European Space Agency (ESA) astronauts have a unique training system. Not only do they train hundreds of miles above the surface of the earth, they also travel hundreds of miles down into the deep, dark recesses of our wonderfully exotic planet. This latter training is part of a caving course that seeks to replicate the disorienting conditions present on a space expedition, as well as to teach astronauts how to work together when faced with an alien environment.

Participants in this unusual CAVES (Cooperative Adventure for Valuing and Exercising) training course hail from a variety of countries and include ESA astronaut Pedro Duque, Japanese astronaut Aki Hoshide, Chinese astronaut Ye Guangfu, Russian cosmonaut Sergei Korsakov, and NASA astronauts Jessica Meir and Richard Arnold. These six space explorers will enter the dark underground caves, which will test their ability to survive without natural light and the sounds that are so familiar to surface dwellers. This harsh environment will push the astronauts out of their comfort zone and force them to assign leadership roles, follow orders, and work together as a team.

The caving course will do more than just train astronauts for space exploration; it also will be used to test new equipment that will allow the team to camp deeper into the caves than ever before. These technological advancements make it possible for the astronauts to explore a new 3D mapping system that uses photo-based measurements. They will be able to communicate using a novel communication system capable of transmitting through 800 kilometers of rock.

The astronauts will begin a weeklong orientation on June 24 before heading underground on July 1. They will remain underground for six nights, where they will work on their teamwork and communication skills. You can follow their progress on the ESA CAVES twitter account or the CAVES blog.