Optical characterization of a 32-meter legacy telecommunications antenna in Mexico

David M. Gale; Stanley E. Kurtz

doi:10.1117/12.2630520

29 August 2022 Optical characterization of a 32-meter legacy telecommunications antenna in Mexico

David M. Gale, Stanley E. Kurtz

Proceedings Volume 12182, Ground-based and Airborne Telescopes IX; 1218228 (2022) https://doi.org/10.1117/12.2630520
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

This paper presents a study of the as-built design and present-day condition of the reflector optics for a 54-year old, out-of-service telecommunications antenna currently being reconditioned for teaching and research in radio astronomy. Reflector surface shape and relative position were mapped using photogrammetry and laser tracker measurements over a range of elevation angles. It was determined that the 32-meter primary reflector has maintained it's original RMS surface error specification of less than 1.4 mm, with the lowest RMS error of 1.09 mm recorded for the antenna at zenith. Similarly the subreflector and tertiary reflector are still within the manufacturer's specification, presenting measured RMS surface errors of 0.2 mm and 0.5 mm respectively. Measurements of subreflector position as a function of elevation angle show that the reflector is displaced vertically by 5 mm at 60°, and 10 mm at 5°, compared to the zenith position, while horizontal displacement remains below 4mm at all elevations. Subreflector defocus increases from zero at zenith to 0.7 mm negative at 45° before reversing direction and reaching 0.6 mm positive for an elevation of 5°. Photogrammetry results confirmed the use of shaped or modified parabolic and hyperbolic surfaces for the primary and subreflector. Principal elevation-independent Zernike terms obtained for the primary surface fit are primary and secondary spherical aberration, while for the subreflector the presence of significant spherical terms up to sixth order is noted. The results were made available to instrumentation groups working on receiver design for the conversion project.

Citation Download Citation

David M. Gale and Stanley E. Kurtz "Optical characterization of a 32-meter legacy telecommunications antenna in Mexico", Proc. SPIE 12182, Ground-based and Airborne Telescopes IX, 1218228 (29 August 2022); https://doi.org/10.1117/12.2630520

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