"We're going to look at the NASA budget, the requests that were made, statements that were made, the final appropriations, and what, if anything, could have been done to prevent this (Columbia accident)," the committee source said. ``We are going to be looking generally on the future of the space program.''

Among the issues is how the agency now contracts out much of the detailed work on the shuttle and whether these contracts affected safety. The committee also wants NASA to explain its plans for returning to Earth the three-man crew on the international space station now that the shuttle fleet is grounded because of Columbia's destruction 3 1/2 weeks ago.

In 113 space shuttle flights, two spacecraft have been destroyed with the loss each time of a seven-member crew. Challenger was lost during launch in 1986 and Columbia came apart over Texas on Feb. 1 while returning to Earth. It is a grim safety record that would not be tolerated in most fields of aviation and the committee plans an intense examination of the true risks of space shuttle flights.

"Everybody has a different opinion (about what is an acceptable level of risk for spaceflight) but about one in 57 is not a very good set of odds,'' said David Goldston, the chief of staff for the House Science Committee. ``We need to know what is the real risk of operating the shuttle. If those risks are high, as they appear to be now, can they be reduced and over what period of time?''

In the past, NASA's estimates of risks for a loss of the shuttle ranged from one in 200 launches to almost one in 500.

"There is a question about whether any of those figures were ever reliable,'' said Goldston. ``We need to at least get an estimate of what the risk actually is. Obviously, the risk will never be anywhere near zero."

Almost certainly, any fixes to the shuttle or to NASA will require a boost in the agency's current $15 billion budget and in the proposed 2004 budget of $15.4 billion, but some in Congress want more from NASA before voting the appropriation.

"I don't think Congress will be prepared to appropriate any significant amount of money until NASA better explains where we're going, what it will cost,'' said Rep. Bart Gordon, D-Tenn., a member of the science committee. ``I think there will be money for incremental fixes for the shuttle, but I don't see any large amount coming forth until we can see the bigger pictures. That's where our hearings need to go.''

One of the major targets of hearings, sources said, will be the contract held by the United Space Alliance, a combine of aerospace companies that does most of the detailed work of maintaining, refurbishing and launching the space shuttle at Florida's Kennedy Space Center. NASA engineers provide oversight in key supervising positions.

"We're not assuming the contractor is responsible, but if you do a complete overview of the shuttle program and where it needs to go in the future, you can't do it without looking over that contract because that's the way the program is run now,'' said Goldston. ``We have to go over that contract with a fine-toothed comb.''

Another issue, said a committee source, is how diligent NASA has been in following up on safety studies by independent boards. Engineering assessments of the shuttle have been conducted for years by expert committees of the National Academy of Sciences and by other panels. There are dozens of reports in NASA's own archives warning about risks linked to the shuttle's thermal tiles, which are thought to have played a role in the Columbia accident.

Yet, it is not clear that NASA responded to those warnings.

"That is an important question,'' Goldston said.

Gordon said a major concern of the committee is how NASA plans to either recover or resupply the crew of the international space station.

The space station crew was to be exchanged next month in a flight of space shuttle Atlantis. But with the shuttle fleet grounded, the station crew may have to rely on the Russian Soyuz spacecraft, the only other manned vehicle able to fly to and from the station. The space station has enough supplies to last until June, but after that the crew must come home.

Just how the space agency plans to handle the problem if the shuttle is still grounded "is an internal issue now being discussed in NASA,'' said a committee staffer, but lawmakers are demanding an answer.

"I asked NASA last March what their plan (for the space station) was if the shuttle fleet was grounded for any length of time," said Gordon. "They didn't have an alternative then and they still don't. That's troubling."