Description of the SCExAO project

Pulpit rock

SCExAO and HiCIAO mounted on their frame at the Nasmyth platform undergoing testing.


Our group will equip the Subaru Telescope with a high performance coronagraphic Extreme Adaptive Optics system for direct imaging of exoplanets & protoplanetary disks. The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system benefits from the most recent development in coronagraphy, adaptive optics, interferometric imaging techniques and detector technologies, many of which have been pioneered by our group at Subaru Telescope.

The SCExAO system will be the first coronagraphic system truly optimized for detecting planets at very small angular separation. This optimization is essential to the success of any exoplanet direct detection program. The ability to probe the inner part of planetary systems will prove invaluable in our attempt at understanding their formation and evolution.

Our proposed work builds upon recent successful developments/achievements at Subaru Telescope: the 188-actuator adaptive optics system, the PIAA coronagraph, and the HiCIAO camera.

System Architecture

Located between the Subaru Telescope AO188 (left on the diagram) and the HiCIAO differential imaging camera (right), SCExAO is made up of several essential sub-systems:

  • A 2000-actuator MEMS Deformable Mirror, driven by a wavefront control algorithm that uses the data acquired by the high frame rate science camera to suppress the quasi-static and slow moving speckles in the field. Details about this sub-system can be found here. In its second version, the system will also include a high sensitivity (visible) wavefront sensor using a photon counting camera to reduce the contribution of the dynamic speckles.

  • A high-contrast high-efficiency coronagraph exploiting for the first time on an actual instrument, the Phase Induced Amplitude Apodization (PIAA) Coronagraph. In addition there are several other state-of-the-art coronagraph types including the vector vortex, four-quadrant phase mask, eight-octant phase mask and shaped pupil versions which will cover a broad spectrum of scientific requirements.

  • An efficient Coronagraphic Low Order Wavefront Sensor (CLOWFS) which uses the light diffracted by the occulting mask to measure tip-tilt residuals with a <100 μas precision (precision of <0.01 λ/D).

Pulpit rock

System level diagram of the SCExAO instrument.

For more technical details please refer to the publications page.