Modular plug-in extension enabling cross-dispersed spectroscopy for Large Binocular Telescope

Hyukmo Kang, David Thompson, Al Conrad, Conrad Vogel, Ariel Lamdan, Dae Wook Kim

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


The LUCI (LBT Utility Camera in the Infrared) instruments are a pair of near infrared (NIR) imagers and spectrographs for the Large Binocular Telescope (LBT) that include a set of cryogenic exchangeable focal plane masks. Although LUCI covers the NIR zJHK bands at different resolutions with existing gratings, it is not currently possible to get zJHK in a single exposure with a single LUCI which is required for some planetary science programs. To produce a simultaneous zJHK spectrum with a single LUCI, we designed a system consisting of small and simple optical elements to fit within the limited space in the focal plane mask frame to cross-disperse fixed short slits. This system, called MOBIUS (Mask-Oriented Breadboard Implementation for Unscrambling Spectra), consists of a double-folding mirror, a collimating spherical mirror with 180 mm radius of curvature, and a dispersing prism with the rear surface mirror-coated. MOBIUS disperses the input slit perpendicular to the dispersion direction of the gratings in LUCI. The resulting order separation is at least ∼2.7 arcsecond, allowing a slit length of up to ∼2.3 arcsec without mixing orders at the LUCI image plane. Since MOBIUS would be introduced into the existing light path via the exchangeable slit mask mechanism, no modification to the current LUCI instrument is needed. Eventually, binocular observations combining one of the Multi-Object Double Spectrographs (MODS) with LUCI+MOBIUS at the LBT will provide simultaneous coverage from 0.3 to 2.4 μm for studies of asteroids and other faint solar system bodies.

Original languageEnglish (US)
Title of host publicationAstronomical Optics
Subtitle of host publicationDesign, Manufacture, and Test of Space and Ground Systems II
EditorsTony B. Hull, Dae Wook Kim, Pascal Hallibert
ISBN (Electronic)9781510629257
StatePublished - 2019
EventAstronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II 2019 - San Diego, United States
Duration: Aug 12 2019Aug 15 2019

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceAstronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II 2019
Country/TerritoryUnited States
CitySan Diego


  • Cross dispersion
  • Instrument Design
  • LBT
  • LUCI
  • Spectrograph

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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