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DAS-2415: Add units attribute override to SMAP L3 timestamp variables #32

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Merged
merged 4 commits into from
Oct 2, 2025
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DAS-2415: Add units attribute override to SMAP L3 timestamp variables #32

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d079551
DAS-2415: Add units attribute override to SMAP L3 timestamp variables
joeyschultz Sep 30, 2025
903f219
DAS-2415: Fix date on CHANGELOG entry
joeyschultz Sep 30, 2025
1c5a89c
DAS-2415: Add release link to CHANGELOG
joeyschultz Sep 30, 2025
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Merge branch 'main' into DAS-2415
joeyschultz Sep 30, 2025
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8 changes: 8 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [v1.4.0] - 2025-09-30

### Changed

- Updates the units attribute on SMAP L3 timestamp variables to
`seconds since 2000-01-01 11:58:55.816Z`.

## [vX.Y.Z] - Unreleased

### Changed
Expand Down Expand Up @@ -100,6 +107,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
for a variable as specified via an `earthdata-varinfo` configuration file.
- Initial repository setup with utility scripts and Dockerfiles.

[v1.4.0]: https://github.com/nasa/harmony-metadata-annotator/releases/tag/1.4.0
[v1.3.0]: https://github.com/nasa/harmony-metadata-annotator/releases/tag/1.3.0
[v1.2.0]: https://github.com/nasa/harmony-metadata-annotator/releases/tag/1.2.0
[v1.1.0]: https://github.com/nasa/harmony-metadata-annotator/releases/tag/1.1.0
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2 changes: 1 addition & 1 deletion docker/service_version.txt
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@@ -1 +1 @@
1.3.0
1.4.0
42 changes: 42 additions & 0 deletions metadata_annotator/earthdata_varinfo_config.json
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Expand Up @@ -1914,6 +1914,48 @@
}
],
"_Description": "SMAP L3 data are HDF5 and without dimension settings. Overrides here define the dimensions, a useful reference name, and critically, the dimension order."
},
{
"Applicability": {
"Mission": "SMAP",
"ShortNamePath": "SPL2SMAP_S",
"VariablePattern": "/Soil_Moisture_Retrieval_Data_(1km|3km)/.*spacecraft_overpass_time_seconds_.*"
},
"Attributes": [
{
"Name": "units",
"Value": "seconds since 2000-01-01 11:58:55.816Z"
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Just a question and I'm curious. How did you get 2000-01-01 11:58:55.816Z vs

time:units = "seconds since 1970-01-01 00:00:00"
time:units = "seconds since 2000-01-01 00:00:00"

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From the granule metadata (this was taken from SPL3SMP), we can see that the epoch is J2000 and the UTCepoch matches what we are using. seconds since 2000-01-01 00:00:00 would be the J2000 epoch in TT. :

string :epochUTCDateTime = "2000-01-01T11:58:55.816Z" ;
:epochJulianDate = 2451545.f ;
string :timeVariableEpoch = "J2000" ;

Also, the value we chose matches what the SMAP L4 collections use for their timestamp variables.

Matt did a deeper dive exploring this in the WhatsUpWithTime.ipynb notebook attached to the ticket and confirmed this is the correct value for us to use.

}
],
"_Description": "SMAP L3 timestamp variables have an incomplete units value."
},
{
"Applicability": {
"Mission": "SMAP",
"ShortNamePath": "SPL3FT(A|P|P_E)",
"VariablePattern": "/Freeze_Thaw_Retrieval_(Data|Data_Global|Data_Polar)/.*time.*"
},
"Attributes": [
{
"Name": "units",
"Value": "seconds since 2000-01-01 11:58:55.816Z"
}
],
"_Description": "SMAP L3 timestamp variables have an incomplete units value."
},
{
"Applicability": {
"Mission": "SMAP",
"ShortNamePath": "SPL3SM(A|P|AP|P_E)",
"VariablePattern": "/Soil_Moisture_Retrieval_(Data|Data_AM|Data_PM|Data_Polar_AM|Data_Polar_PM)/.*time.*"
},
"Attributes": [
{
"Name": "units",
"Value": "seconds since 2000-01-01 11:58:55.816Z"
}
],
"_Description": "SMAP L3 timestamp variables have an incomplete units value."
}
]
}