MIL-M-21188A, MILITARY SPECIFICATION: MIRROR ASSEMBLY, CONCAVE GROUND GLASS, OPTICAL LANDING SYSTEM (26 APR 1972) [NO S/S DOCUMENT]

MIL-M-21188A, MILITARY SPECIFICATION: MIRROR ASSEMBLY, CONCAVE GROUND GLASS, OPTICAL LANDING SYSTEM (26 APR 1972) [NO S/S DOCUMENT]., This specification covers one type of concave front surfaced mirror assembly required for permanent shore-based optical landing systems.