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Commissioning and Science Verification activities
After the first phase closure has been obtained with three 12 m telescopes at the Array Operation Site (AOS), ALMA Commissioning and Science Verification (CSV) has officially started from Jan. 22, 2010. The mission of the CSV is to test and to debug the scientific instruments of the ALMA, and to verify these performances are satisfying the requirements for the coming scientific observations. The CSV activities went well since they started, and in the end of March, 2011, ALMA officially announced the call for proposals for the first early science (Cycle 0) observations. On Jul. 28, 2011, sixteen 12 m telescopes moved to AOS, and on Aug. 6, 2011, fringes have been successfully detected using all these sixteen telescopes by the CSV members, which satisfied the condition for starting the Cycle 0 observations. In the end of September, 2011, the first Cycle 0 observation officially started. Currently, the Cycle 0 observations are continuing, while more antennas are being integrated at the AOS and while the CSV activities continue. Meanwhile, the first 7 m telescope also arrived at the AOS in the end of August 2011, and started the CSV activities for the Atacama Compact Array (ACA), which will be used to detect extended emission from astronomical sources.
ALMA-Taiwan sent one staff member for a long term (1.5 years) to participate in the CSV activities; S. Matsushita stayed in Chile from April, 2010 to October, 2011 for this purpose. He spent 8 days per month at the ALMA site for the on-site tests, and worked at the Santiago office for the other days to mainly reduce various CSV data and write reports. His work is mainly verifying the whole ALMA system, namely checking the stability of visibility phase taken toward astronomical sources. Since the visibility phase information decides the positional accuracy of the astronomical sources, this work is very critical for the early science. With various tests toward astronomical sources, he confirmed that the stability of visibility phase is satisfying the specification for ALMA. Furthermore, he also confirmed that the water vapor radiometers, which correct the phase fluctuation due to the atmosphere, are working well even at long (~600 m) baselines. He was also in the team who successfully detected the first fringes with 16 telescopes at the AOS. In addition to these works, he also helped the verification of ephemeris source tracking, receiver tuning speed, checking delay infusion timing, making observational scripts and debugging various problems. Some of these works are presented at the SPIE conference “Astronomical Telescopes + Instrumentation 2012” in Amsterdam, Netherland, and the proceedings are publised. ( Matsushita et al. “ALMA temporal phase stability and the effectiveness of water vapor radiometer”, Asaki et al. “ACA phasecalibration scheme with the ALMA water vapor radiometers”, and Sramek et al. “ALMA system verification” ).
In addition to having one person based in Chile, ALMA-Taiwan sent several members for short term visits ( < 1 year) since 2010; Ram Rao was helping polarization tests for 1.5 months. There are few polarization experts, and, therefore his knowledge and experience in polarization from the SMA are very helpful for the ALMA polarization testing. Juan-Carlos Alagaba and Edwige Chapillon also joined the polarization campaign. Yu-Nung Su, Masaaki Hiramatsu, and Alfonso Trejo-Cruz visited for 1-2 months, and helped various CSV tests, such as imaging, ACA, and calibration.