BackForwardInstrument:  IRAS 

Instrument details
Acronym IRAS
Full name Infra Red Atmospheric Sounder
Purpose Temperature/humidity sounding
Short description 26-channels (including 6 in short-wave) [see detailed characteristics below]
Background Consolidated technology. Operations on FY-3A stopped in 2010
Scanning Technique Cross-track: 56 steps of 26 km ssp, swath 2250 km - Along-track: one line each 42 km every 6.4 s
Resolution 17 km IFOV
Coverage / Cycle Near-global coverage twice/day
Mass 65 kg Power 80 W Data Rate 0.64 Mbps

 

Providing Agency CMA
Instrument Maturity Flown on operational programme
Utilization Period: 2008 to ≥2019
Last update: 2017-03-29
Detailed characteristics
Wavelength Wave number Bandwidth SNR or NEΔT @ specified input
14.95 µm 669 cm-1 3 cm-1 2.50 K @ 290 K
14.71 µm 680 cm-1 10 cm-1 0.50 K @ 290 K
14.49 µm 690 cm-1 12 cm-1 0.37 K @ 290 K
14.22 µm 703 cm-1 16 cm-1 0.22 K @ 290 K
13.97 µm 716 cm-1 16 cm-1 0.20 K @ 290 K
13.64 µm 733 cm-1 16 cm-1 0.22 K @ 290 K
13.35 µm 749 cm-1 16 cm-1 0.18 K @ 290 K
12.47 µm 802 cm-1 30 cm-1 0.12 K @ 290 K
11.11 µm 900 cm-1 35 cm-1 0.10 K @ 290 K
9.71 µm 1030 cm-1 25 cm-1 0.14 K @ 290 K
7.43 µm 1345 cm-1 50 cm-1 0.27 K @ 290 K
7.33 µm 1365 cm-1 40 cm-1 0.37 K @ 290 K
6.52 µm 1533 cm-1 55 cm-1 0.53 K @ 290 K
4.57 µm 2188 cm-1 23 cm-1 0.10 K @ 290 K
4.52 µm 2210 cm-1 23 cm-1 0.05 K @ 290 K
4.47 µm 2235 cm-1 23 cm-1 0.08 K @ 290 K
4.45 µm 2245 cm-1 23 cm-1 0.08 K @ 290 K
4.19 µm 2388 cm-1 25 cm-1 0.06 K @ 290 K
3.98 µm 2515 cm-1 35 cm-1 0.10 K @ 290 K
3.76 µm 2660 cm-1 100 cm-1 0.11 K @ 290 K
1.64 µm n/a 120 nm …..  @ ..... % albedo
1.24 µm n/a 100 nm …..  @ ..... % albedo
0.94 µm n/a 18 nm …..  @ ..... % albedo
0.94 µm n/a 49 nm …..  @ ..... % albedo
0.885 µm n/a 30 nm …..  @ ..... % albedo
0.69 µm n/a 48 nm …..  @ ..... % albedo
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
Mission objectives
Primary mission objectives
  • Atmospheric temperature
  • Integrated Water Vapour (IWV)
  • Specific humidity
Secondary mission objectives
  • Sea surface temperature
Opportunity objectives
  • Cloud cover
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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
Atmospheric temperature3 - highCloud sensitive.. Coarse vertical resolution.Many MWIR and TIR channels in the 4.3 and 15 micrometer bands
Cloud cover4 - fairDiscontinuous coverage.MWIR and TIR channels
Cloud top height2 - very highDiscontinuous coverage.TIR channels in window and water vapour band (for emissivity) for temperature; and in CO2 band for atmospheric column above cloud top
Cloud top temperature2 - very highDiscontinuous coverage.TIR channels in window and water vapour band (for emissivity)
Cloud type4 - fairDiscontinuous coverage.MWIR and TIR channels
Downward long-wave irradiance at Earth surface3 - highCloud sensitive.. Highly indirect.MWIR and TIR channels including water vapour and CO2 bands
Land surface temperature3 - highCloud sensitive.. Coarse spatial resolution.MWIR and TIR channels in windows and absorption bands for atmospheric corrections
O3 Total Column5 - marginalCloud sensitive.TIR channel(s). Ozone lines in band around 9.7 micrometers
Sea surface temperature2 - very highCloud sensitive.MWIR and TIR window channels (cloud impact reduction, water vapour correction)
Specific humidity3 - highCloud sensitive.. Very coarse vertical resolution.. Middle troposphere only.TIR channels in the water vapour band around 6.3 micrometers
Integrated Water Vapour (IWV)3 - highCloud sensitive.. Inaccurate in high troposphere.TIR channels around 6.3 micrometers and in the 11 micrometers split window
Upward long-wave irradiance at TOA4 - fairSpectral interpolation needed.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
Upward long-wave irradiance at Earth surface3 - highCloud 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