NOVELTY - A solar energy system (454, 466, 478) comprises support unit secured to fixed location; solar energy unit mounted to support unit and comprising surface operable to track in response to movement of sun (496); actuator assembly coupled to solar energy unit for periodically applying torque at first frequency to move solar energy unit in response to movement of sun; and damper assembly including spool. Damper assembly reactively releases and retracts cable about spool in response to changes in torque at first frequency.    USE - Solar energy system.    ADVANTAGE - The system utilizes rotary viscous damper, thus efficiently resisting undesirable movement of solar energy unit due to dynamic load using little to no power from control system.    DETAILED DESCRIPTION - Solar energy system (454, 466, 478) comprises support unit secured to fixed location; solar energy unit mounted to support unit and comprising surface operable to track in response to movement of sun (496); actuator assembly coupled to solar energy unit for periodically applying torque at first frequency to move solar energy unit in response to movement of sun; and damper assembly including spool. Damper assembly reactively releases and retracts cable about spool in response to changes in torque at first frequency. The damper assembly also maintains cable at fixed length released from spool in response to torque at a second frequency greater than the first frequency that is intermittently received by solar energy unit. Cable is coupled to the solar energy unit. INDEPENDENT CLAIMS are included for:    (1) a heliostat control assembly which comprises the solar energy system, and viscous damper coupled to shaft of spool; cable tensioning assembly coupled to shaft and apply substantially constant torque on shaft urging refraction of cable around spool; and housing to sealingly enclose at least portion of damper assembly; and    (2) method for controlling solar energy system which comprises determining, with controller, to move solar energy unit from first position to second position different than first position; operating actuator assembly to apply static torque to solar energy unit to move solar energy unit to second position; in response to static torque, reactively releasing or retracting portion of cable about spool of damper assembly during movement of solar energy unit to second position; and in response to a dynamic torque on the solar energy system, resisting rotational movement of spool by viscous damper of damper assembly to prevent release of cable from spool.    Viscous damper resists rotary movement of shaft to maintain cable at fixed length released from spool in response to dynamic load intermittently received by solar energy unit.    DESCRIPTION OF DRAWING(S) - The drawing is schematic diagram illustrating a solar energy system.    Solar energy array (450)    Solar energy systems (454, 466, 478)    Solar energy receiver (488)    Solar energy (492)    Sun (496)