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spacetelescope / jwst

Python library for science observations from the James Webb Space Telescope
https://jwst-pipeline.readthedocs.io/en/latest/
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Extraction aperture centering for NIRSpec BOTS data #7984

Open stscijgbot-jp opened 9 months ago

stscijgbot-jp commented 9 months ago

Issue JP-3432 was created on JIRA by Melanie Clarke:

The fix for NIRSpec MOS and FS extraction aperture centering by assumed source location in JP-3244 and JP-3245 does not work for BOTS data, since the necessary transform from slit frame to detector pixels is added in resampling, and BOTS data is not resampled. 

For BOTS, the use_source_posn parameter is off by default.  If it is manually set to True, the aperture centering is attempted, but it always fails due to the missing transform, and defaults to placing the aperture at the center of the slit. 

This option is not critical for BOTS mode, since extraction usually has to be manually managed anyway, but it would be nice to have the option to automatically center the aperture.

We've thought of several options for fixing this:

  1. fall back to target RA/Dec if assumed source position is not available
  2. use automated centering from a fit to a spatial profile, as proposed in JP-3244, but applicable to unrectified data
  3. turn on resampling for BOTS data for quicklook extractions
  4. add the transform from slit frame to detector pixels for unrectified data

These options all have drawbacks, so this issue will need more discussion.

stscijgbot-jp commented 1 week ago

Comment by David Law on JIRA:

Assigning to Christian Hayes for discussion by the NIRSpec team