The Mid-Infrared Instrument for the James Webb Space Telescope: IV. The Low Resolution Spectrometer

TL;DR

The paper details the design, testing, and performance of the Low Resolution Spectrometer (LRS) on the MIRI instrument for JWST, optimized for compact sources and exoplanet transit spectroscopy.

Contribution

It provides a comprehensive overview of the LRS design, test results, and operational modes, highlighting its suitability for exoplanet atmosphere studies.

Findings

LRS achieves R~100 spectral resolution from 5 to 12 microns.

Performance tests show consistent image quality and spectrophotometric accuracy.

Slitless mode is effective for exoplanet transit spectroscopy.

Abstract

The Low Resolution Spectrometer of the MIRI, which forms part of the imager module, will provide R~100 long-slit and slitless spectroscopy from 5 to 12 micron. The design is optimised for observations of compact sources, such as exoplanet host stars. We provide here an overview of the design of the LRS, and its performance as measured during extensive test campaigns, examining in particular the delivered image quality, dispersion, and resolving power, as well as spectrophotometric performance, flatfield accuracy and the effects of fringing. We describe the operational concept of the slitless mode, which is optimally suited to transit spectroscopy of exoplanet atmospheres. The LRS mode of the MIRI was found to perform consistently with its requirements and goals.