For NIRSpec flat field, assign 1 if wavelength is out of bounds #2677
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philhodge
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Oct 25, 2018
There are several components for the NIRSpec flat field. For each section of the instrument (the fore-optics, the spectrograph, and the detector), there can be both a fast variation (with wavelength) and a slow variation component. For a given pixel of the science data, it may be that the wavelength of the science data is undefined, or the wavelength might be out of range for one or more components of the flat field, or the pixel can be flagged as bad in the reference file for a component. In any such case, the flat field to be applied to the data will be set to 1, and the associated data quality array will be non-zero, such as UNDEFINED_FLAT or NO_FLAT_FIELD. See issue spacetelescope#2677.
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Closed with PR #2775. |
nden
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Oct 30, 2018
There are several components for the NIRSpec flat field. For each section of the instrument (the fore-optics, the spectrograph, and the detector), there can be both a fast variation (with wavelength) and a slow variation component. For a given pixel of the science data, it may be that the wavelength of the science data is undefined, or the wavelength might be out of range for one or more components of the flat field, or the pixel can be flagged as bad in the reference file for a component. In any such case, the flat field to be applied to the data will be set to 1, and the associated data quality array will be non-zero, such as UNDEFINED_FLAT or NO_FLAT_FIELD. See issue #2677.
nden
pushed a commit
that referenced
this issue
Oct 30, 2018
There are several components for the NIRSpec flat field. For each section of the instrument (the fore-optics, the spectrograph, and the detector), there can be both a fast variation (with wavelength) and a slow variation component. For a given pixel of the science data, it may be that the wavelength of the science data is undefined, or the wavelength might be out of range for one or more components of the flat field, or the pixel can be flagged as bad in the reference file for a component. In any such case, the flat field to be applied to the data will be set to 1, and the associated data quality array will be non-zero, such as UNDEFINED_FLAT or NO_FLAT_FIELD. See issue #2677.
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From James Muzerolle:
"Whenever a pixel wavelength is outside the range of the corresponding reference file, the pipeline should set the flat correction factor to 1 (no extrapolations). It probably would be a good idea to set a DQ flag in that case. The NO_FLAT_FIELD flag will not track cases where some but not all of the 6 components (d/f/s-flat, 2D and fast vector) are missing. Perhaps there should be a "PARTIAL_FLAT_FIELD" flag? I don't know how common this might be; probably not frequent, maybe most often an issue for the S-flat at edges of some MOS subwindows."
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