CAPE CANAVERAL, Fla. – Space shuttle Atlantis is heading home this morning after a late inspection of the ship’s heat shielding Wednesday found nothing wrong.

The inspection was prompted by Tuesday’s sighting of an unknown object that apparently shook loose from Atlantis during pre-landing checkouts of the shuttle’s body flaps and steering thrusters. Eight hours of surveys using cameras on Atlantis’ robot arm and a sensor-laden 50-foot boom failed to detect any sign the object was dislodged from the ship’s critical heat armor.

As a result, NASA managers have cleared Atlantis for landing. The identity of the object, as well as several other small pieces of debris seen floating from the shuttle during the past two days, remains a mystery.

“Nothing was found to be missing or damaged from the thermal protection system – the heat shield of the space shuttle Atlantis – or, in fact, any other part of the shuttle,” said Wayne Hale, NASA’s shuttle program manager. “We feel very confident that we’re heading for a good landing opportunity.”

Weather permitting, Atlantis will touch down at the Kennedy Space Center at 6:21 a.m. today. Meteorologists are forecasting near-perfect conditions at Cape Canaveral this morning, with a few scattered clouds and light winds.

The crew is scheduled to fire the shuttle’s braking rockets at 5:14 a.m. to slow the spacecraft and begin its fiery plunge through Earth’s atmosphere. Atlantis’ flight path will carry the ship across the Yucatan Peninsula and the Gulf of Mexico before it makes landfall over Florida near Fort Myers and zips northeast to Cape Canaveral.

A second KSC landing opportunity is available at 7:57 a.m. The shuttle’s backup runway at Edwards Air Force Base in Southern California’s Mojave Desert will not be activated Thursday, but would be available if the landing is delayed until Friday.

Early Wednesday, Atlantis’ six astronauts began inspecting the shuttle using a camera on the orbiter’s robot arm. Once that work was complete, the crew broke for lunch and mission managers studied the video for any signs of damage to the ship’s thermal skin.

Although nothing of concern was found, shuttle officials ordered a second round of inspections using laser sensors and a camera on the boom to be safe. The crew was carrying out the work when shuttle commander Brent Jett reported three more objects floating away from Atlantis.

Jett said one object had the appearance of a “a reflective cloth or a metallic looking-cloth.” Another astronaut compared the items to a piece of foil and a pair of rings.

Lead flight director Paul Dye later explained it’s not unusual for crews to see bits of debris as they orbit the Earth. Often, he said, the mystery objects are pieces of ice or lint that have come from the shuttle.

“It’s amazing how something in bright sunlight can look much bigger than it really is,” Dye said.

While no damage was discovered in the inspections, NASA managers noted that two objects previously seen on the ship’s belly are no longer there. One is a strip of ceramic fabric called a gap filler that had been lodged between two of the shuttle’s heat-resistant tiles. The other is a small piece of an orange plastic shim used in tile preparations before flight.

Both objects had been visible earlier in the mission but were not seen during Wednesday’s inspections. It’s unclear if the missing items were among the two objects seen Tuesday.

Hale said the shim was “most likely the culprit.”

“It was there before,” he added. “It’s not there now. It was most likely shaken loose during the flight control system checkout. We probably will never know for sure.”

(c) 2006, The Orlando Sentinel (Fla.).

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