OTTAWA -- Canadian astronaut Marc Garneau, acknowledging that he had the jitters on his three space voyages, said yesterday the risks taken by space explorers have not produced monumental scientific breakthroughs for humanity.

But manned space activity will, in time, pay great scientific dividends, the head of the Canadian Space Agency predicted.

What has been learned by experiments conducted in the unique weightlessness of Earth orbit is "in the category of very promising," Mr. Garneau said.

When the International Space Station is fully operational, scientists can conduct research over longer periods instead of brief experiments crammed into 10-day space-shuttle missions.

And at the "end of the life of the space station, we'll have some good things to show for it," Mr. Garneau predicted.

The space station, which is being assembled with the help of the robotic Canadarm, is expected to remain in orbit and serve as a research centre for scientists for about 15 years.

Industry Minister Allan Rock told the Commons that the federal government will remain partners with the United States in space exploration and the space station, despite the tragic loss of the space shuttle Columbia and its seven-astronaut crew on Saturday.

The Canadian Space Agency will help the U.S. National Aeronautic and Space Administration investigate the crash, Mr. Rock said. "And we will fly again with the Americans."

Mr. Garneau told reporters he had private worries about the dangers at each liftoff.

Saturday's crash is "concrete proof that as much as we'd like to think that space flight is safe, it isn't," Mr. Garneau said.

He had fewer concerns about landings, although as flight engineer on one of the missions he was well aware of the strains on the spacecraft as it entered the atmosphere, he said. The Columbia broke apart about 15 minutes before its scheduled landing.

Responding to questions, Mr. Garneau acknowledged that much of the scientific research in space does not require the presence of a human; scientists on the ground directed seven of the eight experiments he conducted during one of his flights.

But in some cases, scientists need to be in space to observe, react and perhaps readjust techniques during the course of an experiment, he said.

Canadian and U.S. astronauts, whose missions may be delayed while the probe into the tragedy continues, will bounce back and be ready again for space.

Although space flight is dramatic and high-profile, only 20 per cent of the Canadian Space Agency's annual budget of $300-million is spent on the manned flight program. Most of the rest goes to satellite projects and experiments conducted on Earth.

Mr. Garneau said it is too early to know the full impact of Columbia's loss on the U.S. and Canadian space programs. But it will cause delay, at least, in the completion of the space station's construction, he told the House public accounts committee.

Canada has a 2.3-per-cent financial stake in the space station.

A Canadian-made, two-armed robot is ready to go up to the station. It was scheduled for a shuttle flight in April, 2005, but that may be delayed, Mr. Garneau said.