Canadian astronaut Dave Williams answers a question during a news conference Wednesday in Houston, Texas. ((David J. Phillip/Associated Press))

A Canadian astronaut says he's spent hundreds of hours preparing foran upcoming trip to the International Space Station that will likely include a record-breaking three spacewalks.

Dave Williams, 53,told reporters in Houston, Texas,on Wednesday that he's been working out in the gym and training on simulators to prepare for his August journey.

"There's nothing you can be complacent about," said Williams, a former emergency room doctor born in Saskatchewan. "Working on keeping the choreography of a 6½ hour spacewalk will be very tough."

Williams, who has been in spaceonce before,will likely break a Canadian record by spending 19 hours floating outside the space station, as he guides and attaches a new segment to the structure. The work is scheduled to be done over the course of three separate spacewalks.

In 2001, astronaut Chris Hadfield became the first Canadian to leave a spacecraft and float freely in space. His two spacewalks spanned 14 hours and 54 minutes.

Williams is scheduled to leave the Kennedy Space Centre in Florida on Aug. 7 and spend 14 days in space. He will be aboard the Endeavour shuttle, which arrived at its launch pad early Wednesday morning for a month of preparations before its liftoff.

"I think it's going to be really exciting, really challenging for us," Williams said. "And certainly, we're really excitedfor the spectacular view and getting the chance to see both Canada and the United States from space."

Williams, who spent 16 days on the space shuttle Columbia in 1998, said this time around he will be bringing a recording with him of his daughter playing What a Wonderful Worldon piano.His daughter gave him the recording of the Louis Armstrong song for his birthday.

"I'm going to be taking that into space with me because it is one of my favourite songs," he said.

Challenger backup candidate to join Williams

Barbara Morgan, an Idahoschool teacherwho was chosen as a backup candidate for the 1985 NASA teacher in space program, will be one of the other astronauts on the mission.

Teacher Christa McAuliffe was selected as the main candidate. She died with the six others aboard the Challenger shuttle when it exploded 75 seconds after it launched in 1986.

Morgan said she wasn't deterred by the tragedy and spent 20 years working to become a full-fledged astronaut.

"What defines teachers is perseverance and patience, so I'm just doing the job of a teacher," she said.

"The legacy of Christa and the Challenger crew is open-ended," she added. "I see this more as a continuation.… I think the great thing is people will be thinking about Challenger and the hard work lots of folk over many years have done to continue their mission."

With files from the Canadian Press