SCALES Status Report

Abstract

SCALES (Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy) is the next-generation, diffraction-limited, thermal infrared, fully cryogenic, coronagraphic exoplanet spectrograph and imager for W.M. Keck Observatory. SCALES is fed by the Keck II Adaptive Optics bench. Both modes use common fore-optics to simplify the optical design and have individual detectors, which are JWST flight spares. The imager mode operates from 1 to 5 microns with selectable narrow- and broadband filters over a field of view 12.3 arcseconds on a side, and the integral field spectrograph mode operates from 2 to 5 microns with both low and mid spectral resolutions (R∼ 100 to R∼ 7500) over a field of view 2.15 arcseconds on a side. The diamond-turned aluminum optics, most of which are already delivered, with the rest being fabricated, provide low distortion, low wavefront error, and high throughput for all modes. The slicing unit, located behind the lenslet array, allows SCALES to reach heretofore unheard-of spatially-resolved spectral resolution for exoplanet and disc observations from the ground with a coronagraphic integral field spectrograph. The SCALES consortium includes UC Observatories, CalTech, W.M. Keck Observatory, the Indian Institute of Astrophysics, and the University of Durham, with over 40 science team members. We report on the overall design and project status during its ongoing fabrication phase, which started in early 2023.