BackForwardInstrument:  GAS-2 

Instrument details
Acronym GAS-2
Full name Greenhouse-gases Absorption Spectrometer - 2
Purpose Atmospheric chemistry - Measurement of CO2, CH4, CO, N2O
Short description Grating spectrometer operating in four NIR/SWIR bands [see detailed characteristics below]
Background Follow-on of GAS flown on FY-3D
Scanning Technique Two views, nadir or pointing to sunglint
Resolution 3 km s.s.p.
Coverage / Cycle Global coverage in one month for cells of 100 km side, in daylight
Mass Power Data Rate


Providing Agency CMA
Instrument Maturity Flown on operational programme
Utilization Period: 2025 to 2031
Last update: 2021-12-13
Detailed characteristics
Spectral range (μm) Spectral range (cm-1) Spectral resolution SNR @ expected input radiance
0.75-0.77 μm 13000-13300 cm-1 0.04 nm > 300
1.56-1.72 μm 5800-6400 cm-1 0.07 nm > 300
1.92-2.08 μm 4800-5200 cm-1 0.09 nm > 300
2.20-2.38 μm 4200-4550 cm-1 0.10 nm > 300
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, nadir and limb
  • UV/VIS/NIR nadir sounder
  • Subcomponent 2
  • NIR/SWIR imaging spectroscopy
  • NIR/SWIR imaging spectrometer
  • Subcomponent 3
  • NIR spectrometer
  • NIR spectrometer
Mission objectives
Primary mission objectives
  • CH4
  • CO
  • CO2
  • N2O
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
CH4*3 - highCloud sensitive.. Daylight only.. Along-track only.SWIR spectrometry. CH4 lines around 2.3 micrometers
Cloud top height4 - fairDaylight only.. Along-track only.NIR spectrometry to estimate the total-column O2 above the cloud top as measured around 760 nm
CO*3 - highCloud sensitive.. Daylight only.. Along-track only.SWIR spectrometry. CO lines around 2.3 micrometers
CO2*3 - highCloud sensitive.. Daylight only.. Along-track only.SWIR spectroscopy. CO2 lines around 1.6 and 2.1 micrometers
N2O*3 - highAlong-track only.. Cloud sensitive.. Daylight only.SWIR spectrometry. N2O lines around 2.3 micrometers