Derivation of requirements for calibrating the advanced X-Ray astrophysics facility (AXAF) telescope

J. P. Hughes, D. A. Schwartz, D. M. Worrall, M. V. Zombeck

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)


The Advanced X-ray Astrophysics Facility (AXAF) will be a 15-year lifetime observatory, intended to investigate the nature of celestial objects and physical processes, and to study the history and evolution of the universe. We are investigating how to translate the requirements for scientific measurements (e.g., fluxes, spectra and sizes of sources) into operational requirements for the calibration of the AXAF X-ray mirrors and scientific instruments. We carry out a complete simulation of the process of acquiring data from an X-ray source, and analyze the data using various calibration errors. We generate an ideal spectrum of an X-ray source and convolve it with hypothetical "true" mirror and instrument responses to simulate an expected spectrum. This spectrum may be randomized, independently, a large number of times to simulate the effects of photon statistics. These data are analyzed as if they were actual flight data. We introduce controlled perturbations in the mirror and instrument responses used in the analysis. Such perturbations may include: The neglect of extended X-ray absorption fine structure (EXAFS), errors in the jump of absorption coefficients across atomic shell energies, changes in the optical constants of mirror coatings, effects of dust contamination, or arbitrary calibration measurement errors. We perform x2 fits, and assess the changes in the fitted results from those resulting when the data are analyzed with the "true" mirror and instrument responses. In this paper we discuss an initial study of exponential energy spectra with galactic absorption. We assume perfect detector response and consider only the effects of errors in the on-axis effective area of the mirror.

Original languageEnglish
Pages (from-to)380-386
Number of pages7
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 21 Dec 1988


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