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Proceedings Paper

Ground-to-orbit transfer of the AXAF-I flux scale: in-situ contamination monitoring of x-ray telescopes
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Paper Abstract

Grazing-incidence optics are quite sensitive to molecular and particulate contamination. For NASA's Advanced X-ray Astrophysics Facility-Imaging (AXAF-I), the sensitivities of the flux scale to contamination on the mirrors' surfaces are typically 0.4% per angstrom of a hydrocarbon film and 0.4% per 10-5 fractional areal coverage by particulates. In view of the goal of calibrating the flux-scale to a few-percent accuracy, it is clearly essential to adopt rigorous procedures to control and to monitor both molecular and particulate contamination. Traditional approaches to monitoring contamination for optical surfaces--using optical witness samples in conjunction with facility airborne monitors--are essential during ground operation. However, such techniques do not directly monitor changes in x-ray reflectance or even in contamination of the mirrors themselves; nor can they determine differences in contamination between ground calibration and orbital operations. In order to transfer the AXAF-I flux scale from ground to orbit, AXAF-I will incorporate x-ray- fluorescing radionuclide sources in the forward contamination cover. Comparison of the telescope's throughput, for these x rays, at ground calibration with that at the commencement of orbital operations will validate the flux-scale calibration. If ground-to-orbit changes were to occur, such a comparison would facilitate correction of the flux scale.

Paper Details

Date Published: 11 November 1994
PDF: 11 pages
Proc. SPIE 2279, Advances in Multilayer and Grazing Incidence X-Ray/EUV/FUV Optics, (11 November 1994); doi: 10.1117/12.193152
Show Author Affiliations
Ronald F. Elsner, NASA Marshall Space Flight Ctr. (United States)
Marshall K. Joy, NASA Marshall Space Flight Ctr. (United States)
Stephen L. O'Dell, NASA Marshall Space Flight Ctr. (United States)
Brian D. Ramsey, NASA Marshall Space Flight Ctr. (United States)
Martin C. Weisskopf, NASA Marshall Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 2279:
Advances in Multilayer and Grazing Incidence X-Ray/EUV/FUV Optics
Richard B. Hoover; Arthur B. C. Walker Jr., Editor(s)

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