Initial State of Gap: It is unknown if the partial gravity found on the lunar surface will be protective of orthostatic tolerance. 

Target for Gap Closure: Provide evidence to determine if 1/6-g prevents OI events upon return to Earth.

Interim steps:

Conduct a flight study before and after a mission to the lunar surface to confirm any detrimental/protective effects of 1/6-g

Approach: No progress will be made toward closing this gap until a directive is received to return to the moon.