MERIS 1B image doesn't match L2_OC product

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davouris
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MERIS 1B image doesn't match L2_OC product

by davouris » Fri May 22, 2020 2:39 pm America/New_York

Hello,

I am downloading FRS MERIS imagery of Florida through the browser interface. I have multiple dates on which the L2_OC product is of Florida, but the accompanying L1B product is of the Outer Banks. Has this happened to anyone else? One clear example is 20 Oct 2008.

Thanks
dulci

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OB.DAAC - SeanBailey
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MERIS 1B image doesn't match L2_OC product

by OB.DAAC - SeanBailey » Fri May 22, 2020 3:56 pm America/New_York

Dulci,

Yes, there's a bit of an issue there.  A backend modification made to support the new filename convention applied to the SST data (which will eventually be applied to all files) had an unintended consequence of occasionally associating the wrong MERIS L1B file with a corresponding L2 file.  Because the filenames are not easily relatable, the selection is based on time.   Occasionally, more than one file gets returned by the query (a time window is used because the time in the database for the L2 may not match the time of the parent L1...).  The example you cite is one such case.

A revision to our browser (and search logic) is in the works...but that doens't help you now.  What might is searching our direct access page for the appropriate files for cases where the wrong on is identified by the browser.  For this day, it would be:https://oceandata.sci.gsfc.nasa.gov/MERIS/L1/2008/294/

This is the file that was matched:
MER_FRS_1PPEPA20081020_153643_000000302073_00097_34720_6653.N1.bz2 
This is the file that *should* have been matched
MER_FRS_1PPEPA20081020_153712_000002022073_00097_34720_6615.N1.bz2

The time element shows they are within 30 seconds of each other (the time window in the search).  Normally, we don't have files so close together in time.  Below is what their coverages look like.

Sorry for the trouble.  Hopefully we'll get a better mousetrap in place soon.

Sean

davouris
Posts: 22
Joined: Wed Oct 07, 2015 2:36 pm America/New_York

MERIS 1B image doesn't match L2_OC product

by davouris » Wed May 27, 2020 2:39 pm America/New_York

Thanks Sean,

Glad to know I wasn't repeatedly making some simple error. I will look for my dates in the database you mentioned. I have many days where that mis-match happens. On the bright side, I have some great images of the Outer Banks!

Take care,
Dulci

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