Design of off-axis PIAACMC mirrors

Self Cite

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: Coronagraph Modelmentioning

confidence: 99%

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

Traub

Breckinridge

Greene

et al. 2016

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“…Alternatively, it is possible for a coronagraph to counteract these obstructions with static phase excursions applied to deformable mirrors 44,62 or custom aspheric optics. 43,65,66,95 However, amplitude-mask-based apodization places less demanding requirements on mirror surface manufacturing tolerances, alignment tolerances, and deformable mirror reliability, thereby mitigating the overall technological risk of our design.…”

Section: Wfirst-afta Cgi Conceptmentioning

confidence: 99%

“…A third coronagraph type, the Phase-Induced Amplitude Apodization Complex Mask Coronagraph, is being pursued in parallel as a backup option. 48,[65][66][67] In the course of our efforts to improve the SPC designs already meeting the minimum performance goals, we investigate a hybrid coronagraph architecture in which a binary shaped pupil functions as the apodizer mask in an APLC-like configuration. 68,69 In effect, this expands on the idea first put forward by Cady et al, 70 who designed a hard-edged, star-shaped apodizer for the Gemini Planet Imager's APLC.…”

Section: Introductionmentioning

confidence: 99%

Shaped pupil Lyot coronagraphs: high-contrast solutions for restricted focal planes

Zimmerman

Riggs

Kasdin

et al. 2016

Coronagraphs of the apodized pupil and shaped pupil varieties use the Fraunhofer diffraction properties of amplitude masks to create regions of high contrast in the vicinity of a target star. Here we present a hybrid coronagraph architecture in which a binary, hard-edged shaped pupil mask replaces the gray, smooth apodizer of the apodized pupil Lyot coronagraph (APLC). For any contrast and bandwidth goal in this configuration, as long as the prescribed region of contrast is restricted to a finite area in the image, a shaped pupil is the apodizer with the highest transmission. We relate the starlight cancellation mechanism to that of the conventional APLC. We introduce a new class of solutions in which the amplitude profile of the Lyot stop, instead of being fixed as a padded replica of the telescope aperture, is jointly optimized with the apodizer. Finally, we describe shaped pupil Lyot coronagraph (SPLC) designs for the baseline architecture of the WFIRST-AFTA coronagraph. These SPLCs help to enable two scientific objectives of the WFIRST-AFTA mission: (i) broadband spectroscopy to characterize exoplanet atmospheres in reflected starlight and (ii) debris disk imaging. and second a "Lyot stop" to block the outer edge of the re-collimated on-axis beam before it is reimaged. 12 To take advantage of the diffraction-limited imaging capabilities of high-order adaptive optics (AO) systems, beginning in the 1990s classical Lyot designs were revised for high-contrast stellar coronagraphy. [13][14][15][16][17][18] Through Fourier optical analysis and modeling, researchers soon discovered the remarkable performance benefits of apodizing the entrance pupil of a coronagraph. [19][20][21] Since then, the transmission profile of this apodizer mask has been a topic of vigorous study. [22][23][24][25][26][27] One resulting family of designs, the apodized pupil Lyot coronagraph (APLC), has been successfully integrated with several AO-fed cameras to facilitate deep observations of young exoplanetary systems at near-infrared wavelengths.As an alternative to a coronagraph with two or more mask planes, pupil apodization by itself is perhaps the simplest and oldest way to reject unwanted starlight from a telescope image. 28,29 Fraunhofer diffraction theory dictates the way any change in the shape or transmission profile of the entrance pupil redistributes a star's energy in the image plane. This relationship can be used to design an apodizer whose point spread function (PSF) has a zone of high contrast near the star, without additional coronagraph masks. This is the shaped pupil approach developed by N. J. Kasdin and collaborators, who pioneered the optimization of apodizers with binary-valued transmission. [30][31][32][33] In recent years, shaped pupil solutions have evolved to work around arbitrary two-dimensional telescope apertures, in parallel with similar breakthroughs in APLC design. [34][35][36][37][38][39] The relative simplicity of a single mask, however, comes with a sacrifice in how close the dark search region can be push...

“…11 Numerical studies have shown that the PIAACMC coronagraph mode with the AFTA pupil has the potential for an increase in science yield due to its smaller inner working angle and increased throughput, 12 but it can be sensitive to low-order aberrations (induced by line-of-sight jitter). 13 Complex phase masks have only been recently manufactured 14 and off-axis PIAACMC mirrors have been designed, 15 with manufacture and laboratory investigations planned in the future.…”

Section: Background On Space Telescope Demonstrationsmentioning

confidence: 99%

“…To reach these deeper contrast levels, our SN strategy is to set aggressive settings for early iterations. These include a larger number of speckles (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) speckles at a time) with a larger radius in which energy is minimized and a more sparsely sampled parameter space for the phase and amplitude probes. As deeper contrast levels are attained, the SN setting aggressiveness is reduced in order to minimize speckle interactions during probing.…”

Section: Wavefront Controlmentioning

confidence: 99%

Demonstration of broadband contrast at 1.2λ/Dand greater for the EXCEDE starlight suppression system

Sirbu

Thomas

Belikov

et al. 2016

Self Cite

Abstract. The EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE) science mission concept uses a visible-wavelength Phase-Induced Amplitude Apodization (PIAA) coronagraph to enable high-contrast imaging of circumstellar debris systems and some giant planets at angular separations reaching into the habitable zones of some of the nearest stars. We report on the experimental results obtained in the vacuum chamber at the Lockheed Martin Advanced Technology Center in 10% broadband light centered about 650 nm, with a median contrast of 1 × 10 −5 between 1.2 and 2.0 λ/D simultaneously with 3 × 10 −7 contrast between 2 and 11 λ/D for a single-sided dark hole using a deformable mirror (DM) upstream of the PIAA coronagraph. These results are stable and repeatable as demonstrated by three measurements runs with DM settings set from scratch and maintained on the best 90% out of the 1000 collected frames. We compare the reduced experimental data with simulation results from modeling observed experimental limits; observed performance is consistent with uncorrected low-order modes not estimated by the Low Order Wavefront Sensor (LOWFS). Modeled sensitivity to bandwidth and residual tip/tilt modes is well-matched to the experiment.