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LSSTDESC / imSim

GalSim based Rubin Observatory image simulation package
https://lsstdesc.org/imSim
BSD 3-Clause "New" or "Revised" License
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Add missing keywords to raw FITS headers #457

Closed jchiang87 closed 3 months ago

jchiang87 commented 5 months ago

For the ops-rehearsal-3 activities, a number of keywords describing the observations were noted as missing, specifically the null ones in this list (see the post in slack):

RA: 124.82881462031425
DEC: -14.893919091079661
RASTART: null
DECSTART: null
RAEND: null
DECEND: null
ROTPA: 116.0158594226007
ROTCOORD: sky
HASTART: -10.490392243587635
ELSTART: null
AZSTART: null
AMSTART: 1.0522574903781972
HAEND: -10.36504999786186
ELEND: null
AZEND: null
AMEND: 1.0522574903781972
TRACKSYS: null
RADESYS: null

However, the *END values aren't used by the metadata translator for the LSST pipelines code, so those can be omitted.

jchiang87 commented 5 months ago

A couple other keyword entries that have been noted as missing:

ORIGIN
TELCODE

TELCODE describes the camera, i.e., MC for main camera and CC for ComCam. ORIGIN describes what produced the file, e.g., imSim v2.0. Also, the DAYOBS values probably need a 12 hour offset.

jchiang87 commented 4 months ago

Also noted during ops-rehearsal-3 preparations: the DAYOBS header value should be defined with a 12 hour offset applied to MJD. Details TBC. See https://rubinobs.atlassian.net/browse/DM-43495

rmjarvis commented 4 months ago

Why are they offsetting the DAYOBS by 12 hours? Seems not great to lie about what time it is. But maybe I don't understand something.

jchiang87 commented 4 months ago

I think it's a question of whether the observing day starts at midnight or at Noon.

rmjarvis commented 4 months ago

Isn't MJD an objective time though? I didn't think there was ambiguity in how it was defined.

https://scienceworld.wolfram.com/astronomy/ModifiedJulianDate.html#:~:text=A%20modified%20version%20of%20the,0%20of%20the%20Julian%20calendar.

jchiang87 commented 4 months ago

The proposal is not to change MJD, but to compute DAYOBS from MJD with an offset. I don't think anyone cares about DAYOBS except the Rubin pipeines.

jchiang87 commented 4 months ago

Some documentation on expected header keywords: https://docushare.lsst.org/docushare/dsweb/Get/LSE-400

cwwalter commented 4 months ago

Do you think there are now some new ones we are missing?

jchiang87 commented 4 months ago

I think the ones we absolutely need have been added here, but I'd like to do some additional checks against the new obs_lsst code with the LsstCamSim instrument model.

jchiang87 commented 3 months ago

addressed by #473