Roman Space Telescope CGI: prism and polarizer characterization modes

Groff, Tyler D.; Zimmerman, Neil; Subedi, Hari; Rizzo, Maxime; Titus, John; Lyons, J. T.; Bell, Dylan; Gaylin, Samuel; Gao, Ge; Pasquale, Bert A.; Nicolaeff, Nicholas; Tamura, Motohide

doi:10.1117/12.2562925

Cited by 8 publications

(3 citation statements)

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“…The last OAP collimates the beam again, sending it to the color filter alignment mechanism (CFAM) and then to the dispersion/polarization alignment mechanism that contains imaging and defocusing lenses, Amici zero-deviation dispersing prisms for spectroscopy, and polarizers (Wollaston prisms that simultaneously produce two images on the detector at orthogonal polarizations; the default mode is no polarizers). 27 One more fold mirror then directs the beam onto the exoplanetary camera (EXCAM), an electron-multiplied charge-coupled device 28 (EMCCD) detector that allows for both conventional analog charge-coupled device (CCD) imaging, using EM gain to reduce read noise, and photon counting in low-flux conditions with effectively zero read noise. EXCAM is used for both two-dimensional imaging and the capture of the dispersed spectrum when the slit and prism are inserted.…”

Section: Layoutmentioning

confidence: 99%

End-to-end numerical modeling of the Roman Space Telescope coronagraph

Krist,

Steeves,

Dube

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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The Roman Space Telescope will have the first advanced coronagraph in space, with deformable mirrors (DMs) for wavefront control (WFC), low-order wavefront sensing and maintenance, and a photon-counting detector. It is expected to be able to detect and characterize mature, giant exoplanets in reflected visible light. Over the past decade, the performance of the coronagraph in its flight environment has been simulated with increasingly detailed diffraction and structural/thermal finite-element modeling. With the instrument now being integrated in preparation for launch within the next few years, the present state of the end-to-end modeling, including the measured flight components such as DMs, is described. The coronagraphic modes, including characteristics most readily derived from modeling, are thoroughly described. The methods for diffraction propagation, WFC, and structural and thermal finite-element modeling are detailed. The techniques and procedures developed for the instrument will serve as a foundation for future coronagraphic missions, such as the Habitable Worlds Observatory.

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Section: Layoutmentioning

confidence: 99%

End-to-end numerical modeling of the Roman Space Telescope coronagraph

Krist,

Steeves,

Dube

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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“…The DPAM contains several standalone lenses as well as two polarization modules (with Wollaston prisms) and two spectroscopy modules (with Amici prisms). 24 The polarization modules are planned for use only in Bands 1 and 4 but could be used without performance degradation in Bands 2 and 3. One spectroscopy module is designed for zero optical deviation and a spectral resolution of 50 at the center wavelength of Band 2, and the other is designed to have those properties at the center of Band 3.…”

Section: Mask Configurations 21 Precision Alignment Mechanisms (Pams)mentioning

confidence: 99%

Flight mask designs of the Roman Space Telescope Coronagraph Instrument

Riggs,

Moody,

Gersh-Range

et al. 2021

Preprint

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Over the past two decades, thousands of confirmed exoplanets have been detected; the next major challenge is to characterize these other worlds and their stellar systems. Much information on the composition and formation of exoplanets and circumstellar debris disks can only be achieved via direct imaging. Direct imaging is challenging because of the small angular separations (< 1 arcsec) and high star-to-planet flux ratios (∼10 9 for a Jupiter analog or ∼10 10 for an Earth analog in the visible). Atmospheric turbulence prohibits reaching such high flux ratios on the ground, so observations must be made above the Earth's atmosphere. The Nancy Grace Roman Space Telescope (Roman), set to launch in the mid-2020s, will be the first space-based observatory to demonstrate high-contrast imaging with active wavefront control using its Coronagraph Instrument. The instrument's main purpose is to mature the various technologies needed for a future flagship mission to image and characterize Earth-like exoplanets. These technologies include two high-actuator-count deformable mirrors, photon-counting detectors, two complementary wavefront sensing and control loops, and two different coronagraph types. In this paper, we describe the complete set of flight coronagraph mask designs and their intended combinations in the Roman Coronagraph Instrument. There are three types of mask configurations included: a primary one designed to meet the instrument's top-level requirement, three that are supported on a best-effort basis, and several unsupported ones contributed by the NASA Exoplanet Exploration Program. The unsupported mask configurations could be commissioned and used if the instrument is approved for operations after its initial technology demonstration phase.

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“…12,13 Although polarimetry is no longer a technology demonstration requirement, Roman/CGI is equipped with two Wollaston prisms oriented at 0 and 45 degrees enabling polarimetry of extended sources at these extreme contrast ratios. 14 The expected performance of this polarimetric mode is limited by calibration and flat-fielding errors, and the expected error on the linear polarization fraction has been estimated to be at the 3% level. 15,16 With careful in-orbit calibration this might be improved.…”

Section: Introductionmentioning

confidence: 99%

FALCO simulations of high-contrast polarimetry with the Nancy Grace Roman Space Telescope coronagraph instrument

Doelman,

Belaouchi,

Riggs

et al. 2023

Techniques and Instrumentation for Detection of Exoplanets XI

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The Coronagraph Instrument of the Nancy Grace Roman Space Telescope (Roman Coronagraph) will be capable of both total intensity and polarization measurements of circumstellar disks. The polarimetric performance is impacted by polarization effects introduced by all mirrors before the Wollaston prisms. In this paper, we aim to characterize these effects for the Roman Coronagraph in bands 1 and 4 using the FALCO and PROPER packages. We simulate the effect of polarization aberrations that impact the polarimetric contrast and the instrumental polarization effects to study the polarimetric accuracy. We include spacecraft rolls, but leave out systematic camera noise. We find that polarimetric differential imaging (PDI) improves the contrast by a factor of six. The PDI contrast of ∼ 8 × 10 −11 is limited by polarized speckles from instrumental polarization effects and polarization aberrations. By injecting polarized companions with at various contrast levels and demodulating their polarimetric signal, we recover their source Stokes vector within 2%.

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Roman Space Telescope CGI: prism and polarizer characterization modes

Cited by 8 publications

References 0 publications

End-to-end numerical modeling of the Roman Space Telescope coronagraph

End-to-end numerical modeling of the Roman Space Telescope coronagraph

Flight mask designs of the Roman Space Telescope Coronagraph Instrument

FALCO simulations of high-contrast polarimetry with the Nancy Grace Roman Space Telescope coronagraph instrument

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