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. Area 5°S - 45°N, 75°E - 145°E.
Mass 110 kg Power Data Rate 10 Mbps

 

Providing Agency ME (NIER)
Instrument Maturity Demonstrated by simulations
Utilization Period: 2020 to 2030
Last update: 2023-11-16
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
  • Earth observation instrument
  • Passive optical radiometer or spectrometer
  • Cross-nadir shortwave (UV/VIS) sounder
WIGOS Subcomponents
  • Subcomponent 1
  • UV/VIS/NIR sounders [in GEO]
  • UV/VIS/NIR sounder [in GEO]
Mission objectives
Primary mission objectives
  • Aerosol Optical Depth
  • Aerosol column burden
  • BrO
  • CH3Br
  • ClO
  • H2O
  • HCHO
  • HCHO Total Column
  • NO
  • NO2
  • NO2 Total Column
  • O3
  • O3 Total Column
  • SO2
  • SO2 Total Column
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
Aerosol column burden*2 - 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 Depth*2 - 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*1 - primaryCloud sensitive.. Daylight only.UV spectrometry. BrO lines around 300 nm. Frequent sampling (GEO) enables monitoring diurnal variations
HCHO*1 - primaryCloud sensitive.. Daylight only.UV spectrometry. HCHO lines around 350 nm. Frequent sampling (GEO) enables monitoring diurnal variations
HCHO Total Column*1 - primaryCloud sensitive.. Daylight only.UV spectrometry. HCHO lines around 350 nm. Frequent sampling (GEO) enables monitoring diurnal variations
CH3Br*3 - highCloud sensitive.. Daylight only.Spectrometry in the HC3Br band from 200 to 250 nm
ClO*1 - 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*3 - highCloud sensitive.. Daylight only.UV and VIS spectrometry. Several weak bands. Frequent sampling (GEO) enables monitoring diurnal variations
NO*1 - primaryCloud sensitive.. Daylight only.UV spectrometry. NO lines around 250 nm. Frequent sampling (GEO) enables monitoring diurnal variations
NO2*1 - primaryCloud sensitive.. Daylight only.UV and VIS spectrometry. Several lines in the ranges around 220 nm and 400 nm
NO2 Total Column*1 - primaryCloud sensitive.. Daylight only.UV and VIS spectrometry. Several NO2 lines. Frequent sampling (GEO) enables monitoring diurnal variations
O3*2 - 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 Column*2 - 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*1 - primaryCloud sensitive.. Daylight only.UV spectrometry. SO2 lines around 350 nm. Frequent sampling (GEO) for sources monitoring
SO2 Total Column*1 - 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