Canada's most famous robot and arguably its greatest engineering achievement has helped NASA perform an unprecedented manoeuvre on its latest mission -- guiding astronaut Steve Robinson to the precarious underbelly of space shuttle Discovery.

There, on Aug. 3, Robinson became the first astronaut to repair a shuttle's fragile thermal skin in space.

It was a seemingly simple but critical procedure, and at 360 km from the earth, required a performance of the highest precision and control by the Canadarm 2.

The task

Officially known as the Shuttle Remote Manipulator System (SRMS), the Canadarm 2 on the International Space Station (ISS) is larger and stronger than the Shuttle's Canadarm.

But its steady hand rather than brute force was necessary for Wednesday's repair job.

The Canadarm 2 acted as Robinson's giant, steady guide during his spacewalk, taking him to two pieces of ceramic fabric (known as "gap fillers") that were protruding from the underside of space shuttle Discovery.

NASA feared the pieces -- located between heat shield tiles and jarred loose during Discovery's launch -- could cause dangerous heat damage when the shuttle plunges through the Earth's atmosphere and lands Monday, lead to a possible repeat of Columbia's disastrous re-entry.

Benoit Marcotte, program manager for the Canadian Space Station Program, said the arm on Wednesday did exactly what it's meant to do: provide support for astronauts during spacewalks by acting as a kind of giant "footrest" after transporting astronauts from one worksite to another.

But Marcotte tells CTV.ca he believes it's the first time the arm has been required to travel near such a fragile section of a shuttle.

"The arm can reach that area, but we have never really done that before."

Canadian Space Agency president Marc Garneau spoke of the extraordinary precision needed by astronaut Jim Kelly -- the arm's operator on the International Space Station (ISS), who was taking orders from Robinson.

During the spacewalk, Kelly would pause to get better views of Robinson via the robot-arm's camera.

"Stand tall and lean forward," he said to Robinson as he brought him to within 8 feet of the sensitive tiled surface.

Robinson quickly spotted the first gap filler and called out directions for Kelly to slowly manoeuvre him closer, moving only inches at a time.

In the end, a few gentle tugs were all it took for Robinson to fix the problem.

"Looks like this big patient is cured," said Robinson.

The evaluation

Like a proud father, Garneau sang the praises of the astronauts and the Canadarm 2's performance during Wednesday's repair mission.

"The arm worked very beautifully with great precision, so I'm going to brag about it," he told reporters Wednesday at a press conference following the job.

He added that this mission has allowed NASA to see, for the first time, the exact state of the tiles on board the orbiter.

"We never could do that before," he said. "We had limited visibility of certain tiles with the Canadarm as far as it can see. But this is now the first time we are able to literally inspect, tile by tile, the entire surface of the orbiter."

The concerns

The crew had to be extremely careful to not allow the repairman or any of the equipment he was carrying to bang against the shuttle's fragile thermal shield.

"Those tiles are there to give thermal protection, and they're there to withstand very high temperatures," Marcotte told CTV.ca.

"But those tiles are fragile in themselves, so you want to make sure you don't scratch them, that you don't break them, or have any contact with them."

Garneau said it was critical that Robinson was directly parallel with the shield; and any tilt to the body could have resulted in the astronaut's body -- especially the unwieldy helmet -- banging into the tiles.

"When you're in the suit, even though it looks like they're ballet dancers in some ways, they're very big, clumsy suits so you need a great deal of precision."

He gave "kudos" to Kelly, who had a limited view of Robinson and had to perform some mental calculation to manoeuvre the repairman using the arm.

"Believe me, if you're operating an arm from inside a box and you can't see the person really well ... it's very easy to not use the controls properly."

"He made it look easy."

Other duties

Before Wednesday's repair mission, Robinson and Japanese astronaut Soichi Noguchi first had to install a new storage platform to the exterior of the ISS, with which Discovery has been docked since last week.

Since its launch into space Tuesday morning, astronauts also inspected the orbiter for damage from the launch, using a 15-metre boom sensor on the robotic arm with lasers and a camera mounted on its tip. No damage was found.

The boom was built by MDA Space Missions Ltd. in Brampton, Ont. -- the company that developed both Canadarms.

Marcotte details further tasks for the Canadarm II during this space mission, which include:

• Grabbing hold of the Raffaello logistics module in preparation for Friday, when that module will be detached from the ISS and stowed back into the payload bay of the shuttle. The module will be transferring material back to Earth that's accumulated in the ISS over two-and-a-half years.
• Capturing the boom and the sensor system at the end of Canadarm.
• Stowing the sensor system on the right hand side of the payload bay in order for it to be properly stowed for the return to earth.

In light of the successful performance of the Canadarm 2 so far, Marcotte described the mood at the Canadian Space Agency as "extremely positive."

"We're happy, we're pleased to see that the mission is progressing. We've got a new storage platform on the space station. We've done some very needed repairs, some resupply of the station. The shuttle is working extremely well."

He added that NASA's failure to figure out exactly how to stop insulation foam from the orbiter's external fuel tank from coming loose at launch remains the "dark side" of the mission. And one which "might have an impact on when the next launch will take place."

"However," he said, " the program continues and we're very much looking forward to continuing the assembly of the ISS with Canadarm 2."

Garneau, meanwhile, said he's looking forward to Canada's third robotic contribution to the space program -- a two-armed robot named Dexter.

"This is the most advanced robot in the world, and it's ready to go," said Garneau. "So we're looking forward to showing the world this robot is going to be able to do things that nobody's seen before."