When the Canadian Space Agency first put out a call for applications for the job of astronaut 25 years ago, Steve MacLean was not waiting on the first day with his resume. In fact, he didn't even know about it.

But after receiving a call from a friend who suggested he give it a shot, MacLean applied and was selected as one of Canada's original six astronauts.

Now MacLean, who flew on two shuttle missions and is the CSA's chief astronaut, is beating the bushes to get the word out on the latest recruitment drive.

"I want to make sure anyone who could make a good candidate knows about the opportunity, and I would encourage them to apply just as I was encouraged," MacLean told CBC News in a telephone interview.

"I remember watching John Glenn and Neil Armstrong, but I thought the job was for Americans only," he said. "It wasn't true then and it isn't true now."

The first phase of the CSA's recruitment drive wraps up next Thursday and MacLean says so far, it has 4,202 applications from aspiring astronauts.

MacLean expects the final number to approach 5,000, about the same number the agency netted in two previous drives.

The agency is encouraging people who are in good shape with at least an undergraduate degree in science or engineering, and either work experience or a master's degree or a licence to practise medicine to apply.

The recruitment drive comes after Dave Williams retired in the spring and Bjarni Tryggvason announced he would retire this month. The agency is looking to fill two positions to bring the astronaut corps to six. After Tryggvason retires, the current corps of astronauts will be composed of MacLean, Julie Payette, Robert Thirsk and Chris Hadfield.

The field of applicants will be whittled down to a shortlist of 40, who will then undergo more extensive tests and interviews, said MacLean. A key trait the agency is looking for is how trainable a person is, he said.

"It's important, because many of the tasks they will be doing they will have never done before," he said.

Once the candidates are selected next May, basic training will begin at NASA in August 2009, followed by training for missions of about six months. Salaries for the positions range from $83,300 to $162,700.

It's an exciting time for potential astronauts, said MacLean, as they will get to train on the crew exploration vehicles, or CEVs, which will take the next generation of astronauts to the moon.