Shuttle Checks Out for Landing

NASA officials on Wednesday cleared the space shuttle Atlantis to land this morning, after final inspections of the spacecraft’s skin turned up no evidence of damage from space debris.

“We are cleared for entry,” said shuttle program manager N. Wayne Hale Jr. “Nothing was found to be missing or damaged.”

Atlantis had been scheduled to land Wednesday, after a 12-day mission that included three spacewalks to install a truss and a set of solar arrays on the International Space Station. The landing was postponed when astronauts on Atlantis saw a piece of debris floating away from the shuttle.

Because the incident appeared to coincide with readings showing that one of the wings may have been struck, NASA asked the crew to scan the craft’s insulating tiles and reinforced carbon panels that protect it from the more than 2,500-degree heat of reentry.

The six-person crew spent much of Wednesday inspecting the craft using a video camera on a robotic arm and a boom extension with a laser scanner able to reveal tiny imperfections.

“I really am very confident we are in good shape,” said Paul Dye, the shuttle’s lead flight director at Johnson Space Center in Houston. The first opportunity to land in central Florida was at 3:21 a.m. PDT.

Steve Stich, the entry flight director, said the weather forecast was good for landing today.

NASA officials said they weren’t sure what the debris was. The most likely explanation is “shim stock,” a 2-by-5-inch piece of red plastic that serves as a spacer when heat-resistant tiles are installed. In earlier inspections, one of the spacers was seen sticking out from the underside of the craft. The latest inspection showed it had vanished.

“It was there before; it’s not there now,” Hale said.

While performing the inspection Wednesday, the crew saw three more possible pieces of debris floating by. That brought to five the number of objects spotted over two days. Besides the apparent shim stock, on Tuesday the crew saw what NASA engineers believed was a plastic bag.

Dye said engineers were still examining pictures of the new objects, but NASA officials said they weren’t concerned about them posing a threat to Atlantis, whatever they were.

Hale said orbiting space debris was an issue of continuing concern to NASA. He said the military was tracking 13,000 pieces of debris in space, ranging from the very large, such as spent rocket bodies, to the very small. There is so much junk in space that the space station and shuttles must sometimes alter their orbits to avoid collisions, Hale said.

Recent shuttle crews have added to the number, losing bolts and a spatula during spacewalks.

Some satellites have been damaged by collisions with debris, and shuttles sometimes return bearing evidence of small debris strikes, Hale said. The Hubble Space Telescope has been repeatedly hit.

NASA training emphasizes the need to avoid contributing to the orbiting dump in space. “We have a little more work to do” on the issue, Hale said.

Another concern was eliminated when analysts were able to link an engine test to instrument readings indicating possible impacts to a wing. Firing the engines sends a shudder through the ship, setting off the instrument warnings, officials said.

Concern over impacts to the wings grew out of the Columbia accident in 2003, when the left wing was catastrophically damaged by a piece of insulating foam that came off the shuttle’s external fuel tank during launch.

With the safety concerns alleviated, NASA managers turned their attention to what Hale called an “outstanding” mission that had “set up in a very good way for the next set of assembly flights.”

The next scheduled mission is Dec. 14, but Hale said he hoped to move it up a week to avoid interfering with the Christmas holidays.

During that mission, spacewalkers will reconfigure the space station’s power and cooling system and wire the new solar arrays into the space station’s main power grid.

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john.johnson@latimes.com