A count-based imaging model for the Spectrometer/Telescope for Imaging X-rays (STIX) in Solar Orbiter

Abstract

The Spectrometer/Telescope for Imaging X-rays (STIX) will look at solar flares across the hard X-ray window provided by the Solar Orbiter cluster. Similarly to the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), STIX is a visibility-based imaging instrument, which will ask for Fourier-based image reconstruction methods. However, in this paper we show that, as for RHESSI, also for STIX count-based imaging is possible. Specifically, here we introduce and illustrate a mathematical model that mimics the STIX data formation process as a projection from the incoming photon flux into a vector made of 120 count components. Then we test the reliability of Expectation Maximization for image reconstruction in the case of several simulated configurations typical of flare morphology.

submitted to A&A

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• Visibility Interpolation in Solar Hard X-ray Imaging: Application to RHESSI and STIX
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• First hard X-ray imaging results by Solar Orbiter STIX