Cluster II

Launched in the summer of 2000, Cluster II was part of the Solar Terrestrial Science Programme Cornerstone (together with SOHO) of ESA's Horizon 2000 programme. The quartet of Cluster spacecraft orbited the Earth exploring the magnetosphere and solar wind close to Earth. The mission was brought to a close on September 8th 2024 when the Salsa spacecraft became the first of the four to re-enter the atmosphere.

Each Cluster spacecraft carried a suite of instruments to study the waves, fields and particles in the magnetosphere. Part of that suite was the PEACE (Plasma Electron And Current Experiment) instrument. Two PEACE sensors on each spacecraft measured the 3D velocity distributions of the electrons that make up part of the space plasma surrounding the Earth.

The PEACE instrument was designed and built by MSSL. MSSL are responsible for the operation of the instruments and the processing and calibration of the raw instrument data. These data are then delivered to the Cluster Active Archive to enable scientists from around the world to participate in the analysis of Cluster data. Prof. Andrew Fazakerley is the instrument's Principal Investigator.

PEACE is one part of a family of particle detectors developed for investigating a range of space plasmas. Instruments based on the heritage of PEACE have been flown on the Cassini and spacecraft and are currently flying onboard the Solar Orbiter spacecraft.