Image calibration between the Extreme Ultraviolet Imagers on Solar Orbiter and the Solar Dynamics Observatory

¹ Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
² High Altitude Observatory, National Center for Atmospheric Research, 3080 Center Green Dr, Boulder, USA
³ Kanzelhöhe Observatory for Solar and Environmental Research, University of Graz, Treffen am Ossiacher See, Austria
⁴ European Space Agency (ESA)-ECSAT, Fermi Avenue, Harwell, UK
⁵ Department of Physics, University of Oxford, Oxford, UK
⁶ Image Processing Laboratory (IPL) Department Universitat de València, València, Spain
⁷ Solar-Terrestrial Centre of Excellence (SIDC), Royal Observatory of Belgium, Ringlaan 3 Av. Circulaire, 1180 Brussels, Belgium
⁸ Trillium Technologies Inc. (Trillium USA), 8668 John Hickman Pkwy, STE 301 Frisco, TX, USA

^⋆ Corresponding author: christoph.schirninger@uni-graz.at

Received: 14 July 2025
Accepted: 19 September 2025

Abstract

To study and monitor the Sun and its atmosphere, various space missions have been launched in the past decades. With rapid improvement in technology and different mission requirements, the data products are subject to constant change. However, for such long-term studies as solar variability or multi-instrument investigations, uniform data series are required. In this study, we built on and expanded the instrument-to-instrument translation (ITI) framework, which provides unpaired image translations. We applied the tool to data from the Extreme Ultraviolet Imager (EUI), specifically the Full Sun Imager (FSI) on Solar Orbiter and the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). This approach allowed us to create a homogeneous dataset that combines the two extreme ultraviolet (EUV) imagers in the 174/171 Å and 304 Å channels. We demonstrate that ITI is able to provide image calibration between Solar Orbiter and SDO EUV imagers, independent of the varying orbital position of Solar Orbiter. The comparison of the intercalibrated light curves derived from 174/171 Å and 304 Å filtergrams from EUI and AIA shows that ITI can provide uniform data series that outperform a standard baseline calibration. We evaluate the perceptual similarity in terms of the Fréchet inception distance, which demonstrates that ITI achieves a significant improvement of perceptual similarity between EUI and AIA. The study provides intercalibrated observations from Solar Orbiter/EUI/FSI with SDO/AIA, enabling a homogeneous dataset suitable for solar cycle studies and multi-viewpoint investigations.