A Canadian team that helped ensure the three astronauts huddled aboard a stricken Apollo 13 made it back to Earth safely 40 years ago was honoured Tuesday for efforts that were part science, part intuition.

Called in to help out, the team at the University of Toronto Institute for Aerospace Studies had just four hours to come up with critical calculations.

"This was life or death for three people," said Prof. Barry French, one of the team members.

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"Next morning we woke up and heard that it had landed successfully and I remember feeling just amazed, relieved, happy. It was a bit awe-inspiring actually."

The call to the Canadians on April 16, 1970 came from U.S.-based Grumman Aerospace, which had been contracted to build the lunar-landing module in which the lives of the three desperate astronauts hung on a thread. Grumman wanted to know what pressure would be needed to separate the module from the crippled service module, which had been badly damaged by an oxygen tank explosion.

People the globe over held their collective breath as the crippled craft aborted its planned moon landing and limped back toward Earth.

The team - also comprising professors Phil Sullivan, Rod Tennyson, Irvine Glass and Ben Etkin - swung into action.

Now 78, Prof. French said the members had to work off "inadequate" information as they sought to figure out what was needed to separate the two parts of the spacecraft using pressurized oxygen.

Too little pressure, and the separating craft might have collided as they hit the Earth's atmosphere. Too much, and the lunar-module hatch would have been fatally damaged.

"We had to guesstimate things; it really was almost what you might say back-of-the-envelope," Prof. French said.

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"It was the intuition and educated guess work that went into it that made it work."

Their calculations proved right. The separation was successful and the astronauts made it home safely in what NASA would later call a "successful failure" of the mission.

In accepting the Pioneer award from the Canadian Air and Space Museum, Prof. Sullivan said the team's largely unsung role in helping save the astronauts was unique and gratifying.

"We assumed that lots of people around the world and the United States would be looking at this issue," said Prof. Sullivan brandishing his original slide-rule.

"We learned later ... that in fact we were the only group that was consulted on this point."

A letter from Fred Haise Jr. was read out at the award ceremony in which the lunar-module pilot praised the team's crucial help.

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"I can certainly vouch for their credentials," Mr. Haise said in the letter.

"My sincere thanks and congratulations."

On April 13 the oxygen tank exploded as the spaceship was four-fifths of the way to the moon.

The calm if unsettling words to Mission Control from the astronauts following the explosion, "Houston, we've had a problem," are now widely recited as, "Houston, we have a problem."

The revised version can be heard in the 1995 film Apollo 13 starring Tom Hanks, which also used "Houston, we have a problem" as its tag line in ads for the movie.