FY-4B Instruments

Advanced Geostationary Radiation Imager (AGRI)

A multiple channel radiation imager, one of the primary instruments aboard FY-4B. Technically featured by precisely designed two-mirror structure, capable of accurate and flexible sensing in two dimensions, and minute-level fast sector scanning. Frequent earth imaging over 15 bands with off-axis three reflections of primary optic system. On-board black body available for IR calibrations at very short time intervals.

AGRI of FY-4

Primary instrument details:

		FY-4B (Operational)	FY-4A (R&D)
Number of bands		15	14
Spatial resolution	VIS	0.5~1km	0.5~1km
	near IR	2km	2km
	IR	4km	4km
Temporal resolution		15min/full-disc	15min/full-disc
Sensitivity	reflection bands	SNR=200@ρ=100%	SNR=200@ρ=100%
Sensitivity	IR bands	NEΔT=0.2K@300K	NEΔT=0.2K@300K
Calibration accuracy	reflection bands	3~5%	3~5%
Calibration accuracy	IR bands	0.7K	1K

Demo of FY-2 VISSR scan mode.	Demo of FY-4 AGRI scan mode.

Parameters of FY-4B AGRI

Band	Center wave length (μm)	Band width (μm)	Spatial resolution(km)	Sensitivity/SNR		Main purpose
1	0.47	0.45~0.49	1	S/N≥90(ρ=100%)		Aerosol
2	0.65	0.55~0.75	0.5	S/N≥150(ρ=100%)@0.5km	S/N≥3(ρ=1%)@1km	Fog, cloud
3	0.825	0.75~0.90	1	S/N≥200(ρ=100%)	S/N≥3(ρ=1%)	Vegetation
4	1.379	1.371~1.386	2	S/N≥120(ρ=100%)	S/N≥2(ρ=1%)	Cirrus
5	1.61	1.58~1.64	2	S/N≥200(ρ=100%)	S/N≥3(ρ=1%)	Cloud, snow
6	2.25	2.10~2.35	2	S/N≥200(ρ=100%)	S/N≥2(ρ=1%)	Cirrus, aerosol
7	3.75	3.50~4.00(high)	2	≤0.7K(315K)		Fire
8	3.75	3.50~4.00(low)	4	0.2K(300K)	2K(240K)	Land surface
9	6.25	5.80~6.70	4	0.2K(300K)	0.9K(240K)	High level water vapor
10	6.95	6.75~7.15	4	0.25K(300K)	0.9K(240K)	Mid level water vapor
11	7.42	7.24~7.60	4	0.25K(300K)	0.9K(240K)	Low level water vapor
12	8.55	8.3~8.8	4	0.2K(300K)	0.4K(240K)	Cloud
13	10.80	10.30~11.30	4	0.2K(300K)	0.4K(240K)	Surface temperature
14	12.00	11.50~12.50	4	0.2K(300K)	0.4K(240K)	Surface temperature
15	13.3	13.00~13.60	4	0.5K(300K)	0.9K(240K)	Cloud and water vapor

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.

GIIRS on FY-4B has spatial resolution of 12km, with better sensitivity and calibration accuracy through improved structure and designs.

Fig. GIIRS of FY-4.

Primary instrument details:

	FY-4B (Operational)	FY-4A (R&D)
Working bands	LWIR: 680～1130 cm^-1	LWIR: 700～1130 cm^-1
	MWIR: 1650～2250 cm^-1	MWIR: 1650～2250 cm^-1
	VIS: 0.55~0.90μm	VIS: 0.55~0.90μm
Spectral resolution	0.8cm^-1	LWIR: 0.8cm^-1, MWIR: 1.6cm^-1
Spatial resolution	IR: 12km SSP VIS: 1km SSP	IR: 16km SSP VIS: 2km SSP
Temporal resolution	45min	1hour

Regional observation at 1 hour intervals.

Parameters of FY-4B GIIRS.

IR bands:

Band	Range	Sensitivity	Calibration accuracy
LWIR	680 ~ 1130 cm^-1	0.5 mW/(m²sr cm^-2)	0.7 K
MWIR	1650 ~ 2250 cm^-1	0.1 mW/(m²sr cm^-2)	0.7 K

VIS band:

○ SNR: S/N ≥ 200(ρ=100%)

○ Calibration accuracy: better than 10 ppm

Geostationary High-speed Imager (GHI)

GHI is capable of making observations from GEO orbit for 2000km×2000km regions with spatial resolution up to 250m in 1 minute intervals.

Such high frequecy surface and atmosphere observations are very important for monitoring and forecasting the rapid evolving extreme weather systems, e.g. typhoon and severe convections.

Fig. GHI of FY-4B.

Regional observation at less than 1 minute intervals.

Primary instrument details:

Band	Range (μm)	Spatial resolution (km)	Accuracy / SNR	Main purpose
1	All color	0.25	＞300@100%	Land surface, vegetation
2	0.445～0.495	0.5	＞200@100%	Small particles aerosol
3	0.52～0.57	0.5	＞300@100%	Aerosol
4	0.62～0.67	0.5	＞300@100%	Aerosol
5	1.371～1.386	0.5	＞150@100%	Cirrus
6	1.58～1.64	0.5	＞300@100%	Snow
7	10.3～12.5	2	0.2K@300K	Surface temperature

Space Environment Monitoring Instrument Package (SEP)

Introduction
Paramter

A suite that contains energetic particle detectors, radiation dosage detectors, electrification detectors, and magnetometer.

SEP on FY-4B adds middle energetic particle detectors and low energetic particle detectors besides the high energetic particle detectors on FY-4B. It has also other improvements to improve the space weather environment observation abilities.

Fig. SEP of FY-4B.

Instrument	Parameter
High Energy Particle Detector	Energy range	Protons: 1MeV~165MeV, integration channel >165MeV
	Energy range	Electrons: 0.4MeV~4MeV, integration channel >2MeV
	Calibration accuracy	better than 10%
	Particle flux sensitivity	∆N/N≤5%
	Detection dimension	orthogonal 3
Middle Energy Electrons Detector	Energy range	30KeV~600KeV
	Calibration accuracy	better than 10%
	Sensitivity	∆N/N≤5%
	Detection dimension	equatorial plane: 7, meridian plane: 9
Middle Energy Protons Detector	Energy range	0.03MeV-1.0MeV
	Calibration accuracy	better than 10%
	Sensitivity	∆N/N≤5%
	Detection dimension	equatorial plane: 7, meridian plane: 9
Low Energy Particle Detector	Energy range	100KeV~40KeV
	Calibration accuracy	better than 10%
	Sensitivity	∆N/N≤5%
	Detection dimension	equatorial plane: 7, meridian plane: 9
Radiation Dosage Detector	Range	0~2.0x106rad(Si)
	Sensitivity	≤500rad(Si)
	Calibration accuracy	better than 10%
Charge Potential Detector	Sensitivity	Surface differential potential	≤0.1kV
		Surface absolute potential	≤10%
		Deep charging potential	≤0.1kV
Magnetometer	Active range	-600nT~+600nT, three bands (orthogonal three components)
	Calibration accuracy	≤1.0nT (after temperature correction)
	Sensitivity	better than 1.0nT/axis