Global Observing Satellite for Greenhouse gases and Water cycle (GOSAT-GW) is a polar-orbiting satellite carrying two mission instruments, Total Anthropogenic and Natural emissions mapping SpectrOmeter-3 (TANSO-3) and Advanced Microwave Scanning Radiometer 3 (AMSR3). TANSO-3 is developed by Ministry of the Environment for the follow-on mission of Greenhouse-gas Observation Satellite 2 (GOSAT-2) launched in 2018. AMSR3 is developed by Japan Aerospace Exploration Agency (JAXA) for the Global Change Observation Mission-Water (GCOM-W) follow-on mission to keep continuity of the passive microwave observation. GCOM-W had completed its nominal mission of five years in 2017 and has transferred to extended operation phase. Continuous observation by the onboard instrument, AMSR2 and early launch of a follow-on instrument are now strongly required both in science community and in operational fields.
Specifications of the AMSR3 is almost equivalent to AMSR2. The characteristics and performances of existing 16 frequency channels are secured by making use of heritage design, meanwhile three high frequency channels (166 GHz, 183±3 GHz and 183±7 GHz) and 10-GHz channels with improved Noise Equivalent Delta Temperature (NEDT) will be added for observation of solid precipitation and humidity and improvement in measurement accuracy of sea surface temperature. These additional channels will enhance data utilization in wide fields such as meteorology, polar research and fishery. To produce long-term continuous data record by succeeding to GCOM-W is also one of the most important targets for studies on global climate change.
Development of GOSAT-GW and AMSR3 had been officially approved in December 2019 and moved into Phase-B. An overview and current status of the mission and AMSR3 are given in this paper.