Why does this not return a second eph2

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oo_processing
Posts: 212
Joined: Wed Apr 06, 2005 12:11 pm America/New_York

Why does this not return a second eph2

by oo_processing » Sat May 01, 2021 2:04 pm America/New_York

From original MOD00.P2021118.1555_1.PDS.bz2

Why does this not return a second eph2?

modis_atteph.py -d ./MOD00.P2021118.1555.BERMUDA_FULL.L1A_LAC
Aqua
Aqua
att1=/shares/cms_optics/apps/seadas/seadas-7.5.3/ocssw/var/anc/2021/118/PM1ATTNR.P2021118.1400.003
att2=/shares/cms_optics/apps/seadas/seadas-7.5.3/ocssw/var/anc/2021/118/PM1ATTNR.P2021118.1600.003
eph1=/shares/cms_optics/apps/seadas/seadas-7.5.3/ocssw/var/anc/2021/118/PM1EPHND.P2021118.1200.003

And then fails with modis_GEO.py ./MOD00.P2021118.1555.BERMUDA_FULL.L1A_LAC -o ./MOD00.P2021118.1555.BERMUDA_FULL.GEO --threshold=95 --ancdb=./ancillary_data.db
STATUS: $ocssw_return_2 = MODIS GEO version 6.1.0, built Aug 16 2019 12:46:24
scan: 0 out of 190 Sat May 1 13:31:08 2021
...
scan: 180 out of 190 Sat May 1 13:31:17 2021
Percent valid data (78.00) is less than threshold (95.00)
ERROR: MODIS geolocation processing failed. Percent valid data (78.00) is less than threshold (95.00)

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gfireman
Posts: 59
Joined: Thu Jan 07, 2010 2:59 pm America/New_York

Re: Why does this not return a second eph2

by gfireman » Mon May 10, 2021 1:36 pm America/New_York

Each "refined" Aqua ephemeris covers 24 hours, so for most granules only one is needed. By contrast, the refined attitude files cover only two hours, so each granule adjacent to an even hour (UTC) will require two attitude files to ensure coverage of the last/first scan lines.

In this case, none of the specified att/eph files shows any error. But the L1A metadata does indicate a significant number of data issues:

Code: Select all

		:Incomplete Scans = 126 ;
		:Missing Packets = 189623 ;
		:Packets with bad CRC = 16547 ;
		:Discarded packets = 16547 ;
However, I can't find any mention of Aqua data outages during that granule, either in the MODIS IOT report or on MODAPS.

gfireman
Posts: 59
Joined: Thu Jan 07, 2010 2:59 pm America/New_York

Re: Why does this not return a second eph2

by gfireman » Mon May 10, 2021 5:22 pm America/New_York

This was in fact an incomplete L0 file. A full-size replacement is now available from oceandata. Please note that this version was compressed with xz instead of our usual bzip2.

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