The NIRSpec instrument is the workhorse near-infrared spectrograph on board the James Webb Space Telescope and is provided by ESA.

The primary goal of NIRSpec is to enable large spectroscopic surveys of astronomical objects such as stars or distant galaxies. This is made possible by its powerful multi-object spectroscopy mode, which makes use of microshutters. This mode is capable of obtaining spectra of up to nearly 200 objects simultaneously, over a 3.6×3.4 arcminute field of view – the first time this capability has been provided from space. This mode makes for very efficient use of Webb’s valuable observing time.

This animation shows the path followed by light from an astronomical object as it travels through the NIRSpec components and onto the detector.

~ 0:22 min: The light from the telescope enters NIRSpec via the Pick-off Mirror.

~ 0.27 min: The second flat mirror directs the beam towards the FORE optics that form an image of the sky onto the Micro Shutter Assembly (MSA).

~ 0:36 min:  The light passes through a Filter Wheel Assembly (FWA) for selecting specific wavelength bands and through the refocusing mechanism (RMA).

~ 0:42 min: A sharp image of the sky is formed onto the MSA plane.

~ 0:46 min: Light that passed through open MSA shutters enters the spectrometer.

~ 0:49 min: The collimator optics brings the beam to the Grating Wheel Assembly (GWA).

~ 0:52 min: The Grating or Prism unravels the incoming beam in all its wavelengths by dispersing it vertically.

~ 0:55 min: The Camera optical system forms spectra of each scientific object onto the detector.

NIRSpec will allow scientists to study objects embedded in shrouds of gas and dust, to find out more about how galaxies formed and evolved, and to characterise the atmospheres of extrasolar planets to determine if water is present.

NIRSpec is built by European industry to ESA’s specifications and managed by the ESA Webb Project at ESTEC, the Netherlands. The prime contractor is Airbus Defence and Space in Ottobrunn, Germany. The NIRSpec detector and Micro-Shutter Array subsystems are provided by NASA’s Goddard Space Flight Center (GSFC).

Learn more about spectroscopy with the Webb telescope.

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