Shuttle astronauts spotted three more pieces of debris floating in space outside Atlantis early Wednesday, but officials said it didn’t seem their appearance would prevent a landing attempt on Thursday.

The objects were sighted during stepped-up inspections a day after the discovery of two other mysterious objects forced a postponement of the planned Wednesday landing.

NASA downplayed the discovery of Wednesday’s objects, saying the important question was whether an in-depth inspection of the shuttle showed no damage to Atlantis’ heat shield.

“It’s not uncommon to see little bits of pieces of things floating by,” said flight director Paul Dye.

Atlantis commander Brent Jett described the objects as two rings and a piece of foil. He told Mission Control the first object, about 100 feet from the shuttle, was “a reflective cloth or a mechanic looking-cloth. … It’s not a solid metal structure.”

Before the postponement Tuesday, Atlantis had been scheduled to touch down just before daybreak Wednesday, when the weather forecast wasn’t favorable for landing anyway. The landing time was reset for early Thursday, but could be put off until Friday.

The extra inspection with the boom followed a 4 1/2-hour inspection using cameras on the space shuttle’s robotic arm early Wednesday

NASA managers didn’t see anything that concerned them during the initial inspection but decided to go ahead with the boom inspection anyway as an extra safety precaution. The boom, which is attached to the shuttle’s 50-foot robotic arm and has cameras and sensors at its end, can look at hard-to-reach places.

The first object sighted appeared to drift away when landing systems were put through a normal but bumpy trial run early Tuesday morning.

Worry about whether it came from a crucial part of Atlantis was enough to make NASA postpone the landing. NASA officials said their best guess was that the object was a plastic filler placed in between thermal tiles which protect the shuttle from blasting heat.

After being unable to determine what the object was Tuesday, NASA managers opted to spend early Wednesday making sure the shuttle was in good shape instead of concentrating on solving the mystery.

The engineers’ main concern was the status of the all-important heat shield, because a damaged shuttle skin led to the 2003 demise of the shuttle Columbia.

“We are going to verify that our critical heat shield is in good shape for entry to the best of our ability,” shuttle program manager Wayne Hale said.

Beginning with the right wing at 12:15 a.m. EDT, astronauts slowly swept the shuttle’s robot arm above and along Atlantis’ heat shield. The two cameras on the arm looked for any damage to the heat shield from the mystery object. NASA doesn’t know how big the object is because there was no frame of reference or distance in the video that captured the dark rectangular shape.

A second mystery object was spotted midday Tuesday and photographed by astronaut Dan Burbank. Jett said the object looked like a picture hanging clip. It may be a garbage bag, which would unlikely be a damage risk, but the issue will be moot if the heat shield looks good, Hale said.

“So far we do not know the identity of the two things that floated away yesterday,” Houston spacecraft communicator Hans Schlegel told Atlantis Tuesday night. “Today we want you to survey the vehicle to make sure it’s ready for entry. Last night we already surveyed from ground.”

Mission controllers also used cameras at the end of the robot arm to take pictures around the payload bay while astronauts slept on Tuesday.

If astronauts are too tired from the shield inspection process Wednesday, NASA could postpone landing until Friday, Hale had said.

NASA has not worked on a contingency plan of parking the shuttle at the international space station for astronauts’ safe haven, but has not ruled that out if serious damage was found.

NASA’s handling of the problem is “the prudent thing,” said George Washington University space policy director John Logsdon, who was a member of the board that investigated the Columbia accident.

“The point is having a clean vehicle for re-entry, not figuring out what this piece of whatever-it-is is,” Logsdon said.

There is little downside to taking an extra day to make sure the heat shield is intact, said risk analysis expert Paul Fischbeck, a Carnegie Mellon University engineering professor. He called it “almost like a freebie, an extra day in space.”

Hale said NASA’s attitude has changed since the Columbia accident.

“Clearly we are taking a much closer look than we ever did,” Hale said. “You can call it anxiety. You can call it smart. It’s what we do these days.”

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