Better document FITS keywords, including what is in primary and extension header

[dsavransky]

There should be a nice table of these somewhere.

The logic of what goes in the primary header vs. extension header is not clear to many people - why are sat spots and star position in the extension header? This was confusing Li Wei and I agree it's confusing so we should better document it.

[dsavransky]

Recovering rm journals for issue:

mperrin: Document the FILETYPE keyword in particular since it's very useful/important but non obvious.

mperrin: Discussed during data telecon, consensus was this could be useful. Let's try to at least get a draft in place by the release 1.4.

Abhi: Can also add warnings about which keywords are sometimes bogus depending on Gemini DIMM stopping, etc.

dsavransky: Roping in Vanessa to work on mapping every header keyword to its origin GMB or EPICS channel. Should provide lots of details and highlight all the keywords with incorrect comments.

mperrin: Some months ago we had discussed making a nice table documenting the FITS keywords that users might want to be aware of. This would be in the pipeline documentation. Does anyone feel like helping (and have time) with a first pass at this in the next week or two? This would also be a chance to help clear up which keywords need changing or updating on the Gemini side.

mperrin: Here is the existing Google spreadsheet of all of these:
https://docs.google.com/spreadsheets/d/1foXZ2lHPX8KCyTlcCfQwlF-5-wV8uxkXsj57quaoSrM/edit#gid=0&vpid=B2

That's somewhat out of date and probably needs cleaning up, then we can extract a subset to include with the pipeline documentation?

mperrin: Does anyone have time to help with this issue (making a nice table of FITS keywords as part of the pipeline docs?). Personally I'm too swamped to get to this, and am comfortable letting it fall off the bottom of the priority list for this release, but I could help out if someone else wants to put some momentum toward this.

kfollette: Discussed in Slack chat. Nobody has time to do before 1.4 release