Characterisation Methodology for Persistence and Anti-persistence in IR Detectors for the Euclid and SVOM Space Missions

H2RG and ALFA are the infrared detectors used in the Euclid and SVOM space missions. These types of detectors may be affected by persistence and anti-persistence, phenomena that distort pixel responses after exposure to light due to simultaneous trapping and release of charges within the pixel. These phenomena have shown to cause biases in flux measurements and potentially false detections, among other effects. This article presents a universal methodology for characterising persistence and anti-persistence using differential ramps, Savitzky--Golay filtering, and non-linearity correction. When applied to ground characterisation data, this approach reveals spatial inhomogeneities, environmental dependencies (in particular fluence, flux, temperature and wavelength), and unexpected spectral effects in ALFA. These preliminary results validate the method and pave the way for in-flight correction models capable of meeting the missions' accuracy requirements.