Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 1: telescope and example instrument configurations

Harrington, David M.; Sueoka, Stacey R.

doi:10.1117/1.jatis.3.1.018002

Cited by 34 publications

(55 citation statements)

References 56 publications

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“…Depolarization is often ignored as it is usually a small fraction of a percent change in the magnitude of a recovered Stokes vector, and it can be modeled with proper system level tools (e.g. for DKIST 11 ).…”

Section: Dkist Optics and Polarization Models For Calibrationmentioning

confidence: 99%

“…The Cryo-NIRSP feed optics and modulator properties are described in our prior references. 16,17,57,65 For the rest of the polarimetric instruments, the beam must propagate through the AO system as shown in Equation 4. The DL-NIRSP, ViSP and VTF all see M7, M8 and M9 as well as the tenth mirror as the adaptive optics system deformable mirror (DM = M10).…”

Section: Mirror Grouping Models Polarization and System Mueller Matricesmentioning

confidence: 99%

“…We begin assessing the DKIST coatings by following our previously published technique 11,66 to select a simple one or two layer coating model. We identify the best fit of the model retardance to the NLSP measurements using only the thickness of the dielectric coating layers as variables.…”

Section: Mirror Coating Models and Fits To Polarizationmentioning

confidence: 99%

“…In prior works, 11,66 we only allowed the thickness of one or two dielectric coating layers to vary as a simple two variable optimization problem. However, the metal layer thickness and refractive index both have large polarimetric impact.…”

Section: Refractive Indices Materials Parameters and Coating Model Intmentioning

confidence: 99%

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Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

Harrington

Sueoka

White

2019

J. Astron. Telesc. Instrum. Syst.

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The Daniel K. Inouye Solar Telescope (DKIST) is designed to deliver accurate spectro-polarimetric calibrations across a wide wavelength range and large field of view for solar disk, limb and coronal observations. DKIST instruments deliver spectral resolving powers up to 300,000 in multiple cameras of multiple instruments sampling nanometer scale bandpasses. We require detailed knowledge of optical coatings on all optics to ensure we can predict and calibrate the polarization behavior of the system. Optical coatings can be metals protected by many dielectric layers or several-micron thick dichroics. Strong spectral gradients up to 60 • retardance per nanometer wavelength and several percent diattenuation per nanometer wavelength are observed in such coatings. Often, optical coatings are not specified with spectral gradient targets for polarimetry in combination to both average and spectral threshold type specifications. DKIST has a suite of interchangeable dichroic beam splitters using up to 96 layers. We apply the Berreman formalism in open-source Python scripts to derive coating polarization behavior. We present high spectral resolution examples on dichroics where transmission can drop 10% with associated polarization changes over a 1 nm spectral bandpass in both mirrors and dichroics. We worked with a vendor to design dichroic coatings with relatively benign polarization properties that pass spectral gradient requirements and polarization requirements in addition to reflectivity. We now have the ability to fit multi-layer coating designs which allow us to predict system level polarization properties of mirrors, anti-reflection coatings and dichroics at arbitrary incidence angles, high spectral resolving power and on curved surfaces through optical modeling software packages. Performance predictions for polarization at large astronomical telescopes requires significant metrology efforts on individual optical components combined with systems-level modeling efforts. We show our custom-built laboratory spectropolarimeter and metrology efforts on protected metal mirrors, antireflection coatings and dichroic mirror samples.

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Section: Dkist Optics and Polarization Models For Calibrationmentioning

confidence: 99%

Section: Mirror Grouping Models Polarization and System Mueller Matricesmentioning

confidence: 99%

Section: Mirror Coating Models and Fits To Polarizationmentioning

confidence: 99%

Section: Refractive Indices Materials Parameters and Coating Model Intmentioning

confidence: 99%

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Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

Harrington

Sueoka

White

2019

J. Astron. Telesc. Instrum. Syst.

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“…For example, four out of the five first-light instruments in the world's largest future solar observatory, the 4m-class Daniel K. Inouye Solar Telescope (DKIST 31 ), will have spectropolarimetric (and optional spectroscopic) capabilities. 32,33 Polarimetry is frequently reviewed using different approaches. Examples of relevant works are given in Ref.…”

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confidence: 99%

Instrumentation for solar spectropolarimetry: state of the art and prospects

Iglesias

Feller

2019

Opt. Eng.

