Open Source Toolkit for Reentry Object ModelingChristopher L. Ostrom II Predicting the mass, position, and velocity of an object during its reentry are critical to satisfy NASA and ESA requirements. This thesis outlines a 3-D orbit and mass determination system for use on low earth orbit as applicable to general objects, of various material and size. The solution uses analytical models to calculate heat flux and aerodynamic drag, with some basic numerical models for simple orbit propagation and mass flow rate due to ablation. The system outlined in this thesis currently provides a framework for rough estimates of demise altitude and final mass, but also allows for many potential accuracy and speed improvements. 77 aerospace materials were tested, in solid spheres, cubes, and cylinders; it was found that materials with low latent heat of fusion (less than 10