STS-88

Node 1, named Unity, was the first space station hardware delivered by the space shuttle. It has two Pressurized Mating Adapters (PMA), one attached to either end. One PMA is permanently mated to Zarya, and the other is used for orbiter dockings and crew access to the station. Unity also contains an International Standard Payload Rack used to support on-orbit activities, which was activated after the fifth Shuttle/Station assembly flight.