SeaWiFS L1a and L2 Filename Datetime Discrepancy
Posted: Wed May 10, 2023 11:22 am America/New_York
Hello,
There appears to be a discrepancy in the datetimes listed in SeaWiFS L1a file names and SeaWiFS L2 file names on Direct Data Access, and between Direct Data Access and the Common Metadata Repository (CMR). I am trying to find the cause behind the discrepancy, or if there is a pattern to it, in order to be able to edit some satellite processing scripts accordingly.
Here is an example:
L2 url: https://oceandata.sci.gsfc.nasa.gov/directdataaccess/Level-2/SeaWiFS/1998/260/SEASTAR_SEAWIFS_MLAC.19980917T165336.L2.OC.nc
L1a url: https://oceandata.sci.gsfc.nasa.gov/directdataaccess/Level-1A/SeaWiFS/1998/260/S1998260165214.L1A_MLAC.bz2
Specifically, refer to the timestamps: 165336 vs 165214.
I work with a field-satellite matchup workflow, that finds matchups within a given time window from the CMR. The workflow scans the repository for matchups and creates a list of matchup L2 urls. We then edit the extensions and convert the datetimes from YYYYMMDDThhmmss to YYYYDoYhhmmss, and use these L1a filenames to download L1a files from Direct Data Access.
The workflow is successful for aqua, terra, and viirs files. However, it is breaking on seawifs files. It appears as if the CMR L2 urls and timestamps match the Direct Data Access L2 urls and timestamps, but that the Direct Data Access L1a urls do not match due to a discrepancy in the timestamps between the L1a and L2 urls. (This discrepancy only occurs for seawifs files, not for aqua, modis, or viirs.)
Is there a reason for this discrepancy, or a pattern behind it?
Thank you.
There appears to be a discrepancy in the datetimes listed in SeaWiFS L1a file names and SeaWiFS L2 file names on Direct Data Access, and between Direct Data Access and the Common Metadata Repository (CMR). I am trying to find the cause behind the discrepancy, or if there is a pattern to it, in order to be able to edit some satellite processing scripts accordingly.
Here is an example:
L2 url: https://oceandata.sci.gsfc.nasa.gov/directdataaccess/Level-2/SeaWiFS/1998/260/SEASTAR_SEAWIFS_MLAC.19980917T165336.L2.OC.nc
L1a url: https://oceandata.sci.gsfc.nasa.gov/directdataaccess/Level-1A/SeaWiFS/1998/260/S1998260165214.L1A_MLAC.bz2
Specifically, refer to the timestamps: 165336 vs 165214.
I work with a field-satellite matchup workflow, that finds matchups within a given time window from the CMR. The workflow scans the repository for matchups and creates a list of matchup L2 urls. We then edit the extensions and convert the datetimes from YYYYMMDDThhmmss to YYYYDoYhhmmss, and use these L1a filenames to download L1a files from Direct Data Access.
The workflow is successful for aqua, terra, and viirs files. However, it is breaking on seawifs files. It appears as if the CMR L2 urls and timestamps match the Direct Data Access L2 urls and timestamps, but that the Direct Data Access L1a urls do not match due to a discrepancy in the timestamps between the L1a and L2 urls. (This discrepancy only occurs for seawifs files, not for aqua, modis, or viirs.)
Is there a reason for this discrepancy, or a pattern behind it?
Thank you.