A near-IR imager for the Gemini InfraRed Multi-Object Spectrograph (GIRMOS)

Jenny Atwood; Jeffrey Crane; Alan McConnachie; Vlad Reshetov; Jordan Lothrop; Masen Lamb

doi:10.1117/12.2627343

29 August 2022 A near-IR imager for the Gemini InfraRed Multi-Object Spectrograph (GIRMOS)

Jenny Atwood, Jeffrey Crane, Alan McConnachie, Vlad Reshetov, Jordan Lothrop, Masen Lamb

Proceedings Volume 12184, Ground-based and Airborne Instrumentation for Astronomy IX; 121840F (2022) https://doi.org/10.1117/12.2627343
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

The GIRMOS instrument is a multi-object spectrograph with four channels combined with an infrared imager housed within a common cryostat. This instrument will be fed by ground-layer adaptive optics (GLAO) or laser tomography AO (LTAO) corrected light from the Gemini North Adaptive Optics (GNAO) system. The combined instrument will provide unique scientific capabilities such as simultaneous imaging/spectroscopy modes (for precision spectrophotometry) and interleaved imaging-spectroscopy-imaging modes (for characterizing time-variable sources). The National Research Council Canada has recently completed the Preliminary Design of the Imager opto-mechanics. In this paper, we present the driving requirements, as derived from the science cases, and the optical and mechanical designs. The optical design maps a large fraction of the GIRMOS field-of-view onto a single engineering-grade 4Kx4K HAWAII 4RG detector with 21 mas pixels, provided by the Gemini Observatory. The imager produces diffraction-limited image quality across Y, J, H, and Ks-bands across an 85x85” field for an f/32 beam. It includes a location for a full filter complement, an accessible pupil for a cold stop to minimize thermal background, and a pupil imaging mode to align the cold stop to the telescope pupil. The lenses are mounted in cells with rolled flexures or athermalized centering pins and are preloaded to withstand 5g accelerations and provide thermal stability. The filters are housed in a double wheel assembly with cryogenic bearings and roller detents. All of the imager components are connected with a substructure that interfaces with the spectrograph optical bench. This substructure allows for easier testing and integration of the imager, independent from the spectrographs.

Conference Presentation

Citation Download Citation

Jenny Atwood, Jeffrey Crane, Alan McConnachie, Vlad Reshetov, Jordan Lothrop, and Masen Lamb "A near-IR imager for the Gemini InfraRed Multi-Object Spectrograph (GIRMOS)", Proc. SPIE 12184, Ground-based and Airborne Instrumentation for Astronomy IX, 121840F (29 August 2022); https://doi.org/10.1117/12.2627343

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