Himawari-8 and -9 are geostationary weather satellites operated by the Japan Meteorological Agency (JMA). They are successors to JMA’s Multi-functional Transport Satellite (MTSAT) series, offering significant improvements in frequency, resolution and precision.
Himawari-8 and -9 use new frequency bands for communication between the satellites and ground stations: The Ka-band (18.1–18.4 GHz) is used for ‘downlinking’ meteorological data, while the Ku-band (12.2–12.75 GHz downlink, 13.75–14.5 GHz uplink) is used for telemetry and command operations. Each satellite carries a transponder to relay environmental data from data collection platforms to sustain the data collection system (International channel: 402.0–402.1 MHz; Domestic channel: 402.1–402.4 MHz).
Like the MTSAT series, Himawari-8 and -9 are three-axis-stabilised satellites—increasing or decreasing the rotational speed of any of ‘wheels’ in each axis can adjust the satellites’ orbital path or correct for roll, pitch and yaw.
The Advanced Himawari Imager (AHI) instrument carried by both Himawari-8 and -9 records more data than previous geostationary meteorological satellites—16 channels, including three visible wavelength bands (red, green and blue) to create ‘true-colour’ images of the Earth. Different channels give us greater insights into different characteristics of the atmosphere.
Imagery from the AHI instruments also has finer spatial resolution (0.5–2 km, compared to 1–4 km for MTSAT) and precision (12–14-bit images, vs 10-bit for MTSAT). It also has higher temporal resolution; that is, new images are recorded more frequently, with one ‘full disk’ scan of the observable area every ten minutes (compared to hourly from MTSAT).
| Band | Central wavelength (μm) | Spatial resolution (km) |
|---|---|---|
| 1 | 0.43–0.48 | 1 |
| 2 | 0.50–0.52 | 1 |
| 3 | 0.63–0.66 | 0.5 |
| 4 | 0.85–0.87 | 1 |
| 5 | 1.60–1.62 | 2 |
| 6 | 2.25–2.27 | 2 |
| 7 | 3.74–3.96 | 2 |
| 8 | 6.06–6.43 | 2 |
| 9 | 6.89–7.01 | 2 |
| 10 | 7.26–7.43 | 2 |
| 11 | 8.44–8.76 | 2 |
| 12 | 9.54–9.72 | 2 |
| 13 | 10.3–10.6 | 2 |
| 14 | 11.1–11.3 | 2 |
| 15 | 12.2–12.5 | 2 |
| 16 | 13.2–13.4 | 2 |
Taken together, these advances enhance our ability to detect and monitor:
- the centres of tropical cyclones over the ocean;
- thunderstorms, as they develop;
- volcanic ash, fire and smoke; and
- fog and low cloud.
Computer-generated impression of Himawari-8 in orbit
Unlike the MTSAT orbital configuration (with MTSAT-1R at 140°E, MTSAT-2 at 145ºE), Himawari-8 and Himawari-9 orbit in close formation, both at around 140.7°E (in line with Japan, Papua and central Australia). This will offer the same view when operations are switched between the satellites.
The Bureau has taken on a regional role in disseminating observational data from Himawari-8 and -9, which we receive free of charge from the JMA via three parallel routes:
- HimawariConnect—a dedicated fibre-optic line from Japan to the Bureau;
- HimawariCloud—an internet service open to various national meteorological services; and
- HimawariCast—data re-broadcast through a communications satellite.
Once received, the data are processed into a number of products for dissemination to the Bureau’s Regional Forecasting Centres and to various other internal and external stakeholders. Data from each new scan of our region (every ten minutes) are available to our forecasters with very short latency, so forecasts are informed by near-real-time information.
The data also feed into numerical weather prediction models, run on the Bureau’s supercomputer.