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Cryogenic Actuators
Energen, Inc. has built and demonstrated cryogenic actuators and linear stepper motors applicable to the needs of the James Webb Space Telescope (JWST) being developed by NASA. These actuators are based on cryogenic magnetostrictor materials that deliver greater motion than any other “smart” material system. Energen has demonstrated prototypes of all four of the actuator identified as critical technology for JWST – shape, position, force, and deformable mirror. Shape actuators provide for short stroke precision shaping of the primary mirror; Position actuators provide tip, tilt and piston motion of mirror segments, force actuators provide direct force control and small compact array of actuators are used in secondary mirrors for adaptive wavefront control.
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Tip-tilt-piston Actuators
Large, ground-based telescopes being developed at many observatories around the world, are being designed with segmented primary mirror following the success of the Keck Observtory in Hawaii. A key requirement of segmented mirros is that the wavefront from all the segments must be phased correctly or the image will be distorted.
To achieve a high degree of coherence between segments, actuators are needed to precisely position each mirror segment to nanometer accuracy. The Keck telescope uses hydraulic actuators, which require frequent maintenance resulting in considerable downtime for observations.
Energen is developing nanometer-class actuators that can deliver the tip-tilt-piston motion needed for ground-based telescopes. These actuators have a coarse and fine positoning system that work together to provide nanometer resolution over 10s of millimeters range. Their low-power design eliminates thermal expansion effects and they hold position when powered off, even under a 250 kg load.
See datasheet for detailed information.
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