Details
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Type:
Story
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Status: Done
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Resolution: Done
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Fix Version/s: None
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Component/s: obs_lsst
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Labels:None
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Story Points:0.5
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Team:Architecture
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Urgent?:No
Description
The obs_lsst LATISS metadata translator assumes that data after RASTART_IS_BAD is off by 37s, but in fact this was fixed on 2021-02-12. Please fix the metadata translator.
I'd do it myself, but I don't understand the comment
# RASTART/DECSTART/RAEND/DECEND used wrong telescope location before this
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# 2020-02-01T00:00 we fixed the telescope location, but RASTART is still
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# in mount coordinates, so off by pointing model.
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RASTART_IS_BAD = Time("2020-05-01T00:00", format="isot", scale="utc")
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and would prefer you to clarify that the problem being fixed is not this one.
There is a more serious problem too, namely that the correction of c. 0.154167 is applied multiple times. The RAEND in the header is 130.211695172908, but:
exposure.getMetadata().get("RAEND"), butler.get("raw_md", dataId).get("RAEND")
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(130.82836183957568, 130.36586183957567)
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To clarify the situation inherited from DM-28783:
- At 2021-02-11T1845Z the headers were decimal degrees but had a 37s error in RASTART.
- At 2021-02-12T0000Z the 37s was fixed.
So it was less than 6 hours of data where the 37s error was a real problem.
Furthermore, the RASTART test will fail because even as I was fixing the translator to deal with the problem of the time offset the problem had been fixed but I had not been informed. This means that the data I was looking at was already correct. The reason I thought it needed fixing was that this did make the number closer to the target RA (260.178 [fixed] vs 260.181 [demand] vs 260.024 [header]).
I took your fix and sorted out the test.
I'm going to do the double fixup fix in a different ticket because that can be done entirely inside astro_metadata_translator.
Looks fine
Do I assume that after the 12th the RASTART/DECSTART are correct in the header and do not need any fixes?
I think for the double correction I'm going to have to finally bite the bullet and add a sentinel to the header indicating that it's been fixed. I've been wary of doing that because I didn't want to surprise people when something weird appears in their header. Maybe I should use something like HIERARCH ASTROMETADATA HEADER FIXED = TRUE.