The NuSTAR (Nuclear Spectroscopic Telescope ARray) spacecraft, set to launch in February 2012, will be capable of performing some of the most detailed X-Ray astronomical observations ever made in the 5-80 keV energy range. The source positioning accuracy of the telescope is limited by the ability to correct for thermal distortions and movement of the optics relative to the focal plane, as well as the overall aspect of the optics bench. These are more than average for space-based observatories, because a ten meter deployable mast, utilized to reduce the size of the launch vehicle, allows for significant thermal distortions. In order to predict the on-orbit performance of the instrument, the NuSTAR team has developed NuSIM, a software based simulation of NuSTAR. My SURF has consisted mainly of the generation of parametrically-changing databases of the mast geometry in order to interrogate the robustness of the on-orbit accuracy of the science system’s data reconstruction algorithms within NuSIM. This method has been used to test the Finite Element Model (FEM) simulation results of the observatory’s structure, by using a conceptual model of the mast geometry. Furthermore, I have explored additional possible sources of error, such as calculating light scattering from the simulated optics. This project has contributed to the verification of key science requirements of NuSTAR in advance, most notably the level one requirement on localization of a point source in celestial coordinates.