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.
NuSTAR is a hard X-ray satellite experiment to be launched in 2012. Two optics with 10.15 m focal length focus Xrays
with energies between 5 and 80 keV onto CdZnTe detectors located at the end of a deployable mast. The FM1 and
FM2 flight optics were built at the same time based on the same design and with very similar components, and thus the
performance of both is expected to be very similar. We provide an overview of calibration data that is being used to
build an optics response model for each optic and describe initial results for energies above 10 keV from the ground
calibration of the flight optics. From a preliminary analysis of the data, our current best determination of the overall
HPD of both the FM1 and FM2 flight optics is 52", and nearly independent of energy. The statistical error is negligible,
and a preliminary estimate of the systematic error is of order 4". The as-measured effective area and HPD meet the toplevel
NuSTAR mission sensitivity requirements.