BackForwardInstrument:  GEMS 

Instrument details
Acronym GEMS
Full name Geostationary Environmental Monitoring Spectrometer
Purpose Ozone profile and total-column or gross profile of other species. Tracked species: BrO, NO2, O3, OClO, SO2 and aerosol
Short description UV/VIS grating imaging spectrometer, range 300-500 nm, spectral resolution < 0.6 nm, spectral sampling < 0.2 nm, SNR > 720 @ nominal radiance of 320 nm, > 1500 @ nominal radiance of 430 nm
Background New development
Scanning Technique Whiskbroom, E-W and S-N step-and-dwell of a detector matrix
Resolution 5 km over Korea
Coverage / Cycle 5000 km x 5000 km centred on Korea each hour during daylight
Mass 110 kg Power Data Rate 10 Mbps

 

Providing Agency ME
Instrument Maturity Demonstrated by simulations
Utilization Period: ≥2020 to ≥2031
Last update: 2018-03-19
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
  • Earth observation instrument
  • Passive optical radiometer or spectrometer
  • Cross-nadir shortwave (UV/VIS) sounder
Mission objectives
Primary mission objectives
  • BrO Mole Fraction
  • ClO Mole Fraction
  • H2O Mole Fraction
  • HC3Br Mole Fraction
  • HCHO Mole Fraction
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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
Aerosol column burden2 - very highCloud sensitive.. Daylight only.UV (for absorbing aerosol) and VIS spectrometry
Aerosol effective radius2 - very highCloud sensitive.. Daylight only.UV (for absorbing aerosol) and VIS spectrometry
Aerosol mass mixing ratio2 - very highCloud sensitive.. Daylight only.UV (for absorbing aerosol) and VIS spectrometry
Aerosol Optical Depth2 - very highCloud sensitive.. Daylight only.UV (for absorbing aerosol) and VIS spectrometry
Aerosol type2 - very highCloud sensitive.. Daylight only.UV (for absorbing aerosol) and VIS spectrometry
BrO Mole Fraction1 - primaryCloud sensitive.. Daylight only.UV spectrometry. BrO lines around 300 nm. Frequent sampling (GEO) enables monitoring diurnal variations
HCHO Mole Fraction1 - primaryCloud sensitive.. Daylight only.UV spectrometry. HCHO lines around 350 nm. Frequent sampling (GEO) enables monitoring diurnal variations
HCHO Total Column1 - primaryCloud sensitive.. Daylight only.UV spectrometry. HCHO lines around 350 nm. Frequent sampling (GEO) enables monitoring diurnal variations
HC3Br Mole Fraction3 - highCloud sensitive.. Daylight only.Spectrometry in the HC3Br band from 200 to 250 nm
ClO Mole Fraction1 - primaryCloud sensitive.. Daylight only.UV Spectrometry. ClO lines around 300 nm Frequent sampling (GEO) enables monitoring diurnal variations
Cloud cover5 - marginalDaylight only.VIS spectroscopy
Cloud optical depth5 - marginalLow-density cloud only.. Daylight only.VIS spectrometry
Earth surface short-wave bidirectional reflectance5 - marginalCloud sensitive.VIS spectrometry. GEO sees changing solar incidence angles as daylight progresses
H2O Mole Fraction3 - highCloud sensitive.. Daylight only.UV and VIS spectrometry. Several weak bands. Frequent sampling (GEO) enables monitoring diurnal variations
NO Mole Fraction1 - primaryCloud sensitive.. Daylight only.UV spectrometry. NO lines around 250 nm. Frequent sampling (GEO) enables monitoring diurnal variations
NO2 Mole Fraction1 - primaryCloud sensitive.. Daylight only.UV and VIS spectrometry. Several lines in the ranges around 220 nm and 400 nm
NO2 Total Column1 - primaryCloud sensitive.. Daylight only.UV and VIS spectrometry. Several NO2 lines. Frequent sampling (GEO) enables monitoring diurnal variations
O3 Mole Fraction2 - very highCloud sensitive.. Daylight only.UV and VIS spectrometry. Ozone lines in the bands around 260 nm (Hartley) and/or 340 nm (Huggins) and 600 nm (Chappuis). GEO enabling frequent sampling (GEO) for diurnal variations
O3 Total Column2 - very highCloud sensitive.. Daylight only.UV and VIS spectrometry. Ozone lines in the bands around 260 nm (Hartley) and/or 340 nm (Huggins) and 600 nm (Chappuis). GEO enabling frequent sampling (GEO) for diurnal variations
PSC occurrence2 - very highMarginal view from GEO.. Daylight only.UV and VIS spectrometry
SO2 Mole Fraction1 - primaryCloud sensitive.. Daylight only.UV spectrometry. SO2 lines around 350 nm. Frequent sampling (GEO) for sources monitoring
SO2 Total Column1 - primaryCloud sensitive.. Daylight only.UV spectrometry. SO2 lines around 350 nm. Frequent sampling (GEO) for sources monitoring
Upward short-wave irradiance at TOA3 - highSpectral interpolation needed.. Information on BRDF needed.UV and VIS spectrometry
Upward spectral radiance at TOA5 - marginalMissing NIR, SWIR and all Long-waves.UV and VIS spectrometry
Aerosol volcanic ash2 - very highCloud sensitive.. Daylight only.UV (specifically sensitive to ash) and VIS spectrometry
Aerosol volcanic ash Total Column2 - very highCloud sensitive.. Daylight only.UV (specifically sensitive to ash) and VIS spectrometry. Frequent sampling (GEO) for early detection of ash plumes