SENTRAN7 is a user friendly interface system to LOWTRAN7 and MODTRAN. The code permits users to rapidly evaluate atmospheric conditions and path geometries. The main features of SENTRAN7 include 1 interactive entry of LOWTRAN7MODTRAN input parameters and directives for their perturbation, 2 intelligent generation of LOWTRAN7MODTRAN input deck images, 3 autonomous post-processing of LOWTRAN7MODTRAN outputs for data extraction, analysis and 3D graphical display, and 4 a help utility. The thrust of the current effort is to incorporate new features and enhancements into SENTRAN7. The new code is called SENTRAN7, Version 2.0. The new features include 1 the capability to impose random and percent perturbations by layer on user-defined profiles of atmospheric constituents, 2 a comprehensive error checking package that checks user-defined profiles of atmospheric constituents, 3 an option to save LOWTRANMODTRAN output as customized file names, and 4 a general purpose module that permits users to view the contents of files of their choosing. SENTRAN7, MODTRAN, LOWTRAN7, Sensitivity studies, Random perturbations, User interface, Users guide.