Solar adaptive optics with the DKIST: status report

Johnson, Luke C.; Cummings, Keith; Drobilek, Mark; Gregory, Scott; Hegwer, S.; Johansson, Erik M. J.; Mariño, José María Solé; Richards, Kit; Rimmelé, Thomas; Sékulic, Predrag; Wöger, Friedrich

doi:10.1117/12.2056990

Cited by 9 publications

(4 citation statements)

References 2 publications

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“…Bottom: Wavefront-correction bench during first solar light achieved at the coudé instrument lab. The diameter of the rotator is 16.5 m. Richards et al, 2010;Johnson et al, 2014Johnson et al, , 2016). Integration and system testing are summarized by Johnson et al (2018Johnson et al ( , 2020.…”

Section: Wavefront Correction Systemmentioning

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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Section: Wavefront Correction Systemmentioning

confidence: 99%

The Daniel K. Inouye Solar Telescope – Observatory Overview

et al. 2020

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“…Dunn Solar Telescope (Rimmele 2004), and later by Schmidt et al (2016). Other recently developed major AO systems for solar telescopes involve that for GREGOR (Berkefeld et al 2012(Berkefeld et al , 2016(Berkefeld et al , 2018, for GST (Shumko et al 2014;Schmidt et al 2014), for DKIST (Johnson et al 2020), and for the Chinese New Vacuum Solar Telescope (Zhang et al 2023).…”

Section: Introductionmentioning

confidence: 99%

The 85-electrode adaptive optics system of the Swedish 1-m Solar Telescope

Scharmer,

Sliepen,

Sinquin

et al. 2024

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We discuss the chosen concepts, detailed design, implementation and calibration of the 85-electrode adaptive optics (AO) system of the Swedish 1-meter Solar Telescope (SST), which was installed in 2013. The AO system is unusual in that it uses a combination of a monomorph mirror with a Shack-Hartmann (SH) wavefront sensor (WFS) and a second high-resolution SH microlens array to aid the characterization, calibration, and modal control of the deformable mirror. An Intel PC workstation performs the heavy image processing associated with cross-correlations and real-time control at a 2 kHz update rate with very low latency. The computer and software continue the successful implementation since 1995 of earlier generations of correlation tracker and AO systems at SST and its predecessor, the 50-cm Swedish Vacuum Solar Telescope, by relying entirely on work-station technology and an extremely efficient algorithm for implementing cross-correlations with the large field of view of the WFS. We describe critical aspects of the design, calibrations, software, and functioning of the AO system. The exceptionally high performance is testified through the highest Strehl ratio (inferred from the measured granulation contrast) of existing meter-class solar telescopes, as demonstrated here at wavelengths shorter than 400 nm and discussed in more detail in a previous separate publication We expect that some aspects of this AO system may also be of interest outside the solar community.

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“…20 - 26 The DKIST active optics system and adaptive optics systems (AO) coordinate alignment of the beam. 4,6,[27][28][29][30][31] As construction progresses, the mirror controllers can position their mirrors based on lookup tables that calculate the best position based on telescope elevation, azimuth, temperature, and temperature gradient across M1. 27 For now, the mirrors are only positioned to a single static position with beam pointing variations as the system changes azimuth, elevation, and coudé table angle as a reasonable alignment.…”

Section: Introduction: Dkist and Polarization Models For Calibrationmentioning

confidence: 99%

Polarization modeling and predictions for DKIST, part 9: flux distribution with FIDO

Harrington

Wöger

White

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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Astronomical instruments greatly improve wavelength multiplexing capabilities by using beam splitters. In the case of the 4-m National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) solar telescope, over 70 W of optical power is distributed simultaneously to four instruments, each with multiple cameras. Many DKIST observing cases require simultaneous observations of many narrow bandpasses combined with an adaptive optics system. The facility uses five dichroic optical stations to allow at least 11 cameras and two wavefront sensors to simultaneously observe ultraviolet to infrared wavelengths with flexible reconfiguration. The DKIST dichroics required substantial development to achieve very tight specifications over very large apertures of 290 mm diameter. Coating spectral variation occurs over <1 nm wavelength, comparable with instrument bandpasses. We measure retardance spectral variation of up to a full wave and diattenuation varying over AE10% per nm. Spatial variation of Mueller matrix elements for coatings in both transmission and reflection requires careful metrology. We demonstrate coatings from multiple vendors exhibit this behavior. We show achievement of 5-nm root mean square (RMS) reflected wavefront and 24-nm RMS power with coatings over 8 μm thick. We show mild impacts of depolarization and spectral variation of polarization on modulation efficiency caused by the dichroic coatings. We show an end-to-end system polarization model for the visible spectropolarimeter instrument, including the dichroics, grating, analyzer, and all coated optics. We show detailed performance for all DKIST dichroics for community use in planning future observations.

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Solar adaptive optics with the DKIST: status report

Cited by 9 publications

References 2 publications

The Daniel K. Inouye Solar Telescope – Observatory Overview

The Daniel K. Inouye Solar Telescope – Observatory Overview

The 85-electrode adaptive optics system of the Swedish 1-m Solar Telescope

Polarization modeling and predictions for DKIST, part 9: flux distribution with FIDO

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