Cornelius J. (Nelis) Willers completed a B.Eng (Honns) Electronics Engineering degree at the University of Pretoria in 1976 and an MS (Optical Engineering) degree at the University of Arizona in 1983. He is registered as a professional/chartered engineer. His 37 years of work experience includes electro-optical system development, system architecture and systems engineering, software development, and infrared scene simulation. His most notable achievements include being the chief architect and technical lead in establishing an imaging missile seeker technology base, and in the process, spearheading advanced physics-based infrared image simulation. The simulation system is currently used for a number of different applications in laboratories across the globe. His current interests include infrared signature measurement and data analysis, infrared system modeling and simulation, and the development of aircraft self-protection systems. He is leading the open-source, Python-based pyradi radiometry toolkit project. He has published a large number of technical and research reports. His conference paper topics include infrared system modeling and simulation, and the modeling of military conflict using agent-based techniques. He teaches radiometry and infrared system design in short courses and at a masters-degree level at the University of Pretoria. He maintains pyradi, a computational radiometry toolkit, available at https://code.google.com/p/pyradi/, with pyradi tutorials at https://github.com/NelisW/ComputationalRadiometry.