CAPE CANAVERAL, Fla. - Two astronauts are pulling double duty during NASA's next shuttle flight, where they'll serve as both spacewalkers and the prime robotics officers during their construction mission to the International Space Station (ISS).

STS-115 mission specialists Daniel Burbank and Steven MacLean are the lead shuttle and ISS robotics arm for their 11-day flight to the ISS aboard the Atlantis orbiter. Both astronauts are shuttle flight veterans, but STS-115 will mark the first time they will done spacesuits and step outside a spacewalk.

Burbank, MacLean and their four STS-115 crewmates plan to deliver two new port-side trusses and a set of new solar panel wings to the ISS that will double station's power output once activated.

First time outside

An astronomer at heart, Burbank is celebrating just over a decade of NASA service since he joined the astronaut ranks in April 1996, but that landmark came at a cost.

"It's kind of ironic as an amateur astronomer," Burbank, 45, said in an interview. "In Houston, with the tempo if our training and other work we do, I probably spend less time at the eyepiece of a telescope now than I did before I came here."

Burbank's road to NASA began in the U.S. Coast Guard, which the Tolland, Connecticut astronaut joined in 1985 to make a difference as a rescue pilot.

"When I was growing up I wanted to be in the Coast Guard," Burbank, a husband and father of two children, said in a NASA interview. "I wanted to go on Coast Guard small boats and rescue people in the surf."

After a fellow Coast Guard pilot became as astronaut, Burbank applied not once - but three times - before finally being accepted. His first spaceflight, NASA's STS-106 mission in September 2000, was also aboard Atlantis and also aimed at outfitting the ISS. But the station today is much different than when Burbank left it.

"We docked to a station that had no people," Burbank said, adding that STS-106 prepared the ISS for permanent human habitation. "The lights were out, the hatches were closed and a lot of the systems were powered down as you expect."

For STS-115, Burbank serves as Mission Specialist-2 and flight engineer, and will assist Atlantis commander Brent Jett and pilot Chris Ferguson on the flight deck during the critical launch and landing phases.

He and MacLean will also conduct the second of three planned spacewalks to install their cargo - the station's Port 3/Port 4 truss segments and new solar arrays - to the ISS. But Burbank will take special joy in easing the 17.5-ton mass of aluminum girders, stowed arrays, batteries and other hardware out of Atlantis' cargo bay with the shuttle arm to a point where MacLean can pluck it up with the ISS robotic arm.

"Flying that arm is just going to be a wonderful thing to do," Burbank said, who is also charged with overseeing the meticulous heat shield inspections using the arm's 50-foot (15-meter) sensor boom early and late in the spaceflight.

Canada's right (robotic) arm man

MacLean, STS-115's Mission Specialist-4, is the odd astronaut out of sorts on Atlantis' STS-115 crew.

As a representative of the CSA, he is the only non-NASA astronaut of the bunch and the only flyer who did not get his start in his country's naval institutions (though his family has a history of shipbuilding). In fact, when Canada's call for its first astronauts went out, he did not even think to apply.

"It took a phone call from colleague of mine to say, 'You know, you should really do this; this is something that maybe you could do,'" said MacLean, an Ottowa, Ontario native with a Ph.D in physics. "And so I did, and six months later I was on that team."

MacLean, 51, was selected one of Canada's first six astronauts in 1983 and served as program manager for the Advanced Space Vision System which uses computer-controlled camera to aid use of the shuttle and ISS robot arms. He first reached orbit in 1992 aboard the space shuttle Columbia during NASA's STS-52 mission, where he performed experiments and tested the robotic arm Space Vision System.

"This is a tremendous privilege for me to be able to operate this technology throughout the course of the mission," MacLean said.

A husband and father, MacLean also led work to develop the first prototype of the laser camera system now used to scan shuttle heat shields during orbital inspections. Canadian engineers beginning planning an early version of the boom-mounted system in the 1980s, he said.

"What I find interesting is that Canada was thinking about [heat shield] repair 20 years ago," MacLean said, referring to the early boom work. "

So we were well positioned to help with respect to the space shuttle return to flight when the [Columbia] accident happened."

The Canadian astronaut said he watched NASA recover from the Challenger accident in 1986 and then again from the 2003 loss of Columbia - which suffered heat shield damage from foam debris at liftoff - and takes heart in the strides since to increase astronaut and vehicle safety.

"Foam is a known problem now, it's not fully understood but it's a known problem," MacLean said. "Foam will not bite us again."

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