On the evening before the Challenger space shuttle disaster, officials of Morton Thiokol Inc., the company that built the shuttle's solid rocket boosters (SRB), twice recommended against going ahead with the mission because of concerns about cold weather, a member of the presidential commission investigating the launch said last night.

Starting at 5 p.m. on Jan. 27, Thiokol officials told the chiefs of NASA's rocket programs at Huntsville, Ala., "Don't go under 51 degrees, don't go beyond our previous launch experience," the panel member said.

But in a third communication, Thiokol changed its recommendation at the urging of the National Aeronautics and Space Administration and officially signed off on the launch, the panel member said. Even at that point, however, a senior Thiokol official at Cape Canaveral "refused" to endorse the recommendation, he said.

"This shook us to the socks," said the panel member, who asked not to be identified. "We were unprepared for it . . . . It changed the whole tone of the investigation."

Immediately after hearing the Thiokol testimony at a closed-door meeting at the cape last week, "We threw everybody out of the room and . . . decided we had to tell the president," he said.

The commission member stressed that the panel did not want to engage in "McCarthy-like witch hunts" against NASA officials and plans to proceed cautiously, taking more testimony from NASA officials in Huntsville.

But, the panel member said, "This certainly indicates fundamental problems with the management of NASA . . . . This did not conform to any previous NASA flight procedures."

The cold weather -- colder than at any previous launch -- is one of the prime suspects in the investigation of what made the Challenger's right SRB malfunction at the moment of ignition.

The presidential commission is investigating the likelihood that the cold destroyed the resilience of O-ring seals, designed to keep hot exhaust gases from bursting out from the joints of the rocket.

Administration sources said yesterday that William P. Rogers, the commission's chairman, told White House chief of staff Donald T. Regan last Friday that he was "appalled" to learn that key information about the shuttle's condition had not reached top space agency officials before the disastrous launch.

Specifically, according to a senior official, Rogers told Regan in a telephone call that Jesse Moore, NASA associate administrator of space flight, had not been informed about low-temperature readings on the shuttle, a fact Moore confirmed yesterday at a Senate hearing on the Challenger explosion.

Rogers also said Moore had not been told about pressure brought by NASA officials on Thiokol to concur in the launch decision.

The sources said Rogers called Regan to inform him of a statement, which was issued Saturday, saying the decision-making process at NASA may have been "flawed," and ordering top officials who participated in the launch decision not to take part in the investigation.

Rogers was "appalled . . . that information did not filter up to the top," said the official, who asked not to be identified.

At the Senate hearing yesterday, Moore confirmed that senior NASA officials at the crucial countdown conference that decided to launch Challenger had not been informed of the unusually low temperature readings from the shuttle's right booster rocket that a launch pad inspection team recorded just hours before liftoff.

Moore told a Senate committee yesterday that if he had known of the readings, he would have "asked more questions" before allowing the countdown to continue.

Moore said that the readings of 7 and 9 degrees Fahrenheit detected by the teams would have been "a material concern," the kind of serious, last-minute issue that is "raised and discussed very very vigorously and openly until . . . people are completely satisfied the shuttle is safe to launch . . . ."

But Moore and other senior shuttle managers in the firing room at Kennedy Space Center never were told of the readings, made by technicians who visited the shuttle three times in the four hours before the launch. Their job is to check for ice formations on the sides of the huge external tank, which contains supercooled liquid hydrogen and liquid oxygen.

Moore and Dr. William R. Graham, NASA acting administrator, confirmed yesterday that a series of intense telephone conferences took place the night before the Jan. 28 launch between NASA officials and Thiokol officials.

Questioned by Sen. Albert Gore Jr. (D-Tenn.), Moore told the packed hearing in the Russell Senate Office Building that "there were discussions at Thiokol, discussions between Thiokol and the Marshall Space Flight Center in Huntsville, Ala. , and in the final analysis, the Thiokol management signed off on a recommendation to launch."

Rogers, when asked by Gore to comment on reports of "heated arguments the night before the launch in which Thiokol recommended against" blastoff, replied tartly, "I don't want to get involved in those types of speculative questions. At the moment, I'm not going to answer any of those questions."

Richard Feynman, a Nobel laureate in physics who is a member of the president's commission on the shuttle explosion, spent yesterday at Cape Canaveral, attempting to determine whether the ice team's readings were accurate.

He said that the "absurdly low" temperatures recorded on the right booster were easy to explain, suggesting that they could have been caused by breezes blowing past the supercooled external fuel tank onto the booster rocket. He said he does not believe that a leak of cold hydrogen from the tank was the cause of the low readings, as has been speculated.

In his remarks, Rogers hinted, without elaboration, that there may have been a failure of at least one of the struts that attached the right-hand booster rocket to the external tank. According to previous speculation, this could have caused the malfunctioning booster to strike the tank during launch and cause the explosion.

At the start of the four-hour hearing, Rogers said he is confident "we're going to be able to determine what happened." He said the right booster "appears to be the area where trouble started," and told the senators that NASA is in for an "unpleasant" period of painful public scrutiny as investigators seek flaws in the agency's decision-making process that led to the disaster.

"The event was overwhelming," Rogers said. "People are having trouble just getting their thoughts collected."

Rogers said morale among NASA staffers and the astronauts has suffered. While there is esprit de corps, he said, "they are worried about the safety aspects of this. They want to get to the bottom of this, but in the process there very likely will be further embarrassment."

Sen. Ernest F. Hollings (D-S.C) asked commission vice chairman Neil Armstrong, the first man to walk on the moon, if he would "get into the shuttle now."

Armstrong replied by recalling that just after the tragedy, John Young, chief of the astronauts, told him, "None of us want to go again until we know what has happened."

Armstrong said he believed the Challenger crew "knew full well the risks" of the flight. Drawing on his years as a test pilot and astronaut, Armstrong said, "It always surprised me when things worked properly. I expected a large number of equipment failures . . . . We very much knew of the risks."