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Atmospheric and hydrospheric sciences
202501202501
The greenhouse gas observation mission with Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW): objectives, conceptual framework and scientific contributions
Hiroshi Tanimoto, Tsuneo Matsunaga, Yu Someya, Tamaki Fujinawa, Hirofumi Ohyama, Isamu Morino, Hisashi Yashiro, Takafumi Sugita et al.Tanimoto H, Matsunaga T, Someya Y, Fujinawa T, Ohyama H, Morino I, Yashiro H, Sugita T, Inomata S, Müller A, Saeki T, Yoshida Y, Niwa N, Saito M, Noda H, Yamashita Y, Ikeda K, Saigusa N, Machida T, Frey MM, Lim H, Srivastava P, Jin Y, Shimizu A, Nishizawa T, Kanaya Y, Sekiya T, Patra P, Takigawa M, Bisht J, Kasai Y, Sato TO
Greenhouse gas, Air pollutant, Carbon dioxide, Nitrogen oxides, Satellite, Global Stocktake
Schematic illustration of TANSO-3 observations onboard the GOSAT-GW, demonstrating the standard wide-swath, push-broom mode (Wide Mode). The color-coded XCO2 concentrations simulated using the NICAM model for July 2019 are also shown.
Locations of co-located ground-based remote sensing spectrometers in Japan that will be used for the TANSO-3 validation as well as other ground-based in situ monitoring stations, and typical monitoring routes for passenger aircraft and cargo ships. The locations of instruments in the Tokyo Metropolitan Area are shown in upper right. EANET: Acid Deposition Monitoring Network in East Asia; GAW: Global Atmospheric Watch.
The Japanese Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW) will be an Earth-observing satellite to conduct global observations of atmospheric carbon dioxide (CO2), methane (CH4), and nitrogen dioxide (NO2) simultaneously from a single platform. GOSAT-GW is the third satellite in the series of the currently operating Greenhouse gases Observing SATellite (GOSAT) and GOSAT-2. It will carry two sensors, the Total Anthropogenic and Natural emissions mapping SpectrOmeter-3 (TANSO-3) and the Advanced Microwave Scanning Radiometer 3 (AMSR3), with the latter dedicated to the observation of physical parameters related to the water cycle. TANSO-3 is a high-resolution grating spectrometer designed to measure reflected sunlight in the visible to short-wave infrared spectral ranges. It aims to retrieve the column-averaged dry-air mole fractions of CO2 and CH4 (denoted as XCO2 and XCH4, respectively), as well as the vertical column density of tropospheric NO2. The TANSO-3 sensor onboard GOSAT-GW will utilize the wavelength bands of 0.45, 0.76, and 1.61 µm for NO2, O2, and CO2 and CH4 retrievals, respectively. GOSAT-GW will fly in a sun-synchronous orbit with a local overpass time of approximately 13:30 and a 3-day ground-track repeat cycle. The TANSO-3 sensor has two observation modes in the push-broom operation: Wide Mode, which provides globally covered maps with a 10-km spatial resolution within 3 days, and Focus Mode, which provides snapshot maps over targeted areas with a high spatial resolution of 1–3 km. The objectives of the GOSAT-GW mission include (1) monitoring atmospheric global-mean concentrations of greenhouse gasses (GHGs), (2) verifying national anthropogenic GHG emissions inventories, and (3) detecting GHG emissions from large sources, such as megacities and power plants. A comprehensive validation exercise will be conducted to ensure that the sensor products’ quality meets the required precision to achieve the above objectives. With a projected operational lifetime of seven years, GOSAT-GW will provide vital space-based constraints on both anthropogenic and natural GHG emissions. These measurements will contribute significantly to climate change mitigation efforts, particularly by supporting the Global Stocktake (GST) mechanism, a key element of the Paris Agreement.
