BackForwardInstrument:  SI-1 

Instrument details
Acronym SI-1
Full name Spectrometer/Interferometer - German Democratic Republic
Purpose Temperature/humidity profiling and total-column ozone
Short description Nadir viewing infrared interferometer developed by the GDR. Spectral region covered 6.25-25 microns wavelength with a resolution of 5cm-1 after apodisation. An on board black body and deep space view were used for calibration. More details:
Background New development - Provided by the German Democratic Republic
Scanning Technique Nadir-only pointing
Resolution 25 km
Coverage / Cycle Global in 10 days for cells of 100 km side
Mass Power Data Rate


Providing Agency Roscosmos
Instrument Maturity Flown on an R&D satellite
Utilization Period: 1976 to 1981
Last update: 2023-03-06
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
  • Subcomponent 1
  • IR hyperspectral sounders [in SSO]
  • IR hyperspectral sounder [in SSO]
Mission objectives
Primary mission objectives
  • Atmospheric temperature
  • Integrated Water Vapour (IWV)
  • Specific humidity
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 temperature3 - highDiscontinuous coverage.. Along-track only.TIR channels in window and water vapour band (for emissivity)
Land surface temperature4 - fairCloud sensitive.. Coarse spatial resolution.. Along-track only.TIR split window channels for water vapour correction
O3 Total Column5 - marginalCloud sensitive.. Along-track only.TIR channel(s). Ozone lines in band around 9.7 micrometers
Sea surface temperature4 - fairCloud sensitive.. Along-track only.TIR split window channels for water vapour correction
Specific humidity*3 - highCloud sensitive.. Very coarse vertical resolution.. Middle troposphere only.. Along-track only.TIR channels in the water vapour band around 6.3 micrometers
Integrated Water Vapour (IWV)*3 - highCloud sensitive.. Along-track only.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.. Along-track only.TIR and FIR channels in the 11 micrometers window, and in water vapour and CO2 bands around 6.3, 15 and 18 micrometers