BackForwardInstrument:  SIRS-B 

Instrument details
Acronym SIRS-B
Full name Satellite Infra-Red Spectrometer - B
Purpose Atmospheric temperature and humidity sounding
Short description Grating spectrometer utilised to select 14 channels in the spectral range 11.1-35.7 µm [see detailed characteristics below]
Background Follow-on of SIRS-A flown on Nimbus-3. Scanning capability added
Scanning Technique Cross-track, nadir and selectable left and right according to 6 steps up to 37.8°. Normally there are three steps: nadir and left and right at 1/3 of the way between successive sub-tracks, i.e. swath about 1800 km at the equator, decreasing with increasing latitude
Resolution 220 km at s.s.p.
Coverage / Cycle Nearly-global twice/day
Mass 31.5 kg Power 30 W Data Rate

 

Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 1970 to 1980-09-30
Last update: 2016-10-29
Detailed characteristics

Wavelength

Wave number

Bandwidth

NEΔT @ specified scene temperature

35.71 µm

280.0 cm-1

7.86 cm-1

.... K @ 250 K

33.11 µm

302.0 cm-1

8.32 cm-1

.... K @ 250 K

25.54 µm

391.5 cm-1

8.10 cm-1

.... K @ 250 K

23.50 µm

425.5 cm-1

8.30 cm-1

.... K @ 250 K

22.91 µm

436.5 cm-1

8.47 cm-1

.... K @ 250 K

18.81 µm

531.5 cm-1

10.14 cm-1

.... K @ 250 K

14.95 µm

668.7 cm-1

10.42 cm-1

.... K @ 250 K

14.71 µm

679.8 cm-1

10.61 cm-1

.... K @ 250 K

14.45 µm

692.0 cm-1

10.81 cm-1

.... K @ 250 K

14.26 µm

701.0 cm-1

10.96 cm-1

.... K @ 250 K

14.10 µm

709.0 cm-1

11.13 cm-1

.... K @ 250 K

13.62 µm

734.0 cm-1

11.70 cm-1

.... K @ 250 K

13.33 µm

750.0 cm-1

11.83 cm-1

.... K @ 250 K

11.12 µm

899.0 cm-1

12.36 cm-1

.... K @ 250 K

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.. Inaccurate in low troposphere.Many TIR channels in the 15 micrometer band
Cloud cover5 - marginalDiscontinuous coverage.TIR channel(s)
Cloud top height3 - highDiscontinuous coverage.TIR channels in window and in CO2 band for atmospheric column above cloud top
Cloud top temperature5 - marginalDiscontinuous coverage.TIR window channel(s)
Sea surface temperature5 - marginalCloud sensitive.TIR window channel(s)
Specific humidity4 - fairCloud sensitive.. High troposphere only.FIR channels in the water vapour rotational band around 18 micrometers
Integrated Water Vapour (IWV)3 - highCloud sensitive.TIR and FIR channels from the 11 micrometers window into the 18 micrometers water vapour rotational band
Upward long-wave irradiance at TOA5 - marginalSpectral interpolation needed.TIR and FIR channels in the 11 micrometers window, and in water vapour and CO2 bands around 6.3, 15 and 18 micrometers