Influence of Solar Cosmic Rays on the Photometric Characteristics of the CCD Detector of the Lasco/C3 Space Telescope

Abstract

Data from the LASCO/C3 space telescope on board the SOHO space observatory are used to study the effect of solar cosmic rays on the telescope’s CCD detector. A special feature of the instrument is that it is located at the L1 Lagrange point of the Sun–Earth system at a distance of 1.5 million km from the planet and is not protected from charged particles by the Earth’s magnetic field. In the period from 2018 to 2024, a decrease in the instrument’s sensitivity is detected at a rate of 0.94 ± 0.03% per year and an increase in signal dispersion at a rate of 4.9 ± 0.1% per year. The main probable reason is the nonuniform decrease in the photometric sensitivity of the detector in different pixels. The effect of charged particles, the source of which are large solar flares, on the detector is also studied. According to the obtained data, the influence of individual flares on the detector is insignificant and cannot be detected within the measurement error. However, this effect can accumulate, which leads to significant changes in the sensitivity of the CCD over several years or more.