Introduction

Two volumes, ISSI Scientific Reports, SR-001: Analysis Methods for Multi-Spacecraft Data and SR-008: Multi-Spacecraft Analysis Methods revisited, were published to document the growing toolset using the multi-spacecraft dataset being collected by Cluster. Two volumes, ISSI Scientific Reports, SR-001: Analysis Methods for Multi-Spacecraft Data and SR-008: Multi-Spacecraft Analysis Methods revisited, were published to document the growing toolset using the multi-spacecraft dataset being collected by Cluster. Cluster was the first phased, multi-spacecraft mission, currently in its 19th year of full science operations, to maintain a close configuration of four spacecraft, evolving around an orbit covering many mid- to outer magnetospheric regions. Such a configuration allowed the estimation of plasma and field gradients, as well as wave vector determinations for the first time. A range of spatial scales were accessed through a sequence of orbital manoeuvres, predominantly from meso- to large scale spacecraft separation distances. Although covering a vast array of science targets, Cluster did not cover the small (sub-ion) spatial scales and did not access the low-Earth orbit (LEO) altitudes suitable for the upper ionosphere. approximately east-west 2014