  This paper presents a conceptual design for a spectrometer designed
specifically for characterizing transiting exoplanets with space-borne infrared
telescopes. The design adopting cross-dispersion is intended to be simple,
compact, highly stable, and has capability of simultaneous coverage over a wide
wavelength region with high throughput. Typical wavelength coverage and
spectral resolving power is 1-13 micron with a spectral resolving power of ~ a
few hundred, respectively. The baseline design consists of two detectors, two
prisms with a dichroic coating and microstructured grating surfaces, and three
mirrors. Moving parts are not adopted. The effect of defocusing is evaluated
for the case of a simple shift of the detector, and anisotropic defocusing to
maintain the spectral resolving power. Variations in the design and its
application to planned missions are also discussed.
