> Wouldn't this be a work of the federal government and in the public domain?
Not necessarily
EDIT: This got prematurely sent and thus was overly terse: contractors and other private parties connected to government test may have been permitted to take photos, and those (even within the scope of work of a government contract) may be subject to copyright. (Also, its theoretically possible that some tests were photographed by people with no formal connection to the test, though the remote locations and lack of announced times make that challenging.)
Not necessarily
EDIT: This got prematurely sent and thus was overly terse: contractors and other private parties connected to government test may have been permitted to take photos, and those (even within the scope of work of a government contract) may be subject to copyright. (Also, its theoretically possible that some tests were photographed by people with no formal connection to the test, though the remote locations and lack of announced times make that challenging.)