Space shuttle manager Ron Dittemore, who became the public face of NASA in the days after the Columbia accident, is planning to resign, and a news briefing will be held this week in the departure, sources said last night.

During the first week after the Feb. 1 disaster, which cost the lives of seven astronauts, Dittemore conducted a series of articulate briefings that won wide public praise for their openness, although they disconcerted some insiders. He also declared himself to be the official who should be held accountable for the accident, if there was something "we missed."

His candor and accessibility contrasted sharply with NASA's confused and evasive performance after the 1986 Challenger accident.

Dittemore discontinued his daily briefings as soon as the Columbia Accident Investigating Board, headed by retired Adm. Harold W. Gehman Jr., could take over the formal probe. He later gave extensive testimony at one of the board's hearings.

Columbia disintegrated over Texas during its reentry after a fatal breach opened in its left wing, allowing superheated air to flow in and trigger a chain of destruction. The initial cause of that breach remains unproven, but investigators have focused heavily on the possibility that the wing area was damaged during the Jan. 16 liftoff when a chunk of foam debris about the size of a suitcase, traveling almost 500 mph, struck it. The debris incident was discovered a day later in a review of launch videos.

Also since the accident, investigators have found evidence that the heat-shielding on the leading edges of the wings has suffered the effects of aging, which may have made it more vulnerable to such an impact. Post-flight inspections on several shuttle flights in recent years had turned up significant damage to the carbon fiber shielding, which NASA classifies as critical to the safety of the crew and vehicle.

During his post-accident briefings, Dittemore expressed strong doubt that the foam strike could have caused the accident.

He joined NASA in 1977 as a shuttle propulsion systems engineer. He became a flight controller and eventually a flight director. Beginning in 1992, he served briefly as deputy assistant director of the space station program before returning to space shuttle management in a variety of posts.

He became shuttle manager in 1999. The Orlando Sentinel reported his pending departure yesterday, saying he likely will take a job with private industry.

Dittemore's replacement could be announced at next week's briefing, a source said.