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.
Super achromatic retarders and polychromatic modulators are required to meet the polarimetry specifications of the Daniel K. Inouye Solar Telescope. These components have been analyzed and toleranced using a birefringent polarization ray trace over wavelength and field of view.
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.
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.
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 ATST scientific instruments are located on benches installed on a large diameter rotating coud lab floor. The light path from the telescope to the instruments is greater than 38 meters and passes from external ambient conditions to the 'shirt-sleeve' environment of the coudé lab. In order to minimize any contribution to local seeing or wavefront distortion, two strategies are implemented. First, an air curtain is installed where the beam passes from ambient conditions to the lab space and second, the coudé lab environmental conditions are tightly controlled. This paper presents the design parameters of the environmental conditions, the basis of each design parameter, an overview of the equipment and components of the system planned to control those conditions, and the thermal and computational fluid dynamic analyses that have been performed in support of the system as designed.
The 4m Advance Technology Solar Telescope (ATST) will be the most powerful solar telescope and the world's leading
ground-based resource for studying solar magnetism that controls the solar wind, flares, coronal mass ejections and
variability in the Sun's output. The project has successfully passed its final design review and the Environmental Impact
Study for construction of ATST on Haleakala, Maui, HI has been concluded in December of 2009. The project is now
entering its construction phase. As its highest priority science driver ATST shall provide high resolution and high
sensitivity observations of the dynamic solar magnetic fields throughout the solar atmosphere, including the corona at
infrared wavelengths. With its 4 m aperture, ATST will resolve features at 0."03 at visible wavelengths and obtain 0."1
resolution at the magnetically highly sensitive near infrared wavelengths. A high order adaptive optics system delivers a
corrected beam to the initial set of state-of-the-art, facility class instrumentation located in the coudé laboratory facility.
The initial set of first generation instruments consists of five facility class instruments, including imagers and spectropolarimeters.
The high polarimetric sensitivity and accuracy required for measurements of the illusive solar magnetic
fields place strong constraints on the polarization analysis and calibration. Development and construction of a fourmeter
solar telescope presents many technical challenges, including thermal control of the enclosure, telescope structure
and optics and wavefront control. A brief overview of the science goals and observational requirements of the ATST
will be given, followed by a summary of the design status of the telescope and its instrumentation, including design
status of major subsystems, such as the telescope mount assembly, enclosure, mirror assemblies, and wavefront
correction
Spectro-polarimetry plays an important role in the study of solar magnetism and strongly influences the design of the
new generation of solar telescopes. Calibration of the polarization properties of the telescope is a critical requirement
needed to use these observations to infer solar magnetic fields. However, the large apertures of these new telescopes
make direct calibration with polarization calibration optics placed before all the telescope optical elements impractical.
It is therefore desirable to be able to infer the polarization properties of the telescope optical elements utilizing solar
observations themselves. Taking advantage of the fact that the un-polarized, linearly, and circularly polarized spectra
originating from the Sun are uncorrelated, we have developed techniques to utilize observations of solar spectra with
redundant combination of the polarization states measured at several different telescope configurations to infer the
polarization properties of the telescope as a whole and of its optical elements. We show results of these techniques
applied to spectro-plarimetric data obtained at the Dunn Solar Telescope.
At future telescopes, adaptive optics systems will play a role beyond the correction of Earth's atmosphere.
These systems are capable of delivering information that is useful for instrumentation, e.g. if reconstruction
algorithms are employed to increase the spatial resolution of the scientific data. For the 4m aperture Advanced
Technology Solar Telescope (ATST), a new generation of state-of-the-art instrumentation is developed that will
deliver observations of the solar surface at unsurpassed high spatial resolution. The planned Visual Broadband
Imager (VBI) is one of those instruments. It will be able to record images at an extremely high rate and compute
reconstructed images close to the telescope's theoretical diffraction limit using a speckle interferometry algorithm
in near real-time. This algorithm has been refined to take data delivered by the adaptive optics system into
account during reconstruction. The acquisition and reconstruction process requires the use of a high-speed data
handling infrastructure to retrieve the necessary data from both adaptive optics system and instrument cameras.
We present the current design of this infrastructure for the ATST together with a feasibility analysis of the
underlying algorithms.
The solar telescope ChroTel is designed as a robotic telescope so that no user interaction is necessary for observation.
The telescope will start tracking in the morning as soon as weather conditions are appropriate and will process a user
defined observation routine until sunset. Weather conditions and system status are continuously monitored to close the
telescope shutter in case of bad weather or to drive to the stow position in case of an error. The ChroTel control software
was programmed in LabVIEW.
Measuring magnetic fields in the solar corona requires a large aperture telescope with exceptionally low levels of
scattered light. For internally-occulted coronagraphs the main source is scattering from dust or microroughness on the
primary lens or mirror. We show refracting primaries offer significantly lower levels for both sources. To observe
magnetic fields in the solar corona with scientifically interesting spatial and temporal resolutions, a 1 meter aperture or
larger is required. For a long time such large-scale refractors have been deemed impractical or impossible to construct
due to gravitational deformation of the lens. We present the results of finite-element and optical analyses of the
gravitational deformation, stress-induced birefringence, and absorptive heating of a (see manuscript)1.5 meter f/5 fused silica lens.
