Update on the Preliminary Design of SCALES: the Santa Cruz Array of Lenslets for Exoplanet Spectroscopy

TL;DR

SCALES is a cryogenic, high-contrast integral-field spectrograph designed for exoplanet and brown dwarf atmospheric characterization in the 2-5 micron range at Keck Observatory, featuring unique medium spectral resolution capabilities.

Contribution

This paper updates the design of SCALES, a novel IFS instrument with medium spectral resolution at the diffraction limit, enabling new exoplanet atmospheric studies.

Findings

Design improvements for SCALES instrument.

Capability to characterize cold exoplanets and brown dwarfs.

Integration of medium spectral resolution mode.

Abstract

SCALES (Santa Cruz Array of Lenslets for Exoplanet Spectroscopy) is a 2-5 micron high-contrast lenslet integral-field spectrograph (IFS) driven by exoplanet characterization science requirements and will operate at W. M. Keck Observatory. Its fully cryogenic optical train uses a custom silicon lenslet array, selectable coronagraphs, and dispersive prisms to carry out integral field spectroscopy over a 2.2 arcsec field of view at Keck with low ($<300$) spectral resolution. A small, dedicated section of the lenslet array feeds an image slicer module that allows for medium spectral resolution ($5000-10 000$), which has not been available at the diffraction limit with a coronagraphic instrument before. Unlike previous IFS exoplanet instruments, SCALES is capable of characterizing cold exoplanet and brown dwarf atmospheres ($<600$ K) at bandpasses where these bodies emit most of their radiation while capturing relevant molecular spectral features.