BackForwardInstrument:  CPI 

Instrument details
Acronym CPI
Full name Comprehensive Plasma Investigation
Purpose To measure the 3-D plasma in the Earth's magnetotail. The plasma data are correlated with the magnetic field, plasma waves, electric particles, and auroral imaging data to determine magnetotail plasma dynamics
Short description Hot plasma and ion composition analyser in the range 1 eV - 50 keV with Z ranging from 1 to 8, and solar wind analyser in the range 0.15-7 keV/particle
Background Part of a package of instruments to observe the Magnetosphere by navigating across its tail
Scanning Technique Travelling cross the Magnetosphere in a highly-elliptical orbit
Resolution N/A
Coverage / Cycle Magnetospheric volume
Mass Power Data Rate


Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 1992-10-02 to ≥2022
Last update: 2021-12-16
Detailed characteristics
Satellites this instrument is flying on

Note: a red tag indicates satellites no longer operational, a green tag indicates operational satellites, a blue tag indicates future satellites

Instrument classification
  • Solar and space environment monitors
  • Energetic particle spectrometer
WIGOS Subcomponents
  • Subcomponent 2
  • Electron sensor [cross magnetosphere]
  • Proton sensor [cross magnetosphere]
  • Alpha-particle sensor [cross magnetosphere]
  • Heavy ion sensor [cross magnetosphere]
  • Subcomponent 3
  • Heavy ions mass spectrometer [from LEO and HEO]
Mission objectives
Primary mission objectives
  • Alpha particles differential directional flux
  • Electron differential directional flux
  • Heavy ion flux energy and mass spectrum
  • Proton differential directional flux
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Tentative Evaluation of Measurements

The following list indicates which measurements can typically be retrieved from this category of instrument. To see a full Gap Analysis by Variable, click on the respective variable.

Note: table can be sorted by clicking on the column headers
VariableRelevance for measuring this variableOperational limitationsExplanation
Electron differential directional flux2 - very highNo specific limitation.Magnetosphere, low energy (up to 40 keV)
Proton differential directional flux2 - very highNo specific limitation.Magnetosphere, low energy (up to 40 keV)
Alpha particles differential directional flux4 - fairNo specific limitation.Cross-magnetosphere. Energy range of major interest (over 10 up to 100 MeV/n)
Heavy ion flux energy and mass spectrum2 - very highNo specific limitation.Cross-magnetosphere. Low-medium energy range (<10 up to 100 MeV/n)