The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the
first focusing hard X-ray (5-80 keV ) telescope to orbit. The ground calibration of the three flight optics was
carried out at the Rainwater Memorial Calibration Facility (RaMCaF) built for this purpose. In this article we
present the facility and its use for the ground calibration of the three optics.