These studies demonstrate the traditional objections to large refractors are unfounded and large refracting primaries have
unique capabilities.
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.
The Chromospheric Telescope (ChroTel) is a 10 cm robotic telescope to observe the full solar disk with a 2k × 2k CCD
at high temporal cadence. It is located at the Observatorio del Teide, Tenerife, Spain, next to the 70 cm German Vacuum
Tower Telescope (VTT). ChroTel contains a turret system that relays a stabilized image of the solar disk into a
laboratory within the VTT building. The control design allows a fully robotic operation. Observations are carried out in
three chromospheric wavelengths (CaK: 393 nm, Ha: 652 nm, HeI 1083 nm).
This paper addresses the issue of calibrating the Advanced Technology Solar Telescope for high-precision polarimetry, in particular of the optical train above the Gregorian station (where suitable calibration optics will be placed). Conventional techniques would not be adequate for this telescope given its large aperture. Here we explore two different methods that are currently being considered by the design team. The first one is the "sub-aperture" method, which uses small calibration optics above the primary mirror to calibrate a small sub-aperture of the system. This calibration is then extended to the full aperture by means of actual observations. The second method is based on analyzing the polarization observed in a spectral line with a peculiar Zeeman pattern, such as the FeII 614.9 nm line, which does not produce any intrinsic linear polarization. Numerical simulations are presented that show the robustness of both techniques and their respective advantages and disadvantages are discussed.
The mission of the ATST visible spectro-polarimeter (ViSP) is to provide precision measurements of the full state of polarization (Stokes parameters) simultaneously at diverse wavelengths in the visible spectrum and fully resolve (or nearly so) the profiles of spectrum lines originating in the solar atmosphere. We present the instrument science requirements, their flow down to instrument specifications, and a preliminary ViSP design. The ViSP spectrograph allows for reconfiguration while maintaining an immediately selectable configuration. We describe how the ViSP will utilize the ATST polarimetry facility.
The 4-m aperture Advanced Technology Solar Telescope (ATST) is the next generation ground based solar telescope. In this paper we provide an overview of the ATST post-focus instrumentation. The majority of ATST instrumentation is located in an instrument Coude lab facility, where a rotating platform provides image de-rotation. A high order adaptive optics system delivers a corrected beam to the Coude lab facility. Alternatively, instruments can be mounted at Nasmyth or a small Gregorian area. For example, instruments for observing the faint corona preferably will be mounted at Nasmyth focus where maximum throughput is achieved. In addition, the Nasmyth focus has minimum telescope polarization and minimum stray light. We describe the set of first generation instruments, which include a Visible-Light Broadband Imager (VLBI), Visible and Near-Infrared (NIR) Spectropolarimeters, Visible and NIR Tunable Filters, a Thermal-Infrared Polarimeter & Spectrometer and a UV-Polarimeter. We also discuss unique and efficient approaches to the ATST instrumentation, which builds on the use of common components such as detector systems, polarimetry packages and various opto-mechanical components.
The National Solar Observatory in collaboration with the High-Altitude
Observatory is developing a new solar polarimeter, the Diffraction Limited Spectro-Polarimeter. In conjunction with a new high-order adaptive optics system at the NSO Dunn Solar Telescope, the DLSP design facilitates very high angular resolution observations of solar vector magnetic fields. This project is being carried out in two phases. As a follow-on to the successful completion of the first phase, the ongoing DLSP Phase II implements a high QE CCD camera system, a ferro-electric liquid crystal modulator, and a new opto-mechanical system for polarization calibration. This paper documents in detail the development of the modulator system and its performance, and presents preliminary results from an engineering run carried out in combination with the new NSO high-order AO system.
The Mk4 K-coronameter records polarization brightness images of the solar corona from the Mauna Loa Solar Observatory, Hawaii, USA. Calibration is required to quantitatively measure coronal polarization brightness, which in turn is used to infer coronal electron density. Matrix techniques are used to map the instrument polarization response. Brightness scaling depends upon precise knowledge of properties of an opal glass attenuator and calibration polarizer, sky transmission, and telescope pointing. In addition, account must be made for polarization at the objective lens and from the terrestrial atmosphere. Calibration parameters are stable to a few percent over a day, but when coupled with uncertainties in calibration optics values, sky transmission, and pointing, the average measurement uncertainty is ±15% ±6×10-9 pB/BSun.
A diffraction limited spectro-polarimeter is under construction at the National Solar Observatory in collaboration with the High Altitude Observatory. The scientific objective of the project is to measure the magnetic fields on the Sun up to the diffraction limit of the Dunn Solar Telescope. The same instrument would also measure the magnetic field of large sunspots or sunspot groups with reasonable spatial resolution. This requires a flexible image scale which cannot be obtained with the current Advanced Stokes Polarimeter (ASP) without loosing 50% of the light. The new spectro-polarimeter is designed in such a way that the image scale can be changed without loosing much light. It can work either in high-spatial resolution mode (0.09 arcsec per pixel) with a small field of view (FOV: 65 arcsec) or in large FOV mode (163 arcsec) with low-spatial resolution (0.25 arcsec per pixel). The phase-I of this project is to design and build the spectrograph with flexible image scale. Using the existing modulation, calibration optics of the ASP and the ASP control and data acquisition system with ASP-CHILL camera, the spectrograph was tested for its performance. This paper will concentrate on the performance of the spectrograph and will discuss some preliminary results obtained with the test runs.
