Fast linearized coronagraph optimizer (FALCO) IV: coronagraph design survey for obstructed and segmented apertures

Abstract

Coronagraph instruments on future space telescopes will enable the direct detection and characterization of Earth-like exoplanets around Sun-like stars for the first time. The quest for the optimal optical coronagraph designs has made rapid progress in recent years thanks to the Segmented Coronagraph Design and Analysis (SCDA) initiative led by the Exoplanet Exploration Program at NASA's Jet Propulsion Laboratory. As a result, several types of high-performance designs have emerged that make use of dual deformable mirrors to (1) correct for optical aberrations and (2) suppress diffracted starlight from obstructions and discontinuities in the telescope pupil. However, the algorithms used to compute the optimal deformable mirror surface tend to be computationally intensive, prohibiting large scale design surveys. Here, we utilize the Fast Linearized Coronagraph Optimizer (FALCO), a tool that allows for rapid optimization of deformable mirror shapes, to explore trade-offs in coronagraph designs for obstructed and segmented space telescopes. We compare designs for representative shaped pupil Lyot and vortex coronagraphs, two of the most promising concepts for the LUVOIR space mission concept. We analyze the optical performance of each design, including their throughput and ability to passively suppress light from partially resolved stars in the presence of low-order aberrations. Our main result is that deformable mirror based apodization can sufficiently suppress diffraction from support struts and inter-segment gaps whose widths are on the order of ∼0.1% of the primary mirror diameter to detect Earth-sized planets within a few tens of milliarcseconds from the star.

The decadal survey testbed two: a technology development facility for future exo-Earth observatories

“…Lastly, FALCO mediates this entire process. 8,[17][18][19] A more detailed description of HCIT's standard dark hole process has been outlined in Ruane et al (2022). 20 All data will be presented in terms of normalized intensity (NI), which for Lyot coronagraphs is an accurate proxy for contrast.…”

Advances in optical engineering for future telescopes

“…In this section, we compare the point spread function (PSF) of a pinwheel pupil (curved edges) and that of a keystone pupil (straight edges) and further illustrate how the curvature of the spokes in the pinwheel pupil plane can impact the PSF in the image plane. The discrete matrix Fourier Transform analysis is performed by Physical Optics Propagation in Python (POPPY) 53,54 , a Python library primarily developed by a team of astronomers at the Space Telescope Science Institute. The investigated pupils are shown in Fig.…”

Towards high throughput and low-order aberration robustness for vortex coronagraphs with central obstructions

“…In order to approximate the impact of the MSAVC on yield, we can use the power-law indices derived in Stark et al 2019 8 that approximate the dependence of yield on various parameters of the coronagraph to extrapolate from the yield of an off-axis charge 6 vortex coronagraph, which is based on the DM-assisted off-axis vortex coronagraph discussed in Ruane et al 2018. 29 The comparison between the two systems is apt because the setups are similar-the differences between the two are the greyscale pupil apodization and the additional vortex and Lyot stage are different. The bandwidth is identical, and the shape of the throughput curve (and therefore how changing the IWA translates to changes in yield) are similar for both sorts of system.…”