CAPE CANAVERAL, Fla. - Six Canadians who have been in space are on hand as the U.S. shuttle program prepares to blast off on its final flight -- but only five of them are human.

Among the participants at the Kennedy Space Center for the last launch of Shuttle Atlantis is this country's most famous robot, the iconic Canadarm that has played a key role in the three-decade shuttle program.

Canadarm is also making its final mission.

The original model of the mechanical limb, designed specifically for the shuttle and first used in 1981, will be retired after its 90th flight. The final launch is scheduled for Friday but rain and lightning around the site have fuelled speculation about delays.

Watching from the ground, perhaps with a bit of nostalgia, will be five Canadian astronauts who have flown on the shuttles through the years including Steve MacLean, the head of the Canadian Space Agency.

Also looking on with pride will be hundreds of people back home who worked on the Canadarm, which became a beloved symbol of technological potential and national know-how.

Mike Hiltz, 46, the technical program manager at MacDonald, Dettwiler and Associates, which built five arms, has been working on the robotic limb for 25 years.

He recalls one particularly proud moment when the arm and its Canadian flag logo were front-and-centre in space. It was in December 1998 when the International Space Station was first being assembled.

Hiltz was at the Johnson Space Center in Houston at the time, watching the Canadarm capture a Russian module and connect it to the U.S. part of the space station.

"There we were as Canadians bringing together these two great space-faring nations -- Russia and the U.S. -- and here was our logo so prominently displayed," he said in a recent interview.

"I remember thinking it really mimicked the way we think of ourselves as Canadians, you know, bringing other nations together for peaceful purposes."

Hiltz says the arm has inspired a young generation of MDA employees who have put their stamp on it. For some, it has become a family affair.

"We've got a few second generations -- even fathers and daughters -- who have worked on it over the years," Hiltz said.

"No matter where I go in the country, there will be somebody whose father or uncle or cousin had worked on some element of the Canadarm and they will always tell me that with great pride."

Steve MacLean and fellow Canadian astronaut Chris Hadfield have both flown on the shuttle Atlantis and are on hand to watch the final flight. The space agency boss expressed mixed feelings.

'It was a tremendous privilege to be a part of something so important," MacLean said in an interview, as he stared at the cloudy skies above the launch site.

"(But this is) bittersweet. I think the shuttle could have continued to fly so there wasn't a gap between this vehicle and the next vehicle that's coming...

"But now that the decision is made, it is time to move on to what we're going to do next."

For the next several years all flights -- including Hadfield's scheduled trip to the space station in 2012 -- will be aboard a Russian Soyuz vessel.

In the meantime, several American companies are developing future spacecraft that will service the station and carry astronauts as early as three years from now.

However, President Barack Obama has said that NASA's next priority will be longer-range flights, possibly to Mars or an asteroid, while private companies develop lower-orbit capsules.

Canadarm 2 is still aboard the space station and will continue being used to capture cargo vessels delivering supplies.

The Canadian Space Agency is also working on the next generation of Canadarms, which would be robotic tow trucks used to service satellites including refuelling and repair tasks.

Maclean reflected on the role that the first-generation Canadarm has played since the early 1980s.

"There's a heritage and a legacy. The critical investments, at the exact right time from the Canadian government, have made a tremendous difference," he said.

"Just the fact that Canada was asked to put an arm on the entire shuttle fleet and then to use robotic technology in order to assemble and operate the space station, is an honour.

"And then the fact that we delivered -- on time, on budget, and on schedule -- is something we can very much be proud of."

Hadfield might be especially wistful while watching the final flight. Atlantis was his first ride into space in November 1995. He spent 10 days in orbit, going to the Russian Space station Mir and back.

"The only problem with Atlantis through the whole flight was one light bulb that burnt out on the flight deck," he said.

"But it's had a tremendous run. It's served its purpose, it's done wonderful things and it's taught us a tremendous amount and it's paved the way for what's coming next."

Julie Payette was the last Canadian astronaut to be on a space shuttle. She flew up in July 2009 on Endeavour to visit fellow Canadian Bob Thirsk, who was spending six months at the space station.

The first Canadarm was on Endeavour, which recently took its last mission. The robotic limb will be shipped back to Canada later this year.

She views the end of the shuttle program in practical terms.

"I'm not that nostalgic," Payette said Thursday.

"It's the end of an era. The space shuttle has been an extraordinary flying machine, a fantastic workhorse -- but decisions were made to pass on to another level and that is fair...

"We've made those decisions with airplanes and automobiles before. You know we don't drive Model T's any more, so we've gotta move on."