Per DoDI 4515.13, Foreign exchange service members on permanent duty with the DoD and their "acccompanied" dependents are elgible for Space-A when in a leave status.
Foreign exchange service officers, as defined in DoDD 5230.20, must have:
(1) A CAC.
(2) A valid leave authorization. Dependents of foreign exchange service officers must have a DD Form 1173. Dependents of uniformed services members who are under the age of 10 and traveling without a DD Form 1173 must travel with the sponsor or eligible parent.
For info on how to signup and other procedures please see the FAQ at www.spacea.net