Polarization modeling and predictions for Daniel K. Inouye Solar Telescope, part 6: fringe mitigation with polycarbonate modulators and optical contact calibration retarders

Harrington, David M.; Jaeggli, Sarah A.; Schad, Thomas A.; White, Amanda J.; Sueoka, Stacey R.

doi:10.1117/1.jatis.6.3.038001

Cited by 11 publications

(53 citation statements)

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“…Misalignment produces spectral oscillations in retardance, which introduce coupling between temperature changes and the spectral drift of these elliptical retardance oscillations. We show here detection of the clocking oscillations outlined in H20 80 with calibrations both on-Sun and with the DKIST calibration lamp. We show here successful on-Sun use of the optically contacted calibration retarder (CalRet) and system calibration with time-efficient calibration sequences (CSs).…”

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confidence: 86%

“…We drop the beam down below the DKIST coudé beam height and package this CN F∕18 focus on a small optical bench containing a system quite similar to our NLSP described in HS18b, 66 H19, 67 and H20. 80 Figure 1 shows a CAD layout of the beam starting in the coudé laboratory with DKIST M7, collimated by M8 and folded to a pupil image inside the CN optics. We refer the reader to Ref.…”

Section: Nso Coudé Spectropolarimeter For Dkist Metrologymentioning

confidence: 99%

“…First, the CalRet and CalPol are not sampled on-axis with a constant beam footprint during all rotations of both optics. Different telescope pointings sample different patches of the optic and produce state-dependent system inputs (see HS18b 66 Sections 6 and 7, and H20 80 ). Thus we are limited by spatial non-uniformity of both polarizer and retarder.…”

Section: System Calibration: Alignment and Optical Challengesmentioning

confidence: 99%

“…The beam deflection was estimated for both these parts through interferometric measurements to be <10 arc sec. For the optically contacted calibrator (OCcal), one of the crystals was deterministically fluid jet polished to 0.05 arc sec deflection flatness, and the contacted pair was measured to have 1.2 arc sec beam deflection (H20 80 ). This beam deflection near a focal plane causes the beam footprints to move slightly on downstream mirrors as a function of each mirror station for each retarder rotation throughout the CS.…”

Section: System Calibration: Alignment and Optical Challengesmentioning

confidence: 99%

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Polarization modeling and predictions for Daniel K. Inouye Solar Telescope, part 7: preliminary NCSP system calibration and model fitting

Harrington

Sueoka

White

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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Daniel K. Inouye Solar Telescope (DKIST) is designed to deliver accurate spectropolarimetric solar data across a wide wavelength range, covering a large field of view simultaneously using multiple facility instruments for solar disk, limb, and coronal observations. We show successful design and implementation of National Solar Observatory Coudé Laboratory Spectropolarimeter, a custom metrology tool for efficient continuous broadband polarization calibration of the telescope mirrors through a coudé laboratory focus. We compare multiple fitting techniques for the 10 to >140 variable DKIST system polarization models. We compare results with the first DKIST solar calibration observations and find small thermally forced retardance changes of AE0.2 deg and AE0.5 deg for two separate SiO 2 retarders. Modulation matrices derived are stable to < AE 0.01 per element during the first on-Sun calibration tests. We achieve good fit agreement to our metrology-based model over a 390-to 1600-nm bandpass. The solutions are robust and efficient using only 10 input Stokes vectors from elliptical calibration retarders. We developed a custom polarizer assembly used with metrology tools to orient the DKIST polarization coordinates to better than 0.1-deg clocking angle. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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confidence: 86%

Section: Nso Coudé Spectropolarimeter For Dkist Metrologymentioning

confidence: 99%

Section: System Calibration: Alignment and Optical Challengesmentioning

confidence: 99%

Section: System Calibration: Alignment and Optical Challengesmentioning

confidence: 99%

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Polarization modeling and predictions for Daniel K. Inouye Solar Telescope, part 7: preliminary NCSP system calibration and model fitting

Harrington

Sueoka

White

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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“…An inter-disciplinary set of new modeling mathematics and algorithms coupled with new laboratory tools for detailed characterization of optical elements was developed. Mueller-matrix spatial-spectral mapping systems covering UV to IR wavelengths were developed and utilized to characterize optics (Harrington et al, 2020a). Retarders were spatially mapped, characterized for elliptical retardance, and this ellipticity is included in the calibration process.…”

Section: Polarimetrymentioning

confidence: 99%

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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The Visible Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope

et al. 2022

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The Daniel K. Inouye Solar Telescope (DKIST) Visible Spectro-Polarimeter (ViSP) is a traditional slit-scanning spectrograph with the ability to observe solar regions up to a $120\times 78~\mbox{arcsec}^{2}$ 120 × 78 arcsec 2 area. The design implements dual-beam polarimetry, a polychromatic polarization modulator, a high-dispersion echelle grating, and three spectral channels that can be automatically positioned. A defining feature of the instrument is its capability to tune anywhere within the 380 – 900 nm range of the solar spectrum, allowing for a virtually infinite number of combinations of three wavelengths to be observed simultaneously. This enables the ViSP user to pursue well-established spectro-polarimetric studies of the magnetic structure and plasma dynamics of the solar atmosphere, as well as completely novel investigations of the solar spectrum. Within the suite of first-generation instruments at the DKIST, ViSP is the only wavelength-versatile spectro-polarimeter available to the scientific community. It was specifically designed as a discovery instrument to explore new spectroscopic and polarimetric diagnostics and test improved models of polarized line formation through high spatial-, spectral-, and temporal-resolution observations of the Sun’s polarized spectrum. In this instrument article, we describe the science requirements and design drivers of ViSP and present preliminary science data collected during the commissioning of the instrument.

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Polarization modeling and predictions for Daniel K. Inouye Solar Telescope, part 6: fringe mitigation with polycarbonate modulators and optical contact calibration retarders

Cited by 11 publications

References 0 publications

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope, part 7: preliminary NCSP system calibration and model fitting

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope, part 7: preliminary NCSP system calibration and model fitting

The Daniel K. Inouye Solar Telescope – Observatory Overview

The Visible Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope

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