Optical layout of FIRE, showing 1:1 pre-slit Offner relay, reflecting collimator, cross-dispersing prism array,
reflective diffraction grating, and four-element camera. (R. Bernstein)
The figure below shows the footprint of an observed object on FIRE's detector. In this figure, the prisms have dispersed light in the vertical direction, and the diffraction grating has dispersed the light at high resolution in the horizontal direction. The prisms have the effect of sorting the different spectral orders from the diffraction grating, in order of central wavelength down the detector.
Each exposure in echellette mode covers the full z-K bands in a single setup — a unique attribute among spectrographs with comparable resolution.
Simulated spectral format for FIRE, showing coverage from l ~ 0.85-2.51 microns per exposure.
Bounding square shows the footprint of the 2K x 2K HAWAII-2RG detector.
Slit length is 7 arcseconds. Only 1 free spectral range is shown for each order;
on an actual spectrum more light will be recovered at the order boundaries