MODIS L1A granules from OB.DAAC and LAADS

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hanzhi.lin
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MODIS L1A granules from OB.DAAC and LAADS

by hanzhi.lin » Wed Sep 07, 2022 5:19 pm America/New_York

Hi there, are MODIS L1A granules stored at OB.DAAC the same with those from LAADS?

When I googled my question, I found a document saying the L1As at OB are a "reduced" version of standard L1As: http://oceancolor.gsfc.nasa.gov (.reprocessing/r2009/band_subsettted_level1a/)

But since this document was for r2009, I was wondering whether at present theMODIS L1A granules for both Terra and Aqua at OB are still reduced?

Thanks in advance for your time.

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OB.DAAC - SeanBailey
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Re: MODIS L1A granules from OB.DAAC and LAADS

by OB.DAAC - SeanBailey » Thu Sep 08, 2022 6:50 am America/New_York

If you looked at:
https://oceancolor.gsfc.nasa.gov/reprocessing/r2009/
you'd see this page linked: https://oceancolor.gsfc.nasa.gov/reprocessing/r2009/format/#level1

But so you don't have to follow the link, it says that (as of the R2009 reprocessing), the L1A file format is identical to that distributed by LAADS :D ...and that is still true.

Regards,
Sean

hanzhi.lin
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Re: MODIS L1A granules from OB.DAAC and LAADS

by hanzhi.lin » Thu Sep 08, 2022 11:01 am America/New_York

Thanks, Sean! I should have dig one more step on google. :)

hanzhi.lin
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Re: MODIS L1A granules from OB.DAAC and LAADS

by hanzhi.lin » Mon Sep 12, 2022 4:19 pm America/New_York

Hi Sean,

I found the production time listed in the local granule ID name inside the L1A granule on OB is different from the normal granule on LAADs which has the same collecting timestamp, nor different from the NRT granule on LANCE that is also with the same timestamp. Does this difference count for something when using the L1A granules on OB?

Cheers,
Hanzhi

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Re: MODIS L1A granules from OB.DAAC and LAADS

by OB.DAAC - SeanBailey » Tue Sep 13, 2022 7:18 am America/New_York

Both are "normal". LAADS and OBPG process from L0, but not at the same time or on the same system. Production time is irrelevant for your purpose - in fact irrelevant for most purposes. It's only informational. Should we (or LAADS) reproduce a granule, you could know if you had the previously processed version, which was newer, but only if obtained from the same source.

Sean

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