MOIS is a multi-object configurable slit spectrograph designed to be used with the 3.6 Devasthal Optical Telescope (DOT). It will cover the near-infrared wavelength band of 0.97 - 2.37 microns and have a spectroscopic field of view of 9.1′×3.1′ and an imaging field of view of 9.6′ diameter. MOIS is being designed as a precursor to a future multi-object spectrograph for the planned National Large Optical Telescope (NLOT) in India. MOIS is currently designed with a modular configurable slit unit of 5 slits created by 10 bars moving pair-wise in opposition. The slit unit can be upgraded independently to increase the multiplexing capability. The design has unique challenges of operating the configurable slits in cryo temperatures and developing the wide-field imager and spectrograph optical design for the input f/9 beam from the telescope. Many unique design optimizations have been used following several trade studies to allow better mechanical tolerances and flexibility in the design for position of coldstop and thermal performance. We will discuss the detailed design and modeling for MOIS that has been completed as part of the preliminary design.
With the imminent launch of the JWST, the field of thermal-infrared (TIR) astronomy will enjoy a revolution. It is easy to imagine that all areas of infrared (IR) astronomy will be greatly advanced, but perhaps impossible to conceive of the new vistas that will be opened. To allow both follow-up JWST observations and a continuance of work started on the ground-based 8m’s, we continue to plan the science cases and instrument design for a TIR imager and spectrometer for early operation on the TMT. We present the current status of our science cases and the instrumentation plans, harnessing expertise across the TMT partnership. This instrument will be proposed by the MICHI team as a second-generation instrument in any upcoming calls for proposals.
The Thirty Meter Telescope (TMT) is a proposed future generation telescope which will be located on either Maunakea, Hawaii or La Palma in the Canary islands. A thermal-infrared (TIR) imager and spectrometer (MICHI) combined with an adaptive optics system is being investigated as a possible second-generation instrument for this telescope. MICHI has been designed to also have a polarimetry capability in both imaging and low dispersion spectroscopic modes. Using polarization ray tracing in Zemax, we have estimated the instrumental polarization (IP) and crosstalk introduced at the focus of the near- and mid-infrared imaging system. In our calculations, we find that the IP varies from 1.0-0.54% and 0.54-0.42%, whereas the polarization crosstalk varies between 25-4% and 4-0.7%, in the near and TIR regions respectively at the instrument port of MICHI. These values of IP and crosstalk may cause problems during the high absolute accuracy polarization observations. Here we present the polarization effects for the imaging system of MICHI and it impacts on the polarization observations.
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