Nerval's Lobster writes: "Building and operating a supercomputer at more than three miles above sea level poses some unique problems, the designers of the recently installed Atacama Large Millimeter/submillimeter Array (ALMA) Correlator discovered. The ALMA computer serves as the brains behind the ALMA astronomical telescope, a partnership between Europe, North American, and South American agencies. It’s the largest such project in existence. Based high in the Andes mountains in northern Chile, the telescope includes an array of 66 dish-shaped antennas in two groups. The telescope correlator’s 134 million processors continually combine and compare faint celestial signals received by the antennas in the ALMA array, which are separated by up to 16 kilometers, enabling the antennas to work together as a single, enormous telescope, according to Space Daily. The extreme high altitude makes it nearly impossible to maintain on-site support staff for significant lengths of time, with ALMA reporting that human intervention will be kept to an absolute minimum. Data acquired via the array is archived at a lower-altitude support site. The altitude also limited the construction crew’s ability to actually build the thing, requiring 20 weeks of human effort just to unpack and install it."