Highlights of the Cluster Ion Spectrometry (CIS) experiment, following 24 years of successful operation

Following 24 years of space operations, during which the Cluster spacecraft have greatly advanced our understanding of the dynamics of the Earth’s magnetosphere and its interaction with the solar wind, the first of the four-spacecraft performed a controlled re-entry into the Earth’s atmosphere in September 2024. The CIS (Cluster Ion Spectrometry) experiment has been one of the spearheads of the Cluster mission, with more than 1300 science papers published, based on the analysis of the data provided by this experiment. Major breakthroughs were possible in topics such as collisionless shocks, boundary layers, substorm development, auroral physics, the dynamics of the plasmasphere, ionospheric ion outflow and escape, ring current dynamics, or extreme space weather events. All the high-resolution CIS data are archived and publicly available at the Cluster Science Archive (https://csa.esac.esa.int).