Update for 6:25 p.m.: Debris spotted by astronaut Mike Fossum shortly after the shuttle Discovery reached orbit today appears to be harmless ice, not an insulating blanket as Fossum first speculated, flight controllers say.

In a brief radio message to the crew, mission control reported "the initial assessment here is it does indeed look like ice. We saw a similar event on STS-114 (Discovery's last flight a year ago) but we're going to continue to look at it further and we certainly appreciate you getting that video to us pronto."

"Wow, that's real good news," a Discovery astronaut replied.

Original story:

Astronaut Mike Fossum, photographing the shuttle Discovery's external fuel tank as it tumbled away in space, told flight controllers today that he also noticed what appeared to be a large piece of debris, presumably from the shuttle itself, floating away in space.

Fossum said the debris looked like flexible reuseable surface insulation, blanket-like fabric insulating material that covers the upper surfaces of the shuttle. But Fossum said he was not sure and engineers in Houston speculated it might have been ice breaking away from the orbiter's main engine nozzles.

Whatever it was, Fossum said he captured the debris on video that will be downlinked to mission control for analysis.

"We saw what really appeared to be some cloth, probably some FRSI or advanced FRSI, that's pure speculation on my part," Fossum radioed. "But it seemed to be stitched-type material, at least four to five feet long, perhaps six to eight. I couldn't really guess at the distance away from us. It was sort of tumbling and twisting, it was kind of a combination of straps and a little bit of squarish material, which is why it really looks a lot like the insulation."

He later estimated the debris, whatever it might have been, was perhaps 40 yards away from Discovery when he spotted it, between the orbiter and the external fuel tank.

Fossum was in the process of photographing the tank to help engineers understand how its foam insulation stood up to the rigors of launch. Astronaut Steve Frick in mission control at the Johnson Space Center in Houston told commander Steve Lindsey that flight controllers saw at least two instances of what appeared to be foam debris breaking away from the tank. But in both cases, the debris separated after the shuttle was out of the thicker, more dangerous regions of the atmosphere.

For foam insulation to pose a threat to the shuttle's heat shield, it must come off in dense enough air to slow down rapidly, allowing the shuttle to ram into it at a high relative velocity. At extreme altitudes, the relative velocity is too low to result in major impact damage.

At about 250 seconds into flight, Frick advised the crew, "they saw some pieces, maybe about five, that came off near the LO2 (liquid oxygen) feedline area. They don't know if they're ice-frost ramps or not. They know that some came near the fuselage, but they didn't see any contact or see any damage. Also, just to note it was about 240,000 feet and the Q (dynamic pressure in pounds per square foot) was all the way down to about one-and-a-half PSF."

"OK, copy that," Lindsey replied.

"The only other item they noticed was noticed later, almost five minutes, about four-forty-five (four minutes and 45 seconds). They saw a piece come off the mid part of the tank, not sure if it's acreage (foam) or close to the feedline, and it did seem to strike the midbody (of the shuttle) somewhere about halfway between the main landing gear and the nose landing gear door.

"We'll, of course, look at it on the (space station approach) photos but the PSF there was about zero, you were way up at 350,000 feet, so that should not be a concern."

Shuttle program manager Wayne Hale plans to brief reporters on the results of quick-look analysis of launch video starting around 7:30 p.m.