NIRSpec

NIRSpec, or the Near-Infrared Spectrograph, is one of the scientific instruments aboard the James Webb Space Telescope. It is designed for spectroscopy in the near-infrared range, enabling sensitive measurements of faint sources from distant galaxies to exoplanet atmospheres. Its wavelength coverage spans roughly 0.6 to 5.3 micrometers.

NIRSpec offers multiple observing modes. Fixed-slits provide single-target spectroscopy, while a programmable microshutter array (MSA) enables multi-object spectroscopy by selecting many targets simultaneously within the instrument’s field of view. The MSA contains about 250,000 individual shutters. An integral field unit (IFU) mode delivers spatially resolved spectra over a compact 3 by 3 arcsecond field of view with fine spatial sampling. Collectively, these modes allow both targeted and survey-style spectroscopic programs within a field of view of several arcminutes across.

Spectral resolution varies by mode. Prism observations achieve low resolution (roughly R around 100), while the high- and medium-resolution gratings yield R values up to approximately 2700, with intermediate options around a few hundred to thousand, enabling a wide range of science from broad-band spectroscopy to detailed line studies.

Detector hardware consists of four HgCdTe H2RG detectors, each 2048 by 2048 pixels, cooled to cryogenic temperatures to minimize noise. The instrument was developed for the JWST by the European Space Agency, with substantial NASA contributions, and is integrated with the telescope for joint operations.

Since its commissioning, NIRSpec has been used to study galaxy formation, the intergalactic medium, stellar populations, and planetary atmospheres, contributing detailed near-infrared spectra to a broad range of astrophysical investigations.