### 6SV1 (vector)

**6SV1** (**S**econd **S**imulation of a **S**atellite **S**ignal in the **S**olar **S**pectrum, **V** version **1**) is a basic RT code used for calculation of look-up tables in the MODIS atmospheric correction algorithm. It enables accurate simulations of satellite and plane observations, accounting for elevated targets, use of anisotropic and Lambertian surfaces, and calculation of gaseous absorption. The code is based on the method of successive orders of scattering (SOS) approximations. The effects of polarization are included through the calculation of four components of the Stokes vector. (Download the code)

**References**

S.Y. Kotchenova, E.F. Vermote, R. Matarrese, & F.J. Klemm, Jr., 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, p. 6762-6774.*

S.Y. Kotchenova & E.F. Vermote, 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, p. 4455-4464.*

### Coulson's tabulated values (vector)

**Coulson's tabulated values** represent the complete solution of the Rayleigh problem for a molecular atmosphere. The present set of tables gives the exact distribution and polarization of the reflected and transmitted light in a plane-parallel atmosphere scattering for a wide range of geometrical, surface boundary reflectance and atmospheric optical conditions. These values are generally considered a __benchmark__ for everybody who is willing to validate a vector RT code.

**Reference**

K.L. Coulson, J.V. Dave, and Z. Sekera. Tables related to radiation emerging from a planetary atmosphere with Rayleigh scattering, *University of California Press, 1960*

### MODTRAN (scalar)

**MODTRAN** is a scalar RT code developed by the Air Force Research Laboratory in collaboration with Spectral Sciences, Inc. The code calculates atmospheric transmittance and radiance, and efficiently simulates molecular and cloud-aerosol emission. It assumes a stratified atmosphere and a spherical earth surface. Different atmospheric characteristics, such as temperature, pressure and atmospheric species concentrations need to be specified at the boundaries of each layer. The DISORT (Discrete Ordinates) code is used as a subroutine in MODTRAN to enable the azimuth dependence of multiple scattering. The latest publicly released version of the code is MOD4v3r1 (MODTRAN 4 Version 3 Revision 1), which is available from its authors by request.

**References**

A. Berk et al., MODTRAN4 radiative transfer modeling for atmospheric correction, in Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Research III, *Proc. SPIE 3756, July 1999.*

A. Berk et al., MODTRAN4 Version 3 Revision 1 User's manual, *February 11, 2003.*