ALMA radio telescope at sunset. The Atacama Large Millimetre/submillimetre Array (ALMA) is a series of 66 giant antennas which observe light with millimetre and submillimetre wavelengths. ALMA is currently the most powerful telescope in the world for observing molecular gas and dust that emits millimetre and sub millimetre light, allowing the array to study the building blocks of stars, planetary systems and galaxies.