Earthdata Forum

Hello everyone:
I recently have trouble in polarization correction. I hope someone can help me:confused:

I want to calculate the polarization correction factor from this equation:
Pc=1/[1-m12*(cos2a*Qt+sin2a*Ut)/Im-m13*(cos2a*Ut-sin2a*Qt)/Im]

I am trying to get m12 and m13 from xcal LUT for modisa,but unfortunately,the m12 and m13 value is almostly NaN in the xcal LUT:cry:?which was downloaded form OC web?for example, xcal_modisa_axc_oc_v1.33d_412.?
I want to know if the xcal LUT is correct or anyother lut should be used in polarization correction?:neutral:

the xcal lut can be downloaded in https://oceandata.sci.gsfc.nasa.gov/Ancillary/LUTs/modisa/xcal/OPER/

Think you very much
Liu

You need the polcor LUTs as well, which are part of the OCSSW distribution.
See the following two pieces of code to understand how the LUTs are applied to get the polarization correction factor:
https://oceancolor.gsfc.nasa.gov/docs/ocssw/polcor_8c_source.html
which calls:
https://oceancolor.gsfc.nasa.gov/docs/ocssw/xcal_8c_source.html

(the xcal defines the change with time - the polcor defines the correction at the start of the mission)
Sean

Dear Sean:

Thanks for your reply,I relearned the code,and have solved this problem:wink:

think you very much!
Liu