TA-MOONS is a multi-object Optical to Near Infrared (NIR) spectrometer with the primary science cases to conduct a spectroscopic survey of Young Stellar Objects (YSO’s) at visible as well as at NIR wavebands simultaneously at a spectroscopic resolution of R~2700. The wavelength coverage of this instrument is from 0.36-2.50 microns. The instrument is jointly developed by TIFR and ARIES, designed for 3.6 meter Devasthal Optical Telescope (DOT)1 as a second generation main port instrument. The instrument is capable of observing 8-sources simultaneously within the sky field of view (FoV) of 12 arcmin diameter with its front optics deployable slit (DS) technique. These are mirror based 8-pickup arms located around the telescope focal plane. The DS is a novel concept consisting of tiny mirror-based arms having translation and rotational motion to pick up the source within each arm’s patrol field. This manuscript presents the optical design of front optics and probe viewer/calibration optics. Conceptual idea of the two-arm spectrometer also presented.
TIFR and ARIES are jointly developing a Multi-Object Optical to Near Infrared Spectrometer for conducting world’s largest spectroscopic survey of Young Stellar Objects (YSO’s) at Visible and Near Infrared (NIR) wavelength bands simultaneously. This will be installed at the 3.6-meter Devasthal Optical Telescope (DOT), at Nainital. The targeted resolution is R~2700. The capability of this instrument is to observe 8-sources simultaneously within the sky field of view (FoV) of 12 arc-min diameter; currently, no other instruments in the world have this capability. This design, what we call deployable slit concept, uses a mirror based pick-up arm system to feed the light from sources at the focal plane to the spectrometer. The 8-arms located around the focal plane brings the light from 8-sources within sky FoV of 12 arcmin diameter to form a compact staggered 1-dimensional slit that forms input to the two arm standard spectrometers. In this manuscript, we present our mechanical design of the prototype of a pickup arm.
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.
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