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 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.
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 ±0.2 deg and ±0.5 deg for two separate SiO2 retarders. Modulation matrices derived are stable to < ± 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.
We describe the design, construction, and expected performance of two new fiber integral field units (IFUs) -
HexPak and GradPak - for the WIYN 3.5m Telescope Nasmyth focus and Bench Spectrograph. These are the
first IFUs to provide formatted fiber integral field spectroscopy with simultaneous sampling of varying angular
scales. HexPak and GradPak are in a single cable with a dual-head design, permitting easy switching between
the two different IFU heads on the telescope without changing the spectrograph feed: the two heads feed a
variable-width double-slit. Each IFU head is comprised of a fixed arrangement of fibers with a range of fiber
diameters. The layout and diameters of the fibers within each array are scientifically-driven for observations
of galaxies: HexPak is designed to observe face-on spiral or spheroidal galaxies while GradPak is optimized
for edge-on studies of galaxy disks. HexPak is a hexagonal array of 2.9 arcsec fibers subtending a 40.9 arcsec
diameter, with a high-resolution circular core of 0.94 arcsec fibers subtending 6 arcsec diameter. GradPak is a
39 by 55 arcsec rectangular array with rows of fibers of increasing diameter from angular scales of 1.9 arcsec to
5.6 arcsec across the array. The variable pitch of these IFU heads allows for adequate sampling of light profile
gradients while maintaining the photon limit at different scales.
We present measurements of how multimode fiber focal-ratio degradation (FRD) and throughput vary with levels
of fiber surface polish from 60 to 0.5 micron grit. Measurements used full-beam and laser injection methods at
wavelengths between 0.4 and 0.8 microns on 17 meter lengths of Polymicro FBP 300 and 400 μm core fiber.
Full-beam injection probed input focal-ratios between f/3 and f/13.5, while laser injection allowed us to isolate
FRD at discrete injection angles up to 17 degrees (f/1.6 marginal ray). We find (1) FRD effects decrease as grit
size decreases, with the largest gains in beam quality occurring at grit sizes above 5 μm; (2) total throughput
increases as grit size decreases, reaching 90% at 790 nm with the finest polishing levels; (3) total throughput
is higher at redder wavelengths for coarser polishing grit, indicating surface-scattering as the primary source of
loss. We also quantify the angular dependence of FRD as a function of polishing level. Our results indicate that
a commonly adopted micro-bending model for FRD is a poor descriptor of the observed phenomenon.
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