The Diffraction-Limited Near-Infrared Spectropolarimeter (DL-NIRSP) of the Daniel K. Inouye Solar Telescope (DKIST)
Sarah A. Jaeggli, H. Lin, Peter M. Onaka, Hubert Yamada, Tetsu Anan, Morgan Bonnet, Gregory K. Ching, Xiao-Pei Huang, Maxim Kramar, Helen McGregor, Garry Nitta, C. Rae, Louis Robertson, Thomas A. Schad, Paul Toyama, Jessica G. Young, Chris Berst, David M. Harrington, Mary Liang, Myles Puentes, Predrag Sékulic, Brett Smith, Stacey R. Sueoka
Abstract
Abstract The Diffraction-Limited Near-Infrared Spectropolarimeter (DL-NIRSP) is one of the first-light instruments for the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST). DL-NIRSP is an integral-field, dual-beam spectropolarimeter intended for studying magnetically sensitive spectral lines in the Sun’s photosphere, chromosphere, and corona with high spectral resolution and polarimetric accuracy. Two novel fiber-optic integral-field units (IFUs), paired with selectable feed optics and a field-scanning mirror provide great flexibility in spatial sampling ( $0.03^{\prime\prime}$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mn>0.03</mml:mn><mml:mrow><mml:mo>″</mml:mo></mml:mrow></mml:msup></mml:math> , $0.08^{\prime\prime}$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mn>0.08</mml:mn><mml:mrow><mml:mo>″</mml:mo></mml:mrow></mml:msup></mml:math> , and $0.5^{\prime \prime}$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mn>0.5</mml:mn><mml:mrow><mml:mo>″</mml:mo></mml:mrow></mml:msup></mml:math> ) and field coverage ( $2^{\prime} \times 2^{\prime }$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mn>2</mml:mn><mml:mo>′</mml:mo></mml:msup><mml:mo>×</mml:mo><mml:msup><mml:mn>2</mml:mn><mml:mo>′</mml:mo></mml:msup></mml:math> ). The IFUs allow DL-NIRSP to record all the spectra from a 2D field of view simultaneously, enabling the instrument to study the evolution of highly dynamic events. The spectrograph is an all-reflecting, near-Littrow design, which achieves a resolving power of approximately 125,000. Multiple wavelengths can be observed simultaneously using three spectral arms: one for visible wavelengths (500 – 900 nm) and two for infrared wavelengths (900 – 1350 nm and 1350 – 1800 nm). Each supporting camera sub-system is capable of a 30-Hz frame rate, making it possible to track dynamic phenomena on the Sun.