ISBN 9783843928946

978-3-8439-2894-6, Reihe Raumfahrt

Enrico Pfüller
Fast EMCCD Cameras for the Optical Characterization of the SOFIA Observatory and its Telescope Subsystems

201 Seiten, Dissertation Universität Stuttgart (2016), Softcover, A5

Zusammenfassung / Abstract

SOFIA is an airborne observatory which consists of a 2.5 meter telescope that is built into a Boeing 747SP aircraft. The objective of SOFIA is astrophysical observations in the infrared and far-infrared wavelength spectrum at flight altitudes up to 13.7 kilometers.

One of the main performance requirements for the SOFIA telescope is the high-frequency image jitter of 0.4 arcseconds RMS or less. The challenge for airborne observatories to achieve this image quality requirement comes with the disturbances that the telescope is subjected to in flight. Vibrations and wind loads directly affect the stability of the optical assembly.

In-flight measurements of the actual pointing are invaluable to analyze the initial telescope behavior. A dedicated stand-alone high frame rate camera system was proposed to analyze the telescope performance with high time resolution. It was the objective of this thesis to characterize a suitable camera and to design and build up a flightworthy diagnostic system that can be used during SOFIA flights.

This document describes the Fast Diagnostic Camera system, its main components, design requirements, integration in the observatory and software for operation. The characterization of the high frequency image jitter is the main application for this camera system, but performance measurements of other telescope subsystems, e.g. the secondary chopping mirror, are carried out frequently and the influence of the cavity shear layer on the image quality has been analyzed as well. A motivation for scientific observations with the FDC is given along with some examples of observing campaigns where this instrument has supplied image data and contributed to the success of the observation.

The contributions to science observations paved the way for the development of this camera to a facility science instrument. With this designation, it is possible to offer the visual wavelength observation capability of SOFIA to the astronomical community and perform astronomical measurements with this instrument in parallel to the infrared science instruments at the main flange.