Hexapod 6-Axis Alignment Systems used in Astronomy and Imaging Applications

Hexapod 6-DOF parallel kinematics precision positioning systems (Stewart Platforms) are ideal supports for fast steering mirrors. They can provide the coarse alignment (coarse meaning sub-micron resolution) to compensate for out of focus deviations. Even though usually only 5 degrees of freedom are required, hexapods are the preferred solution due to their high stiffness (low vibrations), symmetrical design, and large central aperture, allowing light to pass through. PI has 40 years of experience with parallel kinematic structures and delivered the first high precision hexapods for astronomical applications in the early 1990’s. Today, PI provides more standard precision Stewart platforms than any other company in the world. 

ALMA (Atacama Large Millimeter Array) Radio Telescope, Chile

PI supplies 50 custom, weather-proof hexapods. The Alma telescope array was a major contributor in the first imaging of a black hole.

  • Linear travel x/y/z: ±35/±35/±30mm
  • Rotational travel u/v/w: ±7/±7/±9.5°
  • MIM: 2µm
  • Repeatability x/y/z: ±5µm
  • Velocity: 2mm/s
  • Protection class: IP64
  • Load capacity: 750N (any direction)

NASA Goddard – James Webb Telescope

Custom 200kg load capacity hexapod for high resolution positioning of the JWST mirror segments during assembly

NASA / UMass Lowell

"Planetary Imaging Concept Testbed Using a Recoverable Experiment-Coronagraph" - High Altitude Balloon Mission

The mission's long term goal is to directly image Earth-like planets around nearby stars. The telescope was carried by a 39 million cubic feet helium balloon to the outer edge of the atmosphere at 125,000 feet, more than 4 times the height of Mount Everest.

An H-811 miniature hexapod was used in the optical control system. The picture shows electric heaters and sensors applied to the hexapod legs to keep it operating at the extremely low temperatures at the edge of space.

WFIRST - Grism for the Wide Field Instrument

The slitless spectrometer in the WFIRST wide field instrument is based on a compound grism (grating prism).  A compact hexapod was used for the alignment and test of the elements in the grism assembly. More information»

Pan-Starrs, Skymapper, MRO

Pan-Starrs-1 is one of four 1.8m Telescopes on Hawaii; the M2 is equipped with a custom PI hexapod.

Magdalena Ridge Observatory, located in New Mexico, the 2.4m Telescope is equipped with a custom PI hexapod.

Skymapper is a 1.3m Telescope in Australia, also using a PI hexapod.

Hexapod for Pan-Starrs-1 and Skymapper

  • Linear travel x/y/z: ±8/±8/±5mm
  • Rotational travel u/v/w: ±1.4/±1.4/±1.8°
  • MIM: 1µm
  • Repeatability x/y/z: ±2/±2/±1µm
  • Self-locking for mounting horizontal/40°tilted: 2000/600N

Hexapod for Magdalena Ridge Observatory

  • Linear travel x/y/z: ±39/±44/±25mm
  • Rotational travel u/v/w: ±7/±7/±9°
  • MIM: 1µm
  • Repeatability x/y/z: ±2/±2/±1µm

APEx Radiotelescope, Chile

PI supplies a custom weatherproof hexapod.

  • Linear travel x/y/z: ±35/±35/±30mm
  • Rotational travel u/v/w: ±7/±7/±9.5°
  • MIM: 2µm
  • Repeatability x/y/z: ±5µm
  • Velocity: 2 mm/s
  • Protection class: IP64
  • Load capacity: 750N (any direction)

Big Bear Solar Observatory, California

PI supplies a standard M-850.11 hexapod for secondary alignment.

Tenerife Solar Telescope, Spain

Tenerife uses a modified M-850.11 hexapod.

  • Linear travel x/y/z: ±30/±30/±11mm
  • Rotational travel u/v/w: ±10/±10/±15°
  • MIM: 1µm
  • Repeatability x/y/z: ±2/±2/±1µm
  • Self-locking for mounting horizontal: 2000N
  • Velocity: 0.5 mm/s

Steward Mirror Labs, University of Arizona

  • High Load (2000 lb) Custom Hexapod for precision optical system alignment fixture
  • 1 meter diameter baseplate

Advanced Piezo Hexapods

  • Custom double hexapod design provides coarse alignment and high resolution alignment for large telescope mirrors.

United Kingdom Infrared Telescope (UKIRT)

PI supplies custom hexapod and active tip/tilt steering mirror for secondary mirror for UKIRT telescope on Mauna Kea, Hawaii.

  • Mirror diameter: 314mm
  • Tip/tilt range: ±500µrad
  • Resonant frequency: 280Hz

NASA Infrared Telescope Facility (IRTF)

PI supplies custom hexapod and active tip/tilt steering mirror for secondary mirror for NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii.

  • Mirror diameter: 244mm
  • Tip/tilt range: ±250µrad
  • Resonant frequency: 490Hz

Other Hexapod and Hexapod-Like Structures and Applications

National Ignition Facility, Lawrence Livermore

Custom hexapod for laser beam collimation and diagnostics inside the target chamber

  • 250kg Load capacity

ESRS - France Synchrotron Light Source

PI custom “spacefab” hexapod design for X ray goniometric measurements including a high load, large diameter rotary air bearing stage with extended tilt capability

  • 1000lb Load capacity

Testing Capabilities of High Load Hexapods

Custom 6000 lb. load capacity, vacuum compatible hexapod for high resolution positioning of heavy EUV optical assemblies for advanced lithography

  • Shown in hexapod testing bay with test masses

High Load Hexapods – Standard Products

PI standard hexapods provide load capacities up to 2000lbs and custom models with several times that value have been designed and tested.



More Reading