Assuming the astronauts are civilian employees[0], I'm not sure that releasing protected health information could be a condition of employment. There are fairl

Assuming the astronauts are civilian employees[0], I'm not sure that releasing protected health information could be a condition of employment. There are fairly strict rules around human subjects research and a major theme of the rules is that you can't be coerced into participating. This is particularly true when employees are used as experimental subjects; DHHS says that "Employee participation raises questions about the ability of employees to exercise free choice, for example, because of the possibility that a decision to participate could affect performance evaluations or job advancement, even if it is only the employee’s perception that this is the case." Saying "let us release your health records or you're fired" thus appears to be wildly illegal. [0] I think the rules for military employees are slightly different, but I would imagine they're not too far off.