The US National Science Foundation 4m Daniel K. Inouye Solar Telescope (DKIST) on Haleakala, Maui is the largest solar telescope in the world. DKIST’s superb resolution and polarimetric sensitivity will enable astronomers to explore the origins of solar magnetism, the mechanisms of coronal heating and drivers of flares and coronal mass ejections. DKIST operates as a coronagraph at infrared wavelengths, providing crucial measurements of the magnetic field in the corona. During its Operations Commissioning Phase, DKIST has already conducted a significant number of shared-risk observations for community researchers. The complex raw data are calibrated by the DKIST Data Center located in Boulder and distributed to the science community. We’ll present examples of science results and discuss lessons learned. Ongoing instrument development efforts include, an upgrade of the single-conjugate adaptive optics system to a multi-conjugate AO, the implementation of image slicers for the DL-NIRSP instrument and development of infrared detectors the DL- and CRYO-NIRSP instruments.
The Daniel K. Inouye Solar Telescope, with its 4m aperture, is the largest telescope for observations of the Sun, and is currently in its Operations Commissioning Phase. During this phase of the project, the five DKIST first light instruments, the Visible Broadband Imager (VBI), the Visible Spectro-Polarimeter (ViSP), the Diffraction-Limited Near-Infrared Spectro-Polarimeter (DL-NIRSP), the Cryogenic Near-Infrared Spectro-Polarimeter (Cryo-NIRSP) and the Visible Tunable Filter (VTF) are used in selected modes to acquire scientific data. We provide an overview of the DKIST instrumentation system and its inherent flexibility. We further report on lessons learned during commissioning, and present sample data products.
The Polstar NASA medium explorer (MIDEX) design configuration and implementation is strongly driven by the requirement to measure the state of polarization of stellar objects using a space-based sensor. Constraints include, but are not limited to, symmetry of geometry and coatings of the collecting aperture, angle of incidence at optical surfaces, coating uniformity, line of sight jitter and drift, orbit properties, thermal stability, and ground calibration. The Polstar MIDEX will observe scientifically interesting stars. Polstar will simultaneously measure all four Stokes parameters (I, Q, U, V) to high accuracy and precision (~0.001%) of the Stokes vector at high spectral resolving power. The 600-mm diameter aperture telescope images a selected star at the entrance slit of a spectrometer. Polstar offers two spectral channels within one spectrometer: a Far UV 122 nm to 200 nm Channel 1 with R~30K spectral resolving power and a low spectral resolution in Channel 2 channel covering 180 nm to 320 nm with R ~ 120 to 4K and spectroscopy over 115 nm to ~1,000nm. Channel 1 uses a cross-dispersed echelle spectrometer design. Channel 2 achieves its spectral dispersion with a MgF2 prism disperser. The two channels share a common array detector. The spectrometer includes rotating MgF2 retarders and a fixed MgF2 Wollaston prism analyzer to implement a dual beam polarization sensing function. Two orthogonal polarization states are imaged onto the array detector as interleaved echellograms (Channel 1) and as parallel spectra (Channel 2). This paper presents the design resulting from these design constraints and describes the approaches to calibrate the design pre-flight and during flight.
The Polstar Mission uses time domain FUV and NUV spectropolarimetric observations to provide insight into how our galaxy became able to support a solar system like ours. Polstar will study the evolution of massive stars, including the inter-stellar dust and gas that they interact with and the dynamics of protoplanetary disks and lower resolution near UV (180nm – 320 nm) to study interstellar reddening mechanism. Polstar will simultaneously measure at high spectral resolving power all four Stokes parameters (I, Q, U, V)T to high accuracy (0.001) with a precision better than 0.0001 using an instrument comprising a modulator with rotating MgF2 retarders and a fixed MgF2 Wollaston prism analyzer that concurrently measures the two orthogonal polarizations of the retarder modulated signal at six optimized rotational angles on a common detector. The output of the Wollaston prism either directly enters an echelle spectrograph, which provides spectral resolution of ~30K with a wavelength range from 122 nm to 200 nm, or is reflected to a prism spectrograph, which provides spectral resolution ranging from 140– 4000 with a wavelength range from 180 nm to 320 nm. In this paper we outline the instrument calibration approach to obtain the Mueller matrices over the full wavelength range that permit us to determine the Stokes parameters, and to spectrally calibrate the instrument. We also describe the ground support equipment for calibration.
