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I was reviewing absorption/transmittance spectra and was wondering why certain wavelengths are chosen for detectors and not others. Take methane for example enter image description here

For small electronic IR detectors they use the 4.6 micron peak while spectroscopic satellites use the peak at 1.6 and 2 (magnified by 70 times in PIC) yet the peak at 3 is largest(not at 70 zoom) but is not used, why do they choose these peaks? What is the advantage of having a broad peak over a narrow peak to a detector with the appropriate filters? Also what are some of the ways this absorption data is then analyzed i have heard of second derivative fourier transform spectroscopy and absorption spectroscopy

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  • $\begingroup$ Are there any other components of the atmosphere that have absorption bands that overlap with some peaks but not others? $\endgroup$
    – tpg2114
    Commented Feb 14, 2020 at 1:33

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Could it be because the radiation from the sun at high wavelengths is too low enter image description here

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  • $\begingroup$ @ChemEng it seems that the blackbody radiation is affected by the absorption lines of the gases around it and is not continuous in real world scenarios. It also seems like gases themselves do not give out continuous Blackbody spectrums but are instead dictated by partition functions whereas it is continuous for solid bodies. I wonder how this affects satellite spectroscopy and gas detection $\endgroup$
    – ChemEng
    Commented Feb 27, 2021 at 19:52

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