IRMS Technical Detail

The IRMS is a near diffraction-limited multi-slit near-infrared spectrometer and imager. As one of the first-light instruments on the TMT, it is modeled closely after the MOSFIRE instrument on the Keck Telescope and will be fed by the Narrow-Field Infrared Adaptive Optics System (NFIRAOS). See schematic of the instrument in the following figure.





IRMS will provide near-infrared imaging and multi-object spectroscopy at Y (0.97–1.12 micron), J (1.15–1.35 micron), H (1.46–1.81 micron), and K (1.93–2.45 micron) bands. Operating with NFIRAOS on the TMT, it can be used as a diffraction-limited imager and multi-slit spectrograph with moderate resolution. It has a circular field-of-view (FoV) of 2.27 arcmin in imaging mode, and elliptical FoV of 2.0'x0.6' in spectroscopy mode. The spatial scale is 0.06" per pixel, or 0.08" per pixel in the dispersion direction. The spectral resolution R is 3270 for 3 pixel or 0.24" wide slit, or R = 4660 for 2 pixel or 0.16" wide slit. IRMS has a multiplex capability of up to 46 slits using a slit mask system on a cryogenic configurable slit unit. Each slit width can be adjusted arbitrarily, with minimum slit width of 0.16". The IRMS detector will be 2048x2048 Teledyne Technologies Hawaii-2RG with a long wavelength cut-off at 2.5 micron.