The National Science Foundation’s 4m Daniel K. Inouye Solar Telescope (DKIST) on Haleakala, Maui is now the largest solar telescope in the world. DKIST’s superb resolution and polarimetric sensitivity will enable astronomers to unravel many of the mysteries the Sun presents, including the origin of solar magnetism, the mechanisms of coronal heating and drivers of flares and coronal mass ejections. Five instruments, four of which provide highly sensitive measurements of solar magnetic fields, including the illusive magnetic field of the faint solar corona. DKIST operates as a coronagraph at infrared wavelengths where the sky background is low and bright coronal emission lines are available. The high-order, single-conjugate adaptive optics system (AO) provides diffraction limited imaging and the ability to resolve features approximately 20 km on the Sun. A multi-conjugate AO upgrade is in progress. With these unique capabilities DKIST will address basic research aspects of Space Weather and help improve predictive capabilities. DKIST has completed construction and is now in the early phases of operations. Community proposal-based shared-risk observations are conducted by the DKIST operations team.
The Polstar mission will provide for a space-borne 60cm telescope operating at UV wavelengths with spectropolarimetric capability capturing all four Stokes parameters (intensity, two linear polarization components, and circular polarization). Polstar’s capabilities are designed to meet its goal of determining how circumstellar gas flows alter massive stars' evolution, and finding the consequences for the stellar remnant population and the stirring and enrichment of the interstellar medium, by addressing four key science objectives. In addition, Polstar will determine drivers for the alignment of the smallest interstellar grains, and probe the dust, magnetic fields, and environments in the hot diffuse interstellar medium, including for the first time a direct measurement of the polarized and energized properties of intergalactic dust. Polstar will also characterize processes that lead to the assembly of exoplanetary systems and that affect exoplanetary atmospheres and habitability. Science driven design requirements include: access to ultraviolet bands: where hot massive stars are brightest and circumstellar opacity is highest; high spectral resolution: accessing diagnostics of circumstellar gas flows and stellar composition in the far-UV at 122-200nm, including the NV, SiIV, and CIV resonance doublets and other transitions such as NIV, AlIII, HeII, and CIII; polarimetry: accessing diagnostics of circumstellar magnetic field shape and strength when combined with high FUV spectral resolution and diagnostics of stellar rotation and distribution of circumstellar gas when combined with low near-UV spectral resolution; sufficient signal-to-noise ratios: ~103 for spectropolarimetric precisions of 0.1% per exposure; ~102 for detailed spectroscopic studies; ~10 for exploring dimmer sources; and cadence: ranging from 1-10 minutes for most wind variability studies, to hours for sampling rotational phase, to days or weeks for sampling orbital phase. The ISM and exoplanet science program will be enabled by these capabilities driven by the massive star science.
This paper summarizes our current instrument prototyping efforts of miniature near-UV imaging spectro-polarimeters to probe the thermodynamics and magnetism of the solar Chromosphere and Transition Region. This includes our high altitude balloon piggyback instruments DIMS-RADIANCE and DIMS-STOUT, which are scheduled to fly in 2018. These payloads are CubeSat sized instruments designed around commercial off-the-shelf miniaturized spectrographs. Additionally we detail a new optical concept and proposed CubeSat mission called SolarCube. This instrument will be capable of “snapshot polarimetry” with simultaneous 2D imaging, spectroscopy, and linear polarization without mechanisms or scanning. This concept utilizes an integral field unit, diffraction grating, and unique polarization sensitive detector. The design, capabilities, current prototyping efforts, and future plans are discussed. The design goal is to observe the spatially resolved polarization signature of the Mg II h-k doublet at 280nm over the full solar disk.
