The Arizona's Program for the Analysis of Radiation Transfer/Program for the Analysis of Diffracted Energy (APART/PADE) stray light analysis program has been under continuous development and maintenance for about 15 years, and represents over 25 man years of development. APART/PADE is a deterministic computer program that can be used to calculate the propagation of stray radiation via scatter, diffraction, or thermal emission, and it can mix and match the modes in any manner. It has undergone dramatic changes in its structure, code, capabilities, and even its name, in the past seven years. The later change in name has been necessary in order to keep it properly in step with the program's capabilities. The latest enhancement allows the program to perform the deterministic calculations using real rays, thereby removing one of the long-time limitations of APART/PADE. Greatly enhanced graphics have added a new dimension by allowing the user to clearly view the modeled sensor from various positions in order to see that the system is correctly modeled. Internal and user-definable macro and help files, and even user-definable Fortran BRDF subroutines can open up virgin territory to meet the needs of the users. A simple, single baffle command allows the user to direct the program to make a first cut baffle design for eccentric pupil designs, from the entrance aperture to the detector if desired. Many of the other new factors are described in the following text.