Earthdata Forum

Hi,
I have TOA simulated spectra from 6SV code for 1000 different combinations of parameters such as ozone concentration, water vapor, zenith angles, and relative azimuth angles. I want to make Rayleigh corrected reflectance for this 1000 spectra. The wavelength starts from 400 nm till 700 nm. I can resample the spectra to match the spectral bands of different satellites. Is it possible to carry out the Rayleigh correction for these independent spectra in Seadas? Kindly let me know.

It is *possible*, it's just not straight forward. Basically, you have to fool l2gen into thinking it is processing one of the sensors it knows how to process. You can create a "generic" L1B file (using the l1bgen_generic code), then manipulate the file to replace the Lt_<wvl> data sets with your data, then process that modified L1B through l2gen with atmocor=0 to spit out rhos (refered to as "surface reflectance", but it's really rayleigh and gaseous absorption corrected reflectance). You'll also want to set all the vicarious gain coefficients to unity (gain=1.0,...)

Another caveat to the process...the way 6SV computes Rayleigh isn't likely to match the way l2gen computes it. Likewise with the gaseous absorption. It may take some fiddling with options (and ancillary inputs) to get something reasonable out.

Plus, you only only go to 700nm. l2gen isn't going to be happy with fill values in the NIR/SWIR bands, but again, some fiddling with the input options for masking/flagging might get it to work. Or you could use a nominal value for those bands when you create the file.

Might be easier to coerce 6S spit out the Rayleigh and subtract it...

Sean