ISS crew memebers keep fit with two hours of mandatory exercise on a treadmill each day. Image Credit: NASA
The ISS operates on Greenwich Mean Time (GMT), although from the crew’s point of view the Sun rises and sets 16 times a day.
In space, timekeeping is relative, but astronauts are hardwired to live in 24-hour cycles just like the rest of us.
According to ESA astronaut Paolo Nespoli, the choice of GMT comes down to practicality, a compromise between US and Russian time zones.
It also allows European astronauts to wake up at more or less the same time as their fellow citizens on the ground.
Not that it’s easy to sleep – Nespoli says that the crew has to use earplugs in the loudest compartments.
“There is a continuous aircraft-like hum in the air, mostly coming from ventilation and life support systems,” he explains.
All this noise aside, there is no vibration transmitted through the structure of the ISS, and no sense of being inside a spacecraft rapidly orbiting Earth.
Before a mission, each crew member is allowed to choose a 10-day menu cycle, selected from dried or tinned pre-cooked foods, which are heated or hydrated before eating.
“Microgravity dulls the taste buds, so spicy foods are preferred,” says Nespoli.
Even after their assigned seven-hour work shifts are finished, ISS crew members cannot relax until they have completed a minimum of two hours of hard physical exercise on the treadmill. Nespoli (and almost anyone who’s ever been on board the ISS) says that relaxation time is spent, as often as possible, “gazing at Earth whenever the external shutters are open, through the huge cupola windows”.
On 12 March at 9pm, Channel 4 will broadcast Astronauts:Living in Space, the first programme in its Live from Space season, following the day to day routine of astronauts living and working on the International Space Station.
To read more about Nespoli’s day-to-day life aboard the ISS, pick up the April issue of BBC Sky at Night Magazine, on sale 20 March 2014.