Introduction

NuSTAR (the Nuclear Spectroscopic Telescope ARray) is a NASA Small Explorer (SMEX) mission launched in June of 2012 \cite{Harrison_2013} and is first focusing X-ray telescope over the 3-80 keV bandpass. The instrument is composed of two co-aligned hard X-ray optics that focus X-rays onto two nearly identical arrays of CdZnTe detectors. Each detector is a a single monolithic CdZnTe crystal with a pixelated anode readout \cite{Rana_2009}, with each pixel independently triggered and read out by an Application Specific Integrated Circuit (ASIC) \cite{Cook_2000}
composed of two co-aligned, focusing hard X-ray optics covering