BackForwardInstrument:  CO2I and NO2I 

Instrument details
Acronym CO2I and NO2I
Full name Combined Carbon Dioxide and Nitrogen Dioxide Imager
Purpose Measurement of CO2 and NO2 concentration to monitor anthropogenic carbon emissions
Short description Set of VIS/NIR/SWIR grating spectrometers covering four spectral ranges, to measure CO2 Total column with high precision (< 0.7 ppm) and low systematic bias (< 0.5 ppm). Supporting NO2 Total column observation provided by the VIS component (Blue) [See details below].
Background Operating in association with a cloud imager (CLIM) and a multi-angle polarimeter (MAP).
Scanning Technique Cross-track pushbroom scanning. Swath 256 km.
Resolution 0.8 km at SSP.
Coverage / Cycle Near-global coverage in 10 days.
Mass Power Data Rate


Providing Agency ESA
Instrument Maturity Flown on an R&D satellite
Utilization Period: ≥2026 to ≥2031
Last update: 2021-12-13
Detailed characteristics

The CO2 & N2OI imager (CO2I), consisting of four spatially nadir viewing co-registered push-broom imaging spectrometers, measuring spectral radiance and solar irradiance in the VIS, NIR and SWIR wavelengths at moderate spectral resolving power (R=5000-7000).







SNR @ specified input

spectral radiance


405 - 490 nm

0.6 nm

…. @ … W m-2 sr-1 μm-1


747 - 773 nm

0.12 nm

... @ … W m-2 sr-1 μm-1


1590 - 1675 nm

0.30 nm

... @ … W m-2 sr-1 μm-1


1990 - 2095 nm

0.35 nm

… @ … W m-2 sr-1 μm-1

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 3
  • NIR spectrometer
Mission objectives
Primary mission objectives
  • CO2 Mole fraction (SR)
Secondary mission objectives
  • NO2 Total Column
Opportunity objectives
  • Cloud cover
  • Cloud drop effective radius
  • Cloud ice effective radius
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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
Cloud cover4 - fairDaylight only.VIS, NIR and SWIR spectroscopy
Cloud drop effective radius4 - fairAt cloud top.. Daylight only.VIS, NIR and SWIR spectrometry
Cloud ice effective radius4 - fairAt cloud top.. Daylight only.VIS, NIR and SWIR spectrometry
Cloud optical depth2 - very highLow-density cloud only.. Daylight only.VIS, NIR and SWIR spectrometry
Cloud top height4 - fairDaylight only.NIR spectrometry to estimate the total-column O2 above the cloud top as measured around 760 nm
CO23 - highCloud sensitive.. Coarse vertical resolution.. Daylight only.SWIR spectrometry. CO2 lines around 1.6 and 2.1 micrometers
Downward short-wave irradiance at Earth surface1 - primaryCloud sensitive.. Highly indirect.. Daylight only.VIS, NIR and SWIR spectrometry
NO2 Total Column4 - fairDaylight only.. Cloud sensitive.VIS spectrometry in the blue range (400-500 nm)
Short-wave cloud reflectance3 - highNo specific limitation.VIS, NIR and SWIR spectrometry. Unsuitable dynamic range (saturation)