Construction of the Daniel K. Inouye Solar Telescope (DKIST) is well underway on the Haleakalā summit on the Hawaiian island of Maui. Featuring a 4-m aperture and an off-axis Gregorian configuration, the DKIST will be the world’s largest solar telescope. It is designed to make high-precision measurements of fundamental astrophysical processes and produce large amounts of spectropolarimetric and imaging data. These data will support research on solar magnetism and its influence on solar wind, flares, coronal mass ejections, and solar irradiance variability. Because of its large aperture, the DKIST will be able to sense the corona’s magnetic field—a goal that has previously eluded scientists—enabling observations that will provide answers about the heating of stellar coronae and the origins of space weather and exo-weather. The telescope will cover a broad wavelength range (0.35 to 28 microns) and operate as a coronagraph at infrared (IR) wavelengths. Achieving the diffraction limit of the 4-m aperture, even at visible wavelengths, is paramount to these science goals. The DKIST’s state-of-the-art adaptive optics systems will provide diffraction-limited imaging, resolving features that are approximately 20 km in size on the Sun.
At the start of operations, five instruments will be deployed: a visible broadband imager (VTF), a visible spectropolarimeter (ViSP), a visible tunable filter (VTF), a diffraction-limited near-IR spectropolarimeter (DLNIRSP), and a cryogenic near-IR spectropolarimeter (cryo-NIRSP). At the end of 2017, the project finished its fifth year of construction and eighth year overall. Major milestones included delivery of the commissioning blank, the completed primary mirror (M1), and its cell. Commissioning and testing of the coudé rotator is complete and the installation of the coudé cleanroom is underway; likewise, commissioning of the telescope mount assembly (TMA) has also begun. Various other systems and equipment are also being installed and tested. Finally, the observatory integration, testing, and commissioning (IT&C) activities have begun, including the first coating of the M1 commissioning blank and its integration within its cell assembly. Science mirror coating and initial on-sky activities are both anticipated in 2018.
We provide an update on the construction status of the Daniel K. Inouye Solar Telescope. This 4-m diameter facility is designed to enable detection and spatial/temporal resolution of the predicted, fundamental astrophysical processes driving solar magnetism at their intrinsic scales throughout the solar atmosphere. These data will drive key research on solar magnetism and its influence on solar winds, flares, coronal mass ejections and solar irradiance variability. The facility is developed to support a broad wavelength range (0.35 to 28 microns) and will employ state-of-the-art adaptive optics systems to provide diffraction limited imaging, resolving features approximately 20 km on the Sun. At the start of operations, there will be five instruments initially deployed: Visible Broadband Imager (VBI; National Solar Observatory), Visible SpectroPolarimeter (ViSP; NCAR High Altitude Observatory), Visible Tunable Filter (VTF (a Fabry-Perot tunable spectropolarimeter); Kiepenheuer Institute for Solarphysics), Diffraction Limited NIR Spectropolarimeter (DL-NIRSP; University of Hawaii, Institute for Astronomy) and the Cryogenic NIR Spectropolarimeter (Cryo-NIRSP; University of Hawaii, Institute for Astronomy).
As of mid-2016, the project construction is in its 4th year of site construction and 7th year overall. Major milestones in the off-site development include the conclusion of the polishing of the M1 mirror by University of Arizona, College of Optical Sciences, the delivery of the Top End Optical Assembly (L3), the acceptance of the Deformable Mirror System (Xinetics); all optical systems have been contracted and are either accepted or in fabrication. The Enclosure and Telescope Mount Assembly passed through their factory acceptance in 2014 and 2015, respectively. The enclosure site construction is currently concluding while the Telescope Mount Assembly site erection is underway. The facility buildings (Utility and Support and Operations) have been completed with ongoing work on the thermal systems to support the challenging imaging requirements needed for the solar research.
Finally, we present the construction phase performance (schedule, budget) with projections for the start of early operations.
The Daniel K. Inouye Solar Telescope (DKIST, renamed in December 2013 from the Advanced Technology Solar
Telescope) will be the largest solar facility built when it begins operations in 2019. Designed and developed to meet the
needs of critical high resolution and high sensitivity spectral and polarimetric observations of the Sun, the observatory
will enable key research for the study of solar magnetism and its influence on the solar wind, flares, coronal mass
ejections and solar irradiance variations. The 4-meter class facility will operate over a broad wavelength range (0.38 to
28 microns, initially 0.38 to 5 microns), using a state-of-the-art adaptive optics system to provide diffraction-limited
imaging and the ability to resolve features approximately 25 km on the Sun. Five first-light instruments will be available
at the start of operations: Visible Broadband Imager (VBI; National Solar Observatory), Visible SpectroPolarimeter
(ViSP; NCAR High Altitude Observatory), Visible Tunable Filter (VTF; Kiepenheuer Institut für Sonnenphysik),
Diffraction Limited Near InfraRed SpectroPolarimeter (DL-NIRSP; University of Hawai’i, Institute for Astronomy) and
the Cryogenic Near InfraRed SpectroPolarimeter (Cryo-NIRSP; University of Hawai’i, Institute for Astronomy).
