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Astron. Astrophys. Suppl. Ser. 134, 561-567

The ORFEUSII Echelle Spectrometer:
Instrument description, performance and data reduction

J.Barnstedt1 - N.Kappelmann1 - I.Appenzeller2 - A.Fromm1 - M.Gölz1 - M.Grewing1,3 - W.Gringel1 - C.Haas1 - W.Hopfensitz1 - G.Krämer1 - J.Krautter2 - A.Lindenberger1 - H.Mandel2 - H.Widmann1

Send offprint request: J. Barnstedt

1 - Institut für Astronomie und Astrophysik, Abt. Astronomie, Eberhard-Karls-Universität Tübingen, Waldhäuserstr. 64,
D-72076 Tübingen, Germany
2 - Landessternwarte Heidelberg, Königstuhl, D-69117 Heidelberg, Germany
3 - Institut de Radio Astronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint Martin d'Hères, France

Received May 20; accepted September 15, 1998


During the second flight of the ORFEUS-SPAS mission in November/December 1996, the Echelle spectrometer was used extensively by the Principal and Guest Investigator teams as one of the two focal plane instruments of the ORFEUS telescope. We present the in-flight performance and the principles of the data reduction for this instrument. The wavelength range is 90nm to 140nm, the spectral resolution is significantly better than $\lambda$/$\Delta$$\lambda$=10000, where $\Delta$$\lambda$ is measured as FWHM of the instrumental profile. The effective area peaks at 1.3cm2 near 110nm. The background is dominated by straylight from the Echelle grating and is about 15% in an extracted spectrum for spectra with a rather flat continuum. The internal accuracy of the wavelength calibration is better than $\pm$0.005nm.

Key words: instrumentation: spectrographs -- space vehicles -- stars: individual: HD93521 -- ultraviolet: general

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