BackForwardInstrument:  SIRS-A 

Instrument details
Acronym SIRS-A
Full name Satellite Infra-Red Spectrometer
Purpose Atmospheric temperature profile
Short description Grating spectrometer utilised to select 8 spectral channels, 0.1 µm wide, centred on 11.12, 13.33, 14.01, 14.16, 14.31, 14.45, 14.76 and 14.95 µm
Background Prototype of future operational IR sounders
Scanning Technique Nadir only
Resolution 220 km
Coverage / Cycle Global in one week
Mass 41 kg Power 24 W Data Rate 100 bps


Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 1969 to 1972
Last update: 2012-09-13
Detailed characteristics
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
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*3 - highCloud sensitive.. Coarse vertical resolution.. Inaccurate in low troposphere.. Along-track only.Many TIR channels in the 15 micrometer band
Cloud cover5 - marginalDiscontinuous coverage.. Along-track only.TIR channel(s)
Cloud top height3 - highDiscontinuous coverage.. Along-track only.TIR channels in window and in CO2 band for atmospheric column above cloud top
Cloud top temperature5 - marginalDiscontinuous coverage.. Along-track only.TIR window channel(s)
Sea surface temperature5 - marginalCloud sensitive.. Along-track only.TIR window channel(s)