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desihub / desitarget

DESI Targeting
BSD 3-Clause "New" or "Revised" License
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main_cmx_or_sv() may incorrectly report 'main' instead of 'special' #813

Closed weaverba137 closed 3 months ago

weaverba137 commented 6 months ago

As it is currently written desitarget.targets.main_cmx_or_sv() does not have any visible way to distinguish between 'main' and 'special' surveys. What is the definitive way to identify survey = 'special'?

geordie666 commented 6 months ago

desitarget has no concept of a "special" target. I think the "special" term first arises downstream and is attached to a type of tile rather than a type of target, e.g.:

more $SURVEYOPS/ops/tiles-specstatus.ecsv | grep special

But, regardless, there are no "special" targets as far as desitarget is concerned.

Further context: The main, cmx or sv targets are identified via their respective targeting columns DESI_TARGET (for main), CMX_TARGET, SV1_TARGET, SV2_TARGET, SV3_TARGET. There is no SPECIAL_TARGET column.

geordie666 commented 6 months ago

One other thought: It's possible that the term "special" for a tile is being conflated with the term "tertiary" for a target. Tertiary targets often end up on special tiles. Tertiary targets can be identified by having RELEASE bits equivalent to 8888 in their TARGETID, as described in section 3.2.3 of the desitarget paper. But, again, I think "special" is a term related to a tile, not a target.

weaverba137 commented 3 months ago

I think the need to identify main versus special specifically using main_cmx_or_sv() is now moot, so I propose closing this ticket.

geordie666 commented 3 months ago

Agreed, thanks.