ALMA communications requirements and design

The Atacama Large Millimeter Array (ALMA) is a joint project involving astronomical organizations in Europe and North America. ALMA will consist of at least 64 12-meter antennas operating from millimeter to sub-millimeter wavelengths. ALMA will be located at an altitude of about 5000m. in the Chilean Atacama desert. The main challenge for the development of the ALMA software, which will support the whole end-to-end operation, it is the fact that the computing group is extremely distributed. Groups at different institutes have started the design of all subsystems based on the ALMA Common Software framework (ACS) that provides the necessary standardization. The operation of ALMA by a community of astronomers distributed over various continents will need an adequate network infrastructure. The operation centers in Chile are split between an ALMA high altitude site, a lower altitude control centre, and a support centre in Santiago. These centers will be complemented by ALMA Regional Centers (ARCs) in Europe, North America, and Japan. All this will require computing and communications equipment at more than 5000m in a radio-quiet area. This equipment must be connected to high bandwidth and reliable links providing access to the ARCs. The design of a global computing and communication infrastructure is on-going and aims at providing an integrated system addressing both the operational computing needs and normal IT support. The particular requirements and solutions foreseen for ALMA in terms of computing and communication systems will be explained.