MICROCLINE: an innovative tiltmeter concept and its application to the ALMA-EU antennas' wind metrology

摘要

Large radio-telescopes requiring accurate 'blind' pointing accuracy are often equipped with dedicated metrology systems in order to correct for structural deformations. We present here a novel tiltmeter concept conceived specifically to compensate for the fast, wind-induced deformations occurring on such large structures. This instrument combines the typical accuracy and resolution of geodetic devices with an unique capability of recovering quickly from large saturations: this condition often occurs during fast slewing of the antenna. Moreover, the device features a reduced sensitivity to in-plane accelerations. All this allows its installation in favorable positions concerning the observability of the structural deformations to be detected and corrected, thus simplifying the processing from raw instrument data to the pointing correction to be applied. The instrument has been subjected to a thorough characterization and qualification process, by means of extensive tests both in the lab, using a dedicated testbench, and on the ALMA-EU antenna prototype. This activity allowed assessing other critical aspects for the final application, in particular easiness of installation, simplicity of mechanical and electrical interfaces, robustness, reliability and very limited maintenance requirements. The device will be installed on the ALMA-EU production antennas.