Androgynous Peripheral Attach System
The Androgynous Peripheral Attach System serves two functions on the International Space Station. It is used to temporarily dock the orbiter to Pressurized Mating Adapter 2 and to permanently connect the Functional Cargo Block (Zarya) to Pressurized Mating Adapter 1. The device has an active capture ring that extends outward from the system on the orbiter which captures a passive mating ring on the station. After capture, the ring aligns them and pulls them together to allow 12 structural hooks to deploy latching the two systems with an airtight seal. The docking ports on the Russian station modules use the Russian Probe and Cone Mechanism for the docking of Russian spacecraft.
The Androgynous Peripheral Attach System was designed by Moscow-based RSC Energia and has roots in the Apollo-Soyuz program. Its current design is based on that of the Androgynous Peripheral Docking System used in the Shuttle-Mir program.