On the Photometric Accuracy of RHESSI Imaging and Spectrosocopy |
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| Authors: | Aschwanden Markus J Metcalf Thomas R Krucker Säm Sato Jun Conway Andrew J Hurford GJ Schmahl Edward J |
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| Institution: | (1) Lockheed Martin Advanced Technology Center, Solar &; Astrophysics Laboratory, Dept. L9-41, Bldg.252, 3251 Hanover, St., Palo Alto, CA , 94304, U.S.A;(2) Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA , 94720-7450, U.S.A;(3) Dept. of Physics, Montana State University, Bozeman, MO , 59717, U.S.A;(4) Dept. Physics and Astronomy, The Open University, Milton, Keynes, MK7 6AA, U.K;(5) Solar &; Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD~, 20770, U.S.A;(6) Astronomy Dept, University of Maryland, College Park, MD~, 20742, U.S.A; |
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| Abstract: | We compare the photometric accuracy of spectra and images in flares observed with the Ramaty High-Energy Solar Spectroscopic
Imager (RHESSI) spacecraft. We test the accuracy of the photometry by comparing the photon fluxes obtained in different energy
ranges from the spectral-fitting software SPEX with those fluxes contained in the images reconstructed with the Clean, MEM,
MEM-Vis, Pixon, and Forward-fit algorithms. We quantify also the background fluxes, the fidelity of source geometries, and
spatial spectra reconstructed with the five image reconstruction algorithms. We investigate the effects of grid selection,
pixel size, field of view, and time intervals on the quality of image reconstruction. The detailed parameters and statistics
are provided in an accompanying CD-ROM and web page. We find that Forward-fit, Pixon, and Clean have a robust convergence
behavior and a photometric accuracy in the order of a few percent, while MEM does not converge optimally for large degrees
of freedom (for large field of view and/or small pixel sizes), and MEM-Vis suffers in the case of time-variable sources. This
comparative study documents the current status of the RHESSI spectral and imaging software, one year after launch.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/B:SOLA.0000021801.83038.aa |
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