Py6S on Sentinel-2

[Diego Bermejo]

Dear Robin,

thank you very much in first place to make the use of 6S so friendly. I have just started to try it, focusing on Sentinel-2 SWIR bands.

Following the examples, I've noticed the existence of Geometry class, with implementations for several satellites, but not for Sentinel-2. Although there are PredefinedWavelengths for Sentinel-2 A and B. I would like to ask you if I should consider the Geometry for Sentinel-2 just using the generic Geometry.User class and set the parameters accordingly.

Another question I have is the usability of 6S to simulate L1C Sentinel-2 reflectances aimed to study the impact of CH4 abundance on the simulated TOA reflectance. So far, I haven't found a way to "play" with the abundance of CH4, but I would like to confirm this with you.

Thank you very much for your help.

Best,

[Robin Wilson]

Hi,

Yes, there is no built-in Geometry class for Sentinel-2. This is because these Geometry classes represent the configurable satellite geometries provided by the underlying 6S model. Sentinel-2 didn’t exist when 6S was originally written, and hasn’t been added in a more recent update. I’d suggest using the Geometry.User class and setting the parameters appropriately based on the Sentinel-2 image metadata.

As for CH4, there is no built-in way to modify the CH4 values in the 6S simulation. I have done some playing with the underlying 6S model in the past to try add a modifiable CH4 parameter, and have had some success, though due to the methods used this may or may not be suitable for your use-case. I do provide consulting services on 6S and Py6S, so if this is something you’re interested in then contact me at ro...@rtwilson.com and we can discuss.

Best regards,

Robin

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[Diego Bermejo]

Hi  Robin,

thank you for your very quick reply. My goal is to simulate the impact of methane absorption in Sentinel-2 SWIR TOA radiances and estimate its abundance. At this moment I need a short-term solution and I thought that maybe 6S model could help on this. If you think that this might be achievable, the I can contact you and start discussion.

Thank you very much!

Diego