DOS-2

Mission Profile

DOS-2 (Durable Orbital Station 2) was a Soviet military-derived space station of the Salyut series, launched on 29 July 1972 aboard a Proton-K but never successfully occupied due to a docking failure with its Soyuz crew vehicles. The station was publicly unacknowledged at the time, part of the classified program that ran parallel to the civilian Salyut program using the same hardware bus. It reentered the atmosphere on 22 May 1973 after 299 days in orbit without receiving a crew. DOS-2 highlighted the reliability challenges of early Soviet space station operations before the program matured with the successful Salyut 3 and later stations.