Port Array Rotation Joint

The Port Array Rotation Joint, part of the P3 Truss Segment, tracks the Sun for the Port Side Solar Arrays as the Space Station orbits the Earth.  (This segment can also hold unpressurized logistics carriers and attached payloads.)  On the International Space Station the Port Array Rotation Joint will be launched with an array of solar cells known as the P4 Segment, providing a new power source to the station but not shown here.
