The Near-Infrared Spectrograph (NIRSpec) is a near infrared multi-object dispersive spectrograph capable of simultaneously observing more than 100 sources over a field-of-view (FOV) larger than 3' x 3'. The NIRSpec will be the first spectrograph in space that has this capability. Targets in the Field of View are normally selected by opening groups of shutters in a micro-shutter array (MSA) to form multiple apertures. The microshutters are arranged in a waffle-like grid that contains more than 62000 shutters with each cell measuring 100 µm x 200 µm. Sweeping a magnet across the surface of the MSA opens all operable shutters. Individual shutters may then be addressed and closed electronically. NIRSpec is also capable of Fixed-slit and Integral-field spectroscopy and provides medium-resolution spectroscopy over a wavelength range of 1 - 5 µm and lower-resolution spectroscopy from 0.6 - 5 µm.
NIRSpec will address all of the four main JWST science themes, and much more. It will enable large spectroscopic surveys of faint galaxies at high redshift, obtain sensitive spectra of transiting exoplanets and image line emission from protoplanetary disks and protostars. NIRSpec is being built for the European Space Agency (ESA) by the Astrium consortium with Dr. Pierre Ferruit guiding its development as the ESA JWST Project Scientist. Peter Jakobsen, the NIRSpec Instrument PI, retired in December 2011.