The Long-High module is a cross-dispersed echelle spectrograph which covered, in a single pointing, the nominal spectral range from 18.7-37.2 micron at R ≈ 600. It has a small wavelength overlap (18.7-19.6 micron) with the Short-High module. The detector is a 128×128 pixel2 Si:As BIB array with a plate scale of 4.5 arcsec/pixel. As with the SH module, the LH aperture is a single slit. Its length was limited so that nearly an octave of a cross-dispersed echelle spectrum could fit onto the detector array without spatial overlap of orders. Figure 2.7 depicts the LH components and optical paths.
Figure 2.7: Long-High module optical components and paths.