24 July 2014 In-flight PSF calibration of the NuSTAR hard X-ray optics
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We present results of the point spread function (PSF) calibration of the hard X-ray optics of the Nuclear Spectroscopic Telescope Array (NuSTAR). Immediately post-launch, NuSTAR has observed bright point sources such as Cyg X-1, Vela X-1, and Her X-1 for the PSF calibration. We use the point source observations taken at several off-axis angles together with a ray-trace model to characterize the in-orbit angular response, and find that the ray-trace model alone does not fit the observed event distributions and applying empirical corrections to the ray-trace model improves the fit significantly. We describe the corrections applied to the ray-trace model and show that the uncertainties in the enclosed energy fraction (EEF) of the new PSF model is (approximately less than) 3% for extraction apertures of R (approximately greater than) 60″ with no significant energy dependence. We also show that the PSF of the NuSTAR optics has been stable over a period of ~300 days during its in-orbit operation.
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Hongjun An, Hongjun An, Kristin K. Madsen, Kristin K. Madsen, Niels J. Westergaard, Niels J. Westergaard, Steven E. Boggs, Steven E. Boggs, Finn E. Christensen, Finn E. Christensen, William W. Craig, William W. Craig, Charles J. Hailey, Charles J. Hailey, Fiona A. Harrison, Fiona A. Harrison, Daniel K. Stern, Daniel K. Stern, William W. Zhang, William W. Zhang, } "In-flight PSF calibration of the NuSTAR hard X-ray optics", Proc. SPIE 9144, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray, 91441Q (24 July 2014); doi: 10.1117/12.2055481; https://doi.org/10.1117/12.2055481

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