NIRSpec - Near Infrared Spectrograph

The Near Infrared Spectrograph (NIRSpec) will be the spectrograph in the wavelength range of 0.6 to 5 microns. The study of galaxy formation, clustering, chemical abundances, star formation, and kinematics, as well as active galactic nuclei, young stellar clusters, and measurements of the initial mass function of stars (IMF) requires a near-infrared spectrograph.

Here's an animation that shows how the NIRSpec Instrument will work.
Formats: 28.8 .avi, 9.1 MB .mov, 9.1 MB .mp4

The current NIRSpec design provides 3 observing modes: a low resolution R~100 resolving power prism mode, an R~1000 multi-object mode and an R~3000 integral field unit or long-slit spectroscopy mode. For all modes the field of view will be ~3.4x3.4 arcmin.

In the R~100 and R~1000 modes NIRSpec provides users of JWST with the ability to obtain simultaneous spectra of more than 100 objects in a >9 square arcminute field of view. At R~100 one prism spectrum covers the full 0.6 to 5 micron wavelength range. At R~1000 three gratings cover the wavelength range from 1-5 micron. The baseline spectrograph will take advantage of a micro-electromechanical system (MEMS) to provide dynamic aperture shutter masks that will enable users to observe hundreds of different objects in a single field of view.

To improve sensitivity, pixels with a larger projected size on the sky than those on NIRCam will be used (~0.1 arcsec). NIRSpec will be equipped with two Rockwell Scientific HgCdTe 2kx2k detectors.

The European Space Agency (ESA) will be providing the NIRSpec instrument (NASA will provide the detectors and the MEMS aperture masks) as part of their contribution to JWST.