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 Visible Tunable Filter Instrument (VTF) is a 2D imaging spectropolarimeter for high spatial and spectral resolution solar observations in the visible light. Integration into the world largest solar telescope, the 4m aperture Daniel K. Inouye Solar Telescope (DKIST) started in January 2024. In this paper we present an overview over the complete software infrastructure designed and developed for this instrument. In particular the Instrument Control Software (ICS), the Instrument Performance Calculator (IPC) which is a graphical tool enabling scientist to explore instrument performance and create executable observing configurations. Furthermore, real-time monitoring plugins were implemented to verify data acquisition and instrument performance. The main part of the infrastructure is the ICS package which provides the interface between the operator, the instrument and the observatory. It is based on the Common Services Framework (CSF) provided by DKIST and is based on an object-oriented design and written in JAVA. The interface to the operator is given by the engineering GUI that allows the user to monitor and control all system drives and sensors. All observation and calibration tasks can be configured and started from this GUI. The interface to the instrument is realized by a DKIST framework compatible OPC/UA layer developed for this instrument which interfaces to a Beckhoff Programmable Logic Controller (PLC) that manages the real-time requirements of the instrument. All real-time and synchronization requirements are implemented using the DKIST timing and synchronization system (TRADS) based on the precision time protocol (PTP) that allows timing accuracy well below microseconds. Furthermore, the ICS interfaces to the Camera System Software (CSS) and Data Handling System (DHS), where VTF delivers up to 2400 MB/s or roughly 9 TB/hour when used in spectropolarimetric imaging mode.
The Visible Tunable Filter Instrument (VTF) is a 2D imaging spectropolarimeter for high spatial and spectral resolution solar observations in the visible light. It will be operated at the world’s largest solar telescope, the 4m aperture Daniel K. Inouye Solar Telescope (DKIST) in Maui, Hawaii, USA. The VTF is designed and constructed by the Leibniz-Institut f¨ur Sonnenphysik (KIS) with support from the Istituto ricerche solari Aldo e Cele Dacc`o (IRSOL), the Max-Planck-Institut f¨ur Sonnensystemforschung (MPS) and the National Solar Observatory (NSO). KIS started integrating and commissioning the VTF at the DKIST in January 2024. VTF is based on two large Fabry-P´erot etalons (FPIs) acting as spectral filters. The field of view of 1 arcmin combined with a spectral accuracy well below 1 picometer leads to a clear aperture (CA) of 250 mm, an allowed cavity error smaller than 3 nm RMS over the CA, a microroughness below 0.4 nm RMS and a required cavity stability of ±100 pm over one hour. Therefore, the world’s largest tunable etalons for imaging applications had to be built. With these etalons, VTF will be able to drive solar science for the next decades. In this paper we describe the overall design and specifications of the VTF-FPIs. The first etalon was completely assembled and commissioned in the lab in 2023. We present the main characteristics as measured in the laboratory and demonstrate the dynamic response probed by the integrated metrology system.
The Visible Tunable Filter (VTF) is a narrowband tunable filter system for imaging spectroscopy and spectropolarimetry based. The instrument will be one of the first-light instruments of the Daniel K. Inouye Solar Telescope that is currently under construction on Maui (Hawaii). The VTF is being developed by the Kiepenheuer Institut fuer Sonnenphysik in Freiburg as a German contribution to the DKIST. We perform end-to-end simulations of spectropolarimetric observations with the VTF to verify the science requirements of the instrument. The instrument is simulated with two Etalons, and with a single Etalon. The clear aperture of the Etalons is 250 mm, corresponding to a field of view with a diameter of 60 arcsec in the sky (42,000 km on the Sun). To model the large-scale figure errors we employ low-order Zernike polynomials (power and spherical aberration) with amplitudes of 2.5 nm RMS. We use an ideal polarization modulator with equal modulation coefficients of 3-1/2 for the polarization modulation We synthesize Stokes profiles of two iron lines (630.15 nm and 630.25 nm) and for the 854.2 nm line of calcium, for a range of magnetic field values and for several inclination angles. We estimated the photon noise on the basis of the DKIST and VTF transmission values, the atmospheric transmission and the spectral flux from the Sun. For the Fe 630.25 nm line, we obtain a sensitivity of 20 G for the longitudinal component and for 150 G for the transverse component, in agreement with the science requirements for the VTF.
