Optical Positioning Actuators

Linear actuators with high-fidelity positioning capabilities are required for aligning large optical payloads used in ground-based telescopes and the testing of space-based optical systems. Moog has developed and fielded high performance actuators that meet the needs of these demanding applications. High precision components, including a fine pitch, preloaded roller screw, high gear ratio/backlash-free harmonic drive, flexured or preloaded end-joints, and high resolution encoders lead to exceptional positioning capability even under high loads. These customizable actuators can be incorporated into a wide variety of architectures including gimbals, tripods, and hexapods.



Telescope Actuator Features

  • High load capacity
  • High stiffness
  • High resolution
  • High repeatability
  • High accuracy
  • Self-locking
  • Vacuum-compatible
  • Low heat dissipation
  • Long life

High Load Optical Positioning Actuators

The OPA series actuators are used for static positioning or slow tracking operation where minimum incremental step size, repeatability, and/or accuracy are critical. These precision actuators have high stiffness, handle heavy loads, and avoid backdriving making them ideally suited for the alignment of large optics. Outdoor, cleanroom, and vacuum-compatible versions are available. Customization of stroke length, end-joints, and other features is common to meet program-specific requirements.


  • Ground-based telescope mirror positioning
  • Testing of space-based telescopes and optical systems
  • Beam/laser pointing

Performance Characteristics


Model OPA-400 OPA-500
Stroke Length1 28 mm 160 mm
Minimum Incremental Step Size 0.1 μm 0.1 μm
Repeatability (Unidirectional) < 1 μm < 3 μm
Repeatability (Bidirectional) < 3 μm < 10 μm
Accuracy < 0.05% of Full Range < 0.1% of Full Range
Max Speed 1.17 mm/s (0.5 mm/s Continuous) 1.17 mm/s (0.5 mm/s Continuous)
Axial Load Capacity 39.2 kN 39.2 kN
Stiffness (Excluding End-Joints) 217 N/μm 277 N/μm
Dimensions2 (Excluding End-Joints) 230 mm D x 375 mm L 274 mm D x 480 mm L
Mass (Excluding End-Joints) 39 kg 43 kg
Motor Type Brushless Brushless
Gear Reduction 50:1 Harmonic Drive (Zero Backlash) 50:1 Harmonic Drive (Zero Backlash)
Screw Type Recirculating Roller Screw w/Preloaded Nut Recirculating Roller Screw w/Preloaded Nut
Sensor Type Absolute Linear Encoder Rotary Encoder
Backdrivable3 No (Self-Locking) No (Self-Locking)
End-Joint Options Flexures, Universal Joints w/ Preloaded Bearings, Custom Flexures, Universal Joints w/ Preloaded Bearings, Custom
Vacuum Compatibility With Customization Yes
Heritage Usage Rubin Observatory/Large Synoptic Survey Telescope (LSST)

James Webb Space Telescope Testing,

NASA X-Ray and Cryogenic Facility (XRCF)

1. Custom stroke lengths available upon request

2. Length measured at midstroke position

3. Brakes available as additional protection against backdriving