Geostationary Interferometric Infrared Sounder (GIIRS)


An infrared hyper-spectral vertical sounder, also the first space-borne interferometer that flies in geostationary orbit to take measurements of three dimensional atmospheric structure from interference of split light beams. Technically featured by a 32×4 sensor array plane, a Michelson interferometer working over different infrared bands for large-area, continuous, fast, and accurate vertical air soundings of temperature and humidity.

Satellite FY-4A 
Weight 315kg
Dimension 1353.5mm (length) × 2179.9mm (width) × 1549mm (height)
Bands Long-wave: 700∼1130cm-1 (8.85∼14.29μm)
Mid-wave: 1650∼2250cm-1 (4.44∼6.06μm)
Spectral resolution 0.625cm-1 (actual measurement)
No. channels 1650 (actual measurement)
Spatial resolution 16km
Temporal resolution 768km × 960km (30 min)
4480km × 5000km (60 min)
Radiation calibration accuracy 1.5K
Spectral calibration accuracy 10ppm


FY-4A (R&D) FY-4B (Operational)
Spectral parameters (normal mode) Range (cm-1) Resolution No. channels Range (cm-1) Resolution No. channels
LWIR 700∼1130 0.8 538 LWIR 700∼1130 0.625 688
S/MIR 1650∼2250 1.6 375 S/MIR 1650∼2250 1.2 500
VIS 0.55-0.75μm 1 VIS 0.55-0.75μm 1
Spatial Resolution L/S/MWIR 16km L/S/MWIR 8km
VIS 2km
Area China 5000 × 5000 km2 China 5000 × 5000 km2
Mesoscale 1000 × 1000 km2 Mesoscale 1000 × 1000 km2
Temporal resolution China <1 hour China <1 hour
Mesoscale <½ hour Mesoscale <½ hour
Sensitivity (mW/m2sr⋅cm-1) LWIR 0.5∼1.1 LWIR 0.3
S/MIR 0.1∼0.14 S/MIR 0.06
VIS S/N>200(ρ=100%) VIS S/N>200 (ρ=100%)
Calibration accuracy (radiation) 1.5k (3σ) 1.0k (3σ)
Calibration accuracy (spectrum) 10 ppm (3σ) 5 ppm (3σ)
Quantization (bits) 13 13

Scan range of GIIRS (105°E)

Data and Products

Satellite Instrument Datasets
FY-4B GIIRS L1 dataL2L3 product
FY-4A GIIRS L1 dataL2L3 product

Calibration and Validation

GIIRS calibration and validation