FIFI LS: A far-infrared 3D spectral imager for SOFIA

L. W. Looney, W. Raab, A. Poglitsch, N. Geis, D. Rosenthal, R. Hönle, R. Klein, F. Fumi, R. Genzel, T. Henning

Research output: Contribution to journalConference articlepeer-review


FIFI LS is a far-infrared integral field spectrometer for SOFIA that maximizes observing efficiency by spectrally imaging fields in two medium velocity resolution bands simultaneously and nearly independently. Although the two observing bands, Red (110-210 microns) and Blue (42-110 microns), share some common fore-optics, the Field-Imaging Far-Infrared Line Spectrometer (FIFI LS) can observe diffraction-limited spectra at R = 1400 to 6500, depending on wavelength, with two separate Littrow mounted spectrometers. To further increase the observing efficiency, we employ an integral field technique that allows multiplexing spatially. This is achieved by utilizing slicer mirrors to optically re-arrange the 2D field into a single slit for a standard long slit spectrometer. Effectively, a 5 × 5 pixel spatial field of view is imaged to a 25 × 1 pixel slit and dispersed to a 25 × 16 pixel, 2D detector array. The detectors are two large format Ge:Ga arrays, axially stressed in the Red channel to achieve a longer wavelength response and slightly stressed in the Blue channel. Overall, for each of the 25 spatial pixels in each band, the instrument can cover a velocity range of approximately 1500 km/s with an estimated sensitivity of 2 × 10-15 W Hz1/2 per pixel. This arrangement provides good spectral coverage with high responsivity. With this scheme FIFI LS with have advantages over single-slit spectrometers in detailed morphological studies of the heating and cooling of galaxies, star formation, the ISM under low-metalicity conditions as found in dwarf galaxies, active galactic nuclei and their environment, starbursts, and merging/interacting galaxies.

Original languageEnglish (US)
Pages (from-to)47-55
Number of pages9
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Dec 1 2002
Externally publishedYes
EventAirborne Telescope Systems II - Waikoloa, HI, United States
Duration: Aug 27 2002Aug 28 2002


  • FIFI
  • FIR
  • Far-infrared
  • Grating
  • Integral field imaging
  • Optical slicer
  • 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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