The Actuator Control System includes four different sets of actuators, two Actuator Control Units which also provide Power Control (or ACU/PCUs) and a Regenerative Power Unit (or RPU). The actuators include a hoist for hoisting the Boom up and down, a latch for locking it in the stowed position, a telescope for moving the Boom probe in and out and the ruddevator for moving the Boom control surfaces to "fly" the Boom.