The Solar Terrestrial Relations Observatory (STEREO) is a pair of identical satellites that will orbit the Sun so as to drift ahead of and behind Earth respectively, to give a stereo view of the Sun. STEREO is currently scheduled for launch in November 2005. One of the instrument packages that will be flown on each of the STEREO spacecrafts is the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI), which consists of an extreme ultraviolet imager, two coronagraphs, and two side-viewing heliospheric imagers to observe solar coronal mass ejections all the way from the Sun to Earth. We report here on the inner coronagraph, labeled COR1. COR1 is a classic Lyot internally occulting refractive coronagraph, adapted for the first time to be used in space. The field of view is from 1.3 to 4 solar radii. A linear polarizer is used to suppress scattered light, and to extract the polarized brightness signal from the solar corona. The optical scattering performance of the coronagraph was first modeled using both the ASAP and APART numerical modeling codes, and then tested at the Vacuum Tunnel Facility at the National Center for Atmospheric Research in Boulder, Colorado. In this report, we will focus on the COR1 optical design, the predicted optical performance, and the observed performance in the lab. We will also discuss the mechanical and thermal design, and the cleanliness requirements needed to achieve the optical performance.
Bruce Lites, David Elmore, Kim Streander, David Akin, Tom Berger, Dexter Duncan, Chris Edwards, Barbara Francis, Chris Hoffmann, Noah Katz, Michael Levay, Dnyanesh Mathur, William Rosenberg, Ericka Sleight, Theodore Tarbell, Alan Title, Darrel Torgerson
As a Japanese National space mission with international collaboration, Solar-B (2005 launch) will carry a spectro- polarimeter (SP) to be operated in visible light to obtain the first high angular resolution, precision measurements of solar vector magnetic fields from space. The SP is part of the Focal Plane Package (FPP) fed by a diffraction-limited 50-cm optical telescope. The SP will be operated exclusively at the photospheric 630 nm Fe I lines. It features a rotating, low-order crystalline quartz retarder for polarization modulation and a reflecting Littrow spectrograph design that is shortened by using diffraction from the 12micrometers wide slit to fill the grating. Polarization analysis is accomplished by a modified Savart plate beam splitter. A custom CCD detector with two active areas, one for each beam from the beam splitter, allows continuous high duty-cycle sampling of polarization. The spectrograph slit will sample a 0.16 x 164 arcsec2 rectangle of the solar image, which may be scanned across the slit by up to +/- 160 arcsec in order to build up vector magnetic field maps of the solar photosphere. Along with simultaneous, co-spatial imaging and polarimetry with the filter imagers of the FPP, the SP will provide a precise view of active and quiet solar magnetic fields that control the structure, dynamics, and energetics of the upper solar atmosphere.
We describe a ground-based eclipse instrument for measuring solar coronal polarization brightness and intensity, and the calibration procedures for this instrument. We present coronal measurements from the February 26, 1998 total solar eclipse observed at Curacao, N.A.. The instrument employs a liquid crystal variable retarder for analysis of coronal broad band linear polarization and collects data on an array detector spanning a 6.5 solar radius field of view. Polarization calibration of the liquid crystal variable retarder utilizes the tangential orientation of coronal polarization to calculate retardance values.
Systems using optical elements such as linear polarizers, retarders, and mirrors can be represented by Mueller matrices. Some polarimeters include elements with time-varying polarization properties, multiple light beams, light detectors, and signal processing equipment. Standard Mueller matrix forms describing time-varying retarders, and beam splitters are presented, as well as non-Mueller matrices which describe detection and signal processing. These matrices provide a compact and intuitive mathematical description of polarimeter response which can aid in the refining of instrument designs.
A new Stokes polarimeter for high spatial resolution quantitative measurement of magnetic fields at multiple heights in the solar atmosphere has been constructed by the National Center for Atmospheric Research and the National Solar Observatory. The instrument uses the Vacuum Tower Telescope at Sunspot, New Mexico, and its existing horizontal spectrograph, universal birefringment filter, and image motion stabilization system. The polarimeter uses a rotating retarder polarization modulator with polarization calibration optics. Multiple paired CCDs are used for detection followed by video processing to produce spatial maps of the full state of polarization in restricted regions of the solar spectrum. Two spectral regions encompassing lines sensitive to the Zeeman effect, which form in the photosphere and low chromosphere, are recorded simultaneously. Significant developments include: construction of the new telescope post focus optical arrangement, creation of a polarization model for the telescope, construction of high-speed, low-noise solid state cameras, and construction of computer hardware for receiving and processing high-rate 12-bit digital data.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.