Atacama compact array antennas

TL;DR: The Atacama Compact Array (ACA) as mentioned in this paper is an important element of ALMA and consists of four ACA 12m antennas and twelve ACA 7m antennas, and the science performance of these antennas has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in northern Chile since 2007.

Abstract: The ACA (Atacama Compact Array) system is an important element of ALMA and consists of four ACA 12-m antennas and twelve ACA 7-m antennas. The ACA system aims to acquire the total power data with four 12-m antennas and the short baseline interferometer data with 7-m antennas. The ACA system also increases reliability of the interferometer maps of astronomical sources larger than the field view of the 12-m antenna. The science performance of these antennas has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in Atacama desert in northern Chile since 2007. The pointing performance has been verified with a dedicated optical pointing telescope, the servo performance is tested with angle encoders, and the surface accuracy has been measured with a radio holography method. Both ACA 12-m antennas and 7-m antennas have been successfully demonstrated to meet the very stringent ALMA specifications.