Characteristics and Performance of the North American ALMA Prototype Antenna

The submillimeter antennas of the Atacama Large Millimeter Array (ALMA) have specifications that are beyond the current state of the art in accurate reflector antenna technology. Considering that as many as 64 of these antennas would eventually be needed, the ALMA partners AUI/NRAO and ESO each agreed to acquire a prototype antenna, and subject these to an extensive evaluation program. In this paper we summarize the performance of the ALMA North American prototype antenna. 1. Design Characteristics The ALMA antennas are alt-azimuth mounted Cassegrain dual-reflector systems of 12m diameter with a reflector surface and pointing accuracy suitable for observations in the 0.3 mm submillimeter band. On 2003/10/01 VertexRSI delivered the North American prototype antenna to AUI/NRAO. The VertexRSI prototype antenna (Figure 1) includes a number of innovative design features to ensure its performance to the ALMA specifications: 1