Share Email Print
cover

Proceedings Paper

Flight spectral response of the ACIS instrument
Author(s): Paul P. Plucinsky; Norbert S. Schulz; Herman L. Marshall; Catherine E. Grant; George Chartas; Divas Sanwal; Marcus Teter; Alexey A. Vikhlinin; Richard J. Edgar; Michael W. Wise; Glenn E. Allen; Shanil N. Virani; Joseph M. DePasquale; Michael T. Raley
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

We discuss the flight calibration of the spectral response of the Advanced CCD Imaging Spectrometer (ACIS) on-board the Chandra X-ray Observatory (CXO). The spectral resolution and sensitivity of the ACIS instrument have both been evolving over the course of the mission. The spectral resolution of the frontside-illuminated (FI) CCDs changed dramatically in the first month of the mission due to radiation damage. Since that time, the spectral resolution of the FI CCDs and the Backside-illuminated (BI) CCDs have evolved gradually with time. We demonstrate the efficacy of charge-transfer inefficiency (CTI) correction algorithms which recover some of the lost performance. The detection efficiency of the ACIS instrument has been declining throughout the mission, presumably due to a layer of contamination building up on the filter and/or CCDs. We present a characterization of the energy dependence of the excess absorption and demonstrate software which models the time dependence of the absorption from energies of 0.4 keV and up. The spectral redistribution function and the detection efficiency are well-characterized at energies from 1.5 to 8.0~keV primarily due to the existence of strong lines in the ACIS calibration source in that energy range. The calibration at energies below 1.5 keV is challenging because of the lack of strong lines in the calibration source and also because of the inherent non-linear dependence with energy of the CTI and the absorption by the contamination layer. We have been using data from celestial sources with relatively simple spectra to determine the quality of the calibration below 1.5 keV. We have used observations of 1E0102.2-7219 (the brightest supernova remnant in the SMC), PKS2155-304 (a bright blazar), and the pulsar PSR~0656+14 (nearby pulsar with a soft spectrum), since the spectra of these objects have been well-characterized by the gratings on the CXO. The analysis of these observations demonstrate that the CTI correction recovers a significant fraction of the spectral resolution of the FI CCDs and the models of the time-dependent absorption result in consistent measurements of the flux at low energies for data from a BI (S3) CCD.

Paper Details

Date Published: 11 March 2003
PDF: 12 pages
Proc. SPIE 4851, X-Ray and Gamma-Ray Telescopes and Instruments for Astronomy, (11 March 2003); doi: 10.1117/12.461473
Show Author Affiliations
Paul P. Plucinsky, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Norbert S. Schulz, Massachusetts Institute of Technology (United States)
Herman L. Marshall, Massachusetts Institute of Technology (United States)
Catherine E. Grant, Massachusetts Institute of Technology (United States)
George Chartas, The Pennsylvania State Univ. (United States)
Divas Sanwal, The Pennsylvania State Univ. (United States)
Marcus Teter, The Pennsylvania State Univ. (United States)
Alexey A. Vikhlinin, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Richard J. Edgar, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Michael W. Wise, Massachusetts Institute of Technology (United States)
Glenn E. Allen, Massachusetts Institute of Technology (United States)
Shanil N. Virani, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Joseph M. DePasquale, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Michael T. Raley, Harvard-Smithsonian Ctr. for Astrophysics (United States)


Published in SPIE Proceedings Vol. 4851:
X-Ray and Gamma-Ray Telescopes and Instruments for Astronomy
Joachim E. Truemper; Harvey D. Tananbaum, Editor(s)

© SPIE. Terms of Use
Back to Top