JWST uses 132 small actuation motors to position and adjust its optics.
These actuators provide the extremely precise mechanical control needed to turn 18 separate primary-mirror segments into one accurately phased optical surface. Each primary segment has seven actuators: six control its position and orientation, while a seventh adjusts its radius of curvature. The secondary mirror also has positioning actuators, bringing the telescope’s total to 132 controlled degrees of freedom.
During commissioning, engineers moved the segments out of their launch positions and aligned them using wavefront measurements from the Near Infrared Camera, or NIRCam. The motors work in extraordinarily small increments—roughly 10 nanometers—so the reflected wavefronts from neighboring segments combine as though they came from one mirror.
The number is sometimes misunderstood as 132 motors all continuously driving the telescope during observations. They are precision alignment mechanisms, not ordinary tracking motors. Webb’s fine-steering mirror handles rapid image stabilization, while the 132 actuators maintain the large optical system’s shape and alignment. That distinction explains why the figure is tied to optics rather than spacecraft pointing.