BackForwardInstrument:  SEM/MEPED 

Instrument details
Full name SEM / Medium energy proton detector
Purpose Space environment at platform level
Short description Provides both directional (nadir and 90° from nadir) and omni-directional measurements. Directional: protons are measured in 6 bands in the energy range 0.03-6.9 MeV, electrons in thee bands in the range 30-300 keV. Omni-directional: proton energy in the ranges > 16 MeV, >35 MeV, > 70 MeV and > 140 MeV
Background Part of the packages named SEM (Space Environment Monitor) until NOAA-14, and SEM/2 (Space Environment Monitor - 2) from NOAA-15 onward and on MetOp
Scanning Technique N/A (in-situ measurements)
Resolution N/A
Coverage / Cycle N/A
Mass Power Data Rate


Providing Agency NOAA
Instrument Maturity Flown on operational programme
Utilization Period: 1979 to 2027
Last update: 2022-12-19
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 1
  • In-situ plasma probes, and energetic particle spectrometers and magnetometers at GEO and LEO, and magnetic field at GEO
  • Electron sensor at LEO
  • Proton sensor at LEO
  • Plasma density sensor at LEO
  • Plasma temperature sensor at LEO
  • Plasma velocity sensor at LEO
Mission objectives
Primary mission objectives
  • Electron integral directional flux
  • Proton integral directional flux
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
Note: * Primary mission objective.
VariableRelevance for measuring this variableOperational limitationsExplanation
Electron integral directional flux*4 - fairNo specific limitation.Sun pointing, low and medium energy (up to 400 keV)
Proton integral directional flux*4 - fairNo specific limitation.Sun pointing, low, medium and high energy (up to over 1000 keV)