris made multiple hits on four of the heat-resistant tiles lining the forward right side of the shuttle just ahead of where its body and starboard wing meet.

?At this point, what we?re interested in is, ?Is it critical damage and if so, what would we do about it??? Cain said. ?Today, the answer is that it certainly doesn?t look like it will be an issue for us.?

Mission Control radioed Atlantis late Tuesday to say the dings appear so mild that the astronauts will not have to take an extra look at them with the inspection pole later in the mission.

?Alright! You've got some happy [spacewalk] campers up here," Altman called back.

Mission Control did ask the Atlantis crew to keep trying to send images from a stubborn digital camera mounted to the spacecraft?s belly. The camera may have spotted where the debris came from on Atlantis? external tank, but is having trouble relaying the images back to Earth.

The astronauts also plan to perform a standard second inspection of the shuttle before landing to be sure it hasn?t been damaged by space junk. The region of space around Hubble?s 350-mile (563-km) orbit is littered with space debris, adding a slightly increased risk to the shuttle mission.

NASA has been on vigilant watch for any shuttle damage from launch debris since 2003, when a piece of fuel tank foam struck the shuttle Columbia led to its destruction during re-entry. Seven astronauts were killed in the disaster.

Now, astronauts scan their shuttle heat shields at least twice every mission. Atlantis is carrying a standard suite of repair tools just in case they might be needed.

Launch pad also damaged

While the Atlantis crew works in space, NASA is examining unexpected damage on Earth to the shuttle?s launch pad at the Kennedy Space Center in Cape Canaveral, Fla.

The blast from Atlantis? engines damaged some nitrogen and pressure lines, as well as a 25-square-foot section of flame retardant material lining the trench beneath the shuttle?s Launch Pad 39A, NASA spokesperson Allard Beutel told SPACE.com from the Kennedy Space Center in Florida. The so-called flame trench is used to funnel rocket exhaust away from the spacecraft during liftoff.

Beutel said pad workers are expected to be able to repair the launch pad damage in time for the planned June 13 blast off of NASA?s next shuttle mission.

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 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