Gemini IRMOS: conceptual optical design of a multi-object adaptive optics-fed infrared integral-field spectrograph for the Gemini telescope

We discuss the optical design of an infrared multi-object integral-field spectrograph (IRMOS) that is designed to take advantage of the multi-object adaptive optics corrected field at the Gemini telescope. The IRMOS is designed for the Gemini Telescope, so we call this instrument GIRMOS. The GIRMOS has four identical Integral-Field Spectrographs (IFSes), which employ a unique slicer design to arrange the integral field along a slit to obtain two-dimensional spectroscopy. Each IFS can pick off the individual fields of view of 1.0x1.0”, 2.1x2.1”, 4.2x4.2” over a 2’ diameter fieldof- regard, at the spatial sampling scales of 25mas, 50mas, and 100mas, respectively. Spectral resolutions of R~3000 and 8000 are available in J, H, and K-bands from 1.0 to 2.4μm. The primary design constraints are associated with diffractive effects from the grating and spectrograph camera.