jdaviz-cube writer should also write out uncertainty

[Jdaviz-Triage-Bot]

Reporter: pllim

In #2012 , custom writer we added to write out fitted 3D cube only serializing SCI and MASK extensions in FITS file. If the cube has uncertainty, that also should be serialized out to the file. Usually, the order goes like this:

1. Primary header
2. SCI
3. UNCERT
4. MASK

Some telescope use ERR, IVAR, VAR (and so on) instead of UNCERT. I do not know of any official global convention for this.

Care also needs to be given to automatically translate different uncertainty types in this writer into a valid FITS HDU that can be read in exactly the same (roundtripping).

Currently, a lot of operations do not propagate uncertainty, so probably not high priority to implement? Nice to have in case someone has a cube with the uncertainty and wants to use this writer (outside of Cubeviz plugin).

Also see:

• Writer needed for cube data astropy/specutils#592
• Fix and extend wcs1d-fits loader for multi-D WCS astropy/specutils#1009

🐱

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