He's waited almost 10 years. He's faced delay after delay. But finally, this week, Canadian astronaut Dave Williams will return to space, as a crew member aboard space shuttle Endeavour.

Williams, 53, has been thinking about this day for years. He was originally scheduled for a flight in November 2003. But the Columbia disaster in February that year put destroyed that plan.

Then, he was told he'd be flying in April 2007. Then it was June. Now, he's just eager to go. The countdown began Sunday night, for Wednesday's launch.

"I've been training a while and we're ready to go flying," he told CTV's Canada AM back in March when it looked like he'd be flying in June.

In the meantime, Williams has been ensuring he is in peak physical condition for the rigours that his body will endure in space.

"My physical conditioning is one of the key elements as to whether or not we're going to be successful," Williams told AM this week. "So, as a result, I go to the gym four to five times a week and try, at age 53, to stay in good shape and be able to lift weights and run and all these other things."

Williams was last in space in April, 1998,when he spent 15 days high above the Earth aboard, ironically, the Columbia. That was a long time ago, but there are a couple of things about that flight that Williams is looking forward to experiencing again.

"One of the most important is just simply getting back to space, you know, the incredible 8½-minute ride getting out into space, the shaking that you get in the first stage of flight with the solid rocket boosters and then six more minutes of flight until you're out floating around in microgravity," he said in an interview with NASA's website.

"But then the view is absolutely spectacular, being able to look out at the planet and recognizing that the planet is actually quite small, depending upon the perspective that you look at it from."

For Williams, he's living a dream that began in his childhood in Montreal, while watching the original Mercury astronauts on television.

"Seeing images of the Earth for the first time from space, I thought this was absolutely incredible," he says.

He dreamed of being an astronaut but soon realized that there was no opportunity for him, a young boy growing up in Canada. So instead of becoming a rocket scientist, he became a surgeon.

He graduated from the Faculty of Medicine at McGill University in 1983 and obtained a fellowship in emergency medicine in 1988. He eventually became the director of the Department of Emergency Services at Sunnybrook Health Science Centre in Toronto and a professor of Surgery at the University of Toronto and McGill.

Then in 1992, the dream of becoming an astronaut started to seem like something he might be able to achieve after all, when he learned that the Canadian Space Agency was recruiting astronauts. More than 5,000 people applied to be selected. After six months of testing that involved personal interviews, fitness assessments, psychological assessments, and aptitude testing, they whittled the list down to 20 and asked Williams to come for further testing in Ottawa.

"I honestly thought, looking at the other 19 people around me, any one of that group would have been an incredible astronaut," Williams remembers.

In the end, he was one of four chosen.

"To me, it was kind of like winning the lotto. I still don't understand why they picked me; I was just lucky enough to get picked."

He completed basic training with the CSA and in May 1993, was appointed manager of the Missions and Space Medicine Group within the Canadian Astronaut Program. In January 1995, he was selected to join the international class of NASA mission specialist astronaut candidates.

He spent a year in training at the Johnson Space Center and then was assigned to the Payloads and Habitability Branch of the NASA Astronaut Office. In April 1998, Williams finally blasted off into space as Mission Specialist 3 aboard STS-90.

On this mission, Williams will be able to put some of his medical expertise to work. He'll be participating in an experiment called Perceptual Motor Deficits in Space (PMDIS) to investigate why astronauts experience difficulty with hand-eye coordination while in space.

His research should help narrow down three possible explanations: the first: that the brain is not adapting to the near weightlessness of space; the second: it's just too difficult to perform fine movements when floating in zero gravity; and the third: the stress, due to space sickness and sleep deprivation, impairs hand-eye coordination.

"These changes in eye-hand co-ordination do exist in space and they're indicative of some of the changes that take place in the nervous system," Williams told reporters last month.

"The interesting question from a medical perspective (is) why are these changes reversible, yet in the clinical environment, some of the changes we see in the nervous system of patients are irreversible?"

He'll also be attempting to break a record for the longest spacewalk by a Canadian. In 2001, Chris Hadfield became the first Canadian to ever leave a spacecraft and float freely in space. He performed two spacewalks and spent 14 hours and 54 minutes outside over two spacewalks. Williams is scheduled to break that record by spending 19 hours in space during three walks.

During the walks, he and his fellow crewmembers will install a truss element on the space station.

Williams has been training for this task by manipulating 3-D resolution images projected on to his goggles with gloves equipped with sensors to record his hand movements.

"The space station has this big long central truss and we're out on the starboard side putting the element on that enables us to attach solar panels to provide more power to the station," he explained to Canada AM.

"The second spacewalk will be to install the gyro on the station. There are four gyros on the space station to stabilize the station. One of them is not working properly so we'll be replacing that."

"The spacewalks that we're doing have a number of challenging objectives and take us way out to the extreme limits of the space station where we're working, essentially looking out into free space," Williams says.

"So, it's going to be a very exciting mission for me."

Williams' excitement is confirmed by his wife, who spoke to him Tuesday morning on the eve of the launch.

"He is getting a chance to relax aside from his fitness training and he and (astronaut) Barbara Morgan will get to go on board the Endeavour (Tuesday) afternoon to check out video cables," Cathy Fraser, told CTV Newsnet. "He's excited to get one last look before he gets strapped in."

The mission is also exciting for their children, Evan, 12, and Olivia, 9 according to Fraser, who is herself an airline pilot with Air Canada.

"They are enjoying a lot of the excitement surrounding the whole mission," Fraser said. "Dave has been really good at keeping them involved in his training and showing them a little bit about what he is doing."

The children will stay in contact with their father through email during his mission.

Despite the excitement, there will be some tension during the mission for the family.

"We'll be holding our breaths and looking forward to a successful mission with a safe return," Fraser said.