Imaging bands

Himawari-8 and Himawari-9 have a new payload called the Advanced Himawari Imager (AHI) for dedicated meteorological mission.

Table 1 shows the AHI observation bands. The functions and specifications are notably improved from those of the imagers on board MTSATs, and the AHI contributes to better nowcasting, improved numerical weather prediction accuracy and enhanced environmental monitoring. Color images are derived by compositing three visible band (blue: 0.47 µm; green: 0.51 µm; red: 0.64 µm).

^* The Himawari-8/9 band corresponding to the MTSAT-1R/2 IR1 band was changed from 11.2 µm to 10.4 µm on 31 October, 2013.

Table 1: Imager specifications.

Wave length [µm]	Himawari-8/9				MTSAT-1R/2
	Band number	Spatial resolution at SSP [km]	Central wave length [µm]		Channel name	Spatial resolution at SSP [km]
	Band number	Spatial resolution at SSP [km]	AHI-8 (Himawari-8)	AHI-9 (Himawari-9)	Channel name	Spatial resolution at SSP [km]
0.47	1	1	0.47063	0.47059	-	-
0.51	2	1	0.51000	0.50993	-	-
0.64	3	0.5	0.63914	0.63972	VIS	1
0.86	4	1	0.85670	0.85668	-	-
1.6	5	2	1.6101	1.6065	-	-
2.3	6	2	2.2568	2.2570	-	-
3.9	7	2	3.8853	3.8289	IR4	4
6.2	8	2	6.2429	6.2479	IR3	4
6.9	9	2	6.9410	6.9555	-	-
7.3	10	2	7.3467	7.3437	-	-
8.6	11	2	8.5926	8.5936	-	-
9.6	12	2	9.6372	9.6274	-	-
10.4	13	2	10.4073	10.4074	IR1	4
11.2	14	2	11.2395	11.2080	-	-
12.4	15	2	12.3806	12.3648	IR2	4
13.3	16	2	13.2807	13.3107	-	-
SSP: sub satellite point

Spectral Response Functions

The figures below show the SRFs (Spectral Response Functions) of the AHIs on board Himawari-8 (as of September 2013) and -9 (as of October 2013). Microsoft Excel workbooks (zip files) of the SRFs for AHIs on Himawari-8 and -9 can also be downloaded from the hyperlinks below.

Figure 1-1: Himawari-8/AHI SRFs. [Left: VIS and NIR, Right: IR (Click figure to enlarge.)]

Figure 1-2: Himawari-9/AHI SRFs. [Left: VIS and NIR, Right: IR (Click figure to enlarge.)]

Comparison of Spectral Response Functions between AHI-8 and -9 (PNG, 250 KB)
AHI-8_SpectralResponsivity.zip (1.1 MB) (update September 2013; provided by ITT Exelis)
AHI-9_SpectralResponsivity.zip (1.1 MB) (update October 2013; provided by ITT Exelis)

Test results

The performance of the AHI on board Himawari-8 is evaluated in ground testing. The test results, including data on the center wavelength, bandwidth, bits, SNR, dynamic range, radiometric calibration accuracy, internal calibration target (ICT) emissivity and out-of-band response, can be accessed via the following link:

AHI-8_performance_test_en.pdf (100 kB)

Observation area and periodicity

Himawari-8 and -9 AHI scanning is conducted in the categories of Full Disk (whole-earth images), Japan Areas (Regions 1 and 2), Target Area (Region 3) and Landmark Areas (Regions 4 and 5). The Full Disk and Japan Area scan ranges are fixed, while those for Target Area and Landmark Area scanning are set in prompt response to changes in meteorological conditions.

Landmark Area scanning data are used only for Himawari-8 navigation, and are not intended for use as satellite products. JMA plans to use Region 5 for observation of rapidly developing cumulonimbus cloud enabling provision of data to users. Each 10-minute period incorporates one Full Disk scan, four Japan Area and Target Area scans, and twenty scans for each Landmark Area. This 10-minute sequence is a basic unit of the observation schedule timeline. In Himawari-8 and -9 baseline observations, the timeline is repeated every 10 minutes except during housekeeping operation. Observation areas and frequencies are shown in Table 2, timeline-based scan images are shown in Figure 2, the Japan Area is shown in Figure 3, and observation areas/pixel numbers are shown in Table 3 (subject to in-orbit-test in regional observation).

The following animation shows the concept of the AHI observation sequence on a 10-minute timeline:

Figure 2: AHI observation sequence within a 10-minute time frame (Click figure to enlarge.)

Figure 3: Coverage of the Japan Area
(Subject to slight changes based on the results of in-orbit testing after launch)

Table 2: Himawari-8 and -9 observation areas and frequencies

	Observations per timeline	Time cycle [min.]	Observations per day
Full Disk (Fixed)	1	10	144
Japan Area (Fixed) (Region 1 + Region 2)	4	2.5	576
Target Area (Flexible) (Region 3)	4	2.5	576
Landmark Area (Flexible) (Region 4)	20	0.5	2,880
Landmark Area (Flexible) (Region 5)	20	0.5	2,880

Table 3. Himawari-8 and -9 observation areas and numbers of pixels

Observation area	Band number (see Table 1)	Spatial resolution at SSP (sub satellite point)[km]	Numbers of pixels
Observation area	Band number (see Table 1)	Spatial resolution at SSP (sub satellite point)[km]	East-west direction	North-south direction
Full Disk	3	0.5	22,000	22,000
	1,2,4	1	11,000	11,000
	5-16	2	5,500	5,500
Japan Area (Region 1 + Region 2)	3	0.5	6,000	4,800
	1,2,4	1	3,000	2,400
	5-16	2	1,500	1,200
Target Area (Region 3)	3	0.5	2,000	2,000
	1,2,4	1	1,000	1,000
	5-16	2	500	500
Landmark Area (Region 4)	3	0.5	2,000	1,000
	1,2,4	1	1,000	500
	5-16	2	500	250
Landmark Area (Region 5)	3	0.5	2,000	1,000
	1,2,4	1	1,000	500
	5-16	2	500	250

Photographs (Click figure to enlarge.)

Sensor unit

Cryocooler electronics

Electronics unit

Contents

Imaging bands

Spectral Response Functions

Test results

Observation area and periodicity

Photographs (Click figure to enlarge.)