Low Order Aberrations in Band-Limited Lyot Coronagraphs

Abstract

We study the way Lyot coronagraphs with unapodized entrance pupils respond to small, low order phase aberrations. This study is applicable to ground-based adaptive optics coronagraphs operating at 90% and higher Strehl ratios, as well as to some space-based coronagraphs with intrinsically higher Strehl ratio imaging. We utilize a second order expansion of the monochromatic point-spread function (written as a power spectrum of a power series in the phase aberration over clear aperture) to derive analytical expressions for the response of a `band-limited' Lyot coronagraph (BLC) to small, low order, phase aberrations. The BLC possesses a focal plane mask with an occulting spot whose opacity profile is a spatially band-limited function rather than a hard-edged, opaque disk. The BLC is, to first order, insensitive to tilt and astigmatism. Undersizing the stop in the re-imaged pupil plane (the Lyot plane) following the focal plane mask can alleviate second order effects of astigmatism, at the expense of system throughput and angular resolution. The optimal degree of such undersizing depends on individual instrument designs and goals. Our analytical work engenders physical insight, and complements existing numerical work on this subject. Our methods can be extended to treat the passage of higher order aberrations through band-limited Lyot coronagraphs, by using our polynomial decomposition or an analogous Fourier approach.

8 pages, 3 figures, 1 table; ApJ accepted

References in corpus (9)

• Apodized Pupil Lyot Coronagraphs for Arbitrary Telescope Apertures
• A Coronagraph with a Band-Limited Mask for Finding Terrestrial Planets
• The Structure of High Strehl Ratio Point-Spread Functions
• Detection of Earth-like Planets Using Apodized Telescopes
• Ground-Based Coronagraphy with High Order Adaptive Optics
• Polarization Effects in Reflecting Coronagraphs for White Light Applications in Astronomy
• Lyot Coronagraphy on Giant Segmented-Mirror Telescopes
• Tip-tilt Error in Lyot Coronagraphs
• An Analysis of Fundamental Waffle Mode in Early AEOS Adaptive Optics Images

Cited by in corpus (9)

• Speckle noise and dynamic range in coronagraphic images
• Astrometry and Photometry with Coronagraphs
• Lyot-based Low Order Wavefront Sensor for Phase-mask Coronagraphs: Principle, Simulations and Laboratory Experiments
• Coronagraphic Low Order Wavefront Sensor: Principle and Application to a Phase-Induced Amplitude Coronagraph
• Comparative Lyot Coronagraphy with Extreme AO Systems
• Improved achromatization of phase mask coronagraphs using colored apodization
• Propagation of Aberrations through Phase Induced Amplitude Apodization coronagraph
• Laboratory Testing of a Lyot Coronagraph Equipped with an Eighth-Order Notch Filter Image Mask
• Analytical analysis of Lyot coronographs