What does the cosine_i band in the EMIT L1B data indicate? If we divide cos_i, would the radiance be equivalent to the satellite viewing the earth at the same elevation angle as the sun is at that pixel giving us the normalised maximum return radiation?
Any documentation on understanding this variable would be appreciated.
EMIT L1B data cosine_i variable
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vishalbatchu
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LP DAAC - dgolon
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Re: EMIT L1B data cosine_i variable
Hello @vishalbatchu We are speaking with our Science Team to confirm our answer and will post the answer soon. Just didn't want you to think we were ignoring your question. Thanks -- Danielle
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Re: EMIT L1B data cosine_i variable
The cosine_i band is the apparent local illumination factor based on
DEM slope and aspect and to sun vector, 0 to 1, as per: https://lpdaac.usgs.gov/documents/1568/EMITL1BRAD_User_Guide_v1.pdf
A more detailed description of its influence on the at-sensor radiance can be found in these papers by Nimrod Carmon (https://doi.org/10.3389/frsen.2022.916155, https://www.sciencedirect.com/science/article/pii/S0034425723000482). The first one has some nice diagrams to help you get your head around the geometry. In short, however, the cos_i is one of two factors that modulates the ratio of direct and diffuse radiation terms; meaning that a simple division here may not be what you're after.
DEM slope and aspect and to sun vector, 0 to 1, as per: https://lpdaac.usgs.gov/documents/1568/EMITL1BRAD_User_Guide_v1.pdf
A more detailed description of its influence on the at-sensor radiance can be found in these papers by Nimrod Carmon (https://doi.org/10.3389/frsen.2022.916155, https://www.sciencedirect.com/science/article/pii/S0034425723000482). The first one has some nice diagrams to help you get your head around the geometry. In short, however, the cos_i is one of two factors that modulates the ratio of direct and diffuse radiation terms; meaning that a simple division here may not be what you're after.