A Twin Otter plane. Credit:southpolestation.com Roughly 50 people overwinter at Amundsen-Scott station each year, most of them employed by the National Science Foundation or lead contractor Lockheed Martin. They help maintain the station, oversee long-term monitoring on the atmosphere and climate change, conduct research on the early history of the universe via two radio telescopes and observe the behaviour of subatomic particles using at the station's IceCube Neutrino Observatory. But evacuation efforts like this are exceedingly uncommon - only two have been undertaken in the 60 years since the South Pole research station opened. The brutal cold and total darkness that blankets Antarctica during the austral winter make flight in and out of the station all but impossible. In 1999, a doctor who discovered a cancerous lump in her right breast treated herself - even performing her own biopsy and administering her own chemotherapy - for almost six months until the weather thawed enough for a rescue plane to arrive. A decade later, when a manager for the station suffered a stroke during August, the question of whether or not they could be airlifted out led to a tense standoff. "We were stuck in a place that's harder to get to than the International Space Station," said Ron Shemenski, a former physician for the station who in 2001 became the first person to be evacuated during the dark winter months. "We know we're on our own."

A photo of the station in the night under the glow of the aurora australis. Credit:Chris Danals, National Science Foundation Between February and October, only one type of craft can fly to, land at and take off again from the South Pole: the tiny Twin Otter. Two of these hardy, winter-proof bush planes, operated by Canadian polar service firm Kenn Borek, are now headed south, Falkner said, each of them carrying a pilot, co-pilot, engineer and a medic. Once they reach the British research station Rothera on Adelaide Island, one plane and its crew will remain behind to provide search and rescue capability should the main plane go down. The second Twin Otter will continue on toward the pole, flying into the deeper cold (current temperature at Amundsen-Scott is minus 60 degrees, or 76 degrees Fahrenheit) and impenetrable night. If all goes well, it could arrive as early as June 19, though that depends on whether the pilots can find a window in the brutal Antarctic winter weather to fly. Amundsen–Scott South Pole Scientific Station. Credit:WikiCommons "It's a 10-hour flight, and you only have 12 or 13 hours of fuel on board," said Alberta bush pilot Sean Loutitt. "You're monitoring the weather the whole time, but eventually you get to a point of no return. Then you're committed to the pole, no matter what."

Loutitt was the chief pilot for Kenn Borek during the mission to evacuate Shemenski in 2001. Before that rescue effort, no one had ever flown to Amundsen-Scott through the polar night. It was assumed that it couldn't be done. The IceCube observatory, the world's .largest neutrino detector, at the Amundsen-Scott South Pole Station in Antarctica. Credit:New York Times That belief is part of the mythology of the pole, Shemenski said. "It was like a macho thing," he recalled. "At that point when the last plane left you were there for six months. That was it." But about a month and a half after the last flight out, in April 2001, Shemenski started suffering stomach pains and throwing up repeatedly. As the physician for the station, he diagnosed himself with pancreatitis. The National Science Foundation's Amundsen-Scott South Pole Station

The doctor was determined not to leave the pole, arguing that he could treat himself on his own (indeed, by the time rescuers arrived, he was on his way to recovery, he said). But a medical expert consulted by the National Science Foundation said that Shemenski had a 50 per cent chance of dying in the six months until regular flights to the pole resumed. Officials pointed out that, though Shemenski had a right to take his own chances, they couldn't risk the possibility that his 49 colleagues would be left at the station without a doctor. "It's like being in the military," Shemenski said. "I was ordered off. So I left." The initial call went to the U.S. Air Force, which began to assemble dozens of military personnel and three C-130 Hercules planes for the rescue mission. But the temperatures at the pole were already too cold for the C-130s. The mission was scrubbed and the NSF sought out an alternative: Kenn Borek's Twin Otters. The planes are certified to fly at temperatures as low as minus 75 degrees Celsius (minus 103 degrees Fahrenheit), according to Falkner. Their systems are a good deal simpler than the C-130's, and they require less fuel - essential when every ounce of fuel has to be warmed for flight. At the pole's low temperatures, petrol freezes into an unusable jelly. So does the grease in a plane's hinges and gears. Winter storms can flare up in a heartbeat. And if anything goes awry, pilots may need to land on unknown terrain in total darkness. All of this was on Loutitt's mind as he prepared for the mission south. He'd flown to Amundsen-Scott before, and had done countless flights into the Arctic Circle during the northern polar night. But this was different.

"You're the only plane flying on an entire continent," he said. "You have to be prepared to be totally self reliant if something goes wrong." Luckily, the trip was relatively smooth. After hours of flying in darkness, Loutitt and his crew finally glimpsed a glimmer of light below them: barrels of gasoline were burning along the makeshift runway the South Pole station workers had prepared. They'd reached the bottom of the Earth. The replacement doctor for the station disembarked, and the ailing Shemenski clambered onto the plane. But as they started up the engines, the crew realised they couldn't take off. The Twin Otter's skis had stuck to the ice beneath them, and the grease on the wing flaps had frozen them in the fully extended position. While the station workers hacked at the ice on the skis, the plane's mechanic jerry-rigged the controls to allow it to take off. It was one of the longest, slowest take-offs any of them had ever attempted, but eventually, they were in the air. The journey back to Rothera was unlike anything Shemenski had experienced. "During the initial part when you're in the darkness it's hardly a sensation of moving at all because you can't see anything," he recalled. "Everything's black."

But then a thin line of pink appeared - sunlight on the horizon. "It was really beautiful to watch it grow," co-pilot Mark Cary told Canadian broadcaster CTV for a documentary about the mission. "It was like a gift and a sign to say everything's going to work out and you guys are going the right way." Cary and Loutitt would repeat the flight two years later, when Barry McCue, an environmental health and safety officer employed by contractor Raytheon Polar Services, developed a serious infection in his gallbladder. This time, Shemenski was the medical director for Raytheon and helped coordinate the rescue. McCue and his rescuers made it off the frozen continent safely, and McCue recovered fully from a successful surgery to treat his infection. "You can tell they're getting better at the planning of it," McCue told the Antarctic Sun, a newspaper run by the National Science Foundation. "For me it was just take the plan off the shelf, blow the dust off and then just figure out what the people should do."

Still, any mission to the darkest and most distant place on Earth is risky. That the National Science Foundation has decided an evacuation is its best option, Shemenski pointed out, means that those at the pole must be seriously ill. The Twin Otters are set to arrive on the Antarctic continent by the end of the week US time. Washington Post Follow Fairfax World on Facebook Follow Fairfax World on Twitter