((a)) Subject to subsection (b), the Secretary concerned may authorize reimbursement to a civilian employee who is accompanying a Member of Congress or a congressional employee on official travel for actual travel and transportation expenses incurred for such travel.

((b)) The allowance provided in subsection (a) may be paid—

((1)) at a rate that does not exceed the rate approved for official congressional travel; and

((2)) only when the travel of the member is directed or approved by the Secretary concerned.

((c)) In this section:

((1)) The term “Member of Congress” means a member of the Senate or the House of Representatives, a Delegate to the House of Representatives, and the Resident Commissioner from Puerto Rico.

((2)) The term “congressional employee” means an employee of a Member of Congress or an employee of Congress.

((3)) The term “Secretary concerned” includes the Secretary of Defense with respect to civilian employees of the Department of Defense other than a military department.