NASA hopes to begin a 13-day undersea training mission off Key Largo on Thursday, after a tropical storm system in the Gulf of Mexico delayed its planned start Monday.
American astronaut Shannon Walker and two international astronaut candidates, Takuya Onishi of Japan and David Saint-Jacques of Canada, will live on the Aquarius Undersea Laboratory in the Florida Keys National Marine Sanctuary in the Atlantic Ocean.
The crew also includes scientist Steven Squyres of Cornell University, principal investigator for the Mars Exploration Rover Project, and professional aquanauts James Talacek and Nate Bender.
They'll perform "spacewalks" and other exercises intended to simulate a mission landing on an asteroid, which NASA is exploring as an option for a deep space mission by 2025.
Mission operations plan to study how to anchor to the surface of an asteroid, how to move around and how best to collect data.
Several other veteran astronauts and spacewalkers -- Stan Love, Richard Arnold and Mike Gernhardt -- will participate by piloting a submersible vehicle that will interact with crew members on dives.
The mission is the 15th for NASA's NEEMO -- short for NASA Extreme Environment Mission Operations -- program. Read more background here.