BackForwardInstrument:  SESS/SSUSI 

Instrument details
Full name SESS / Special Sensor Ultraviolet Spectrographic Imager
Purpose To measure UV radiation from the Earth's atmosphere and ionosphere, also measuring visible radiation (airglow and terrestrial albedo).
Short description Assemblage of a scanning Imaging spectrometer and a nadir-looking photometer system. The spectrometer has 160 spectral channels in 5 selectable sub-ranges of the Far UV interval from 115 to 180 nm, inclusive of the H Lyman-alpha line at 121.6 nm. The photometer monitors airglow at 427.8 and 630 nm and the terrestrial albedo near 630 nm
Background Part of the SESS (Space Environment Sensor Suite) package
Scanning Technique Scanning spectrometer: cross-track scan up to beyond the horizon opposite to sun, till tangent altitude of 520 km; fast scanning along-track of 16 IFOVs. Swath: 3000 km. Photometer: nadir only
Resolution UV: 10 km at s.s.p., 300 km for limb viewing; VIS: 25 km at s.s.p.
Coverage / Cycle Global, daily. UV sampled at 22 s intervals, VIS at 180 s intervals
Mass Power Data Rate


Providing Agency DoD
Instrument Maturity Flown on operational programme
Utilization Period: 2004 to 2025
Last update: 2021-12-09
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
  • Space radiometer or spectrometer
WIGOS Subcomponents
  • Subcomponent 2
  • Magnetospheric energetic particles and magnetometers
  • Ionospheric electron density sensor [in LEO and cross magnetosphere]
  • Ionospheric plasma density
  • Subcomponent 3
  • UV spectral imagery (e.g. GEO, HEO, MEO, LEO)
  • UV spectral imager [from GEO, HEO, MEO, LEO]
Mission objectives
Primary mission objectives
  • Aurora
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
UV flux spectrum1 - primaryNo specific limitation.Earth's limb observed, high spectral resolution
UV sky image1 - primaryNo specific limitation.Earth's limb observed, spectrometry with high spatial resolution
Aurora*1 - primaryNo specific limitation.Observed down to Earth's surface in UV and VIS
Ionospheric plasma density5 - marginalNo specific limitation.UV imaging spectrometer measuring ionospheric plasma density in the Earth's limb
Electron Density5 - marginalNo specific limitation.UV spectrometry of the Earth's limb