Hi!

As you know, we have MODIS DB problems from Aug. 3, right ?
I hope to hear good news from MODIS DB investigating team.

Anyway, I downloaded MODIS L0 from 
<ftp://oceans.gsfc.nasa.gov/MODIST/L0/2007/225/MOD00.A2007225.0325_1.PDS.bz2>
and LAADS.
<ftp://ladsweb.nascom.nasa.gov/allData/5/MOD00F/2007/225/MOD00F.A2007225.0325.20072250851.001.PDS>

Both of them are L0, so I thought that they are same.

$ bzip2 -cd MOD00.A2007225.0325_1.PDS.bz2 > MOD00.A2007225.0325_1.PDS
-rw-r--r--   1 kath users 395148432 Aug 15 13:10 MOD00.A2007225.0325_1.PDS
-rw-r--r--   1 kath users 395148432 Aug 15 12:22 MOD00F.A2007225.0325.20072250851.001.PDS
Size seems same. 

$ hexdump MOD00F.A2007225.0325.20072250851.001.PDS | less
0000000 4008 4d6d 7b02 c946 bb00 57b0 9c01 800e
0000010 ff1f c008 08a2 8460 c008 08a2 8450 c008
0000020 08a0 8350 a008 089e 8140 f006 068e 6100
...
$ hexdump MOD00.A2007225.0325_1.PDS | less
0000000 4008 8d6e 7b02 c946 bb00 52b2 8900 000e
0000010 ff1f b116 1b5c 0b82 511a 1c97 6102 3117
0000020 168f 8f61 d112 1343 9b01 b341 41be 7744
...

Content looks different.
Is it correct ?
And why ?

With best regards,

Yama

I'm not sure why there is a difference but one thing you could do is process the files to L1A or L1B and compare the products.. you could compare them usng hdiff or by loading products in a software package and subtracting the data or imagery from one another (SeaDAS is good for this). I'm guessing you'll get identical results but it would be a good verification..

Mike,

Thank you very much for your response.
I will compare L1 files derived from SeaDAS and LAADS.

With best regards,

Yama,

Yama,

The difference is that the oceans (OBPG) file starts one physical scan later (~1.47 seconds) than the LAADS file.  There is some slop in the process of dividing the downlinks into 5-minute intervals, and apparently the two data sources are handling the slop differently.  The OBPG file comes directly from the NOAA near-real-time system.  They should be using the same chunking logic and code that LAADS (MODAPS) is using, but apparently that is not the case.  NOAA NRT has bigger problems at the moment, but I'll ask them to look into it.

-- bryan

Bryan,

I visited to SIMBIOS project about one month for the GLI calibration
5 or 6 years ago. Do you remember me ?
If you get the answer of my question about this, please let me know.
Our collaborated receiving station processes the data downloaded from
ftp://oceans.gsfc.nasa.gov/MODIST/L0
from Aug 3, when MODIS DB problems happened.
But other collaborated researchers use LAADS L1.
I think that this is a good opportunity to compare the products,
as Mike pointed out.

With best regards,

Yama,