The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope I. Overview of the instrument and its capabilities

TL;DR

NIRSpec on the James Webb Space Telescope is a versatile near-infrared spectrograph capable of low and high-resolution spectroscopy in various modes, enabling detailed astronomical observations from 0.6 to 5.3 micrometers.

Contribution

This paper provides a comprehensive overview of NIRSpec's design, capabilities, and performance, highlighting its innovative multi-mode operation and field coverage.

Findings

NIRSpec can perform spectroscopy from 0.6 to 5.3 micrometers.

It offers multiple modes including single-object, multi-object, and integral field spectroscopy.

The instrument's sensitivity and detector performance under space conditions are characterized.

Abstract

We provide an overview of the design and capabilities of the near-infrared spectrograph (NIRSpec) onboard the James Webb Space Telescope. NIRSpec is designed to be capable of carrying out low-resolution ($R\!=30\!-330$) prism spectroscopy over the wavelength range $0.6-5.3\!~\mu$m and higher resolution ($R\!=500\!-1340$ or $R\!=1320\!-3600$) grating spectroscopy over $0.7-5.2\!~\mu$m, both in single-object mode employing any one of five fixed slits, or a 3.1$\times$3.2 arcsec$^2$ integral field unit, or in multiobject mode employing a novel programmable micro-shutter device covering a 3.6$\times$3.4~arcmin$^2$ field of view. The all-reflective optical chain of NIRSpec and the performance of its different components are described, and some of the trade-offs made in designing the instrument are touched upon. The faint-end spectrophotometric sensitivity expected of NIRSpec, as well as its dependency on the energetic particle environment that its two detector arrays are likely to be subjected to in orbit are also discussed.