The Greenhouse Gases Observing SATellite (GOSAT) and its successor, GOSAT-2, collectively known as the GOSAT series, have observed carbon dioxide (CO2) and methane (CH4) since 2009 and 2018, respectively, providing one of the longest and most consistent global greenhouse gas (GHG) observation records from space. Jointly developed by the National Institute for Environmental Studies (NIES), the Ministry of the Environment, Japan, and the Japan Aerospace Exploration Agency (JAXA), the series aims to advance scientific understanding of global CO2 and CH4 cycles and to support climate research and related policymaking.NIES is responsible for higher-level data processing, validation and distribution of GOSAT data products. Observational data are routinely processed at NIES data processing systems and distributed through the GOSAT data platforms. The product suite spans multiple processing levels: calibrated radiance spectra (Level 1); retrieved results of the global column-averaged dry-air mole fractions of CO2 and CH4 (XCO2 and XCH4; Level 2) etc.; gridded and temporally averaged concentrations (Level 3); and CO2 and CH4 surface flux estimates derived through inverse modeling (Level 4A), along with simulated concentrations (Level 4B). The Level 2 XCO2 and XCH4 products are validated with observations from the Total Carbon Column Observing Network (TCCON), a global ground-based network of solar-viewing Fourier transform spectrometers. These products have contributed essential datasets to major climate assessments, including the IPCC Sixth Assessment Report, and were submitted to the first Global Stocktake in 2022 under the Paris Agreement.The third satellite in the series, the Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW), launched in June 2025, carries the TANSO-3 grating spectrometer with wide and focus observation modes for monitoring XCO2, XCH4, and nitrogen dioxide from local to global scales. Product processing is ongoing, and the resulting datasets will support global GHG monitoring and verification of national anthropogenic emission inventories.