Development and future use of the echelon-cross-echelle spectrograph on SOFIA

The Echelon-cross-Echelle Spectrograph (EXES) will provide the Stratospheric Observatory for Infrared Astronomy (SOFIA) with high spectral resolution capabilities in the mid-infrared. EXES will have a maximum spectral resolving power of 100,000 along with lower resolution options (R=10,000; R=3000). EXES on SOFIA will provide sensitivity and spectral resolution never before available from an orbital or sub-orbital platform. Because of the wealth of molecular features in the EXES spectral range, 4.5 to 28.3 μm, and the dramatic reduction in telluric atmospheric interfence provided by SOFIA, EXES will be particularly relevant for studies of the solar system, star formation and the interstellar medium. We report on the EXES design and current status, provide descriptions of observing modes and sensitivity estimates, discuss the calibration and likely data products, and describe the potential gains of incorporating a 1024 × 1024, low-background, Si:As detector array.