NIRSpec is the near-infrared spectrometer of the JWST.

The instrument features about a quarter of a million  individually addressable shutters, covering a field of view (FOV) of 9 arcmin2 (MOS mode) for multi-object spectroscopy, an integral field unit (IFU) with 3x3 arcsec2 FOV, and five fixed slits, for high-contrast long-slit spectroscopy (SLIT mode). The MOS mode allows slit-spectra of ~ 100 sources to be obtained simultaneously.  NIRSpec will be the first spectrograph in space that has this capability. The instrument operates in the wavelength range 0.6-5.3 micron, with a spectral resolutions of 100, 1000, and 2700.

NIRSpec was developed by ESA with Airbus Defence and Space Germany (formerly EADS Astrium Germany GmbH) as the prime contractor.

NIRSpec at the end of integration at AIRBUS (Germany) before undergoing a comprehensive test campaign in 2013

A description of NIRSpec design is given here.