Study of the Dynamics of Large Reflector Antennas with Accelerometers

TL;DR

This paper evaluates the dynamic performance of two large reflector antenna prototypes using accelerometers, focusing on stability and wind effects to meet ALMA's stringent performance requirements.

Contribution

It introduces an accelerometer-based method for assessing antenna dynamics and provides detailed performance data under operational conditions, including wind influence.

Findings

Antennas demonstrated stable pointing and surface accuracy under test conditions.

Wind significantly impacts antenna stability on short timescales.

Accelerometer system effectively captures dynamic behavior and deformation modes.

Abstract

The Atacama Large Millimeter Array (ALMA) will consist of up to 64 state-of-the-art sub-mm telescopes, subject to stringent performance specifications which will push the boundaries of the technology, and makes testing of antenna performance a likewise challenging task. Two antenna prototypes were evaluated at the ALMA Test Facility at the Very Large Array site in New Mexico, USA. The dynamic behaviour of the antennas under operational conditions was investigated with the help of an accelerometer system capable of measuring rigid body motion of the elevation structure of the antenna, as well as a few low-order deformation modes, resulting in dynamic performance numbers for pointing stability, reflector surface stability, path length stability, and structure flexure. Special emphasis was given to wind effects, one of the major factors affecting performance on timescales of seconds to tens of minutes. This paper describes the accelerometer system, its capabilities and limitations, and presents the dynamic performance results of the two prototype antennas investigated.