BackForwardInstrument:  GHI 

Instrument details
Acronym GHI
Full name Geosynchronous High-speed Imager
Purpose Very frequent imagery of limited areas
Short description 5-channel VIS/IR radiometer [see datails in the table below].
Background Complementary to the main FY-4 imager (AGRI) for partial areas rapid scanning
Scanning Technique Wiskbroom scanning of areas of 2000 km x 2000 km at one-minute rate.
Resolution Ranging with channel between 250 m in VIS to 2 km in TIR
Coverage / Cycle Selected segments of 2000 km x 2000 km of the Earth disk at one-minute rate
Mass Power Data Rate

 

Providing Agency CMA
Instrument Maturity Flown on operational programme
Utilization Period: ≥2018 to ≥2025
Last update: 2017-07-28
Detailed characteristics

Central wavelength

Spectral interval

SNR or NEΔT @ specified input

IFOV at s.s.p.

0.65 mm

0.55-0.75  mm

> 4 @ 1 % albedo

250 m

1.61 mm

1.58-1.64  mm

> 4 @ 1 % albedo

1000 m

2.23  mm

2.10-2.36  mm

> 4 @ 1 % albedo

1000 m

6.95  mm

6.30-7.60 mm

0.2 K @ 300 k

2000 m

10.80  mm

10.30-11.30  mm

0.2 K @ 300 k

2000 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
Mission objectives
Primary mission objectives
  • Cloud cover
  • Cloud top height
  • Cloud top temperature
  • Cloud type
  • Integrated Water Vapour (IWV)
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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
Fire fractional cover4 - fairCloud sensitive.. Coarse spatial resolution.VIS and TIR channels
Fire radiative power3 - highCloud sensitive.. Coarse spatial resolution.TIR channels. Frequent sampling (GEO) enables early detection
Fire temperature3 - highCloud sensitive.. Coarse spatial resolution.TIR channels. Frequent sampling (GEO) enables early detection
Precipitation intensity at surface (liquid or solid)5 - marginalConvective precipitation dominant.. Calibration by MW needed.TIR channel(s) in the 11 micrometers window. Frequent sampling (GEO) consistent with precipitation temporal variability
Sea surface temperature5 - marginalCloud sensitive.TIR window channel(s) around 11 micrometers .
Snow cover3 - highCloud sensitive.. Daylight only.VIS and SWIR channels enabling screening snow from clouds. Frequent sampling (GEO) improves probability of cloud-free views
Soil moisture at surface4 - fairCloud sensitive.. Index only.VIS and TIR window channels. Soil moisture inferred from thermal inertia, that is accurately measured by frequent sampling (GEO)
Wind (horizontal)3 - highCloud or water vapour tracers needed.VIS channel(s) and TIR channels around 6.3 and 11 micrometers. Frequent sampling (GEO) enables inference from cloud or water vapour pathces motion
Accumulated precipitation (over 24 h)3 - highConvective precipitation dominant.. Calibration by MW needed.TIR channel(s) in the 10-13 micrometers range. Frequent sampling (GEO) is essential for accumulated precipitation
Aerosol volcanic ash5 - marginalCloud sensitive.. Daylight only.VIS and SWIR channels
Aerosol volcanic ash (Total column)1 - primaryCloud sensitive.TIR channel(s). Frequent sampling (GEO) enables early detection of ash plumes
Integrated Water Vapour (IWV)4 - fairCloud sensitive.. Middle troposphere dominant.TIR channels in the water vapour band around 6.3 micrometers
Leaf Area Index (LAI)3 - highCloud sensitive.. Daylight only.VIS and SWIR channels
Cloud cover4 - fairNo specific limitation.VIS and TIR channels
Cloud top temperature3 - highNo specific limitation.TIR channels in window and water vapour band (for emissivity)
Cloud top height3 - highNo specific limitation.TIR channels in window and water vapour band (for emissivity) to estimate cloud top height from its temperature
Cloud type4 - fairDaylight only.VIS and TIR channels