FIFILS, a Field-Imaging Far-Infrared Line-Spectrometer for SOFIA

We present FIFI LS, an instrument that will provide a unique tool for astronomical 3D spectral imaging of line emission in the far-infrared. Observing in the far-infrared, which is largely unaffected by dust extinction and contains a large number of important emission lines, will allow FIFI LS to make significant contributions to a number of astrophysical problems. It will utilize the high angular resolution and sensitivity of SOFIA (the Stratospheric Observatory for Infrared Astronomy) to adress many key questions in modern astronomy like the relation between AGN' s and starburst galaxies or the powering mechanisms of ULIRGs. As a state-of-the-art astronomical instrument, FIFI LS will enable simultaneous 3D observation in two separate bands (42-110 and 110-210 μm). The instrument will allow diffraction-limited spectral imaging at R=1400 to 6500, depending on wavelength, with two separate Littrow mounted grating-spectrometers. To achieve spatial information effectively a 5 × 5 pixel spatial field of view is rearranged to a 25 × 1 pixel slit. This slitimage is 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.