FIFI LS: The far-infrared integral field spectrometer for SOFIA

W. Raab, A. Poglitsch, L. W. Looney, R. Klein, N. Geis, R. Hoenle, W. Viehhauser, R. Genzel, M. Hamidouche, T. Henning, E. E. Haller

Research output: Contribution to journalConference articlepeer-review


FIFI LS is a far-infrared integral field spectrometer for the SOFIA airborne observatory. The instrument is designed to maximize the observing efficiency by simultaneous and nearly independent imaging of the field of view in two medium spectral resolution bands. Both spectral channels - covering a wavelength range of 42 to 110 microns and 110 to 210 microns respectively - allow diffraction limited spectral imaging. Reflective image slicers rearrange the 5×5 pixel field of view into the 1×25 pixel entrance slit of a grating spectrograph. Littrow mounted gratings with anamorphic collimators are used for spectral multiplexing with a spectral resolution between R = 1400 - 6500, depending on observing wavelength. Each spectral band employs two large format 25×16 pixel Ge:Ga detector arrays, axially stressed for the long wavelength band to achieve a longer wavelength response and slightly stressed for the short wavelength band. For each of the 25 spatial pixels, we are able to cover a velocity range of approximately 1500 km/s around a selected far-infrared line. This arrangement provides good spectral coverage with high responsivity. We present a summary of the FIFI LS design and the current status of instrument integration.

Original languageEnglish (US)
Pages (from-to)1074-1085
Number of pages12
JournalProceedings of SPIE - The International Society for Optical Engineering
Issue numberPART 2
StatePublished - 2004
EventGround-based Instrumentation for Astronomy - Glasgow, United Kingdom
Duration: Jun 21 2004Jun 25 2004


  • FIFI
  • Far-Infrared
  • Integral Field Imaging
  • Spectrometer

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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