The RHESSI Imaging Concept |
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Authors: | Hurford GJ Schmahl EJ Schwartz RA Conway AJ Aschwanden MJ Csillaghy A Dennis BR Johns-Krull C Krucker S Lin RP McTiernan J Metcalf TR Sato J Smith DM |
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Institution: | (1) Space Sciences Laboratory, University of California, Berkeley, CA, 94720, U.S.A;(2) Astronomy Department, University of Maryland, College Park, MD, 20742, U.S.A;(3) Lab for Astronomy and Solar Physics, NASA Goddard Space Flight Center, USA;(4) Department of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, U.K;(5) Solar & Astrophysics Laboratory, Dept. L9-41, Lockheed Martin Advanced Technology Center, Palo Alto, CA, 94304, U.S.A;(6) University of Applied Sciences, CH-5210 Windisch, Switzerland;(7) Department of Physics and Astronomy, Rice University, Houston, TX, 77005, U.S.A;(8) Department of Physics, University of California, Berkeley, CA, 94720, U.S.A;(9) Department of Physics, Montana State University, Bozeman, MT, 59717, U.S.A |
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Abstract: | The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) observes solar hard X-rays and gamma-rays from 3 keV to
17 MeV with spatial resolution as high as 2.3 arc sec. Instead of focusing optics, imaging is based on nine rotating modulation
collimators that time-modulate the incident flux as the spacecraft rotates. Starting from the arrival time of individual photons,
ground-based software then uses the modulated signals to reconstruct images of the source. The purpose of this paper is to
convey both an intuitive feel and the mathematical basis for this imaging process. Following a review of the relevant hardware,
the imaging principles and the basic back-projection method are described, along with their relation to Fourier transforms.
Several specific algorithms (Clean, MEM, Pixons and Forward-Fitting) applicable to RHESSI imaging are briefly described. The
characteristic strengths and weaknesses of this type of imaging are summarized. |
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