The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope

I. Overview of the instrument and its capabilities

¹ Cosmic Dawn Center, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
e-mail: pjakobsen@nbi.ku.dk
² European Space Agency, European Space Astronomy Centre, Madrid, Spain
³ Centro de Astrobiologia (CSIC-INTA), Departamento de Astrofisica, Madrid, Spain
⁴ European Space Agency, European Space Research and Technology Centre, Noordwijk, The Netherlands
⁵ Airbus Defence and Space GmbH, Friedrichshafen, Germany
⁶ Space Telescope Science Institute, Baltimore, Maryland, USA
⁷ European Space Agency, Space Telescope Science Institute, Baltimore, Maryland, USA
⁸ Department of Physics, University of Oxford, Oxford, UK
⁹ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, Paris, France
¹⁰ Airbus Defence and Space GmbH, Ottobrunn, Germany
¹¹ Leiden Observatory, Leiden University, Leiden, The Netherlands
¹² NASA Goddard Space Flight Center, Greenbelt, MD, USA
¹³ ATG Europe for the European Space Agency, European Space Research and Technology Centre, Noordwijk, The Netherlands
¹⁴ Airbus Defence and Space SAS, Toulouse, France
¹⁵ Holota Optics, Neuhaus, Germany
¹⁶ AURA for the European Space Agency, Space Telescope Science Institute, Baltimore, MD, USA
¹⁷ Aurora Technology for the European Space Agency, European Space Astronomy Centre, Madrid, Spain
¹⁸ Kavli Institute for Cosmology, University of Cambridge, Cambridge, UK
¹⁹ Quantum Circuits, Inc., New Haven, CT, USA
²⁰ OHB System AG, Bremen, Germany
²¹ Max-Planck Institute for Astronomy, Heidelberg, Germany
²² NRC Herzberg, National Research Council, Victoria, British Columbia, Canada
²³ Ball Aerospace, Boulder, CO, USA

Received: 15 November 2021
Accepted: 26 January 2022

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 μm and higher resolution (R = 500−1340 or R = 1320−3600) grating spectroscopy over 0.7–5.2 μm, both in single-object mode employing any one of five fixed slits, or a 3.1 × 3.2 arcsec² integral field unit, or in multiobject mode employing a novel programmable micro-shutter device covering a 3.6 × 3.4 arcmin² 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.