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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
WIGOS Subcomponents
No WIGOS subcomponents have been defined.
Mission objectives
Primary mission objectives Atmospheric temperature Integrated Water Vapour (IWV) Specific humidity Secondary mission objectives
Opportunity objectives Cloud top height Cloud top temperature Upward long-wave irradiance at TOA Show all Show fewer
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
Variable Relevance for measuring this variable Operational limitations Explanation
Atmospheric temperature 3 - high Cloud sensitive.. Coarse vertical resolution.. Inaccurate in low troposphere. Many TIR channels in the 15 micrometer band
Cloud cover 5 - marginal Discontinuous coverage. TIR channel(s)
Cloud top height 3 - high Discontinuous coverage. TIR channels in window and in CO2 band for atmospheric column above cloud top
Cloud top temperature 5 - marginal Discontinuous coverage. TIR window channel(s)
Sea surface temperature 5 - marginal Cloud sensitive. TIR window channel(s)
Specific humidity 4 - fair Cloud sensitive.. High troposphere only. FIR channels in the water vapour rotational band around 18 micrometers
Integrated Water Vapour (IWV) 3 - high Cloud sensitive. TIR and FIR channels from the 11 micrometers window into the 18 micrometers water vapour rotational band
Upward long-wave irradiance at TOA 5 - marginal Spectral 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
Instrument: SIRS-B