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Given its unchallenged capabilities in terms of sensitivity and spatial resolution, the combination of imaging spectropolarimetry and numeric Stokes inversion represent the dominant technique currently used to remotely sense the physical properties of the solar atmosphere, and in particular, its important driving magnetic field. Solar magnetism manifests itself in a wide range of spatial, temporal and energetic scales. The ubiquitous but relatively small and weak fields of the so called quiet Sun are believed today to be crucial for answering many open questions in solar physics, some of which have substantial practical relevance due to the strong Sun-Earth connection. However, such fields are very challenging to detect because they require spectropolarimetric measurements with high spatial (subarcsec), spectral (< 100 m) and temporal (< 10 s) resolution along with high polarimetric sensitivity (< 0.1% of the intensity). In this review we collect and discuss both well-established and upcoming instrumental solutions developed during the last decades to push solar observations towards the above-mentioned parameter regime. This typically involves design trade-offs due to the high dimensionality of the data and signal-to-noise-ratio considerations, among others. We focus on the main three components that form a spectropolarimeter, namely, wavelength discriminators, the devices employed to encode the incoming polarization state into intensity images (polarization modulators), and the sensor technologies used to register them. We consider the instrumental solutions introduced to perform this kind of measurements at different optical wavelengths and from various observing locations, i.e., ground-based, from the stratosphere or near space.

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The Daniel K. Inouye Solar Telescope – Observatory Overview

et al. 2020

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We present an overview of the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), its instruments, and support facilities. The 4 m aperture DKIST provides the highest-resolution observations of the Sun ever achieved. The large aperture of DKIST combined with state-of-the-art instrumentation provide the sensitivity to measure the vector magnetic field in the chromosphere and in the faint corona, i.e. for the first time with DKIST we will be able to measure and study the most important free-energy source in the outer solar atmosphere – the coronal magnetic field. Over its operational lifetime DKIST will advance our knowledge of fundamental astronomical processes, including highly dynamic solar eruptions that are at the source of space-weather events that impact our technological society. Design and construction of DKIST took over two decades. DKIST implements a fast (f/2), off-axis Gregorian optical design. The maximum available field-of-view is 5 arcmin. A complex thermal-control system was implemented in order to remove at prime focus the majority of the 13 kW collected by the primary mirror and to keep optical surfaces and structures at ambient temperature, thus avoiding self-induced local seeing. A high-order adaptive-optics system with 1600 actuators corrects atmospheric seeing enabling diffraction limited imaging and spectroscopy. Five instruments, four of which are polarimeters, provide powerful diagnostic capability over a broad wavelength range covering the visible, near-infrared, and mid-infrared spectrum. New polarization-calibration strategies were developed to achieve the stringent polarization accuracy requirement of 5×10−4. Instruments can be combined and operated simultaneously in order to obtain a maximum of observational information. Observing time on DKIST is allocated through an open, merit-based proposal process. DKIST will be operated primarily in “service mode” and is expected to on average produce 3 PB of raw data per year. A newly developed data center located at the NSO Headquarters in Boulder will initially serve fully calibrated data to the international users community. Higher-level data products, such as physical parameters obtained from inversions of spectro-polarimetric data will be added as resources allow.

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Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 1: telescope and example instrument configurations

Cited by 34 publications

References 56 publications

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope part 5: impacts of enhanced mirror and dichroic coatings on system polarization calibration

Instrumentation for solar spectropolarimetry: state of the art and prospects

The Daniel K. Inouye Solar Telescope – Observatory Overview

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