Overview
The initial ALMA array will be composed of 66 high-precision antennas, and operate at wavelengths of 0.3 to 9.6 mm. The array will have much higher sensitivity and higher resolution than existing sub-millimeter telescopes such as the single-dish James Clerk Maxwell Telescope or existing interferometer networks such as the Submillimeter Array or the Institut de Radio Astronomie Millimétrique (IRAM) Plateau de Bure facility.
The antennas can be moved across the desert plateau over distances from 150 m to 16 km, which will give ALMA a powerful variable "zoom", similar in its concept to that employed at the Very Large Array (VLA) site in New Mexico, US.
The high sensitivity is mainly achieved through the large numbers of telescopes that will make up the array.
The telescopes are provided by the European, North American and East Asian partners of ALMA. The American and European partners have each placed orders for twenty-five 12-metre diameter antennas, that will compose the main array. East Asia is contributing 16 antennas (four 12-metre diameter and twelve 7-metre diameter antennas) in the form of the Atacama Compact Array (ACA) which is also part of the enhanced ALMA.
By using smaller antennas than the main ALMA array, larger fields of view can be imaged at a given frequency using ACA. Moving the antennas closer together will enable the imaging of sources of larger angular extent. The ACA will work together with the main array in order to enhance the latter's wide-field imaging capability.
Read more about this topic: Atacama Large Millimeter Array