50 U.S.C. § 3616

(a) The Secretary of Defense may pay the expenses referred to in section 5742(b) of title 5 in the case of any employee of the National Security Agency who dies while on a rotational tour of duty within the United States or while in transit to or from such tour of duty. (b) For the purposes of this section, the term “rotational tour of duty”, with respect to an employee, means a permanent change of station involving the transfer of the employee from the National Security Agency headquarters to another post of duty for a fixed period established by regulation to be followed at the end of such period by a permanent change of station involving a transfer of the employee back to such headquarters.