At the National Air and Space Museum yesterday afternoon, several hundred people quietly gathered for the unveiling of a black-draped commemorative photograph of the seven Challenger crew members, just a few feet from the TV monitor where passing tourists had watched them soar and perish 24 hours earlier.

Visitors crowded around the railings of the museum's five-story-high atrium in virtual silence as museum Director William Boyne read a poem he had found taped to the building early yesterday morning. It was signed "Gregory Baker" and read: "We are saddened and shocked./A moment's freedom,/a moment's exultation . . . And now tragedy./And yet, though we mourn/and we remember those who died,/life goes on, and we must continue/onward and outward."

Boyne said he and his staff "felt the same sense of loss as all Americans . . . maybe a little more personal, because we've worked so closely with the crews."

Former astronaut Sen. John Glenn (D-Ohio), in a moving speech, reminded the audience that three of his own colleagues died in a space capsule almost 19 years to the day before the Challenger's demise.

"We are people who are curious . . . who want to know what roads lead into the future," he said. "Along with curiosity we are a questing people . . . out of that quest we have formed the greatest land in history. We triumph and try, triumph and try. Then comes a day when we are brought up short and our triumph turns to tragedy . . . We hope and pray today that the good Lord will help and comfort the families . . . "

Education Secretary William Bennett said he was addressing his remarks to the schoolchildren of America.

"Yesterday was a very sad day for all of us," he said. "You should be proud of Christa McAuliffe, one of your teachers, and of the other brave Americans who were willing to take great risks for the good of our country. In this place there are reminders of the sacrifices made by others who have gone before the Challenger seven. Let us today honor all who have gone before. And let us remember these men and women for their costly sacrifice on the path of discovery."

He then offered words from the poet Virgil:

"Here the honorable finds its due/and there are tears for passing things./Here too, things mortal touch the mind."

Sen. Jake Garn (R-Utah), who went up in the space shuttle last year, said, "This is a day of great mourning, a day of great personal loss to me . . . I had a chance to live with all of these astronauts for four months, and they are the finest this country can produce."

Said Sen. James Sasser (D-Tenn.), "We as a nation have rejoiced in the successes of the space program, and now we as a nation must mourn."

"We will miss them," said Rep. Norman Mineta (D-Calif.), "not only because they are talented experts but because they touched our hearts."

At the end of the 20-minute ceremony, Bennett unveiled the black-and-white photograph draped in black cloth, and the crowd filed by in silence.