1. Episode 1

Chris Hadfield, Dr Kevin Fong and Dr Iya Whiteley put 12 candidates through a series of physical and psychological tests to find out who has what it takes to be an astronaut.

2. Episode 2

The remaining astronaut candidates are put through more demanding tests. They have to escape from an underwater capsule and operate a groundbreaking robot - the Mars Rover.

4. Episode 4

The competition becomes more intense as the remaining candidates are deprived of oxygen to see if they can recognise the signs of hypoxia, critical for an astronaut on a spacewalk.

5. Episode 5

The astronaut candidates fight for their place in the final. Their leadership skills are assessed in a survival test and they head off to the Kennedy Space Centre in Florida.

6. Episode 6

The finalists head to the Shuttle Landing Facility on Florida's Space Coast for a tough test in weightlessness, and back in London the winner is decided.