Which space station was intended for prolonged occupancy?

The space station intended for prolonged occupancy is Mir. Mir, launched by the Soviet Union in 1986, was designed specifically for long-term missions and was inhabited continuously for over 15 years until its decommissioning in 2001. This design allowed for extensive scientific research and international collaboration in space exploration.

Salyut was the first series of space stations launched by the Soviet Union, but many of its missions were relatively short-lived, focusing more on military and experimental objectives rather than long-term occupation. Spacelab, while it enabled scientific experiments in microgravity, was not a permanently inhabited station but rather a reusable laboratory that was flown in the Space Shuttle for specific missions. Gemini, a series of crewed spacecraft, was primarily focused on testing technologies for future long-duration missions and did not function as a space station.

Thus, Mir stands out as the clear choice designed for prolonged human habitation and sustained scientific research in space.