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  • 1
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    Univ. Stuttgart
    Publication Date: 2021-03-29
    Description: In this work the dune model introduced by Sauermann et al. (2001) is extended and applied to investigate the formation of different dune shapes on Mars and on Earth as function of wind directionality and sand availability. The formation of sand dunes on Mars under the present atmospheric conditions of the red planet is studied and conclusions about wind speed, migration velocity of dunes and changing wind regimes on Mars are presented. Field measurements of the shape of coastal transverse dunes are presented and the formation of coastal dune fields is explained. Finally, the formation of linear dunes by bimodal wind regimes is calculated. The simulations explain the appearance of exotic bimodal dune shapes in areas of low sand availability on Mars and on Earth.
    Description: thesis
    Keywords: 523 ; 551 ; 550 ; TGG 545 ; VAN 100 ; Marsoberfläche {Astronomie} ; Abspülung {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 171 S.
    Format: application/pdf
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  • 2
    Publication Date: 2021-03-29
    Description: The aim of this thesis is to present an alternative for the solution of a fundamental problem of geodesy. This problem, the so-called classical geodetic boundary value problem, comprises the determination of the figure of the Earth as well as the recovery of the Earths̉ gravity field in the exterior of the terrestrial masses. Already in 1849, G.G. Stokes addressed the problem of finding the Earths̉ gravity potential together with the physical shape of the Earth, i.e. the geoid. Later on in 1962, M.S. Molodensky proposed his famous theory for the direct gravimetric determination of the Earths̉ topographical surface along with the external gravity potential. Both approaches solve the initially nonlinear free boundary value problem, which implies considerable mathematical difficulties in the investigation of its existence and uniqueness properties, by means of a twofold linearization strategy. For this purpose, adequate approximations for the solution of the physical problem component, i.e. the determination of the gravity field, and for the geometrical part, i.e. the determination of the shape of the Earths̉ body, must be assumed. In detail, a normal potential to approximate the true potential as well as a reference surface for the geoid or the topography is required ...
    Description: thesis
    Keywords: 526.7 ; 550
    Language: English
    Type: monograph , publishedVersion
    Format: 149 S.
    Format: application/pdf
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  • 3
    Publication Date: 2021-03-29
    Description: SOFIA, the Stratospheric Observatory for Infrared Astronomy, is an airborne observatory that will study the universe in the infrared spectrum. A Boeing 747-SP aircraft will carry a 2.5 m telescope designed to make sensitive infrared measurements of a wide range of astronomical objects. It will fly at and above 12 km, where the telescope collects radiation in the waveƠlength range from 0.3 micrometers to 1.6 millimeters of the electromagnetic spectrum. During flight, a door will be opened to allow clear optical observations from the cavity environment where the telescope is mounted. The telescope pointing control is achieved during science observations by an array of sensors including three imagers, gyroscopes and accelerometers. In addition, throughout alignment and calibration of the telescope assembly, the High-speed Imaging Photometer for Occultation (HIPO) is used as a reference instrument. A theoretical concept has been developed to compensate the perturbations in the airborne environment and to correct them within the attitude control loop. A set of Cartesian reference frames is established to describe and manipulate the orientations of the various subsystems, sensor and pointing orientations.
    Description: thesis
    Keywords: 522.2 ; 550 ; TCE 230 ; TC 000 ; Weltraumbasierte UV-, Optische und Infrarotteleskope {Astronomische Instrumente} ; Astronomische Beobachtungstechnik und Instrumente ; Sauter, Martin ; Infrarotteleskop ; Ausrichtung ; Kalibrieren 〈Messtechnik〉 ; Gyroskop ; SOFIA 〈Astronomie〉 ; Lageregelung ; Online-Publikation
    Language: English
    Type: monograph , draft
    Format: 181 S., 3,93 MB
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