If it's "big" as reported, then that'd be difficult. My first guess is still "ice," though.
Sigh. It's times like this that I wish I was still down in Houston, working Shuttle missions....
spaceflightnow.com
1745 GMT (1:45 p.m. EDT)
NASA managers today ordered the Atlantis astronauts to stop their landing preparations and to delay re-entry 24 hours to Thursday to give flight controllers additional time to assess the implications of an unusual object spotted earlier today flying below the shuttle.
The object may have shaken off the shuttle earlier today, possibly due to vibrations associated with routine pre-landing tests of the shuttle's hydraulic system and maneuvering jets. The concern is the possibility of damage to the shuttle's heat shield or some other critical component that could cause problems during re-entry.
In what could be a coincidence, engineers monitoring data from sensors mounted behind the ship's carbon composite wing leading edge panels recorded eight "events" over a two-minute period earlier today. It's not yet clear whether the data indicates an actual impact event, vibrations associated with the entry tests or some other phenomenon. While the timing was coincidental, an impact event would not be expected to trigger multiple signatures. But engineers do not yet have an explanation.
I thought that at first as well, until I saw a video clip of the object from a ground station as it passed over a cloudless area. not sure where the clip came from, but it showed the station, the shuttle, and a shiny object that was pulsing as it caught the light. It appeared to be large enough to do so, and was, I would surmise, probably the size of 1/2 sheet of plywood to do this as it related to the size of the shuttle. There was no explanation of the clip, but it was related to this problem.
The size aspect aside, the debris must have come from the shuttle to be close and at the same speed.
Some new info reported, they think the sensors picked up hydraulic noise and vibrations or the thruster pops, but they are not sure which. They don't think it was a debris strike as earlier reported on ABC.
Also, I am not hearing anything that verifies the size of the object. I don't know if I saw something that they did not, or if they just have not yet put everything together.
The object to me, appeared large and I trust my ability to judge spatial relationships on these 2-D pics. I'm thinking it is a reflective blanket section. These are pretty big, about 3x5 in some places.
I am still pretty worried about this, although NASA is not panicking. The crew is in sleep mode and there will be little more for the next 8 hours.