In the VLBI mode, ground-based observatories capable of observing in the millimeter and submillimeter ranges will work together with the Millimeter space telescope. Such observatories are usually located in arid regions high above sea level. The success of observations in the Space-Earth interferometer mode will largely be determined by the number of ground-based telescopes involved in the observation, as well as their distribution over the Earth's surface. Currently, most of the telescopes that are suitable for the Millimetron project participate in the Event Horizon Telescope collaboration. Today it is:

Antenna diameter 10 m
Antenna construction solid, deployable and adjustable in orbit
Antenna surface accuracy (wave front error) 6 μm RMS
Antenna surface temperature < 10 K, mechanically cooled
Wavelength coverage 10 mm – 70 μm
Orbit Halo round Lagrangian L2 & Near Earth orbit
Operational life time 10 year, including cryo >3 years
Space Earth-VLBI 10 – 0.5 mm wavelength
Single dish 3 - 0.07 mm wavelength
Provisional launch date 2029
Mission status Approved by Russian Space agency