Beam pattern measurements and observational evaluations of the ALMA/ACA 12-m antenna

Abstract

We have evaluated the beam pattern of the ALMA/ACA 12-m antenna with total power observations of Jupiter and the Moon. Models of the expected beam pattern as it passes across Jupiter and the Moon were derived in consideration of the radiation pattern of the actual receiving system and the surface error of the main reflector. Since the profiles of the measured beam patterns were consistent with those of the models within the range from the peak to -20 dB, we confirmed that the antenna achieved the beam pattern expected from its optical design. After this confirmation, we performed astronomical observations. In addition to the detection of the CS J = 3-2 (146.969026GHz) spectrum toward Orion KL, the change in the Moon intensity was successfully detected during the total lunar eclipse during 2008 February 20-21. A time lag longer than lOmin in the millimeter-wave eclipse relative to the corresponding optical eclipse ephemeris was detected. Mapping observations of the Sun revealed the structure of the chromospheric networks at 147 GHz. These astronomical observations confirmed that the ACA 12-m antenna could be successfully operated under various operating conditions. © 2009. Astronomocal Society of Japan.