These stations have re-entered the atmosphere and disintegrated. The Soviet Union ran two programs simultaneously in the 1970s, both of which were called Salyut publicly. The Long Duration Orbital Station (DOS) program was intended for scientific research into spaceflight. The Almaz program was a secret military program that tested space reconnaissance. = Never crewed Note: Prototypes and various parts of Chinese, Japanese, and Russian, U.S. programs are in orbit, but not necessarily operational.