ALMA radio astronomy antennas. ALMA (Atacama Large Millimeter/sub-millimeter Array) is an array of 66 radio antennas located at an elevation of 5000 meters on the arid Chajnantor plateau in the Chilean Andes. Data from the separate antennas is combined by interferometry, making it one of the most powerful telescopes in the world. Observations began in 2011, and the array is scheduled to be fully operational by 2013. In the night sky are stars of constellations Canis Major, Orion and Taurus. The Pleiades star cluster appears on the upper left, and Sirius, the brightest star in the night sky, is on the right .