Hello ENVI community,

I'm new to this so sorry for the noob questions. I'm trying to detect atmospheric methane in hyperspectral satellite data, specifically PRISMA and EnMAP, so the process should be similar to using AVIRIS-ng. The L3Harris tutorials have good guidance on how to perform spectral profile processing for ground features, but my target is atmospheric methane and I have a few questions that I hope the community can help me with.
Firstly, as my target spectrum is in the atmosphere and most guides start with atmospheric correction, I expect that this step is not necessary, is that correct? Is there a way of reversing the process to remove the influence of ground features to leave atmospheric gas spectra?

Spectral libraries generally don't offer gas absorption profiles in IR but I found one from NIST, but the formatting (JCAMP-DX) is not what ENVI expects. Any help on converting this or knowing what ENVI needs would be greatly appreciated! Or if there's a better source of target spectra. (spectrum found here: https://webbook.nist.gov/cgi/cbook.cgi?ID=C74828&Type=IR-SPEC&Index=1#IR-SPEC). TBH it looks like the NIST absorption profile isn't correct anyway.

And if anyone has had experience with this task, I'd be keen to talk through my approach in case there's a better way.

Thanks in advance.