As of mid-2014, the key subsystems have been designed and fabrication is well underway, including the site
construction, which began in December 2012. We provide an update on the development of the facilities both on site at
the Haleakalā Observatories on Maui and the development of components around the world. We present the overall
construction and integration schedule leading to the handover to operations in mid 2019. In addition, we outline the
evolving challenges being met by the project, spanning the full spectrum of issues covering technical, fiscal, and
geographical, that are specific to this project, though with clear counterparts to other large astronomical construction
projects.
KEYWORDS: Visible radiation, Calibration, Solar telescopes, Solar processes, Spatial resolution, Coronagraphy, Near infrared, Data centers, Telescopes, Adaptive optics
The Daniel K. Inouye Solar Telescope is a 4-meter-class all-reflecting telescope under construction on Haleakalā
mountain on the island of Maui, Hawai’i. When fully operational in 2019 it will be the world's largest solar telescope
with wavelength coverage of 380 nm to 28 microns and advanced Adaptive Optics enabling the highest spatial resolution
measurements of the solar atmosphere yet achieved. We review the first-generation DKIST instrument designs, select
critical science program topics, and the operations and data handling and processing strategies to accomplish them.
The Daniel K. Inouye Solar Telescope (formerly Advanced Technology Solar Telescope) will be the world's largest solar
telescope and polarimeter when completed in 2019. Efficient use of the telescope to address key science priorities calls
for polarization measurements simultaneously over broad wavelength ranges and calibration of the telescope and
polarimeters to high accuracy. Broadband polarization modulation and calibration optics utilizing crystal optics have
been designed for this application. The performance of polarization modulators and calibration retarders is presented
along with a discussion of the unique challenges of this application.
Polarimeters operate over the ranges of 0.38-1.1 microns, 0.5-2.5 microns, and 1.0-5.0 microns. Efficient polarization
modulation over these broad ranges led to modulators utilizing multiple wave plates and that are elliptical, rather than
linear, retarders. Calibration retarders are linear retarders and are constructed from the same sub-component wave plate
pairs as the polarization modulators. Polarization optics must address efficiency over broad wavelength ranges while
meeting beam deflection, transmitted wave front error, and thermal constraints and doing so with designs that, though
large in diameter, can be affordably manufactured.
The Visible Spectro-Polarimeter (ViSP) is one of the first light instruments for the Advanced Technology Solar
Telescope (ATST). It is an echelle spectrograph designed to measure three different regions of the solar spectrum in
three separate focal planes simultaneously between 380 and 900 nm. It will use the polarimetric capabilities of the ATST
to measure the full Stokes parameters across the line profiles. By measuring the polarization in magnetically sensitive
spectral lines the magnetic field vector as a function of height in the solar atmosphere can be obtained, along with the
associated variation of the thermodynamic properties. The ViSP will have a spatial resolution of 0.04 arcsec over a
2 arcmin field of view (at 600 nm). The minimum spectral resolving power for all the focal planes is 180,000. The
spectrograph supports up to 4 diffraction gratings and is fully automated to allow for rapid reconfiguration.
One of the biggest challenges in heliophysics is to decipher the magnetic structure of the solar chromosphere.
