New JAXA's satellite launched, strengthening G3W monitoring efforts
The Japan Aerospace Exploration Agency (JAXA) has successfully launched the Greenhouse Gases and Water Cycle Observation Satellite (GOSAT-GW). This satellite will contribute to the Global Greenhouse Gas Watch (G3W) initiative coordinated by the World Meteorological Organization (WMO).
With this launch, there are now three GOSAT satellites in orbit, the first of which was launched in 2009. GOSAT-GW is an important mission that enhances global greenhouse gas (GHG) monitoring capabilities and aligns with the Committee on Earth Observation Satellites (CEOS) greenhouse gas (GHG) Roadmap.
The satellite follows a sun-synchronous orbit at an altitude of 666 km, with a repeat cycle of three days - consistent with previous GOSAT missions. It travels from the south-east to the north-west during daytime, crossing the equator at approximately 1:30 p.m. local time.
GOSAT-GW is equipped with a grating imaging spectrometer, known as TANSO-3, which offers higher spatial resolution compared to GOSAT-1 and GOSAT-2. It features a selectable swath width:
- A wide mode covering 911 km, with a 10 km footprint, enabling global coverage every three days.
- A focus mode covering 90 km, with a footprint of 1–3 km, suitable for analyzing localized emission sources.
Satellite observations will be assimilated into the NIES data assimilation system, alongside other space- and surface-based observations. Surface networks include Fourier Transform Spectrometers from the Total Carbon Column Observing Network (TCCON) and the Collaborative Carbon Column Observing Network (COCCON), which provide validation data for column-averaged CO₂ (XCO₂) and methane (XCH₄) concentrations.
Airborne measurements also play a key role in validating CO₂ and CH₄ data. Notably, the Comprehensive Observation Network for Trace gases by AirLiner (CONTRAIL) provides long-term, global-scale airborne observations that are especially valuable for satellite data validation.
Further reading
- Tanimoto, H., Matsunaga, T., Someya, Y. et al., The greenhouse gas observation mission with Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW): objectives, conceptual framework and scientific contributions. Prog Earth Planet Sci 12, 8 (2025).
