The Milky Way glitters brightly over the Atacama Large Millimeter/Submillimeter Array’s (ALMA) antennas, in this image taken by the ESO Ultra High Definition Expedition team as they capture the site in 4K quality.
Currently under construction in the thin, dry air of northern Chile’s Atacama desert at an altitude of 5,000 meters above sea level, ALMA will initially be composed of 66 high-precision antennas working together at millimeter and submillimeter wavelengths, with a possible extension in the future. To operate properly, ALMA must have its 66 antennas and electronics working in perfect synchrony, with a precision of one millionth of a millionth of a second.
In addition, the signals from the different antennas must be combined in a way that the path followed from each antenna until it is combined at the central computer (the correlator) must be known with an accuracy equal to the diameter of a human hair (hundredths of a millimeter). And, as if the above were not challenging enough, there is the problem of reducing the possible attenuation and perturbation suffered by the signal from the time it touches each antenna until it is digitalized and transmitted over several kilometers of optic fiber to the central computer.
Even earlier, as soon as the signal penetrates the Earth’s atmosphere, it is partially absorbed, deviated and delayed by molecules of CO2, oxygen and water. Seven weather stations, and specially-built Water Vapor Radiometers to measure the amount of line-of-sight water vapor present in the atmosphere, will be used to correct for these atmospheric effects.
Thanks to its high resolution and sensitivity, ALMA will open an entirely new “window” on the Universe, allowing scientists to unravel longstanding and important astronomical mysteries, in search of our cosmic origins.
ALMA is expected to begin science operations with a limited number of antennas and to start full science operations with 66 antennas. Scientists from around the world will soon employ this facility to probe the very first stars and galaxies, and directly image exo-planets, possibly discovering the first traces of life.