A supercomputer's home in the Chajnantor Plateau

This photo shows the buildings of the ALMA Array Operations Site in the Chilean Atacama Desert surrounded by snow. Wait a minute — there’s snow in the desert? 

The Atacama Desert is one of the driest places in the world — more specifically, the driest place on Earth outside the polar regions in terms of average rainfall. The very low levels of water vapour in the atmosphere and the almost constantly clear skies make it an ideal location for astronomical observations. However, as this photo from August 2023 — wintertime in Chile — shows, snow can occasionally visit the desert.  

The Atacama Large Millimeter/sub-millimeter Array (ALMA), in which ESO is a partner, is one of the largest astronomical projects in the world. The telescope’s 66 radio antennas are located at the Array Operations Site (AOS) on Llano de Chajnantor, an impressive 5000 metres above sea level and about 40 km east of San Pedro de Atacama. The large yellow truck in this picture is one of the two transporters used to periodically rearrange the antennas into different configurations.

The telescope’s signals are processed in a supercomputer in the nearby AOS Technical Building, pictured above — one of the highest-altitude buildings in the world! The digitised signals are then transmitted to the data storage facilities housed at the Operations Support Facility (OSF) site, at a more benign altitude of 2900 metres.