In VLBI mode, Millimetron space telescope will observe together with ground observatories in millimeter and submillimeter wavelength ranges. Such observatories are usually located in arid regions high above the sea level. The number of ground-based telescopes participating in the observation, as well as their distribution over the Earth’s surface determines the success of space-ground VLBI observations. Most of the telescopes that are suitable for Millimetron project are participating in the Event Horizon Telescope collaboration. Currently, the observatories are following:
The Korean VLBI Network (KVN) is a three-element Very Long Baseline Interferometry (VLBI) network in Korea, which is dedicated to VLBI observations at millimeter wavelengths. Three 21-m radio telescopes are located in Seoul, Ulsan and Jeju island, Korea.
The world's largest single-aperture telescope operating in millimeter and submillimeter wavelength range (50 meters in diameter). Located at an altitude of 4850 meters on top of the extinct volcano Sierra Negra in the Mexican state of Puebla.
An array that consists of eight radio telescopes with a diameter of 6 meters each located at an altitude of 4080 meters above sea level, on Mount Mauna Kea on the island of Hawaii, the Hawaiian archipelago.
12-meter radio telescope installed at Tula Air Base in northwestern Greenland. Later, it will be moved to the territory of the Summit Camp year-round research station, located in the center of the Greenland ice sheet, at an altitude of 3210 meters.