BackForwardInstrument:  CAPI 

Instrument details
Acronym CAPI
Full name Cloud and Aerosol Polarization Imager
Purpose Image mask and optical depth of clouds and aerosol
Short description
  • 5-channel UV/VIS/NIR/SWIR radiometer with three polarisations in two channels, and resolution changing with channel [see datails in the table below]
  • Calibration monitoring here
Background

Support to the CO2 measurements from the TANSAT Atmospheric Carbon-dioxide Grating Spectrometer (ACGS)
Scanning Technique

Pushbroom, cross-track swath ~200 km, operated within a solar zenith angle < 65 degree
Resolution 250 or 1000 m at s.s.p. (see table)
Coverage / Cycle Global in two weeks
Mass 80 kg Power 70 W Data Rate

 

Providing Agency MOST
Instrument Maturity Flown on an R&D satellite
Utilization Period: 2017 to 2022
Last update: 2024-09-09
Detailed characteristics

Central frequency

Bandwidth

SNR @ typical radiance

Polarization angles

Resolution at s.s.p.

380 nm

43 nm

260 @ 28.0 W·m-2·μm-1·sr-1

-

250 m

670 nm

50 nm

160 @ 22.0 W·m-2·μm-1·sr-1

0°, 60°, 120°

250 m

870 nm

30 nm

400 @ 25.0 W·m-2·μm-1·sr-1

-

250 m

1375 nm

30 nm

180 @ 6.0 W·m-2·μm-1·sr-1

-

1000 m

1640 nm

20 nm

110 @ 7.3 W·m-2·μm-1·sr-1

0°, 60°, 120°

1000 m
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
  • Moderate resolution optical imager
WIGOS Subcomponents
  • Subcomponent 2
  • Multi-angle, multi-polarization radiometers
  • Multi-angle, multi-polarization radiometer
Mission objectives
Primary mission objectives
  • Aerosol Optical Depth
  • Aerosol column burden
  • Aerosol effective radius
  • Aerosol mass mixing ratio
  • Aerosol type
  • Aerosol volcanic ash
  • Aerosol volcanic ash Total Column
  • Cloud cover
  • Cloud optical depth
  • Short-wave cloud reflectance
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
Aerosol column burden*5 - marginalCloud sensitive.. Daylight only.VIS (with narrow bandwidth), NIR and SWIR channels
Aerosol effective radius*5 - marginalCloud sensitive.. Daylight only.VIS (with narrow bandwidth), NIR and SWIR channels
Aerosol mass mixing ratio*5 - marginalCloud sensitive.. Daylight only.VIS (with narrow bandwidth), NIR and SWIR channels
Aerosol Optical Depth*5 - marginalCloud sensitive.. Daylight only.VIS (with narrow bandwidth), NIR and SWIR channels
Aerosol type*5 - marginalCloud sensitive.. Daylight only.VIS (with narrow bandwidth), NIR and SWIR channels
Biomass4 - fairCloud sensitive.. Index only.. Daylight only.VIS, NIR and SWIR channels. Biomass inferred from NDVI and LAI
Cloud cover*5 - marginalDaylight only.VIS and NIR channels
Cloud optical depth*3 - highLow-density cloud only.. Daylight only.VIS, NIR and SWIR channels
Cloud type5 - marginalDaylight only.VIS and NIR channels
Downward short-wave irradiance at Earth surface3 - highCloud sensitive.. Highly indirect.VIS, NIR and SWIR channels
Fire fractional cover5 - marginalCloud sensitive.. Coarse spatial resolution.. Daylight only.VIS channels
Leaf Area Index (LAI)2 - very highCloud sensitive.. Daylight only.VIS, NIR and SWIR channels
Normalised Difference Vegetation Index (NDVI)3 - highCloud sensitive.VIS and NIR channels
Sea-ice cover4 - fairCloud sensitive.. Daylight only.VIS, NIR (for contour enhancement) and SWIR (for discrimination from clouds) channels
Short-wave cloud reflectance*4 - fairNo specific limitation.VIS, NIR and SWIR channels
Snow cover2 - very highCloud sensitive.. Daylight only.VIS, NIR and SWIR channels, enabling screening snow from clouds
Soil moisture at surface5 - marginalCloud sensitive.. Index only.. Daylight only.VIS, NIR and SWIR channels. Soil moisture inferred from differential brightness
Upward short-wave irradiance at TOA4 - fairSpectral interpolation needed.. Information on BRDF needed.UV, VIS, NIR and SWIR channels
Aerosol volcanic ash*5 - marginalCloud sensitive.. Daylight only.VIS, NIR and SWIR channels
Aerosol volcanic ash Total Column*5 - marginalCloud sensitive.. Daylight only.VIS, NIR and SWIR channels