BackForwardInstrument:  IRS 

Instrument details
Acronym IRS
Full name InfraRed Sounder
Purpose Temperature/humidity sounding and wind profile derivation by tracking water vapour features; tracking of atmospheric constituents.
Short description

Fourier transform interferometer with large detector arrays for simultaneous sounding of more pixels. The IRS is based on an imaging Fourier-interferometer with a hyperspectral resolution of 0.604cm-1 wave-number, taking measurements in two bands: MWIR: 1600 to 2250cm-1 (4.44–6.25µm) and LWIR: 680 to 1210cm-1 (8.26–14.70µm).

Monitoring and calibration information here
Background

First operational hyperspectral infrared sounder in GEO at 0° longitude; based on IASI heritage.
Scanning Technique

The Earth disc is covered in 4 latitude belts (Local Area Coverage, LAC) which covered in an interleaved, 6-hourly pattern of step-and-stare “dwells” of the instrument. The northermost belt that includes Europe (LAC4), is imaged at 30-min intervals for the whole 6-hour period (12 images). The following belt to the South (LAC3) is covered in two sequences of three images in 30-minute intervals, separated by 2 hours (total of 6 images). The other two belts in the Southern Hemisphere (LAC2, LAC1) are each covered by a sequence of 3 images in 30-minute intervals, separated by 5 hours (each a total of 3 images). Each dwell has a duration of about 10s and consist of 160x160 pixels (soundings), i.e 25600 spectra in 1960 spectral channels per dwell. It takes 15 minutes to complete the scan of a belt (LAC). More details and scanning animation at https://www.eumetsat.int/mtg-infrared-sounder
Resolution 4.0 km at s.s.p.
Coverage / Cycle Every 30min over Europe (LAC4); 6-hourly full-disc scan pattern of all LACs described under “Scanning technique”
Mass 400 kg Power 750 W Data Rate

 

Providing Agency ESA
Instrument Maturity Demonstrated by simulations
Utilization Period: 2025 to 2045
Last update: 2024-09-23
Detailed characteristics

Wavelength

Wave number

Spectral resolution (unapodised)

