CAPE CANAVERAL, Fla. (AP) - The Atlantis astronauts uncovered a 21-inch stretch of nicks on their space shuttle Tuesday, but NASA said the damage did not appear to be serious.

The damage was likely the result of debris that came off the fuel tank shortly after liftoff Monday. The astronauts were inspecting their ship while racing to the Hubble Space Telescope when they came across the nicks spread over four to five thermal tiles.

A NASA photo shows what appears to be about 10 white scuff marks - officials hadn't counted how many yet - around the edge of the shuttle where the right wing joins the fuselage and the belly curves up to the top of Atlantis.

"It doesn't look very serious," Mission Control said. "Those tiles are pretty thick. The nicks look to be pretty small."

And a decision late Tuesday by NASA managers indicated that the problem was minor and wouldn't require much more examination.

This repair mission is especially risky - a rescue shuttle is on standby for the first time ever - because of the debris-littered orbit of Hubble. Unlike other space flights, the astronauts can't reach the international space station because it is in a different orbit than the telescope.

NASA managers weren't too worried Tuesday, saying this type of damage looks similar to nicks seen in the past five or six missions that were safe.

"The area is not as critical" as other parts on the shuttle wing, deputy shuttle program manager LeRoy Cain said in a Tuesday afternoon news conference. "The damage itself appears to be relatively shallow and it's not a very large area of damage."

The debris strike was detected in launch images as well as sensors embedded in the wings.

Damage to the shuttle during liftoff has been a worry for NASA since Columbia was doomed by a chunk of fuel-tank insulating foam that broke off during launch in 2003. Columbia's left wing was punctured, along a vulnerable edge and at the time NASA managers ignored an engineer's request for more photos of potential damage. NASA said the nicks on Atlantis are in a less sensitive location.

NASA managers initially said they wanted to spend Tuesday night and Wednesday looking at photos of the damage to see if a more detailed inspection of the tiles would be needed on Friday. But just before astronauts went to sleep, Mission Control told them that the examination with Atlantis' robot arm was not required.

Even before damage was discovered, NASA was preparing shuttle Endeavour to rush to the astronauts' rescue if needed. Nothing so far has been found that would require a rescue.

Atlantis will catch up with the 19-year-old Hubble on Wednesday. The astronauts will capture the aging observatory and, the next day, begin the first of five grueling spacewalks to install new cameras and equipment and repair some broken science instruments.

Meanwhile, Atlantis' launch pad took more of a beating than usual during Monday's launch. The heat-resistant material that covers the bricks beneath the pad was blasted off a roughly 25-square-foot area. Some nitrogen gas and pressurized air lines also were damaged.

The damage to the bricked flame trench - which deflect the flames at booster rocket ignition - was near a previously repaired spot but not an area severely battered last year. Monday's damage was not as bad, said NASA spokesman Allard Beutel.

And the other launch pad, where Endeavour sits, was struck twice by lightning late Monday, but the shuttle appears to have no damage because of a lightning protection system, Cain said.


AP Science Writer Seth Borenstein contributed to this report from Washington.

Copyright 2009 The Associated Press.