GCOM-W1 (Shizuku)

GCOM-W1 (Shizuku) is a Japanese Earth observation mission operated by the Japan Aerospace Exploration Agency (JAXA). It is the first satellite in the GCOM-W (Global Change Observation Mission - Water) programme, a series designed to improve understanding of water circulation and energy exchange within the climate system.^[1]

The spacecraft launched aboard an H-IIA rocket from Tanegashima Space Center and entered a sun-synchronous orbit at 699.6 km altitude with a 98.2-degree inclination and a 13:30 local time ascending node (A-Train slot).^[2][3] The launch took place on 18 May 2012 in Japan Standard Time^[2] and on 17 May 2012 in Coordinated Universal Time.^[3] GCOM-W1 joined the A-Train constellation at that orbit slot, enabling coordinated afternoon-crossing observations alongside other constellation members.

The mission carries a single primary instrument: AMSR2 (Advanced Microwave Scanning Radiometer 2), a conically scanning passive microwave radiometer that measures thermal emission from the Earth surface and atmosphere across multiple frequency channels spanning 6.9 to 89 GHz. AMSR2 provides geophysical retrievals including sea surface temperature, sea ice concentration and extent, soil moisture, precipitation rate, integrated atmospheric water vapour, and snow water equivalent. Its 1,450 km swath and two-day global revisit cycle deliver near-complete coverage at temporal resolution suitable for operational applications in numerical weather prediction and cryospheric monitoring.^[4][3][1]

GCOM-W1 was designed for a five-year operational life. The mission remained in extended operations beyond that design horizon as of 19 January 2026.^[4] GCOM-W1 provides a long-term passive microwave data record used for climate, water-cycle, weather-model, sea-ice, and land-surface monitoring applications.^[5][1]