BackForwardInstrument:  SEM/HEPAD 

Instrument details
Full name SEM / High Energy Proton and Alpha Particles Detector
Purpose Observation of high-energy protons and alpha-particles at platform level
Short description Assemblage of detectors for the energy ranges 350 to over 700 Mev (protons), and 2.56 to over 3.4 GeV (alpha-particles)
Background Part of the SEM (Space Environment Monitor) package
Scanning Technique N/A (in-situ measurement in the platform environment)
Resolution N/A
Coverage / Cycle N/A
Mass Power Data Rate


Providing Agency NOAA
Instrument Maturity Flown on operational programme
Utilization Period: 1974 to 2027
Last update: 2022-07-25
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 GEO
  • Proton sensor at GEO
  • Alpha-particle sensor at GEO
Mission objectives
Primary mission objectives
  • Alpha particles 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
Proton integral directional flux*5 - marginalNo specific limitation.Platform environment, high energy (over 1000 keV)
Alpha particles integral directional flux*5 - marginalNo specific limitation.Platform environment. Medium-high energy (over 10 to >100 MeV/n)