Chris Hadfield, already famous as a former test pilot, veteran astronaut and social-media sensation, assumed a new role Wednesday. Mr. Hadfield, whose online posts are followed by half a million fans on Twitter, took command of Expedition 35 of the International Space Station, the first Canadian to lead such a mission.
Since people began living permanently aboard the space station 11 years ago, Mr. Hadfield is only the second astronaut who is not American or Russian to command a mission.
"I have devoted pretty much my whole adult life … to getting to this position where someone would trust me to command what is, in effect, the world's spaceship," Mr. Hadfield said in an interview with The Globe and Mail before he left in December for his five-month mission.
The 53-year-old retired Canadian Forces colonel took the helm from NASA's Kevin Ford, who is flying back to Earth this week with his two Russian flight engineers.
Mr. Ford surprised Mr. Hadfield when he played the Canadian national anthem over a speaker as part of the transfer of command.
A member of the ground crew also relayed congratulations to Mr. Hadfield and passed along best wishes from the Queen.
With the arrival of another group of astronauts at the end of the month, Mr. Hadfield will command two American and three Russian crew members.
The crew will keep busy operating scores of medical experiments and maintaining the ISS, often described as the most complex and expensive structure ever launched into orbit.
The commander's job is most critical when there are emergencies, Mr. Hadfield says.
"If someone has a serious medical problem … If we had a major technical emergency on board, a puncture, so that we start losing pressure, or contaminated atmosphere or smoke or a fire, then … I am in charge."
The risks aren't theoretical. In 1997, an oxygen-generating canister aboard the aging Russian Mir space station burned out of control for 15 minutes, filling the cabin with smoke and soot. Four months later, a supply ship crashed into Mir. The station began to depressurize until the crew sealed off the leaking module.
In such situations, Mr. Hadfield says, the decisions a commander makes within the first minutes of a crisis can be the difference between life and death.
"Professionally, it is both an enormous thrill but also a great challenge to be asked to do this."
With a report from Paul Taylor