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Proceedings Paper

Centroiding and point response function measurements of the mirror/detector combination for the x-ray telescope on the SWIFT gamma-ray burst explorer
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Paper Abstract

The essential optical components of the Swift X-ray Telescope (XRT) are already developed items. They are: the flight spare x-ray mirror from the JET-X/Spectrum-X program and a MOS CCD (CCD22) of the type currently operating in orbit as part of the EPIC focal plane camera on the XMM- Newton. The JET-X mirrors were first calibrated at the Max Plank Institute for Extraterrestrial Physics' (MPE) Panter facility, Garching, Germany in 1996. Half energy widths (HEW) of 16 arc seconds at 1.5 keV were confirmed for the two flight mirrors and the flight spare. The calibration of the flight spare was repeated at Panter in July 2000 in order to establish whether any changes had occurred during the four years that the mirror had been in storage at the OAB, Milan, Italy. This results reported in this paper, confirm that the resolution of the JET-X mirrors has remained stable over this storage period. In an extension of this test program, the flight spare EPIC camera was installed at the focus of the JET-X mirror to simulate the optical system of the Swift X-ray telescope. On-axis and off-axis point spread functions (PSFs) were measured and calibration data sets were used to obtain centroid positions of X-ray point sources. The results confirmed Swift's ability to determine the centroid positions of sources at 100mCrab brightness to better than 1 arc second and provided a calibration of the centroiding process as a function of source flux and off axis angle. The presence of background events in the image frame introduced errors in the centroiding process, making the choice of centroiding algorithm important. Algorithm performance and the trade-off between processing speed and centroiding accuracy were investigated.

Paper Details

Date Published: 25 January 2002
PDF: 12 pages
Proc. SPIE 4497, X-Ray and Gamma-Ray Instrumentation for Astronomy XII, (25 January 2002); doi: 10.1117/12.454228
Show Author Affiliations
Richard M. Ambrosi, Univ. of Leicester (United Kingdom)
Anthony F. Abbey, Univ. of Leicester (United Kingdom)
Ian Hutchinson, Univ. of Leicester (United Kingdom)
Richard Willingale, Univ. of Leicester (United Kingdom)
Sergio Campana, Osservatorio Astronomico di Brera (Italy)
Giancarlo Cusumano, Istituto di Fisica Cosmica con Applicazioni dell' Informatica (Italy)
Wolfgang Burkert, Max-Planck-Institut fuer Extraterrestrische Physik (Germany)
Alan A. Wells, Univ. of Leicester (United Kingdom)
Alexander T. Short, Univ. of Leicester (United Kingdom)
Oberto Citterio, Osservatorio Astronomico di Brera (Italy)
Mauro Ghigo, Osservatorio Astronomico di Brera (Italy)
G. Tagliaferri, Osservatorio Astronomico di Brera (Italy)
Heinrich W. Braeuninger, Max-Planck-Institut fuer Extraterrestrische Physik (Germany)

Published in SPIE Proceedings Vol. 4497:
X-Ray and Gamma-Ray Instrumentation for Astronomy XII
Kathryn A. Flanagan; Oswald H. W. Siegmund, Editor(s)

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