Status update of LLAMAS: a wide field-of-view visible passband IFU for the 6.5m Magellan telescopes

Gabor Furesz; Robert A. Simcoe; Mark Egan; Andrew Malonis; Rebecca Masterson; Joshua Brown; Gregory Cappiello; Christian Chesbrough; Kristin Clark; David Coppeta; Danielle Frostig; Michelle Gabutti; Samuel Halverson; Erik Hinrichsen; Sabrina Kahn; Madeline M. Lambert; Nathan Lourie; John Piotrowski; Christopher Semisch

doi:10.1117/12.2562803

13 December 2020 Status update of LLAMAS: a wide field-of-view visible passband IFU for the 6.5m Magellan telescopes

Gabor Furesz, Robert A. Simcoe, Mark Egan, Andrew Malonis, Rebecca Masterson, Joshua Brown, Gregory Cappiello, Christian Chesbrough, Kristin Clark, David Coppeta, Danielle Frostig, Michelle Gabutti, Samuel Halverson, Erik Hinrichsen, Sabrina Kahn, Madeline M. Lambert, Nathan Lourie, John Piotrowski, Christopher Semisch

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Proceedings Volume 11447, Ground-based and Airborne Instrumentation for Astronomy VIII; 114470A (2020) https://doi.org/10.1117/12.2562803
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Abstract

The Large Lenslet Array Magellan Spectrograph (LLAMAS) is an NSF-funded facility-class Integral Field Unit (IFU) spectrograph under construction for the 6.5-meter Magellan Telescopes. It covers a 37" x 37" solid angle with 2,400 optical fibers efficiently coupled by a double-sided microlens-array, producing R = 2, 000 spectra with 0.7511 spatial resolution. Its broad passband from λ = 350 970nm offers access to line and continuum measurements over a wide range in redshift. Light is multiplexed by the IFU into 8 compact, carbon-fiber bench mounted spectrographs utilizing VPH grisms. We employed several trades on cost-performance ratio while optimizing LLAMAS’ system design including: (a) Splitting the passband between 3 fast all-refractive camera systems with modest entrance pupils, (b) limiting the fibers per unit (i.e. slit length) and building more spectrographs to leverage on production volume, and (c) using a commercial CCD camera built around a common detector (e2v 42-40) and thermoelectric + liquid cooling. To boost blue throughput and achieve high-quality sky subtraction the spectrograph cluster is mounted next to the focal plane on a folded Cassegrain port with gravity-invariant support. This also allows the instrument to deploy quickly, and be fully accessible within 10 minutes on any night, serving as a facility unit for observing astrophysical transients. A sub-sized IFU (169 fibers), mounted in a full-sized front end package with a single spectrograph (2 cameras) was delivered to Magellan in March 2020. We present as-measured laboratory performance from this prototype, though on-sky commissioning was unfortunately cancelled because of the COVID-19 pandemic. This contribution therefore focuses on subsequent design evolution and status of the full facility instrument.

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Gabor Furesz, Robert A. Simcoe, Mark Egan, Andrew Malonis, Rebecca Masterson, Joshua Brown, Gregory Cappiello, Christian Chesbrough, Kristin Clark, David Coppeta, Danielle Frostig, Michelle Gabutti, Samuel Halverson, Erik Hinrichsen, Sabrina Kahn, Madeline M. Lambert, Nathan Lourie, John Piotrowski, and Christopher Semisch "Status update of LLAMAS: a wide field-of-view visible passband IFU for the 6.5m Magellan telescopes", Proc. SPIE 11447, Ground-based and Airborne Instrumentation for Astronomy VIII, 114470A (13 December 2020); https://doi.org/10.1117/12.2562803

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KEYWORDS

Spectrographs

Telescopes

Visible radiation

Optical fibers

Cameras

Imaging systems

Microlens array

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