 Missile Defense Alarm System was a series of Air Force satellites flown between 1960 and 1966 for infrared detection of ballistic missile exhaust plumes on Atlas-Agena A, B, and D. There were several failures and overall program performance was poor, but it would give way to the more successful DSP satellites.Samos was a series of Air Force satellites flown between 1960 and 1962 for photoreconnaissance on Atlas-Agena A and B.There were several failures, including an on-pad explosion of an Atlas, and the program was cancelled at the end of 1962 without ever demonstrating any operational capability.