Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope's Main Reflector in a Bundle Adjustment

Christoph Holst; David Schunck; Axel Nothnagel; Rüdiger Haas; Lars Wennerbäck; Henrik Olofsson; Roger Hammargren; Heiner Kuhlmann

doi:10.3390/s17081833

Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope's Main Reflector in a Bundle Adjustment

Sensors (Basel). 2017 Aug 9;17(8):1833. doi: 10.3390/s17081833.

Authors

Christoph Holst¹, David Schunck², Axel Nothnagel³, Rüdiger Haas⁴, Lars Wennerbäck⁵, Henrik Olofsson⁶, Roger Hammargren⁷, Heiner Kuhlmann⁸

Affiliations

¹ Institute of Geodesy and Geoinformation, University of Bonn, Bonn D-53115, Germany. c.holst@igg.uni-bonn.de.
² Institute of Geodesy and Geoinformation, University of Bonn, Bonn D-53115, Germany. s7daschu@uni-bonn.de.
³ Institute of Geodesy and Geoinformation, University of Bonn, Bonn D-53115, Germany. nothnagel@uni-bonn.de.
⁴ Onsala Space Observatory, Chalmers University of Technology, Onsala SE-43992, Sweden. rudiger.haas@chalmers.se.
⁵ Onsala Space Observatory, Chalmers University of Technology, Onsala SE-43992, Sweden. lars.wennerback@chalmers.se.
⁶ Onsala Space Observatory, Chalmers University of Technology, Onsala SE-43992, Sweden. henrik.olofsson@chalmers.se.
⁷ Onsala Space Observatory, Chalmers University of Technology, Onsala SE-43992, Sweden. roger.hammargren@chalmers.se.
⁸ Institute of Geodesy and Geoinformation, University of Bonn, Bonn D-53115, Germany. heiner.kuhlmann@uni-bonn.de.

Abstract

For accurate astronomic and geodetic observations based on radio telescopes, the elevation-dependent deformation of the radio telescopes' main reflectors should be known. Terrestrial laser scanning has been used for determining the corresponding changes of focal lengths and areal reflector deformations at several occasions before. New in this publication is the situation in which we minimize systematic measurement errors by an improved measurement and data-processing concept: Sampling the main reflector in both faces of the laser scanner and calibrating the laser scanner in situ in a bundle adjustment. This concept is applied to the Onsala Space Observatory 20-m radio telescope: The focal length of the main reflector decreases by 9.6 mm from 85 ∘ to 5 ∘ elevation angle. Further local deformations of the main reflector are not detected.

Keywords: bundle adjustment; calibration; deformation analysis; parameter estimation; radio telescope; terrestrial laser scanning; very long baseline interferometry.