ESA trainers and caving specialists are pictured here underground in Sardinia, Italy, setting the scene for space-like astronaut training next month.
The trainers descended into the caves on a 'dry run' without the astronauts to test their planned tasks and operations.
CAVES – short for Cooperative Adventure for Valuing and Exercising human behaviour and performance Skills – offers astronauts, trainers and planners a chance to test space-like procedures while exploring uncharted caverns in new environments.
This year, the CAVES team are stepping up the space realism and exploration while testing more technology and procedures.
Clambering down to basecamp hundreds of metres below the surface using safety tethers is similar to conducting a spacewalk, and this year the procedures have been updated to include astronaut terminology.
In space an object can quickly float away and be lost forever. While caving, dropped equipment can be lost for ever in crevices or holes.
Passing equipment, cavers and astronauts must make sure the recipient is grasping the item before the first person lets go: 'make before break' in astronaut lingo.
No opportunity is missed to make the week-long stay underground resemble a space mission. The trainees will follow a timeline and procedures, including handling equipment and communication protocols, just as on the International Space Station.
Explore further: Training astronauts in uncharted caverns