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Cluster II

The launch of Cluster from the Baikonur Cosmodrome
(Credit: ESA)

The Cluster II mission and the Solar Heliospheric Observatory (SOHO) comprise the Solar Terrestrial Science Programme (STSP) first Cornerstone of European Space Agency’s (ESA) Horizon 2000 Programme. Together Cluster II and SOHO investigate the relationship between the Sun and the Earth’s environment.

Cluster II consists of a collection of four satellites free flying in a tetrahedral formation around Earth. ESA launched the Cluster II satellites in pairs from the Baikonur Cosmodrome in Kazakhstan in July and August of 2000.

The satellites relay the most detailed ever information in three dimensions about how the solar wind affects the Earth's magnetosphere. Each satellite has the same eleven instruments on board sampling the plasma environment around the Earth, including magnetic and electric fields, ions and electrons. The relative positions and distances of the four satellites can be adapted to the various regions of scientific interest in the Earth's magnetosphere. Cluster is currently approved to the end of 2016 (subject to a mid-term review in 2014).

The Cluster Joint Science Operations Centre (JSOC) was set up within RAL Space to support the ESA Project Science Team, the instrument teams and ESA's Mission Operation Centre. JSOC designed, developed, implemented, tested and now operates the system and tools required to support Cluster II science operations, under contract to ESA. In August 2010 Cluster celebrates its tenth year in space.

The Cluster Spacecraft
(Credit: ESA)

Instruments on Cluster

  • FluxGate Magnetometer (link opens in a new window) (FGM), located on a 5 metre boom, measures magnetic fields along the Cluster orbit.
  • Electron Drift Instrument (link opens in a new window) (EDI) measures the strength of the electric field.
  • Electric Field and Wave (link opens in a new window) (EFW) experiment uses sensors on four 50 metre long wire booms to measure electric field in order to study plasma convection and waves.
  • Cluster Ion Spectrometry (link opens in a new window)(CIS) experiment analyses the composition, mass and distribution functions of ions in the nearby (magnetosphere) space plasma and solar wind.
  • Research with Adaptive Particle Imaging Detectors (link opens in a new window) (RAPID) studies the highest energy electrons and ions.
  • Plasma Electron And Current Experiment (link opens in a new window) (PEACE) studies electrons in the space plasma.
  • Active Spacecraft Potential Control (link opens in a new window) (ASPOC) experiment prevents a build-up of positive electrical charge on the spacecraft (earths it) by emitting ions at a rate adjusted according to the measurements from EFW and PEACE.
  • Spatio-Temporal Analysis of Field Fluctuations  (link opens in a new window)(STAFF) experiment, on the end of a 5 metre boom, looks at rapid variations in the magnetic fields (waves).
  • Wide Band Data (link opens in a new window) (WBD) instrument listens for radio whistles and hisses from the particles that bounce around near the Earth's magnetic poles.

    Assembling Cluster
    (Credit: ESA)

  • Waves of High frequency and Sounder for Probing Electron density by Relaxation (link opens in a new window) (WHISPER) experiment sends out radio pulses from two 50 metre long wire booms and detects their echo revealing particle concentration as well as monitoring natural wave activity.

  • Digital Wave Processing (link opens in a new window) (DWP) experiment is the control and computing brain for the wave experiments (WEC).
  • Wave Experiment Consortium (link opens in a new window) (WEC) consists of five of the Cluster instruments (DWP, EFW, STAFF, WBD, WHISPER) designed to measure electric and magnetic fields and waves, grouped together in order to maximise resources such as power and telemetry information.

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Last updated: 19 August 2019


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