36 research outputs found
Shaped Pupil Lyot Coronagraphs: High-Contrast Solutions for Restricted Focal Planes
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 Wide-Field Infrared Survey
Telescope-Astrophysics Focused Telescope Assets (WFIRST-AFTA) coronagraph.
These SPLCs help to enable two scientific objectives of the WFIRST-AFTA
mission: (1) broadband spectroscopy to characterize exoplanet atmospheres in
reflected starlight and (2) debris disk imaging.Comment: 41 pages, 15 figures; published in the JATIS special section on
WFIRST-AFTA coronagraph
Numerically optimized coronagraph designs for the Habitable Exoplanet Imaging Mission (HabEx) concept
The primary science goal of the Habitable Exoplanet Imaging Mission (HabEx), one of four candidate flagship missions under investigation, is to image and spectrally characterize Earth-like exoplanets. It is well known that pupil obscurations degrade coronagraphic performance and complicate coronagraph design, so HabEx is planned to have an off-axis, unobscured primary mirror. We utilize the circular symmetry of the aperture to investigate 1D-radial coronagraph optimization methods that are prohibitively time-consuming or intractable in 2D, such as diffractive pupil remapping and concurrent, multi-plane optimization. We also directly constrain sensitivities to dynamic, low-order Zernike aberrations, which are separable in polar coordinates and can thus be propagated as 1D-radial integrals. The mask technologies in our designs claim heritage from the extensive modeling and testbed experiments performed by the Wide-Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) project. In this paper, we detail our optimization methods and outline future work to complete our design survey
Prospects for Exoplanet Imaging in Multi-Star Systems with Starshades
We explore the capabilities of a starshade mission to directly image multi-star systems. In addition to the diffracted and scattered light for the on-axis star, a multi-star system features additional starlight leakage from the off-axis star that must also be controlled. A basic option is for additional starshades to block the off- axis stars. An interesting option takes the form of hybrid operation of a starshade in conjunction with an internal starlight suppression. Two hybrid scenarios are considered. One such scenario includes the coronagraph instrument blocking the on-axis star, with the starshade blocking off-axis starlight. Another scenario uses the wavefront control system in the coronagraph instrument and using a recent Super-Nyquist Wavefront Control (SNWC) technique can remove the off-axis stars leakage to enable a region of high-contrast around the on-axis star blocked by the starshade. We present simulation results relevant for the WFIRST telescope
Experimental analysis of the achromatic performance of a vector vortex coronagraph
The vector vortex coronagraph is an instrument designed for direct detection and spectroscopy of exoplanets over a broad spectral range. Our team is working towards demonstrating contrast performance commensurate with imaging temperate, terrestrial planets orbiting solar-type stars using the High Contrast Imaging Testbed facility at NASA's Jet Propulsion Laboratory. To date, the best broadband performance achieved is ~10⁻⁸ raw contrast over a bandwidth of Δλ/λ=10% in the visible regime (central wavelengths of 550 nm-750 nm), while monochromatic tests yield much deeper contrast (~10⁻⁹ or better). In this study, we analyze the main performance limitations on the testbeds so far, focusing on the quality of the focal plane mask manufacturing. We measure the polarization properties of the masks and the residual electric field in the dark hole as a function of wavelength. Our results suggest that the current performance is limited by localized defects in the in the focal plane masks. A new generation of masks is under test that have fewer defects and promise performance improvements
Experimental comparison of model-free and model-based dark hole algorithms for future space telescopes
Coronagraphic instruments provide a great chance of enabling high contrast
spectroscopy for the pursuit of finding a habitable world. Future space
telescope coronagraph instruments require high performing focal plane masks in
combination with precise wavefront sensing and control techniques to achieve
dark holes for planet detection. Several wavefront control algorithms have been
developed in recent years that might vary in performance depending on the
coronagraph they are paired with. This study compares 3 model-free and
model-based algorithms when coupled with either a Vector (VVC) or a Scalar
(SVC) Vortex Coronagraph mask in the same laboratory conditions: Pairwise
Probing with Electric Field Conjugation, the Self-Coherent Camera with Electric
Field Conjugation, and Implicit Electric Field Conjugation. We present
experimental results from the In-Air Coronagraph Testbed (IACT) at JPL in
narrowband and broadband light, comparing the pros and cons of each of these
wavefront sensing and control algorithms with respect to their potential for
future space telescopes.Comment: Conference Proceedings of SPIE: Techniques and Instrumentation for
Detection of Exoplanets XI, vol. 12680 (2023
Numerically optimized coronagraph designs for the Habitable Exoplanet Imaging Mission (HabEx) concept
The primary science goal of the Habitable Exoplanet Imaging Mission (HabEx), one of four candidate flagship missions under investigation, is to image and spectrally characterize Earth-like exoplanets. It is well known that pupil obscurations degrade coronagraphic performance and complicate coronagraph design, so HabEx is planned to have an off-axis, unobscured primary mirror. We utilize the circular symmetry of the aperture to investigate 1D-radial coronagraph optimization methods that are prohibitively time-consuming or intractable in 2D, such as diffractive pupil remapping and concurrent, multi-plane optimization. We also directly constrain sensitivities to dynamic, low-order Zernike aberrations, which are separable in polar coordinates and can thus be propagated as 1D-radial integrals. The mask technologies in our designs claim heritage from the extensive modeling and testbed experiments performed by the Wide-Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) project. In this paper, we detail our optimization methods and outline future work to complete our design survey
Achromatizing scalar vortex coronagraphs with radial phase mask dimples
The Habitable Worlds Observatory mission will require coronagraphs capable of
achieving contrasts of 1e-10 to detect exo-Earths. The choice of coronagraph
depends on finding a solution that is achromatic within a 20\% bandwidth,
insensitive to low order aberrations and polarization independent. We present
two scalar vortex phase mask designs which employ a Roddier phase dimple and a
dual zone phase dimple to improve the achromatic performance by addressing the
chromatic stellar leakage not handled by the vortex. We show that using these
dimples, it is possible to substantially improve the broadband contrast
performance of existing scalar vortex phase masks.Comment: Conference Proceedings of SPIE: Techniques and Instrumentation for
Detection of Exoplanets XI, vol. 12680 (2023