The importance of measuring the chromospheric magnetic field is due to both the key role the chromosphere
plays in energizing and structuring the outer solar atmosphere and the inability of extrapolation of photospheric
fields to adequately describe this key boundary region. Over the last few years, significant progress has been
made in the spectral line formation of UV lines as well as the MHD modeling of the solar atmosphere. It is
found that the Hanle effect in the Lyman-alpha line (121.567 nm) is a most promising diagnostic tool for weaker
magnetic fields in the chromosphere and transition region. Based on this groundbreaking research, we propose
the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) to NASA as a sounding rocket experiment, for
making the first measurement of the linear polarization produced by scattering processes and the Hanle effect
in the Lyman-alpha line (121.567 nm), and making the first exploration of the magnetic field in the upper
chromosphere and transition region of the Sun. The CLASP instrument consists of a Cassegrain telescope, a
rotating 1/2-wave plate, a dual-beam spectrograph assembly with a grating working as a beam splitter, and
an identical pair of reflective polarization analyzers each equipped with a CCD camera. We propose to launch
CLASP in December 2014.
The solar chromosphere is an important boundary, through which all of the plasma, magnetic fields and energy in the
corona and solar wind are supplied. Since the Zeeman splitting is typically smaller than the Doppler line broadening in
the chromosphere and transition region, it is not effective to explore weak magnetic fields. However, this is not the case
for the Hanle effect, when we have an instrument with high polarization sensitivity (~ 0.1%). "Chromospheric Lyman-
Alpha SpectroPolarimeter (CLASP)" is the sounding rocket experiment to detect linear polarization produced by the
Hanle effect in Lyman-alpha line (121.567 nm) and to make the first direct measurement of magnetic fields in the upper
chromosphere and lower transition region. To achieve the high sensitivity of ~ 0.1% within a rocket flight (5 minutes) in
Lyman-alpha line, which is easily absorbed by materials, we design the optical system mainly with reflections. The
CLASP consists of a classical Cassegrain telescope, a polarimeter and a spectrometer. The polarimeter consists of a
rotating 1/2-wave plate and two reflecting polarization analyzers. One of the analyzer also works as a polarization beam
splitter to give us two orthogonal linear polarizations simultaneously. The CLASP is planned to be launched in 2014
summer.
The Visible Spectro-Polarimeter (ViSP) is one of the first light instruments for the Advanced Technology Solar
Telescope (ATST). It is an echelle spectrograph designed to measure three different regions of the solar spectrum in
three separate focal planes simultaneously between 380 and 1600nm. It will use the polarimetric capabilities of the
ATST to measure the full Stokes parameters across the line profiles. By measuring the polarization in magnetically
sensitive spectral lines the magnetic field vector as a function of height in the solar atmosphere, along with the
associated variation of the thermodynamic properties can be obtained. The ViSP will have a spatial resolution of 0.04
arc seconds over a 2 minute field of view (at 600nm). The minimum resolving power for all the focal planes is 180,000.
The spectrograph supports up to 5 diffraction gratings and is fully automated to allow for rapid reconfiguration.
An increasing number of astronomical applications depend on the measurement of polarized light. For example, our
knowledge of solar magnetism relies heavily on our ability to measure and interpret polarization signatures introduced
by magnetic field. Many new instruments have consequently focused considerable attention on polarimetry. For solar
applications, spectro-polarimeters in particular are often designed to observe the solar atmosphere in multiple spectral
lines simultaneously, thus requiring that the polarization modulator employed is efficient at all wavelengths of interest. We
present designs of polarization modulators that exhibit near-optimal modulation characteristics over broad spectral ranges.
Our design process employs a computer code to optimize the efficiency of the modulator at specified wavelengths. We
will present several examples of modulator designs based on rotating stacks of Quartz waveplates and Ferroelectric Liquid
Crystals (FLCs). An FLC-based modulator of this design was recently deployed for the ProMag instrument at the Evans
Solar Facility of NSO/SP. We show that this modulator behaves according to its design.
We are constructing a spectro-polarimeter using the 40-cm coronagraph at the Evans Solar Facility of the National
Solar Observatory in Sunspot, NM for the purpose of measuring the vector magnetic field in prominences and
filaments. The Prominence Magnetometer (ProMag) is comprised of a polarization modulation package and a
spectrograph. The modulation optics are located at the prime focus of the coronagraph along with calibration
optics and a beamsplitter that creates two beams of orthogonal Stokes states. The spectrograph resides at the
coude focus of the coronagraph. The polarizations of the two chromospheric lines of neutral helium, at 587.6 nm
and 1083.0 nm, are to be observed simultaneously. We present details of the design of the spectro-polarimeter.
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