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: ≥2019 to ≥2026
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
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
Cloud cover4 - fairNo specific limitation.VIS and TIR channels
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 top temperature3 - highNo specific limitation.TIR channels in window and water vapour band (for emissivity)
Cloud type4 - fairDaylight only.VIS and TIR channels
Fire fractional cover4 - fairCloud sensitive.. Coarse spatial resolution.VIS and TIR channels
Fire radiative power5 - marginalCloud sensitive.. Coarse spatial resolution.TIR channels. Frequent sampling (GEO) enables early detection
Fire temperature5 - marginalCloud sensitive.. Coarse spatial resolution.TIR channels. Frequent sampling (GEO) enables early detection
Leaf Area Index (LAI)3 - highCloud sensitive.. Daylight only.VIS and SWIR channels
Precipitation intensity at surface (liquid or solid)3 - highConvective 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 cover2 - very 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)
Integrated Water Vapour (IWV)4 - fairCloud sensitive.. Middle troposphere dominant.TIR channels in the water vapour band around 6.3 micrometers
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
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