Abstract
The Atacama Large Millimeter/Submillimeter Array (ALMA) is an international millimeter/submillimeter interferometer under construction in the Atacama Desert of northern Chile. ALMA will be situated on a high-altitude site at 5000 m elevation which provides excellent atmospheric transmission over most of the wavelength range of 0.3 to 3 mm. At the shortest planned wavelength and most extended configuration, the angular resolution of ALMA will be 5 milliarcseconds. This will give us the ability to, for example, image the gas kinematics in protostars and in protoplanetary disks around young Sun-like stars at a distance of 150 pc, or to image the redshifted dust continuum emission from evolving galaxies at epochs of formation as early as z = 10. The instrument will use superconducting (SIS) mixers to provide the lowest possible receiver noise contribution, and special-purpose water vapor radiometers to assist in calibration of atmospheric phase distortions.
At present, the first 7 antennas have been delivered and assembled at the Operations Support Facility (OSF) at 3000 m near San Pedro de Atacama. These antennas will be assessed by ALMA engineering and science staff and then moved to the high site for commissioning. Array commissioning will begin in 2009 with fringes and phase closure amongst at least 3 fully functioning antennas at the high site, and early science observations are expected in late 2010, with full operations in 2012.