Acting director William R. Graham announced continuation of NASA's teacher-in-space program yesterday and said at a news conference that the late Christa McAuliffe's backup teacher will be offered the opportunity to fly aboard the next shuttle that carries a civilian passenger.

Because the National Aeronautics and Space Administration's investigation of the Jan. 28 Challenger tragedy is still going on, it is too early to say when shuttle flights will resume, Graham said. Other NASA sources said, however, that one or more flights probably will carry only military and NASA personnel before a civilian is allowed aboard.

At the same news conference in NASA headquarters here, two other space-teacher finalists voiced continued faith in the safety of the shuttle program.

"I'm sure that NASA is doing everything possible to make it as safe as possible," Judy Garcia of Alexandria said. "When they deem that it is flight-ready," she added, "I would be confident that to their knowledge it is ready to go and I would be willing to go."

Michael Metcalf, a teacher from Hardwick, Vt., said he was a former Air Force pilot and was aware when he boarded an aircraft that it could crash, "but you go ahead with your job."

Mary Hatwood Futrell, president of the National Education Association (NEA), gave her support to the teacher program at the news conference and called on NASA to pledge "that future space projects will be infused by the spirit that Christa McAuliffe stamped on the Challenger mission."

If that goal is honored, Futrell said, "we will truly be able to say that although Christa McAuliffe never reached her destination, her mission was accomplished."

When President Reagan announced the teacher-in-space program in 1984, the NEA, which had not been consulted, branded it a public relations gimmick. An NEA official said yesterday that the program and McAuliffe's death "had created an enormous amount of interest from teachers and children."

Barbara Morgan, 33, a teacher from McCall, Idaho, who went through NASA training as McAuliffe's backup, met with Graham on Tuesday to discuss taking McAuliffe's place. Graham quoted her as saying that "her decision will depend on circumstances" at the time the flight is scheduled.

"We're going to offer her the opportunity," Graham said. "We're not asking her to make a specific commitment today to a time frame that has not been established." In the meantime, he said, Morgan would work at NASA headquarters on the teacher program.

Morgan told reporters Wednesday in Boise, "I want to fly just like a lot of people in the country and that's up to NASA to make that decision," according to United Press International.

Graham also announced that a journalist would be the third civilian to fly on the shuttle, although the selection process may be slower than scheduled.

Several questions were directed at Graham and the space teacher finalists about how much information was given on the risks of shuttle flight.

"I was aware of the potential for disaster," Garcia said. At one point during briefings they were told it could explode, she said.

Neither teacher had been told of the potential problem in the solid rocket booster seals being examined as a potential cause of the Challenger explosion, they said. But Metcalf told a questioner, "If we had known then what we know now, NASA would have known then what we know and nobody would have gone up." NASA employes in the back of the conference room applauded.

Acting director Graham said he did not learn about the seal problem until four days after the explosion. At that time, he said, it was presented to him "as part of an enormous engineering data base" identified as "possible sources of the problem."

Graham restated his warning against assuming that the cause of the Challenger disaster has been pinpointed. "We have to be careful to get the cause and effect right," he said.