Alex Feller

Publications (2)0 Total impact

• Source

  Available from: Wolfgang Schmidt

  Article: The Sunrise Mission

  Peter Barthol, Achim Gandorfer, Sami K. Solanki, Manfred Schüssler, Bernd Chares, Werner Curdt, Werner Deutsch, Alex Feller, Dietmar Germerott, Bianca Grauf, [......], Alberto Álvarez-Herrero, Lola Sabau-Graziati, Christoph Widani, Peter Haberler, Klaus Härtel, Dirk Kampf, Thorsten Levin, Isabel Pérez Grande, Angel Sanz-Andrés, Elke Schmidt
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  ABSTRACT: The first science flight of the balloon-borne \Sunrise telescope took place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern Canada. We describe the scientific aims and mission concept of the project and give an overview and a description of the various hardware components: the 1-m main telescope with its postfocus science instruments (the UV filter imager SuFI and the imaging vector magnetograph IMaX) and support instruments (image stabilizing and light distribution system ISLiD and correlating wavefront sensor CWS), the optomechanical support structure and the instrument mounting concept, the gondola structure and the power, pointing, and telemetry systems, and the general electronics architecture. We also explain the optimization of the structural and thermal design of the complete payload. The preparations for the science flight are described, including AIV and ground calibration of the instruments. The course of events during the science flight is outlined, up to the recovery activities. Finally, the in-flight performance of the instrumentation is briefly summarized. Comment: 35 pages, 17 figures
  09/2010;
• Source

  Available from: Wolfgang Schmidt

  Article: Quiet-Sun intensity contrasts in the near ultraviolet

  Johann Hirzberger, Alex Feller, Tino L. Riethmüller, Manfred Schüssler, Juan M. Borrero, Nadine Afram, Yvonne C. Unruh, Svetlana V. Berdyugina, Achim Gandorfer, Sami K. Solanki, Peter Barthol, Jose A. Bonet, Valentin Martínez Pillet, Thomas Berkefeld, Michael Knölker, Wolfgang Schmidt, Alan M. Title
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  ABSTRACT: We present high-resolution images of the Sun in the near ultraviolet spectral range between 214 nm and 397 nm as obtained from the first science flight of the 1-m Sunrise balloon-borne solar telescope. The quiet-Sun rms intensity contrasts found in this wavelength range are among the highest values ever obtained for quiet-Sun solar surface structures - up to 32.8% at a wavelength of 214 nm. We compare with theoretical intensity contrasts obtained from numerical magneto-hydrodynamic simulations. For 388 nm and 312 nm the observations agree well with the numerical simulations whereas at shorter wavelengths discrepancies between observed and simulated contrasts remain. Comment: 6 pages, 4 figures, accepted by ApJL
  09/2010;