低～高周波数までをカバーする衛星搭載マイクロ波イメージャは、雲の中や地球表面の水に関する変数の観測にとって非常に強力なツールである。高性能マイクロ波放射計（AMSR）シリーズは、大口径の主反射鏡による高空間解像度、6.9~89GHzの周波数帯、全球の高頻度観測を実現した。2002年打上げのAqua衛星搭載のAMSR-E、2012年打上げで運用中の水循環変動観測衛星（GCOM-W）搭載のAMSR2により、23年以上、全球水循環変動の観測を行っている。AMSRシリーズは、各国気象機関で広く定常利用され、極域海氷の監視やGSMaP等の複数衛星を複合した降水量プロダクトの作成にも貢献している。
最新のAMSR3は、2025年6月打上げの温室効果ガス・水循環観測技術衛星（GOSAT-GW）に搭載され、AMSR2の観測を継続するとともに、新たなユーザ要求に対応し、降雪推定及び水蒸気解析のための高周波チャネルと、安定した海面水温推定のための温度分解能を向上した10.25GHzチャネルを追加した。
本セッションでは、これまでのAMSRシリーズの成果やAMSR3による初期観測や利用成果を紹介する。

Space-based microwave imagers with low-to-high frequency channels are a strong tool for monitoring water-related variables inside of clouds and Earth's surface through clouds on a daily basis. The Advanced Microwave Scanning Radiometers (AMSR) are a series of Japanese microwave imagers that have unique capabilities in their high spatial resolution with large-sized main reflector, dual polarization channels for all frequency bands from 6.9- to 89-GHz, and frequent global observation with wide swath. The series of instruments provide continuous global water cycle observations for more than 23 years by AMSR-E on board the NASA's Aqua satellite launched in 2002 and AMSR2 on board the Global Change Observation Mission - Water (GCOM-W) launched in 2012 and currently in operation. Data from the AMSR series is widely used in meteorological agencies in Japan, U.S., Europe, Australia, etc., and is also used for monitoring of sea ice in polar oceans. It also contributes to producing satellite based merged precipitation products, such as GSMaP, IMERG, CMORPH, etc., to monitor hourly global rainfall distribution in a near-real-time basis.
The latest instrument, AMSR3 on board the Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW) launched in June 2025, succeeds the afternoon orbit observation of AMSR2, and expands its observation capability to respond to new user needs. Major improvements in AMSR3 are new high-frequency channels (166- & 183-GHz) for snowfall retrievals and water vapor analysis in numerical weather predictions, and additional 10.25-GHz channels with better Noise Equivalent Delta Temperature (NEDT) for robust sea surface temperature estimates.
In this session, we will focus on the observation results and outcomes obtained by the past and current AMSR series, and early observation, calibration, and validation results from AMSR3.