National Science Foundation selects National Solar Observatory to build world’s largest solar telescope

The Advanced Technology Solar Telescope will be the world's flagship facility for the study of magnetic phenomena in the solar atmosphere.Provided by the National Solar Observatory, Sunspot, New Mexico
By | Published: January 22, 2010 | Last updated on May 18, 2023
The Sun
Double prominences.
January 22, 2010
The National Science Foundation has awarded a $298 million cooperative support agreement to the Association of Universities for Research in Astronomy (AURA) to build the 4-meter Advanced Technology Solar Telescope (ATST).

“I want to congratulate everyone who has helped make this happen,” said Stephen L. Keil, director of the National Solar Observatory (NSO) and AURA’s principal investigator for ATST. “It should be an exciting next several years as we bring ATST to reality.”

ATST will be the largest and most capable solar telescope. No comparable facility exists or is planned. ATST will be the world’s flagship facility for the study of magnetic phenomena in the solar atmosphere and will be the first large, ground-based, open-access solar telescope in the United States in more than 40 years.

“This is an exciting opportunity for the NSO to lead the community,” said William Smith, president of AURA. “We look forward to achieving a first-rate, cutting-edge facility.”

ATST is to be built atop Haleakala, Maui, Hawaii, pending completion of a Conservation District Use Agreement and other permits. Haleakala was selected after considering 72 sites and then narrowing those down to six for additional consideration through on-site testing. Of those six sites, only the Haleakala site met all of ATST’s requirements — the least atmospheric blurring, the most annual hours of low sky brightness, the lowest dust levels, and the smallest temperature extremes. The site is next to the existing Mees Solar Observatory that is owned and operated by the University of Hawaii’s Institute for Astronomy, a principal partner in the project.

Understanding the role of magnetic fields in the outer regions of the Sun is crucial to understanding the solar dynamo, solar variability, and solar activity, including flares and mass ejections, which can significantly affect life on Earth. ATST research will investigate solar variability and its impact on terrestrial climate — the conditions responsible for solar flares, coronal mass ejections, and other activities that can impact terrestrial communications and power systems, disrupt satellite communications, and endanger astronauts and air travelers.

ATST’s 4-meter primary mirror will feed an advanced array of instruments designed to study the Sun in light ranging from near ultraviolet (350 nm) into the far infrared (28,000 nm, or 28 microns). High-order adaptive optics, pioneered by the NSO and its partners at NSO’s Dunn Solar Telescope at Sunspot, New Mexico, will correct blurring of solar images caused by Earth’s atmosphere, thus allowing ATST to observe features in the solar atmosphere with unprecedented sharpness, down to structures only a few tens of kilometers in size.

ATST will observe both on the bright solar disk and in the ultra-faint corona. ATST will accurately measure magnetic fields in the ultra-faint corona, which is only a few parts in a million as bright as the solar disk.