Support for satellite zenith angles up to 90 degrees

[adybbroe]

While it is possible to apply Pyspectral to correct for Rayleigh scattering of a full disk Himawari/GOES-16 image, the correction is not strong enough at large viewing angles. This is because the RTM simulations and LUT tables actually only cover the 0-70 degree interval. We need to extend the LUTs down to 90 degrees.