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Siarkowski M., Mrozek T., Sylwester J., Litwicka M., Dąbek M. (2020). The non-Fourier image reconstruction method for the STIX instrument. Open Astronomy, Volume 29, Issue 1, pp.220-230, doi: 10.1515/astro-2020-0022.

Abstrakt/Abstract: In this work we aimed to develop the image reconstruction algorithm without any analytical simplicationsand restrictions. In our method we abandon Fourier’s approach to image reconstruction, and instead use the number ofcounts recorded in each detector pixel, and then reconstruct each image using a classical Richardson-Lucy algorithm.Among similar works performed in the past, our approach is based, for the rst time, on the real geometry of STIX. Wemade a preliminary analysis of expected dierences in STIX imaging which may occur due to usage of slightly dierentgeometries. The other dierence is that we use single-pixel-response maps. Namely, knowing the instrument geometrywe are able to calculate the detector response for point sources covering entire the solar disc. Next, we iteratively combinethem with varying weights until the best match between reconstructed and observed detector responses is achieved.Preliminary tests revealed that the developed algorithm reproduces high quality images. The algorithm is moderatelyfast, but the result comparable to CLEAN algorithm is obtained within 20-50 iteration steps which takes less than 2seconds on typical portable computer conguration. The location, size and intensity of reconstructed sources are veryclose to simulated ones. Therefore the algorithm is very well suited for the detailed photometry of the solar HXR sources.Moreover, its simplicity allows to improve photon transmission calculation in case of any grids uncertainties measuredafter the launch.

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