The Visible Tunable Filter (VTF) is a narrowband tunable instrument for imaging spectropolarimetry in the wavelength range between 520 and 870 nm. It is based on large-format Fabry Perots with a free aperture of 250 mm. The instrument will be one of the first-light instruments of the 4 m aperture Daniel K. Inoue Solar Telescope (DKIST) that is currently under construction on Maui (Hawaii). To provide stable and repeatable spectral scanning by tuning the air gap distance of the Etalons, a metrology system with 20 pm resolution and drift stability of better 100 pm per hour is needed. The integration of the metrology system must preserve the tight optical specifications of the Etalon plates. The HEIDENHAIN LIP 382 linear encoder system has a selected linear scale for low noise high signal interpolation. The signal period is 128nm and the interpolated signal from the sensor can be read out at 128 nm/ 14 bit = 7.8125 pm. To qualify the LIP 382 system for the VTF, we investigated the resolution and stability under nominal VTF operation conditions and verified a mounting concept for the sensor heads. We present results that demonstrate that the LIP 382 system fulfills the requirements for the VTF Etalons. We also present a design for the sensor head mounts.
The Visible Tunable Filter (VTF) is a diffraction-limited narrowband tunable instrument for imaging spectropolarimetry in the wavelength range between 520 and 860 nm. It is based on large-format Fabry Perot. The instrument will be one of the first-light instruments of the 4m aperture Daniel K. Inoue Solar Telescope (DKIST). To provide a field of view of 1 arcmin and a spectral resolution λ/Δλ of about 100.000, the required free aperture of the Fabry Perot is 250mm. The high reflectivity coatings for the Etalon plates need to meet the specifications for the reflectivity over the entire wavelength range and preserve the plate figure specifications of better λ/300, and a micro roughness of < 0.4 nm rms. Coated surfaces with similar specifications have successfully been made for reflecting mirrors on thick substrates but not for larger format Fabry-Perot systems. Ion Beam Sputtering (IBS) based coatings provide stable, homogeneous, and smooth coatings. But IBS coatings also introduce stresses to the substrate that influence the plate figure in our case at the nm level. In a joint effort with an industry partner and a French CNRS research laboratory, we developed and tested processes on small and full size substrates, to provide coated Etalon plates to the required specifications. Zygo Extreme Precision Optics, Richmond, CA, USA, is polishing and figuring the substrates, doing the metrology and FE analysis. LMA (Laboratoire Matériaux Avancés, Lyon, France) is designing and making the IBS coatings and investigating the detailed behavior of the coatings and related processes. Both partners provide experience from manufacturing coated plane optics for gravitational wave detection experiments and EUV optics. The Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany is designing and building the VTF instrument and is leading the coating development. We present the characteristics of the coatings and the substrate processing concept, as well as results from tests on sample size and from full size substrate processing. We demonstrate that the tight specifications for a single Etalon can be reached.
KEYWORDS: Control systems, Cameras, Optical proximity correction, Photonic integrated circuits, Modulators, Sensors, Fabry–Perot interferometers, Human-machine interfaces, Control systems design, OLE for process control
The Visible Tunable Filter (VTF) is a narrowband tunable filter system for imaging spectroscopy and spectropolarimetry based on large-format Fabry Perot interferometers that is currently built by the Kiepenheuer Institut fuer Sonnenphysik for the Daniel K. Inouye Solar Telescope (DKIST). The control software must handle around 30 motorised drives, 3 etalons, a polarizing modulator, a helium neon laser for system calibration, temperature controllers and a multitude of sensors. The VTF is foreseen as one of the DKISTs first-light instruments and should become operational in 2019.
In the design of the control software we strongly separate between the high-level part interfacing to the
DKIST common services framework (CSF) and the low-level control system software which guarantees real-time performance and synchronization to precision time protocol (PTP) based observatory time. For the latter we chose a programmable logic controller (PLC) from Beckhoff Automation GmbH which supports a wide set of input and output devices as well as distributed clocks for synchronizing signals down to the sub-microsecond level.
