A military radar system shows indications that an object might have separated from the shuttle Columbia in orbit, prompting a review of telemetry by NASA flight controllers to look for signs of anything - including impact by high-velocity space debris - that might have contributed to the shuttle's breakup Feb. 1 during re-entry.

NASA sources said the radar data apparently shows a small object suddenly separating from the shuttle at about five meters per second, or roughly 11.2 mph, on Jan. 17, about 24 hours after Columbia's launch from the Kennedy Space Center.

NASA officials late Saturday confirmed shuttle engineers are reviewing telemetry from the ship to determine if any sort of propulsive or other event might have happened that could explain such radar observations.

Shuttle crews routinely dump waste water overboard, which instantly turns into a rapidly expanding cloud of ice crystals. It's not yet known whether a routine water dump could have resulted in the observed radar "signature."

Occasionally, large plugs of ice develop on the water dump nozzles. Whether such an ice plug might have been blown off during an otherwise routine water dump - showing up on radar as an object moving away from the orbiter - is not yet known.

It's also possible some piece of non-critical hardware was somehow released or ejected from the shuttle without the crew's knowledge, something that would not have played a role in Columbia's re-entry breakup Feb. 1 over Texas.

Columbia was destroyed 16 minutes from landing when it veered out of control. Telemetry from the shuttle shows elevated temperatures in a landing gear wheel well and along the left side of the fuselage during the final eight minutes of flight.

Telemetry also shows an unusual aerodynamic drag on the left wing, which tended to force the ship to pull to the left. Columbia's flight control system attempt to correct for this drag by adjusting the craft's trim. Moments later, contact was lost.

What might have caused problems for the left wing is not yet known.

During launch Jan. 16, foam debris from the shuttle's external tank hit the underside of the wing and outside analysts have speculated that impact might have weakened the shuttle's thermal protection system tiles enough to trigger the catastrophe during re-entry.

But it's also possible impact by space debris could have damaged the heat shield tile or the carbon-carbon panels protecting the leading edge of the wing by knocking a piece off the shuttle. While a tile would be visible to a powerful radar, NASA engineers have not yet confirmed such an impact took place. Agency officials stress they are investigating those possibilities and many others.

In east Texas, meanwhile, a large section of the shuttle Columbia's lower fuselage - possibly part of its rear body flap or a piece of a landing gear door - was recovered today near Nacogdoches. But NASA engineers have not yet determined whether debris found earlier near Fort Worth is part of the ship's left or right wing.

The debris found near Nacogdoches appears to have curved hinge components on each side, indicating it was moveable hardware. Heavily damaged black heat shield tiles on the debris show it came from the bottom of the spacecraft.

The only large hinged panels on the shuttle's fuselage are the nose and main landing gear doors, the external tank umbilical attachment covers and a large "body flap" at the rear of the shuttle that shields the main engines from heat during re-entry.

The debris found today appeared to be part of the body flap, but television views were not conclusive. While its shape was roughly correct, it was smaller than a complete body flap, indicating a large piece is still missing.

NASA officials, meanwhile, said work continues to establish a reliable timeline showing when various sensors failed during re-entry or detected higher-than-normal temperatures on the left side of the shuttle. The timeline is not yet complete, but officials hope to finalize the details over the next few days.

NASA officials also dismissed media reports earlier today that raised the possibility precautions could have been taken before Columbia's return to Earth that might have helped minimize left-wing heating during re-entry.

During a flight in 2000, engineers studying launch video were concerned a six-inch piece of ice falling away from the ship's external fuel tank might have hit and damaged protective tiles on one of the wings. Playing it safe, flight controllers re-oriented the shuttle just before re-entry, "shadowing" the area in question to help lower its temperature. The idea was to slow the onset of entry heating.

In Columbia's case, officials said today, the shuttle's orientation, or attitude, during the mission resulted in lower-than-normal temperatures across the lower fuselage. As a result, Columbia was re-oriented to warm the belly slightly, part of a routine procedure to properly control main landing gear tire pressure.

NASA spokesman Kyle Herring said the re-entry flight profile was normal and dismissed speculation flight controllers could have re-oriented the shuttle during its descent through the atmosphere to ease the effects of heating.

"There is no protected, secret attitude we can fly," he said. "We already fly the most benign entry possible."

Shuttle program manager Ron Dittemore said much the same thing last week, pointing out that any attempt to favor one wing would subject the other wing to extreme, inherently hazardous conditions.