CAPE CANAVERAL, Florida (Reuters) - The U.S. space shuttle Atlantis apparently was hit by a piece of debris that nicked part of its heat shield but the damage appeared very minor, NASA said on Tuesday.

Atlantis and its seven-member crew blasted off from Florida on Monday on an 11-day mission to repair the Hubble Space Telescope.

It will be the U.S. space agency’s last chance to tinker with the telescope -- which has vastly expanded scientists’ knowledge of the universe -- before NASA ends the shuttle program in 2010.

NASA told the Atlantis crew additional inspections might be needed of the area where the ship’s right wing joins the fuselage around where the debris hit. But agency officials said later that a detailed inspection was unlikely.

Early analysis of images relayed by the crew revealed a scratch about 21 inches long across four heat-resistant ceramic tiles.

“It looks like something just kind of chattered its way down along that edge,” deputy shuttle program manager LeRoy Cain said at a briefing, showing a picture of unidentified debris that hit the ship 104 seconds after liftoff. “This is not something we’re very concerned about.”

SHALLOW SCRATCH

NASA was trying to establish exactly what had caused the scratch, but it is “relatively shallow” and is not in a critical area that would endanger the ship during the extreme heat of reentry, Cain said.

The liftoff also damaged about 25 square feet (2.3 square meters) of the shuttle’s launch pad flame trench, NASA said.

In 2003 space shuttle, Columbia, disintegrated as it was returning to Florida, killing its seven crew members because of heat shield damage from a piece of foam insulation that fell off the fuel tank during launch.

NASA redesigned the tanks so they would shed less foam and implemented in-orbit inspections.

Technicians were trying to retrieve pictures from a digital camera in the shuttle’s belly that should have photographed the external fuel tank after it was jettisoned.

The Atlantis astronauts spent Tuesday panning a sensor-studded boom over the ship’s wings and nose cone, a routine task on all shuttle missions since the Columbia accident.

Slideshow ( 15 images )

After that, NASA also drew up plans to shelter shuttle astronauts aboard the International Space Station in case their ship was too damaged to fly through the atmosphere for landing.

Since the Atlantis is heading to the Hubble Telescope and will be too far away to reach the space station, NASA has a second shuttle on the launch pad ready to mount a rescue if needed. Atlantis is due to reach the Hubble Telescope on Wednesday.

While the shuttle astronauts scoured their ship for damage, teams on the ground inspected the launch pad.

Slideshow ( 15 images )

Damage was discovered in an area known as the flame trench, which lies beneath the shuttle’s mobile launcher platform. The affected area deflects flames from the solid rocket boosters.

The launch pad is next scheduled to be used for a June 13 mission to the International Space Station.

“Right now there’s no indication that this would delay launch,” said Kennedy Space Center spokeswoman Candrea Thomas.

The launch pad damage does not affect NASA’s contingency provisions for a standby rescue mission for the Atlantis crew, which would be launched from different pad.

The Atlantis astronauts plan five days of spacewalks to install two new cameras in Hubble, replace positioning gyroscopes and batteries and repair two broken science instruments.

It is NASA’s fifth and final servicing mission to the observatory, which has been operational since 1990. Hubble is one of the most productive and ground-breaking science instruments of modern day astronomy.

With the upgrades, NASA hopes to keep the Hubble Telescope running until at least 2014.