Mauna Loa Solar Observatory

Mauna Loa Solar Observatory (MLSO) is a Solar Observatory on Mauna Loa in Hawaii. Its altitude is 3394 meters (11135 feet). It is operated by High Altitude Observatory (HAO), a unit of NCAR (National Center for Atmospheric Research). The unit's focus is solar phenomena that affect Earth, i.e., space weather. The MLSO is co-located with (or part of) the Mauna Loa Observatory (MLO), which is an atmospheric observatory rather than an astronomy observatory. MLSO instruments:

• K-Cor (coronagraph).
• UCOMP (upgraded CoMP).

Former instruments:

• CoMP (Coronal Multi-cannel Polarimeter).
• PSPT (Precision Solar Photometric Telescope).
• Mk4 (Mark-IV K-Coronameter).
• ACOS (Advanced Coronal Observing System).
• CS60 (Coronado Solarmax 60).
• CHIP (Chromospheric Helium-I Imaging Photometer).
• PICS (Polarimeter for Inner Coronal Studies).
• DPM (Digital Prominence Monitor).
• POM (Prominence Monitor).
• Mk3 (Mark-III K-Coronameter).
• Mk2 (Mark-II K-Coronameter).
• Mk1 (Mark-I K-Coronameter).

Coronal Solar Magnetism Observatory (COSMO) is a plan for three new instruments, one of which is completed (K-Cor).

MLSO (and all of MLO) suffered an extended outage due to a November 2026 Mauna Loa volcanic eruption, which took out its power and access roads. MLSO reopened in March 2026 when a replacement access road was completed.

The Hawaiian Islands, which feature tall mountain peaks with dry air and dark sky, also host observatories on Mauna Kea (Mauna Kea Observatories), also on the island of Hawaii, and on Haleakala (Haleakala Observatory), on the island of Maui.