NASA officials and the astronauts' families were joined at the Kennedy Space Center here by dozens of visitors to remember the crew members whose fiery deaths on January 28, 1986 shocked the country.

"It is a beautiful day here," June Scobee Rodgers, the widow of Challenger pilot Francis "Dick" Scobee, said on a sunny yet windy Saturday, in front of a black granite monument bearing the names of the 24 astronauts who have died since 1964.

Scobee Rodgers, who delivered the main speech, said her late husband was aware of the potential danger he faced as a shuttle pilot.

"He knew about the risks and accepted them as a test pilot," she said. "Without risk, there is no knowledge. ... The greatest risk is to take no risks."

She said the space program should continue, adding that "(God) gives us curiosity and challenges us to discover."

The family of Challenger's most famous crew member, high school teacher Christa McAuliffe, declined to attend the ceremony.

McAuliffe's participation in the launch as a civilian had made her a national star, but her family has largely remained out of the public eye since the national tragedy.

The disaster turned into a national trauma much like president John F. Kennedy's assassination 23 years earlier and the September 11 attacks 15 years later.

Then-president Ronald Reagan told the nation that the Challenger crew "slipped the surly bonds of Earth to touch the face of God."

Scobee Rodgers read a letter written by her daughter Kathy years after her father's death. The explosion "was a national tragedy, everyone saw it," her daughter wrote. "My dad died a 100 times a day on TV."

Twelve children saw their parents die in the 1986 accident, Scobee Rodgers said.

Saturday's ceremony was also attended by relatives of victims of the shuttle Columbia tragedy, which also killed seven astronauts in February 2003, and the Apollo I accident, in which three astronauts were killed in 1967.

Relatives placed flowers in front of the granite monument to the US space program's fallen astronauts.

Visitors at the ceremony recalled where they were and what they were doing the day of the Challenger explosion.

William Potter, chairman of the Astronauts Memorial Foundation, vividly remembers the accident. "I watched it unfold from my office window 20 years ago," he said.

Richard Norman, a 57-year-old retiree who came from Michigan for the ceremony, was at work when Challenger exploded.

"I can't remember what I ate yesterday, but I can remember that," Norman said. "It's so traumatic ... it touches you deeply."

The Challenger launch, originally scheduled for January 22, 1986, came on January 28 at 11:38 am under a brilliant blue sky and near-freezing temperatures.

All appeared normal in the first moments after liftoff, the 25th since the shuttle program began in April 1981.

But after 73 seconds, at an altitude of 14,000 meters (46,200 feet), Challenger exploded in an enormous fireball of hydrogen and liquid oxygen.

Its two booster rockets took off in different directions leaving a trail of flame and smoke, forming an immense "V" in the sky.

In addition to McAuliffe, 37, and Scobee, 46, the Challenger disaster killed co-pilot Michael Smith, 40; physicist Ronald McNair, 38, only the second black astronaut; Gregory Jarvis, 42, a mission specialist; Ellison Onizuka, 40, a Haitian-born astronaut of Japanese descent; and mission specialist Judith Resnik, 37.

Twenty years later, the US space shuttle program has still not overcome doubts about its safety and value.

A presidential commission concluded the accident was caused by a defective seal on a solid rocket booster. NASA carried out an elaborate review of its rocket design and spent more than two billion dollars on modifications.

But the credibility of the US space agency was again called into question after the space shuttle Columbia disintegrated during re-entry into the atmosphere in February 2003, due to a loose piece of insulating foam that punctured its wing on take off.

"In each case, we learned that we have to have honest communications. You've got to not ignore anything," said Scott Hubbard, director of NASA's Ames Research Center in California and a member of the board that investigated the Columbia disaster.

Despite yet more modifications at a cost of 1.5 billion dollars, space shuttle Discovery lost a large piece of insulation during launch in July 2005.

It caused no accident but forced NASA to ground its three shuttles at least until May 2006, amid growing criticism that the program has become a dead end for space flight.

Related Links
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