Daniel K. Inouye Solar Telescope

The Daniel K. Inouye Solar Telescope (DKIST) is a scientific facility for studies of the Sun under construction at Haleakala Observatory on the Hawaiian island of Maui named after Daniel K. Inouye, a US Senator for Hawaii. With a planned completion date of 2019, it is expected to become the world's largest solar telescope, sporting a 4-meter aperture. The DKIST is funded by National Science Foundation and managed by the National Solar Observatory. Until 2013 it was known as the Advanced Technology Solar Telescope (ATST). It is a collaboration of numerous research institutions. The DKIST shall be capable of observing the Sun in visible to near-infrared wavelengths and will feature a 4.24-meter primary mirror in an off-axis Gregorian configuration that provides a 4-meter clear, unobstructed aperture. Adaptive optics shall correct for atmospheric schlieren in the solar image known as astronomical seeing to enable high-resolution observations of features on the Sun as small as 20 km (10 mi). The off-axis, clear aperture design avoids a central obstruction, minimizing scattered light. It also eases operation of adaptive optics and digital image reconstruction such as speckle imaging. The site on the Haleakalā volcano was selected for its clear daytime weather and favourable atmospheric seeing conditions. The contract to build the telescope was awarded in 2010, with a then-planned completion date of 2017. Physical construction at the DKIST site began in January 2013, and work on the telescope housing was completed in September 2013. The primary mirror was delivered to the site the night of 1–2 August 2017 and as of August 2017 the telescope structure is nearly complete, with first light expected in 2019. The 75 mm thick f/2 primary mirror is a 4.24-meter off-axis section of a 12-meter diameter, f/0.67 concave parabola. It was cast from Zerodur by Schott and polished at the Richard F. Caris Mirror Laboratory of the University of Arizona. The 0.65-meter secondary mirror, a concave ellipsoid with a focal length of 1 meter, was made from silicon carbide and is mounted on a hexapod to compensate for thermal expansion and bending of the telescope structure keeping the mirror in its optimal position.