image: (a) Global observation (July 14, 2025, radiance (light intensity) at a wavelength of 767 nm), (b) Focus Mode observation over Tokyo (July 17, 2025, radiance at a wavelength of 767 nm), and (c) spectral data (wavelength range of approximately 750–780 nm).
Credit: JAXA/MOE/NIES
1. Summary
The National Institute for Environmental Studies (NIES), in cooperation with the Ministry of the Environment of Japan (MOE) and the Japan Aerospace Exploration Agency (JAXA), has been observing atmospheric carbon dioxide, methane, and other gases by utilizing the Greenhouse Gases Observing Satellite (GOSAT) Series, with the aim of advancing climate change science and contributing to the evaluation of climate change policies and initiatives.
The Global Observing SATellite for Greenhouse gases and Water cycle “IBUKI GW” (GOSAT-GW)1, developed jointly by MOE, NIES, and JAXA, was successfully launched at 1:33 a.m. on June 29, 2025 (JST). Since the launch, initial functional verification operations2 of “IBUKI GW” (GOSAT-GW) have been conducted.
The first observation by the Total Anthropogenic and Natural emissions mapping SpectrOmeter-3 (TANSO-3) onboard this satellite was carried out from July 14 to July 20, 2025, and the proper operation of TANSO-3 was confirmed.
After the initial functional verification operations are completed over a period of three months after the launch, a sensor accuracy test and an initial calibration will be performed. Following these processes, GOSAT-GW will shift to the nominal operation phase, with the aim of beginning to provide data to relevant parties towards the end of 2025.
2. First observational data by TANSO-3
Figure 1 shows the first observational data by TANSO-3.
(a) In Wide Mode3, global observations are made with a swath width of over 900 km and a spatial resolution of 10 km. The Wide Mode observations cover the entire globe within three days.
(b) In Focus Mode4, observations are made with a swath width of over 90 km and a spatial resolution of 1–3 km.
(c) For each pixel (observation point) in the images shown in (a) and (b), spectral data5 can be obtained, as shown in the graph in (c). The first observation operation of TANSO-3 successfully acquired spectral absorption data for carbon dioxide, methane, and nitrogen dioxide as planned, confirming that the observation functions of TANSO-3 are operating properly.
Figure 2 shows observation images captured in Wide Mode and Focus Mode on July 14, 2025. The Focus Mode images are shown within the Wide Mode images inside the red dotted rectangles. In Wide Mode, observations are made from south to north along the satellite orbit with a swath width of over 900 km, which enables global observations approximately once every three days. TANSO-3 is the only sensor in the world that can observe global greenhouse and other gases at high frequency and over a wide area by selecting Wide Mode and Focus Mode observations. It is expected that TANSO-3 will contribute to the observation of greenhouse gases on a global scale.
Figure 3 shows an example of the Wide and Focus Modes. On the left is an observation image of the area from Kinki to Hokkaido obtained in Wide Mode at around 1:00 p.m. on July 20, 2025. On the right is an observation image of the Tokyo area captured in Focus Mode at around 1:00 p.m. on July 17, 2025. In addition to the Wide Mode, which can observe an area such as that from Kinki to Hokkaido at once, TANSO-3 has Focus Mode. In Focus Mode, the sensor can collect images with a higher spatial resolution than in Wide Mode by pointing at the targeted observation points with the onboard scanner mirror.
Figure 4 shows the spectral data of each observation band obtained at observation points along the white line in Figure 3 (right). The data are displayed two-dimensionally, with the horizontal axis representing the wavelength direction (WL) and the vertical axis representing the spatial direction perpendicular to the orbit (CT). Below the two-dimensional image of each band, the spectral data of the 15th pixel in the CT direction are shown. The spectral data of each band show variations in the wavelength direction. These variations indicate that sunlight is absorbed at specific wavelengths by nitrogen dioxide (Band 1), oxygen (Band 2), and greenhouse gases such as carbon dioxide and methane (Band 3) as it passes through the atmosphere. The detailed analysis of these variations (absorption degrees) makes it possible to calculate the concentrations of greenhouse gases in the atmosphere.
Figure 5 shows the global observational data (Band 2, wavelength of 767 nm) obtained in Wide Mode of TANSO-3 during the period July 14 to 16, 2025, confirming that TANSO-3 can observe the entire globe within three days.
Note: In Figures 1, 2, 3, and 5, the areas observed by TANSO-3 are shown in grayscale images. Other areas are shown in color Google Earth images.
3. Annotations
1. IBUKI GW (GOSAT-GW: Global Observing SATellite for Greenhouse gases and Water cycle)
A satellite that observes the Earth’s water cycle and greenhouse gases from space; it carries two mission instruments, the Advanced Microwave Scanning Radiometer 3 (AMSR3) and the Total Anthropogenic and Natural emissions mapping SpectrOmeter-3 (TANSO-3).
2. Initial functional verification operations
Operations that verify the satellite, including its onboard sensors, has the specified functional performance in orbit.
3. Wide Mode
A TANSO-3 observation mode that maps the entire globe with a swath width of over 900 km and a spatial resolution of 10 km.
4. Focus Mode
A TANSO-3 observation mode that maps urban areas or other areas with a swath width of over 90 km and a spatial resolution of 1–3 km.
5. Spectral data
Data measured for each wavelength (color) of sunlight intensity after absorption by the Earth’s atmosphere.
Method of Research
Observational study
Subject of Research
Not applicable