In this paper we present the design of the required control system software as well as our work on extending the DKIST CSF to use the OPC Unified Architecture (OPC UA) standard which provides a cross-platform communication standard for process control and automation as an interface between the high-level software and the real-time control system.
The Visible Tunable Filter (VTF) is a narrowband tunable filter system for imaging spectropolarimetry. The instrument
will be one of the first-light instruments of the Daniel K. Inouye Solar Telescope (DKIST) that is currently under construction
on Maui (Hawaii). The DKIST has a clear aperture of 4 meters. The VTF is being developed by the Kiepenheuer
Institut für Sonnenphysik in Freiburg, as a German contribution to the DKIST.
The VTF is designed as a diffraction-limited narrowband tunable instrument for Stokes spectro-polarimetry in the
wavelength range between 520 and 860 nm. The instrument uses large-format Fabry-Perot interferometers (Etalons) as
tunable monochromators with clear apertures of about 240 mm. To minimize the influence of gravity on the interferometer
plates, the Fabry-Perots are placed horizontally. This implies a complex optical design and a three-dimensional support
structure instead of a horizontal optical bench.
The VTF has a field of view of one arc minute squared. With 4096x4096 pixel detectors, one pixel corresponds to an
angle of 0.014” on the sky (10 x 10 km on the Sun). The spectral resolution is 6 pm at a wavelength of 600 nm. One 2Dspectrum
with a polarimetric sensitivity of 5E-3 will be recorded within 13 seconds. The wavelength range of the VTF
includes a number of important spectral lines for the measurement flows and magnetic fields in the atmosphere of the
Sun. The VTF uses three identical large-format detectors, two for the polarimetric measurements, and one for broadband
filtergrams.
The main scientific observables of the VTF are Stokes polarimetric images to retrieve the magnetic field configuration of
the observed area, Doppler images to measure the line-of-sight flow in the solar photosphere, and monochromatic
intensity filtergrams to study higher layers of the solar atmosphere.
The Kiepenheuer-Institut will develop for the Advanced Technology Solar Telescope (ATST) a narrowband tunable
filter system (Visible Tunable Filter, VTF) for imaging spectroscopy and spectropolarimetry based on large-format
Fabry Perot interferometers. A major challenge for the realization of this instrument is the development of large-format
Fabry-Perots with a free aperture of about 250 mm. The instrument will operate in the spectral range between 500 and
900 nm with access to a host of magnetically sensitive lines. The instrument is designed to match the diffraction limit of
the 4m-aperture ATST and will be able to observe processes on the sun at spatial scales of 35 km. Its multi-line
capability, together with a field of view of one arc minute, and the ability to measure polarization states of the incoming
light allow to probe different layers of the solar atmosphere within a couple of seconds. The instrument is capable to
vary the spectral sampling, the integration time, and the temporal cadence over a wide range without changing or
compromising the opto-mechanical setup. This versatility gives unique possibilities to apply different measurement
schemes to a variety of science questions. The ATST is a fully funded US project, with the VTF as the only non-US
contribution, and is ready to start construction at the Haleakala summit. The VTF is foreseen as one of the ATST’s firstlight
instruments and should become operational in 2018.
With the integration of a 1-meter Cesic primary mirror the GREGOR telescope pre-commissioning started. This is the
first time, that the entire light path has seen sunlight.
The pre-commissioning period includes testing of the main optics, adaptive optics, cooling system, and pointing system.
This time was also used to install a near-infrared grating spectro-polarimeter and a 2D-spectropolarimeter for the visible
range as first-light science instruments. As soon as the final 1.5 meter primary mirror is installed, commissioning will be
completed, and an extended phase of science verification will follow. In the near future, GREGOR will be equipped with
a multi-conjugate adaptive optics system that is presently under development at KIS.
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.
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).
The telescope structure including control system and the complete retractable dome of the new 1.5 m solar telescope GREGOR were assembled during 2004 at Izana on Tenerife, Spain. The GREGOR telescope is build by a consortium of the Kiepenheuer Institut fuer Sonnenphysik, the Astrophysikalische Institut Potsdam, the Institut fuer Astrophysik Goettingen and additional national and international Partners. Pointing, tracking and thermal tests were made to verify the proposed performance. The results of these tests and a progress report of the project will be presented.
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.