NSF to proceed with demolition and site restoration at Sacramento Peak Observatory

The U.S. National Science Foundation announced today it will proceed with demolition and site restoration at the Sacramento Peak Observatory, also known as Sunspot Solar Observatory, in Sunspot, New Mexico, following years of reduced operations and in light of recent safety concerns involving the Richard B. Dunn Solar Telescope.

The Dunn Solar Telescope was originally constructed by the U.S. Air Force in 1969. The telescope's one-of-a-kind design was state-of-the-art for its time. Its 250-ton optical system smoothly rotated by floating on 120 gallons of liquid mercury sealed within a bearing. The Air Force transferred ownership of the facility to NSF in 1976, and the observatory was operated by the NSF National Solar Observatory until 2017. Operations were taken over by a global consortium led by New Mexico State University in Las Cruces, New Mexico and the site was renamed Sunspot Solar Observatory. The telescope has been in limited operation since 2019.

On Jan. 5, 2026, liquid mercury was discovered inside the telescope building. Safety protocols were immediately implemented, and appropriate authorities were notified. Sacramento Peak Observatory, including the visitor center and surrounding areas, was closed to the public and has remained closed.

The observatory is located on public land in Lincoln National Forest, which is managed by the U.S. Department of Agriculture Forest Service. The Forest Service requested that NSF remove all mercury and remediate the site.

After assessing the engineering challenges, anticipated repair costs and safety and environmental risks, NSF determined that removing and safely disposing of the telescope's mercury is the most prudent course of action. This process will render the Dunn Solar Telescope inoperable. Following remediation, NSF will move forward with demolishing the telescope and restoring the site.

Until the advent of the NSF Daniel K. Inouye Solar Telescope and other more advanced facilities, the Dunn Solar Telescope was central to the scientific exploration of the sun, enabling the study of sunspots, solar flares and the dynamics of the solar atmosphere. NSF is working with local stakeholders to develop an educational exhibit about the legacy and scientific contributions of the Dunn Solar Telescope and Sacramento Peak Observatory.