Low-order wavefront sensing and control for WFIRST-AFTA coronagraph

Abstract. The coronagraph instrument (CGI) on the Wide-Field Infrared Survey Telescope will directly image and spectrally characterize planets and circumstellar disks around nearby stars. Here we estimate the expected science yield of the CGI for known radial-velocity (RV) planets and potential circumstellar disks. The science return is estimated for three types of coronagraphs: the hybrid Lyot and shaped pupil are the currently planned designs, and the phase-induced amplitude apodizing complex mask coronagraph is the backup design. We compare the potential performance of each type for imaging as well as spectroscopy. We find that the RV targets can be imaged in sufficient numbers to produce substantial advances in the science of nearby exoplanets. To illustrate the potential for circumstellar disk detections, we estimate the brightness of zodiacal-type disks, which could be detected simultaneously during RV planet observations.

Section: Speckle Contrast Versus Anglementioning

confidence: 99%

Science yield estimate with the Wide-Field Infrared Survey Telescope coronagraph

Traub

Breckinridge

Greene

et al. 2016

“…Much of the current development effort for the project is focused on low-order wavefront sensing and control to mitigate these effects. 45,46 We can also see significant improvements in the coronagraph design since the versions evaluated in Sec. 3.1, as the probability of zero planet detections is <2% in the case of the highest jitter level, and is well below 1% for all other cases.…”

Section: Comparison Of Hybrid Lyot Coronagraph Parametersmentioning

confidence: 74%

WFIRST-AFTA coronagraph science yield modeling with EXOSIMS

Savransky

Garrett

2015

Abstract. We present and discuss the design details of an extensible, modular, open-source software framework called EXOSIMS (Exoplanet Open-Source Imaging Mission Simulator), which creates end-to-end simulations of space-based exoplanet imaging missions. We motivate the development and baseline implementation of the component parts of this software with models of the wide-field infrared survey telescope-astrophysics focused telescope assets (WFIRST-AFTA) coronagraph and present initial results of mission simulations for various iterations of the WFIRST-AFTA coronagraph design. We present and discuss two sets of simulations. The first compares the science yield of completely different instruments in the form of early competing coronagraph designs for WFIRST-AFTA. The second set of simulations evaluates the effects of different operating assumptions, specifically the assumed postprocessing capabilities and telescope vibration levels. We discuss how these results can guide further instrument development and the expected evolution of science yields. © The Authors. Published by SPIE under a Creative CommonsAttribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requiresfull attribution of the original publication, including its DOI.

“…With an intensity transmittance of about 10 −4 , the metal-dielectric focal plane mask immediately rejects most of the starlight, removing it from the coronagraph system while directing the reflected starlight to the low-order wavefront sensor (LOWFS). 13 The remaining fraction of the star's PSF passes through and around the occulting mask. A thickness-profiled dielectric layer superimposed on the base metallic layer of the focal plane mask shapes the phase of the light transmitted by the focal plane mask, such that coherent remnants of the starlight interfere to further darken the highcontrast dark field.…”

Section: Hybrid Lyot Coronagraph Design Elementsmentioning

confidence: 99%

“…The tilted focal plane mask reflects about 60% of the incident starlight, which is captured by LOWFS camera 13 to provide both a bias-free guide signal for pointing jitter stabilization and a monitor of low-order wavefront drifts. The guide signal is used by a fast steering mirror internal to the coronagraph to reduce the pointing jitter inherent to the AFTA telescope system.…”

Section: Hybrid Lyot Coronagraph Design Elementsmentioning

confidence: 99%

Hybrid Lyot coronagraph for WFIRST-AFTA: coronagraph design and performance metrics

Trauger

Moody

Krist

et al. 2016

Abstract. The prospect of extreme high-contrast astronomical imaging from space has inspired developments of new coronagraph methods for exoplanet imaging and spectroscopy. However, the requisite imaging contrast, at levels of 1 billion to one or better for the direct imaging of cool mature exoplanets in reflected visible starlight, leads to challenging new requirements on the stability and control of the optical wavefront, at levels currently beyond the reach of ground-based telescopes. We review the design, performance, and science prospects for the hybrid Lyot coronagraph (HLC) on the WFIRST-AFTA telescope. Together with a pair of deformable mirrors for active wavefront control, the HLC creates a full 360-deg high-contrast dark field of view at 10 −9 contrast levels or better, extending to within angular separations of 3 λ 0 ∕D from the central star, over spectral bandwidths of 10% or more.