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.
The National Science Foundation Daniel K. Inouye Solar Telescope (DKIST) is a 4-m off-axis telescope that points directly at the sun. Pointing at the sun generates a tremendous amount of heat (approximately 12kW) which requires an innovative cooling method and thermal control to avoid damaging telescope equipment and the building. The heat stop is one component DKIST implemented as part of the thermal control system. The heat stop is located at the telescope’s prime focus and blocks most light from proceeding to the M2 mirror and subsequent optics with a five (5) arcmin field of view diameter. The surface temperatures of the heat stop are also maintained near ambient temperatures to minimize self-induced seeing and maintain high-quality images. The heat stop comprises of the following: a reflector and an absorber. Computational fluid dynamics (CFD) modeled the thermal performance of the current heat stop reflector and absorber design. Installed temperature sensors and historical data shall then determine the actual fluid thermal heat loads and rise in surface temperatures. The results shall verify the thermal performance of the heat stop. Future work includes investigating whether or not the heat stop contributes to any seeing that may be present in the instrumentation images.
The coudé lab is one of the central components of the Coudé Environmental Systems (CES) at the Daniel K. Inouye Solar Telescope (DKIST). The scientific instruments for DKIST are located on benches inside the coudé lab. The light path from the telescope to the coudé lab goes from ambient to conditioned space, therefore, in order to minimize local seeing or wave front distortion, the CES was designed. The CES is composed of the Air Knife and equipment that condition the coudé lab to the desired cleanliness, temperature, and humidity design parameters. The Air Knife uses an air curtain to divide the external ambient space from the conditioned coudé lab through a series of fan operated and filtered ducted assemblies. The coudé lab is conditioned using filtered air handling units, makeup air handling units, a HEPA filter plenum ceiling, floor dampers, and humidifiers. The installed CES equipment shall be tested and results shall be presented to determine whether the design parameters
The Daniel K. Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, housing a 4 meter primary mirror that will enable observation of specific regions of the sun in higher resolution and greater detail than any existing telescope. The DKIST Facility Thermal Systems is comprised of various systems and components that contribute to maintaining an appropriate thermal environment for solar observation. One of these systems is the Carousel Cooling System, which contributes to active control of the Enclosure thermal environment. This system is intended to actively maintain the Enclosure exterior at, or just below, ambient temperature through a system of plate heat exchangers. These heat exchangers, termed plate coils, are designed to reject solar radiation from the Enclosure cladding in order to mitigate dome seeing effects caused by turbulent air of dissimilar temperatures. Per DKIST's specifications, OMEGA Thermo Products fabricated 232 type 304 stainless steel plate coils that are categorized into 104 different dimensions. These are in the process of being installed on the following sections of the Enclosure: Aperture Stop, Shutter, Arches and Vent Gates. This has further complicated installation as each section yields different requirements for lifting, integrating, mounting, and piping the various plate coils. Presented here is a review of the installation progress and future planning for the Carousel Cooling System.
KEYWORDS: Solar telescopes, Observatories, Telescopes, Thermal analysis, Systems modeling, Solar radiation models, Cooling systems, Data modeling, Solar radiation, MATLAB
The climate of Haleakalā requires the observatories to actively adapt to changing conditions in order to produce the best possible images. Observatories need to be maintained at a temperature closely matching ambient or the images become blurred and unusable. The Daniel K. Inouye Solar Telescope is a unique telescope as it will be active during the day as opposed to the other night-time stellar observatories. This means that it will not only need to constantly match the ever-changing temperature during the day, but also during the night so as not to sub-cool and affect the view field of other telescopes while they are in use.
To accomplish this task, plate coil heat exchanger panels will be installed on the DKIST enclosure that are designed to keep the temperature at ambient temperature +0°C/-4°C. To verify the feasibility of this and to validate the design models, a test rig has been installed at the summit of Haleakalā. The project’s purpose is to confirm that the plate coil panels are capable of maintaining this temperature throughout all seasons and involved collecting data sets of various variables including pressures, temperatures, coolant flows, solar radiations and wind velocities during typical operating hours. Using MATLAB, a script was written to observe the plate coil’s thermal performance. The plate coil did not perform as expected, achieving a surface temperature that was generally 2ºC above ambient temperature. This isn’t to say that the plate coil does not work, but the small chiller used for the experiment was undersized resulting in coolant pumped through the plate coil that was not supplied at a low enough temperature. Calculated heat depositions were about 23% lower than that used as the basis of the design for the hillers to be used on the full system, a reasonable agreement given the fact that many simplifying assumptions were used in the models. These were not carried over into the testing.
The test rig performance showing a 23% margin provides a high degree of confidence for the performance of the full system when it is installed. If time allows, additional testing could be done that includes additional incident angles and times of day. This would allow a more complete analysis. If additional testing were to be performed, it’s recommended to use a larger chiller capable of reaching lower temperatures. The test rig design could also be optimized in order to bring the plate coil up to its maximum efficiency. In the future, the script could be rewritten in a different computer language, so that the data could be solved for quicker. Further analysis could also include different types of coolants.
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