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ORFEUS-SPAS, Berkeley Extreme and Far-UV

NSSDCA ID: 1996-065B-02

Mission Name: ORFEUS-SPAS II
Principal Investigator:Dr. Mark V. Hurwitz


The Berkeley Extreme and Far-UV Spectrometer (BEFS) was also known as the Extreme Ultraviolet (EUV) Spectrometer. BEFS operated from 39 - 120 nm, however most observations were conducted in the 90 - 120 nm range. The instrument was designed to provide high-resolution (lambda/5000) spectroscopy of point sources.

Light coming into the ORFEUS 1-m telescope fell onto BEFS when a movable collimator mirror is moved out of the beam. When the mirror was in the beam, light was directed to the Tubingen Ultraviolet Echelle Spectrometer (TUES). Four diffraction gratings dispersed a unique sub-bandpass across one of two spectral detectors near the focal plane of the spectrometer. To maximize resolution and minimize astigmatism, spherical optics with mechanically ruled varied line-spacing in a non-Rowland mounting was used. The BEFS instrument was altered from the first flight (on ORFEUS-SPAS I) by over-coating two of the four diffraction gratings with silicon carbide and modifying the detector electronics to improve the imaging at high count rates.

BEFS, on ORFEUS-SPAS II, obtained Far-UV spectra of about 105 objects. The first flight on ORFEUS-SPAS I resulted in spectra of about 75 objects. EUV spectra were obtained for a subset of targets.

Alternate Names

  • ORFEUS-SPASII/ORFEUS-SPAS,BerkeleyExtremeandFar-UV

Funding Agency

  • NASA-Office of Space Science (United States)


  • Astronomy: Ultraviolet

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Dr. Mark V. HurwitzPrincipal InvestigatorUniversity of California,
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