JWST Integral Field Spectroscopy Roadmap

A roadmap for designing observing programs using JWST integral field units (IFUs)—the MIRI medium resolution spectrometer and the NIRSpec IFU—is provided in this article.

For example programs that use this roadmap, please see the Cas A Example Science Program and the MRS Spectroscopy of a Late M Star Example Program.

Each step listed below is followed by a list of articles with additional details.


  1. Pick one or both of the JWST IFU observing modes based on needed wavelength coverage.
    MIRI Medium Resolution Spectroscopy (MRS) (4.9 to 27.9 μm)
    NIRSpec IFU Spectroscopy (0.6–5.3 μm)

  2. Pick wavelength setting(s).
    MIRI MRS: Select SHORT, MEDIUM, or LONG channel, or some combination thereof
    NIRSpec IFU: Select dispersers and filters, depending on needed wavelength coverage and resolving power

  3. For MIRI MRS, determine whether you should choose simultaneous imaging with the MIRI Imager.
    MIRI MRS Simultaneous Imaging

  4. Decide if you need to do a mosaic.
    JWST Mosaic Overview
    MIRI MRS Mosaics

  5. Pick a dither pattern.
    MIRI MRS PSF and Dithering, MIRI MRS Recommended Strategies
    NIRSpec IFU Dither and Nod Patterns, NIRSpec Bright Spoilers and the IFU Recommended Strategies

  6. Determine whether you need a dedicated background observation.
    MIRI MRS Dedicated Sky Observations
    NIRSpec Background Recommended Strategies

  7. For NIRSpec IFU: Decide whether you need to obtain leakcal observations to mitigate the effects of light that leaks through the NIRSpec Micro-Shutter Assembly (MSA) shutters
    NIRSpec MSA Leakage Correction for IFU Observations, NIRSpec MSA Leakage Subtraction Recommended Strategies

  8. Decide if you should do a target acquisition (TA)
    MIRI MRS Target Acquisition
    NIRSpec Target Acquisition, NIRSpec Target Acquisition Recommended Strategies

  9. Calculate the required exposure time and detector readout parameters using the Exposure Time Calculator (ETC).
    JWST ETC IFU Strategies
    JWST ETC MIRI Target Acquisition
    JWST ETC NIRSpec Target Acquisition

  10. Fill out the Astronomer's Proposal Tool (APT) for your observation
    MIRI MRS APT Template
    NIRSpec IFU Spectroscopy APT Template


Go to the Getting Started with Planning JWST Observations to complete the steps for proposal submission.



Notable updates
Originally published