- The following text is adapted from (Vermote et al., 1997) and the 6SV site -
The 6SV (Second Simulation of the Satellite Signal in the Solar Spectrum) (Vermote et al., 1997) is a computer code that can accurately simulate the radiative transfer of an optical electromagnetic signal through the atmosphere. The 6S code is an improved version of 5S, developed by the Laboratoire d'Optique Atmospherique, that permits calculations of near-nadir (down-looking) aircraft and satellite observations, accounting for target elevation, non lambertian surface conditions, and absorbing species (O2, O3, H2O, CH4, N2O, CO). The computational accuracy for Rayleigh and aerosol scattering effects is based on the use of state-of-the-art approximations and implementation of the successive order of scattering (SOS) algorithm. 6S simulates the atmospheric radiative transfer in the 400-2500 nm spectral range at a spectral resolution of 2.5 nm.
Nevertheless, the 6S code has still limitations. It cannot handle spherical atmosphere and as a result, it cannot be used for limb observations. In addition, the decoupling of absorption and scattering effects does not allow to use the code in presence of strong absorption bands.
ALG v1.2 toolbox supports usage of the latest vector version of the 6S code (6SV2.1) (Kotchenova et al., 2006), (Kotchenova et al., 2007), (Kotchenova et al., 2008). 6SV2.1 was released in June 2015, and is available to download here.
Vermote, E.F., Tanré, D., Deuzé, J.L., Herman, M., & Morcrette, J.-J. (1997), "Second Simulation of the Satellite Signal in the Solar Spectrum, 6S: An Overview." IEEE Transactions on Geoscience and Remote Sensing. Vol. 35, No. 3, pp. 675‒ 686.
Kotchenova, S.Y., Vermote, E.F., Matarrese, R, & Klemm, Jr., F.J. (2006), "Validation of a vector version of the 6S radiative transfer code for atmospheric correction of satellite data. Part I: Path radiance." Applied Optics. Vol. 45, No. 26, pp. 6762‒ 6774.
Kotchenova, S.Y., & E.F. Vermote, E.F. (2007), "Validation of a vector version of the 6S radiative transfer code for atmospheric correction of satellite data. Part II: Homogeneous Lambertian and anisotropic surfaces." Applied Optics. Vol. 46, No. 20, pp. 4455‒ 4464.
Kotchenova, S. Y., Vermote, E. F., Levy, R., & Lyapustin, A. (2008), "Radiative transfer codes for atmospheric correction and aerosol retrieval: intercomparison study." Applied Optics. Vol. 47, No. 13, pp. 2215‒ 2226.