Abstract
Radio interferometry is a powerful technique to observe astronomical objects with a very high angular resolution. This technique was developed in 1940s, and then synthesis technique using earth-rotation and large number of antennas allowed us to achieve high-angular resolution imaging in 1960s. Atacama Large Millimeter/Submillimeter Array (ALMA), which is now being developed at Atacama desert in Chilean Andes, has an ultimate capability with less than ∼10-milli-arcsecond resolution and unprecedented sensitivity at millimeter and submillimeter radio wavelengths. From 2011, ALMA has started its operation with limited capability (called early science) and initial scientific results have been come up. In this paper, we review the basic principle of radio interferometry and aperture synthesis, and introduce advanced techniques developed for ALMA. In particular, Atacama Compact Array (ACA) and related techniques for wide-field imaging adapted to ALMA are presented.
