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Proceedings Paper

Absolute calibration of the AXAF telescope effective area
Author(s): Edwin M. Kellogg; Lester M. Cohen; Richard J. Edgar; Ian N. Evans; Mark D. Freeman; Terrance J. Gaetz; Diab Jerius; Walter C. McDermott; Phillip J. McKinnon; Stephen S. Murray; William A. Podgorski; Daniel A. Schwartz; Leon P. Van Speybroeck; Bradford J. Wargelin; Martin V. Zombeck; Martin C. Weisskopf; Ronald F. Elsner; Stephen L. O'Dell; Allyn F. Tennant; Jeffery J. Kolodziejczak; Gordon P. Garmire; John A. Nousek; Stefan Kraft; Frank Scholze; R. Thornagel; Gerhard Ulm; Kathryn A. Flanagan; Daniel Dewey; Mark W. Bautz; Scott C. Texter; Jonathan W. Arenberg; R. R. Carlson
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Paper Abstract

The prelaunch calibration of AXAF encompasses many aspects of the telescope. In principle, all that is needed is the complete point response function. This is, however, a function of energy, off-axis angle of the source, and operating mode of the facility. No single measurement would yield the entire result. Also, any calibration made prior to launch will be affected by changes in conditions after launch, such as the change from one g to zero g. The reflectivity of the mirror and perhaps even the detectors can change as well, for example by addition or removal of small amounts of material deposited on their surfaces. In this paper, we give a broad view of the issues in performing such a calibration, and discuss how they are being addressed in prelaunch preparation of AXAF. As our title indicates, we concentrate here on the total throughput of the observatory. This can be thought of as the integral of the point response function, i.e. the encircled energy, out to the largest practical solid angle for an observation. Since there is no standard x-ray source in the sky whose flux is well known to the approximately 1% accuracy we are trying to achieve, we must do this calibration on the ground. We also must provide a means for monitoring any possible changes in this calibration from prelaunch until on-orbit operation can transfer the calibration to a celestial x-ray source whose emission is stable. In the paper, we analyze the elements of the absolute throughput calibration, which we call the effective area. We review the requirements for calibrations of components or subsystems of the AXAF facility, including the mirror, detectors, and gratings. We show how it is necessary to have an absolute calibrated detection system available during the prelaunch calibrations to measure the flux in the x-ray beam used for calibrating AXAF. We show how it is necessary to calibrate this ground-based detection system at standard man-made x-ray sources, such as electron storage rings. We present the status of all these calibrations, with indications of the measurements remaining to be done, even though the measurements on the AXAF flight optics and detectors will have been completed by the time this paper is presented. We evaluate progress toward the goal of making 1% measurements of the absolute x-ray flux from astrophysical sources, so that comparisons can be made with their emission at other wavelengths, in support of observations such as the Sunyaev-Zeldovitch effect, which can give absolute distance measurements independent of the traditional distance measuring techniques in astronomy.

Paper Details

Date Published: 11 July 1997
PDF: 11 pages
Proc. SPIE 3113, Grazing Incidence and Multilayer X-Ray Optical Systems, (11 July 1997); doi: 10.1117/12.278885
Show Author Affiliations
Edwin M. Kellogg, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Lester M. Cohen, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Richard J. Edgar, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Ian N. Evans, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Mark D. Freeman, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Terrance J. Gaetz, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Diab Jerius, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Walter C. McDermott, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Phillip J. McKinnon, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Stephen S. Murray, Harvard-Smithsonian Ctr. for Astrophysics (United States)
William A. Podgorski, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Daniel A. Schwartz, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Leon P. Van Speybroeck, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Bradford J. Wargelin, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Martin V. Zombeck, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Martin C. Weisskopf, NASA Marshall Space Flight Ctr. (United States)
Ronald F. Elsner, NASA Marshall Space Flight Ctr. (United States)
Stephen L. O'Dell, NASA Marshall Space Flight Ctr. (United States)
Allyn F. Tennant, NASA Marshall Space Flight Ctr. (United States)
Jeffery J. Kolodziejczak, Universities' Space Research Association (United States)
Gordon P. Garmire, The Pennsylvania State Univ. (United States)
John A. Nousek, The Pennsylvania State Univ. (United States)
Stefan Kraft, Physikalisch-Technische Bundesanstalt (Netherlands)
Frank Scholze, Physikalisch-Technische Bundesanstalt (Germany)
R. Thornagel, Physikalisch-Technische Bundesanstalt (Germany)
Gerhard Ulm, Physikalisch-Technische Bundesanstalt (Germany)
Kathryn A. Flanagan, Massachusetts Institute of Technology (United States)
Daniel Dewey, Massachusetts Institute of Technology (United States)
Mark W. Bautz, Massachusetts Institute of Technology (United States)
Scott C. Texter, TRW, Inc. (United States)
Jonathan W. Arenberg, TRW, Inc. (United States)
R. R. Carlson, TRW, Inc. (United States)


Published in SPIE Proceedings Vol. 3113:
Grazing Incidence and Multilayer X-Ray Optical Systems
Richard B. Hoover; Arthur B. C. Walker, Editor(s)

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