To Research, Evaluate, Assess, and Treat Astronauts Act or the TREAT Astronauts Act This bill directs the National Aeronautics and Space Administration (NASA) to establish a program that provides for the medical monitoring, diagnosis, and treatment of crewmembers for space flight-associated medical conditions. The bill defines "crewmember" as an individual certified by NASA to be: a former NASA astronaut or payload specialist who has flown on at least one orbital space mission, or a management NASA astronaut who has flown on at least one such mission and is currently employed by the federal government. Medical monitoring, diagnosis, and treatment shall be provided under the program without any deductibles, copayments, or other cost sharing obligations required of participating crewmembers. NASA shall design the program to facilitate reasonable access of a crewmember to medical monitoring, diagnosis, and treatment under the program, including, at crewmember's option: through NASA; or from a health care provider selected by the crewmember and which enters into an agreement with NASA to provide such services to the crewmember. Participation by a crewmember under the program shall be voluntary and subject to the crewmember's written consent. Under the program, NASA shall provide for the uniform collection of data on space flight-associated medical conditions and the identification of any new space flight-associated conditions. NASA shall arrange with an independent organization to determine an estimate of the cost to NASA and the federal government for the implementation and administration of the program.