The operational aspects of JWST's NIRSpec instrument define how instrument-level capabilities can be applied for science. These features include target acquisition methods, dither/nods for each observing mode, and special considerations for science observations.


The JWST Near Infrared Spectrograph (NIRSpec) enables 0.6–5.3 μm spectroscopy at resolving powers of ~100, ~1,000, and ~2,700 in multi-object spectroscopy (MOS)integral field unit (IFU) spectroscopy, fixed slits (FSs) spectroscopyand bright object time-series (BOTS) spectroscopy modes.  

These NIRSpec science modes include the following operational capabilities:


NIRSpec auto-cals (auto-calibrations) are internal calibration exposures that can be acquired with lamps within the NIRSpec calibration assembly (CAA). These auto-cals can be acquired for flat fields, wavelength reference exposures, and broad line peaks measured for dispersion verification.

It is not recommended for users to acquire NIRSpec auto-cals with their science for two reasons:

  • Acquiring auto-cals can cause moderate overheads, ~5 minutes or more per exposure.
  • Acquiring auto-cals with lamp illumination may cause low levels persistence in subsequent science that could effect very deep sky exposures on faint objects.

NIRSpec auto-cals have been added to the science templates for FS, IFU, and MOS observing modes to make it possible to acquire lamp exposures at the same time as on-sky external exposures. It is expected this capability will primarily be used for instrument commissioning and observatory calibration observations.

Last updated

Published March 29, 2017


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Updated April 05, 2017

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Published March 02, 2017