NASA Extreme Environment Mission Operations (NEEMO) sends groups of astronauts, engineers, and scientists to live in the world's only undersea research station for three weeks at a time to prepare for future ISS and space exploration activities.

In June the space agency announced two NEEMO missions that would take place this summer: one already began on July 21 and the other is set for September 7. On Monday, NEEMO Aquanaut Crew 18 began their nine-day mission 62 feet underwater off the coast of Key Largo, Florida. Three other international space agencies - Japan Aerospace Exploration Agency (JAXA), European Space Agency (ESA), and Canadian Space Agency (CSA) - will also be a part of the mission that will focus on studies in behavioral health and performance, human health issues, and habitability.

On September 7, NEEMO Aquanaut Crew 19 will feature astronauts from NASA, ESA, and CSA who will spend one week underwater, also off the coast of Key Largo, Florida. This crew will focus on the evaluation of ESA tele-mentoring operations - when a crew member is given instruction for a task by an expert who is located remotely but is virtually present via a video and voice connection. Both missions will take place in Florida International University's undersea research habitat Aquarius Reef base.

"It is both challenging and exciting for our astronaut crews to participate in these undersea missions in preparation for spaceflight," said Bill Todd, NEEMO project manager at NASA's Johnson Space Center in Houston, in this NASA news release. "It is critical that we perform science applicable to NASA's exploration goals in a high-fidelity space operational context. The extreme environment of life undersea is as close to being in space as possible."

Both NEEMO Missions will focus on Extravehicular Activity (EVA), which is any activity performed by a pressure-suited crewmember in unpressurized or space environments. NASA and other space agencies are now focusing on EVA training because it can provide an effective means for service, maintenance, repair, or replacement of space equipment without the need to remove it to a pressurized environment, return it to Earth, or abandon it. NEEMO Crews 18 and 19 will study EVA tools and techniques for exploration tasks in varying levels of gravity in preparation for future asteroid missions and Mars missions. Herve Stevenin is the ESA's Head of EVA Training in Germany and he will be a part of NEEMO Crew 19.

The last NEEMO mission was NEEMO 16 back in June of 2012. NEEMO 17 was skipped, so the one that is taking place right now is the first such mission in over two years. The results that come out of these underwater studies will hopefully provide further insight for deep space missions.

You can read more about the NEEMO missions on the NASA NEEMO webpage.