NE∆T @ specified scene temperature

4.44–6.25 µm

1600 to 2250 cm-1

0.604 cm-1

Between

8.26–14.70 µm

680 to 1210 cm-1

0.604 cm-1

Between
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 infrared sounder, possibly including VIS channels
WIGOS Subcomponents
  • Subcomponent 1
  • IR hyperspectral sounders [in GEO]
  • IR hyperspectral sounder [in GEO]
Mission objectives
Primary mission objectives
  • Atmospheric temperature
  • Height of the top of PBL
  • Height of the tropopause
  • Integrated Water Vapour (IWV)
  • Specific humidity
  • Temperature of the tropopause
  • Wind (horizontal)
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
Atmospheric temperature*1 - primaryCloud sensitive.MWIR and TIR spectrometry in the CO2 4.3 and 15 micrometer bands. Frequent sampling (GEO) enables monitoring instability onset
C2H23 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. C2H2 lines around 7.5 and 13.7 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
C2H63 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. C2H6 lines around 12 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
CFC-113 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. CFC-11 lines around 9.2 and 11.7 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
CFC-123 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. CFC-12 lines around 8.8 and 10.8 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
CH4 mole fraction2 - very highCloud sensitive.. Coarse vertical resolution.MWIR and TIR spectrometry. CH4 lines around 4.3 and 7.7 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
ClONO22 - very highCloud sensitive.. Coarse vertical resolution.MWIR and TIR spectrometry. ClONO2 lines around 5.7, 7.7 and 12.5 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
Cloud cover3 - highDiscontinuous coverage.MWIR and TIR spectrometry
Cloud top height2 - very highDiscontinuous coverage.MWIR and TIR spectrometry in window and water vapour band (for emissivity) to estimate cloud top height from its temperature
Cloud top temperature1 - primaryDiscontinuous coverage.TIR spectrometry in window and water vapour band (for emissivity)
Cloud type4 - fairDiscontinuous coverage.MWIR and TIR spectrometry
CO3 - highCloud sensitive.. Coarse vertical resolution.MWIR spectrometry. CO lines around 4.6. Frequent sampling (GEO) enables monitoring diurnal variations
CO2 mole fraction3 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. CO2 lines around 15 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
COS3 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. COS lines around 11.6 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
Downward long-wave irradiance at Earth surface1 - primaryCloud sensitive.. Highly indirect.MWIR and TIR spectrometry including water vapour and CO2 bands
H2O2 - very highCloud sensitive.. Coarse vertical resolution.MWIR/TIR spectrometry in a range centred on 6.3 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
Height of the top of PBL*4 - fairCloud sensitive.MWIR and TIR spectrometry. Height of PBL top from temperature profile. Frequent sampling (GEO) enables monitoring the PBL evolution
Height of the tropopause*4 - fairCloud sensitive.TIR spectrometry. Height of tropopause from temperature profile. Frequent sampling (GEO) enables monitoring the tropopause evolution
HNO33 - highCloud sensitive.. Coarse vertical resolution.MWIR and TIR spectrometry. HNO3 lines around 5.9, 7.6 and 11.3 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
Land surface temperature2 - very highCloud sensitive.. Coarse spatial resolution.MWIR and TIR spectrometry (inclusive of several narrow-bandwidth windows and absorption bands for atmospheric corrections)
Long-wave Earth surface emissivity1 - primaryCloud sensitive.. Long time series needed.MWIR and TIR spectrometry measuring land temperature in many windows. Emissivity inferred by statistical analysis
N2O mole fraction2 - very highCloud sensitive.. Coarse vertical resolution.MWIR and TIR spectrometry. N2O lines around 4.5 and 7.7 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
N2O53 - highCloud sensitive.. Coarse vertical resolution.MWIR and TIR spectrometry. N2O5 lines around 5.8 and 8 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
NO3 - highCloud sensitive.. Coarse vertical resolution.MWIR spectrometry. NO lines around 5.3 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
NO23 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. NO2 lines around 6.1 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
NO2 Total Column4 - fairCloud sensitive.TIR spectrometry. NO2 lines around 6.1 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
O33 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. Ozone band around 9.7 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
O3 Total Column3 - highCloud sensitive.TIR channel(s). Ozone lines in band around 9.7 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
PAN3 - highCloud sensitive.. Coarse spatial resolution.MWIR and TIR spectrometry. PAN lines around 5.7, 8.6 and 12.5 micrometers. Frequent sampling (GEO) enables monitoring diurnal variations
PSC occurrence2 - very highMarginal view from GEO.. Coarse vertical resolution.MWIR and TIR spectroscopy
Sea surface temperature1 - primaryCloud sensitive.MWIR and TIR spectrometry (inclusive of several narrow-bandwidth windows and absorption bands for atmospheric corrections)
SF63 - highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. SF6 lines around 10.5 micrometers. Frequent sampling (GEO) for diurnal variations
SO22 - very highCloud sensitive.. Coarse vertical resolution.TIR spectrometry. SO2 lines around 7.3 and 8.6 micrometers. Frequent sampling (GEO) for sources monitoring
SO2 Total Column2 - very highCloud sensitive.TIR spectrometry. SO2 lines around 7.3 and 8.6 micrometers. Frequent sampling (GEO) for sources monitoring
Specific humidity*1 - primaryCloud sensitive.TIR spectrometry in the water vapour band around 6.3 micrometers. Frequent sampling (GEO) enables monitoring instability onset
Integrated Water Vapour (IWV)*2 - very highCloud sensitive.TIR spectrometry in the bands around 6.3 and above 11 micrometers. Frequent sampling (GEO) enables monitoring instability onset
Temperature of the tropopause*3 - highCloud sensitive.TIR spectrometry. Tropopause temperature from temperature profile. Frequent sampling (GEO) enables monitoring the tropopause evolution
Upward spectral radiance at TOA2 - very highMissing all Short-waves.MWIR and TIR spectrometry resolving water vapour lines in the bands around 6.3 micrometers and 11 to 15 micrometers; and other greenhouse gases
Upward long-wave irradiance at TOA3 - highSpectral interpolation needed.MWIR and TIR spectrometry in the windows regions around 3.7 and 11 micrometers, and in water vapour and CO2 bands around 4,3, 6.3 and 15 micrometers
Upward long-wave irradiance at Earth surface1 - primaryCloud sensitive.. Highly indirect.MWIR and TIR channels in windows around 3.7 and 11 micrometers, and in water vapour and CO2 bands around 4,3, 6.3 and 15 micrometers
Wind (horizontal)*2 - very highCloud sensitive.. Water vapour tracers needed.TIR spectrometry in the 6.3 micrometers band. Wind profile in clear air by tracking water vapour patches in the humidity profile