Low‐Order Aberration Sensitivity of Eighth‐Order Coronagraph Masks

Shaklan, Stuart; Green, Joseph J.

doi:10.1086/430204

Cited by 54 publications

(32 citation statements)

References 15 publications

(11 reference statements)

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“…The sensitivity of some coronagraphs to tip-tilt errors has been investigated by several authors (see, e.g., Lloyd & Sivaramakrishnan 2005;Shaklan & Green 2005;Sivaramakrishnan et al 2006).…”

Section: Effect Of Stellar Angular Diameter In Existing Coronagraph Dmentioning

confidence: 99%

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Theoretical Limits on Extrasolar Terrestrial Planet Detection with Coronagraphs

Guyon¹,

Pluzhnik²,

Kuchner³

et al. 2006

ASTROPHYS J SUPPL S

304

273

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Many high-contrast coronagraph designs have recently been proposed. In this paper, their suitability for direct imaging of extrasolar terrestrial planets is reviewed. We also develop a linear algebra based model of coronagraphy that can both explain the behavior of existing coronagraphs and quantify the coronagraphic performance limit imposed by fundamental physics. We find that the maximum theoretical throughput of a coronagraph is equal to 1 minus the nonaberrated noncoronagraphic PSF of the telescope. We describe how a coronagraph reaching this fundamental limit may be designed, and how much improvement over the best existing coronagraph design is still possible. Both the analytical model and numerical simulations of existing designs also show that this theoretical limit rapidly degrades as the source size is increased: the ''highest performance'' coronagraphs, those with the highest throughput and smallest inner working angle (IWA), are the most sensitive to stellar angular diameter. This unfortunately rules out the possibility of using a small IWA (

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Section: Effect Of Stellar Angular Diameter In Existing Coronagraph Dmentioning

confidence: 99%

“…The CPA owes its relative immunity to tip-tilt errors to the field-invariance of its PSF. The sensitivity of the BL8 to tip-tilt errors was studied in detail by Shaklan & Green (2005), who also find that the BL8 can tolerate relatively high levels of focus, coma, and astigmatism.…”

Section: Effect Of Stellar Angular Diameter In Existing Coronagraph Dmentioning

confidence: 99%

Theoretical Limits on Extrasolar Terrestrial Planet Detection with Coronagraphs

Guyon¹,

Pluzhnik²,

Kuchner³

et al. 2006

ASTROPHYS J SUPPL S

304

273

View full text Add to dashboard Cite

show abstract

“…Coronagraphs with small IWA are very sensitive to low-order aberrations and small pointing errors upstream of their focal plane mask. These aberrations diffract a part of the stellar light through the coronagraph aperture and strongly decrease the coronagraph performance (Lloyd & Sivaramakrishnan 2005;Sivaramakrishnan et al 2005;Shaklan & Green 2005). To detect very faint companions close to their stars, it is then necessary to accurately measure and correct for the low-order aberrations such as tip-tilt, focus, and astigmatism.…”

Section: Introductionmentioning

confidence: 99%

Tip-tilt estimation and correction using FQPM coronagraphic images

Mas

Baudoz

Rousset

et al. 2012

A&A

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Context. Direct imaging of exoplanets located a few AU from their hosting star requires angular resolution at the diffraction limit of large telescopes and a contrast level in the image of 10 5 to 10 10 . Simultaneous use of adaptive optics and coronagraphy is mandatory to fulfil these requirements. Aims. Coronagraphs are usually very sensitive to pointing errors upstream of their focal plane mask. Approaches to measuring these errors in conventional adaptive optics systems consist in setting a wavefront sensor in an additional channel. Differential aberrations between the coronagraphic channel and the additional one induce a loss in performance. To tackle this limitation, we propose a new technique for measuring the tip-tilt errors directly from the coronagraphic image. Methods. Our method uses the relations between the intensity distribution in the coronagraphic image and upstream tip-tilt errors. We also propose a method of estimating the tip-tilt errors downstream of the focal plane mask. We validate at visible wavelength our upstream and downstream tip-tilt estimation and compensation techniques with numerical simulation images and on laboratory images. Results. Numerical simulations predict that our techniques correct for the tip-tilt errors to a 1.3 × 10 −2 λ/D level when considering a λ/40 wavefront error upstream of the coronagraph. In laboratory, where the coronagraph is mostly limited by wavefront errors, we correct for the tip-tilt errors with an accuracy better than 6.5 × 10 −2 λ/D. Conclusions. We demonstrate in numerical simulations and in laboratory that our technique can efficiently estimate the tip-tilt errors directly from the coronagraphic image with no additional channel. It is robust and can be used with small wavefront errors. It should be applicable to planet imager systems currently in preparation, such as SPHERE and MIRI/JWST.

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“…Laboratory tests in a high-dynamic range coronagraph are underway.. The baseline Lyot coronagraph is a linear 8th-order mask (Kuchner et al (2005), Shaklan & Green (2005)). The 8th-order null is effective at filtering low-order aberrations that will result when the primary mirror sees thermal gradients and when the secondary mirror moves relative to the primary.…”

Section: Aperturesmentioning

confidence: 99%