pixel_scale has wrong units

[schlafly]

We specify that pixel_scale and pixel_scale_ref have units of arcsec / pix, but in romancal we create them with units of degree / pix. We seem to be doing this consistently in romancal, so if we want to change it we need to change it in a number of places. The skycell reference file specified arcsec / pix and is actually in arcsec / pix, which would be one reason to make the wholesale change rather than a documentation change.

rad/latest/meta/l3_wcsinfo.yaml

Lines 70 to 71 in b56d5a4

	pixel_scale:
	title: Pixel Scale at Image Center (arcseconds per pixel)

I started one PR to make these changes here:
spacetelescope/romancal#2211
but abandoned it when I realized that we were using degree / pixel more consistently than I had thought. If we wanted to move to arcsec / pixel (as we intended), we would need at least the changes in that PR plus additional changes in the skycell code which generates wcsinfo from the reference file, plus checks to see if any users of pixel_scale (source_catalog, multiband_catalog, others?) use these values.

The last concern would be with matching Webb, but I don't immediately see a Webb equivalent of pixel_scale (surprisingly??). There are cdelts in wcsinfo that are presumably in degrees / pixel that I suspect would be the equivalent, which we wouldn't really need to feel bound by.

We should either update the documentation or update romancal to agree with the documentation.

[schlafly]

Let's just update the documentation for now.

[PaulHuwe]

@stscijgbot-rstdms

[stscijgbot-rstdms]

This issue is tracked on JIRA as RAD-265.

[stscijgbot-rstdms]

Comment by Paul Huwe on JIRA:

This is implemented in RAD PR-854: #854