Olivier Guyon's webpage

Subaru Coronagraphic Extreme Adaptive Optics (SCExAO): overview

For more info on SCExAO, see the Subaru Telescope SCExAO website
For a recent update on SCExAO, see the SCExAO blog maintained by F. Martinache

Purpose

The Objective of the SCExAO project is to develop a Coronagraphic Extreme-Adaptive Optics (SCExAO) system for the Subaru Telescope. The main scientific goals of this new instrument are to:

Image extrasolar planets orbiting nearby stars. The prime scientific targets will be nearby young (= still bright in the near-IR) stars, at most a few 100Myr old (Hyades, Uma, Pleiades/Alpha Per and TW Hyd associations).
Image disks around nearby stars
Better understand the formation, evolution and architecture of planetary systems
Perform other observations requiring coronagraphy (QSO host galaxies, faint satellites)

The SCExAO instrument will be able to image planets as close as 0.04" from their parent star: this is closer in than any other existing or planned instrument on 8-m class telescopes. It will be able to image planets about 15 to 17 magnitudes fainter than their parent star.

Method/Approach

Our approach is to develop a coronagraphic platform with wavefront control to be inserted between the AO188 adaptive optics system and the HiCIAO imaging camera optimized for high contrast work. By taking advantage of these two existing instruments, we have a unique strategic opportunity to offer Subaru Telescope a high performance CEAO system on a fast schedule. Key technical choices for this system include:

An extremely accurate wavefront control scheme using the science camera (HiCIAO) images to measure the wavefront. This approach does not require us to build any wavefront sensor optics and offers high accuracy with no non-common path errors.
We take full advantage of already existing instruments: AO188 and HiCIAO. AO188 is an ideal "first stage" wavefront correction system for our project, and HiCIAO was designed to be modifiable and upgradeable, betting on extrapolations of current R&D progresses. A huge saving in cost/schedule is achieved by utilizing LGS188 and HiCIAO.
We use the most efficient coronagraph and wavefront control scheme currently known. The Phase-Induced Amplitude Apodization (PIAA) has been developed by our team.
We take advantage of the high degree of flexibility offered at Nasmyth focus. Our system is modular and easily upgradable

SCExAO coronagraph optics design

The SCExAO key optics (PIAA lenses, Spider Removal Plate) are described in this document, which was written to identify vendors for our optics. The document refers to several files which are included in this webpage:

File pup.dat: Apodization profile (amplitude) produced by the lenses.
File lens1_type1.dat
File lens2_type1.dat
File lens1_type2.dat
File lens2_type2.dat

Pictures of SCExAO

The SCExAO system is contained in a box, which is inserted between the AO188 facility AO system and the HiCIAO camera. The box is shown in this picture as it is craned at the telescope. The box holds a 1.2m long by 0.9m wide optical bench, onto which all components are bolted.

SCExAO bench, top view (Oct 2011). The beam comes into the SCExAO from AO188 at the top right as seen in this picture, and is delivered to the HiCIAO camera to the top left of this picture. The bottom half of the bench is dedicated to visible light science imaging and wavefront sensing. The top half of the bench is dedicated to near-IR coronagraphy and wavefront control. The 32x32-actuator MEMS deformable mirror is visible in the top left.
[High resolution image - 3.2MB]

SCExAO bench (Oct 2011). The beam comes into the SCExAO from AO188 at the front side of the bench, as seen in this picture. The left side of the bench is dedicated to visible light science imaging and wavefront sensing. The right side of the bench is dedicated to near-IR coronagraphy and wavefront control. The 32x32-actuator MEMS deformable mirror is visible in the front right.
[High resolution image - 5.5MB]

SCExAO pyramid wavefront sensor (Oct 2011). The optics for the wavefront sensor are visible just below the center of the image. The WFS camera, a low noise CMOS camera ( Neo sCMOS, Andor), is visible just above the center of the image.
[High resolution image - 5.1MB]

SCExAO visible cameras (Oct 2011). This image shows the two visible EMCCD cameras used for scientific imaging (bottom) as well as the CMOS camera used for wavefront sensing (top). The two EMCCDs acquire images simultaneously in two colors.
[High resolution image - 5.2MB]