06 Fakultät Luft- und Raumfahrttechnik und Geodäsie

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Institute: search.filters.UBSInstitut.Institut für RaumfahrtsystemePublication Type: search.filters.UBSTyp.Studienarbeit

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    Operational modal analysis and its application for SOFIA telescope assembly vibration measurements
    (2009) Greiner, Benjamin
    The Stratospheric Observatory For Infrared Astronomy, SOFIA, is an airborne observatory that will serve the scientific community to study the universe in the infrared spectrum. SOFIA consists of a Boeing 747SP aircraft equipped with a 2.5 m telescope in the rear part of the fuselage. During operational flight, a door will be opened to allow a clear view into the sky. One particular challenge of such an observatory in an airborne environment is to provide a highly stable image in the focal plane, where the science instrument picks up the light from the telescope. Image jitter at the focal plane is caused by external disturbance loads, e.g. aircraft inertial loads and aerodynamic loads, which cause rigid as well as flexible body motion of the telescope. Flexible body motions play an important role in the pointing optimization effort. Therefore, a good understanding of the dynamic characteristics of the telescope structure needs to be generated. This study thesis discusses the methods of Operational Modal Analysis (OMA) in order to obtain such an understanding and shows how they can be applied to the SOFIA observatory development and improvement process with respect to pointing stabilization and image quality. Operational Modal Analysis acquires information about the dynamic characteristics of a structure in terms of eigenfrequencies, damping and mode shapes, without the need for explicit measurement of the vibration inducing loads. Since the exact influence of aerodynamic disturbance loads during operational flight conditions is not measurable, the OMA approach is a promising contribution the SOFIA optimization effort.