The Visible Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope

The Daniel K. Inouye Solar Telescope (DKIST) Visible Spectro-Polarimeter (ViSP) is a traditional slit-scanning spectrograph with the ability to observe solar regions up to a 120×78arcsec2 area. The design implements dual-beam polarimetry, a polychromatic polarization modulator, a high-dispersion echelle grating, and three spectral channels that can be automatically positioned. A defining feature of the instrument is its capability to tune anywhere within the 380 – 900 nm range of the solar spectrum, allowing for a virtually infinite number of combinations of three wavelengths to be observed simultaneously. This enables the ViSP user to pursue well-established spectro-polarimetric studies of the magnetic structure and plasma dynamics of the solar atmosphere, as well as completely novel investigations of the solar spectrum. Within the suite of first-generation instruments at the DKIST, ViSP is the only wavelength-versatile spectro-polarimeter available to the scientific community. It was specifically designed as a discovery instrument to explore new spectroscopic and polarimetric diagnostics and test improved models of polarized line formation through high spatial-, spectral-, and temporal-resolution observations of the Sun’s polarized spectrum. In this instrument article, we describe the science requirements and design drivers of ViSP and present preliminary science data collected during the commissioning of the instrument.