ALMA innovation

High-altitude supercomputer starts up in Chile’s Atacama Desert

A groundbreaking step towards the Atacama Large Millimeter/submillimeter Array (ALMA) telescope’s completion, its supercomputer correlator is now ready for use. 

Monday, January 28, 2013  
The special-purpose ALMA correlator now up and running in Chile’s northern Atacama Desert. Photo cou The special-purpose ALMA correlator now up and running in Chile’s northern Atacama Desert. Photo courtesy of European Southern Observatory (ESO).


Despite unspeakable challenges, the world’s highest altitude supercomputer is up and running as part of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile’s northern Atacama Desert. The completion of the special-purpose ALMA correlator, or simply the correlator, marks the final stages in ALMA’s assembly which is projected for March of 2013.


The correlator serves as an astronomical telescope made up of 66 disc-like receptors. These receptors are separated across the desert, some as many 16 kilometers apart. All of these receptors work together to function as one gargantuan telescope capable of perceiving faint and far away celestial vibrations.


The correlator has over 134 million processors, enabling it to perform 17 quadrillion operations per second.


The University of Bordeaux in France had a hand in devising one of the correlator’s most innovative aspects: its cutting-edge digital filtering system. Thanks to this improved system, the correlator will be able to split wavelengths of light up to 32 times more thinly than the original model.


“This vastly improved flexibility is fantastic; it lets us ‘slice and dice’ the spectrum of light that ALMA sees, so we can concentrate on the precise wavelengths needed for a given observation,” Alain Baudry, from the University of Bordeaux described. “Whether it’s mapping the gas molecules in a star-forming cloud, or searching for some of the most distant galaxies in the Universe.”


“The completion and installation of the correlator is a huge milestone towards the fulfillment of North America’s share of the international ALMA construction project,” Mark McKinnon, North American ALMA Project Director at NRAO, said in an online statement. “The technical challenges were enormous, and our team pulled it off.”


One of the numerous technical challenges described by McKinnon was the sheer altitude of the ALMA Array Operations Site (AOS) Technical Building. At 16,400 feet (5,000 meters) above sea level it’s considered the highest altitude high-tech building in the world. At this altitude the air is so thin that much more airflow is needed to maintain cool temperatures inside the computer, an activity that requires tremendous amounts of power.


Another challenge was that the location experiences frequent tremors, necessitating that the correlator be resistant to seismic activity of any kind.


The correlator’s unique design, as well as its construction and installation, were pioneered by the US National Radio Astronomy Observatory (NRAO). The U.S. National Science Foundation as well as European Southern Observatory (ESO) helped to fund the initiative.