Rayleigh radiance calculation

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wolf.1_1
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Joined: Wed Nov 30, 2005 8:06 am America/New_York

Rayleigh radiance calculation

by wolf.1_1 » Thu Apr 27, 2017 10:37 am America/New_York

Hi, I want to use the Rrs data of MISR sensor onboard the EOS-Terra , and I am trying to do the atmospheric correction for MISR Lt data over ocean.
I tried to calculate the Rayleigh scattered radiance according to the MODIS atbd and SeaDAS l2gen code. I have a question about how to calculate the Rayleigh scattered radiance using SeaDAS Rayleigh LUTs:
On MODIS ATBD-18 Page 56 (https://oceancolor.gsfc.nasa.gov/docs/technical/atbd_mod18.pdf), it shows:
Ir(theta_v,theta_s)=Ir0(theta_v,theta_s)+2*(Ir1(theta_v,theta_s)*cos(delt_phi)+Ir2(theta_v,theta_s)*cos(2*delt_phi)) ;
But in the Rayleigh code of SeaDAS L2gen (Line 339-340 on https://oceancolor.gsfc.nasa.gov/docs/ocssw/rayleigh_8c_source.html), it is :
Ir(theta_v,theta_s)=Ir0(theta_v,theta_s)+(Ir1(theta_v,theta_s)*cos(delt_phi)+Ir2(theta_v,theta_s)*cos(2*delt_phi)) ;
There is no 2 in the second equation.

Which way is the correct one to calculate the Rayleigh scattering using the SeaDAS Rayleigh LUTs?
Thanks a lot!

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OB.DAAC - SeanBailey
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Rayleigh radiance calculation

by OB.DAAC - SeanBailey » Mon May 01, 2017 9:22 am America/New_York

Well, if you're planning to use the LUTs provided with SeaDAS, you probably want to follow the code in SeaDAS.  Although, I'm not entirely sure the ATBD definition and the code differ (but may just be lack of caffeine...).  There's nothing magical in there, it's just an expansion of the Stokes vector.  

Now, as for using the SeaDAS Rayleigh LUTs for MISR...there aren't any and MODIS and MISR do not have the same spectral response functions.  The tables were generated using the relative spectral response of the instrument, so the tables for MODIS are not going to be entirely appropriate for MISR.  Something to keep in mind...

Sean

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