The goal of this working group is to provide a comprehensive “tool book” of analysis techniques for ionospheric multi-satellite missions. The immediate need for this book is motivated by the upcoming ESA Swarm satellite mission, but the tools that will be described are general and can be used for any future ionospheric multi-satellite mission with comparable instrumentation. The title is intentionally chosen similar to the earlier ISSI book that was motivated by the ESA Cluster multi-satellite mission in the magnetosphere. In the ionosphere, a different plasma environment prevails that is dominated by interactions with neutrals, and the Earth’s main magnetic field clearly dominates the total magnetic field. Further, an ionospheric multi-satellite mission has different research goals than a magnetospheric one, namely in addition to the study of the immediate plasma environment and its coupling to other regions also the study of the Earth’s main magnetic field and its anomalies caused by core, mantle, or crustal sources. Therefore, different tools are needed for an ionospheric multi-satellite mission as compared to a magnetospheric one, and different parameters are desired to be determined with those tools. Besides currents, electric fields and plasma convection, such parameters include ionospheric conductances, Joule heating, neutral gas densities and neutral winds.