Description : Samos (Satellite and Missile Observation System), originally named Sentry or Program (or Project) 101, was the second program that evolved from WS 117L and aimed at developing a heavier reconnaissance satellite that would be launched by an Atlas booster instead of the Thor used to launch the project Discoverer (Corona).
The first successful satellite in the series, Samos 2, was launched 31 January, 1961. Beginning with the launch of the second satellite, Samos was highly classified.