Hi all,
I generate L1B file from L1A and when I try to extract the F0 (with matlab), I can't found it. Does the name of F0 change or it is the version wrong?

Regards

MODIS or SeaWiFS?  Is this really something that worked in the past?  There is an F0 SDS in the Level-2 files.

-- bryan

Hi Bryan,
I am using L1B file of SeaWiFS and want to extract the F0 with MATLAB;

DIOUF

There is no F0 data set in a SeaWiFS Level-1B.  There never was.  I think you want to process to Level-2.

-- bryan

In level-2 I am sur that we can found Es but not F0.
I need it for calculating reflectance.

> ncdump -h S1997262224952.L2_LAC | grep F0

This is mean solar irradiance, band-averaged:

        float F0(band number) ;
                F0:long_name = "Mean Solar Flux" ;
                F0:units = "mW cm^-2 um^-1" ;

Exactly which solar irradiance you need would depend on which quantity you are computing.  If it is TOA reflectance, you need instantaneous, band-averaged, solar irradiance.  You need to adjust the above F0 for earth-sun distance. This is also in the Level-2:

> ncdump -h S1997262224952.L2_LAC | grep Earth-Sun

                :Earth-Sun Distance Correction = 0.9914332628250122 ;

F0' = F0 * Earth-Sun Distance Correction

rho_toa = pi * Ltoa/F0'/cos(solar-zenith)

Note, however, that if it is Rrs from nLw that you wish to compute, then mean, band-centered F0 is what you need.

Thanks you Bryan !

Diouf