JWST ETC Target Acquisition

The JWST Exposure Time Calculator (ETC) offers target acquisition (TA) modes for all the JWST instruments, which allows users to estimate the exposure time required to obtain the required signal-to-noise for the TA source.

All spectroscopic and coronagraphic observations will require a science instrument assisted target acquisition (TA) procedure. Science observations that can tolerate absolute pointing errors of up to 0.45" to 0.30" (1-σ radial error), require no further TA procedures following the usual guide star acquisition by the FGS. TA is used to place sources accurately in apertures or subarrays that are small when compared to the 3σ accuracy of the guide stars. The on-board system uses the measurement of the source position and the known central position of the aperture of interest to perform a small move of the telescope to put the source in the aperture.



List of articles

  1. JWST ETC MIRI Target Acquisition: Details of TA procedures in the ETC for the various MIRI observing modes.
  2. JWST ETC NIRCam Target Acquisition: Details of TA procedures in the ETC for the various NIRCam observing modes.
  3. JWST ETC NIRISS Target Acquisition: Details of TA procedures in the ETC for the various NIRISS observing modes.
  4. JWST ETC NIRSpec Target Acquisition: Details of TA procedures in the ETC for the various NIRSpec observing modes.




Published

Latest updates
  •  
    Updated for ETC v1.5.


  • Updated for ETC v1.3

  •  
    Corrected 30" to 40" in MIRI Spectroscopic TA required separation
    Provided link to MRS Best Practices page for explanation for this separation