CLEAN and multiscale CLEAN for STIX in Solar Orbiter

¹ MIDA, Dipartimento di Matematica, Università di Genova via Dodecaneso 35 16146 Genova, Italy
² University of Applied Sciences and Arts Northwest Switzerland (FHNW), School of Computer Science Bahnhofstrasse 6 Windisch 5210, Switzerland
³ Osservatorio Astrofisico di Torino, Istituto Nazionale di Astrofisica via Osservatorio 20 10025 Pino Torinese, Italy

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Received: 5 September 2025
Accepted: 4 January 2026

Abstract

CLEAN is a well-established deconvolution approach to Fourier imaging at radio wavelengths and hard X-ray energies. One of the main limitations of CLEAN for hard X-ray imaging is that it requires a final convolution step by means of a convolution kernel whose width is strongly user dependent, and moreover, under-resolution effects are often introduced. This paper describes a multiscale version of CLEAN that is specifically tailored to the reconstruction of images from measurements observed by the Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter. Using synthetic STIX data, this study shows that multiscale CLEAN might represent a reliable solution to the two CLEAN limitations described above. Further, we show the performances of CLEAN and its multiscale release in reconstructing experimental real scenarios characterized by complex emission morphologies.