Friday, November 10, 2017

HiCAT: functional description of the testbed


HiCAT has been designed to combine wavefront sensing, wavefront control, and starlight suppression with complex aperture telescopes. The scheme below indicates the components that are dedicated to the different functionalities of the testbed.

  • The star is simulated thanks to a fiber source, brought to infinity thanks to an off-axis parabola.
  • The telescope pupil is defined using two different components, set in two consecutive pupil planes: a pupil mask, to define the edges of the telescope, including the central obstruction and the spiders, and a segmented mirror (Iris-AO) of 37 segments that can be controlled in piston, tip, and tilt. 
  • The starlight is suppressed thanks to a Apodized Lyot Coronagraph, that combines an apodizer, a focal plane mask, and a Lyot Stop.
  • The wavefront control is done thanks to two deformable mirrors (Boston-Micromachines), one set in a pupil plane and one out of pupil plane, to correct for both phase and amplitude aberrations. 
  • The wavefront sensing is done thanks the final focal plane camera, set on a guiding rail for phase retrieval. Other techniques of wavefront sensing do not require the use of a guiding rail and combine the final camera with the pupil plane deformable mirror.
  • The testbed is also provided with a second camera, set in the final pupil plane.
In a next article, we will describe the current status of the testbed on our way to achieve all these functionalities.

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