They stood together in the special viewing area at Cape Canaveral, their faces shining with pride and wonder. But in the next moment, they were joined in a trial of private grief under a public spotlight.

In the last three days, the families of the seven crew members of the shuttle Challenger -- ordinary citizens themselves -- have had to cope not only with the loss of their loved ones but also with instant and unwanted celebrity.

"We are very private people," said Kerry Smith of Beaufort, N.C., the sister-in-law of Challenger pilot Michael Smith. "At first, Tony and Pat [the pilot's brothers] just wanted to close the shutters. But then they thought that their brother would want them to be positive.

"Publicity was a part of Mike's life," she said, "and we know that people are only interested because they care."

Many relatives of the shuttle crew will gather once more this morning for a national memorial service at the Lyndon B. Johnson Space Center in Houston. President Reagan, accompanied by his wife, Nancy, will speak at the nationally televised ceremony scheduled to begin at 12:40 p.m. EST. A NASA spokeswoman said the 30-minute service will end with the singing of "God Bless America."

But the crew's families have also sought to keep some part of the memorials for themselves.

When Patrick Smith realized the full meaning of the ball of fire over Cape Canaveral Tuesday, he began to plan a memorial Sunday afternoon in the small fishing town of Beaufort.

"I felt that it just had to be a family thing, that in this small part, the family had to have the say," Smith said in a soft voice that sometimes cracked. "I'm hoping that the public likes what we do, but this will be his funeral, really, and it had to be a family thing."

The ceremony at Beaufort Elementary School will include military honors and reminiscences about Smith's boyhood, Kerry Smith said. The gathering will include longtime friends and political dignitaries, including North Carolina Gov. James G. Martin (R).

The relatives of astronaut Judith A. Resnik have decided to forgo the Houston services to attend a memorial ceremony planned this afternoon at Temple Israel in Akron, her home..

"We have a large extended family," said David Altounian, a family spokesman. "They have come from all over the country to Akron, and they don't want to travel further.

"The past few days have been hard," Altounian said. "We've teetered between the feelings of 'please leave us alone,' and realizing that, on a one-to-one basis, people have been wonderful.

"I think it comes down to the fact that watching someone you love die is a thing that cannot be comprehended. It's such a naked grief."

Resnik's mother, Sarah Belfer of Bedford Heights, Ohio, has spent the past few days dealing with the ringing telephone and the intimate questions about her daughter and her sorrow.

"The attention has been nice, and it has been not nice," Belfer said. "My daughter was a very private person, and I am the same way. I am aware that the news media is only doing their jobs. However, I just want to be alone."

Resnik lived in Clear Lake, Tex., near NASA's Houston space center, as did her crewmates, mission commander Francis R. (Dick) Scobee, Lt. Col. Ellison S. Onizuka and Ronald E. McNair. The other crew members were Gregory B. Jarvis and New Hampshire teacher Christa McAuliffe.

In the small town of Lake City, S.C., Eric McNair was keeping a log of the hundreds of calls placed to his mother, Pearl, the mother of astronaut McNair. "There has not been a spare moment," he said, "not a moment to let it all sink in."

"I'm afraid that some of the family members still entertain the hope that maybe, just maybe, he survived," said family friend Hessie Rantin who helped Eric McNair with the calls. "That's how unreal it all seems."

Like several of the other families involved, the husband and two small children of Christa McAuliffe -- the crew's only "ordinary citizen," as she called herself -- have remained in seclusion since Tuesday. In a statement released yesterday by his Concord, N.H., law firm, Steven McAuliffe expressed thanks for the wave of sympathy.

"My children and I are very aware of the tremendous outpouring of grief and support across America," McAuliffe said. "We wish to thank you all and hope you can understand our need for these private moments. We have all lost Christa."

A spokesman for his law firm said Steve McAuliffe would attend today's service in Houston.

Yesterday afternoon, McAuliffe's parents, Edward and Grace Corrigan, made their first public appearance since witnessing their daughter's death at Cape Canaveral. They attended a memorial service attended by 1,500 at Framingham (Mass.) State College. Sitting in the front row of the auditorium, the Corrigans wept as they sang the hymn, "Let There Be Peace on Earth."

Charles Sposato, a teacher at Framingham South High who was among the 11,000 applicants to become the first teacher in space, told the gathering, "When trying out for the program, Christa said, 'What are we doing here?' and before I could answer, she said, 'We're reaching for the stars . . . . ' " The phrase became her trademark.

As the service ended, students released seven black balloons into the chilly blue sky, one for each of the crew members. The Corrigans departed silently.