Abstract
The effects of photon noise, aliasing, wave front chromaticity, and scintillation on the point-spread function (PSF) contrast achievable with ground-based adaptive optics (AO) are evaluated for different wave front sensing schemes. I show that a wave front sensor (WFS) based on the Zernike phase contrast technique offers the best sensitivity to photon noise at all spatial frequencies, while the Shack-Hartmann WFS is significantly less sensitive. In AO systems performing wave front sensing in the visible and scientific imaging in the near-IR, the PSF contrast limit is set by the scintillation chromaticity induced by Fresnel propagation through the atmosphere. On an 8 m telescope, the PSF contrast is then limited to 10 -4 to 10-5 in the central arcsecond. Wave front sensing and scientific imaging should therefore be done at the same wavelength, in which case, on bright sources, PSF contrasts between 10-6 and 10 -7 can be achieved within 1″ on an 8 m telescope in optical/near-IR. The impact of atmospheric turbulence parameters (seeing, wind speed, turbulence profile) on the PSF contrast is quantified. I show that a focal plane wave front sensing scheme offers unique advantages, and I discuss how to implement it. Coronagraphic options are also briefly discussed.
Original language | English (US) |
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Pages (from-to) | 592-614 |
Number of pages | 23 |
Journal | Astrophysical Journal |
Volume | 629 |
Issue number | 1 I |
DOIs | |
State | Published - Aug 10 2005 |
Keywords
- Instrumentation: adaptive optics
- Instrumentation: interferometers
- Methods: data analysis
- Techniques: high angular resolution
- Techniques: interferometric
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science