Status of the Global Change Observation Mission (GCOM)

Japan Aerospace Exploration Agency (JAXA) started the long term observation mission named GCOM (Global Change Observation Mission) in 2006. The GCOM is the Earth observation mission by two kinds of satellite series, that are GCOM-W (Water) and GCOM-C (Climate) series. To realize the long term observation for more than 10 years, 3 generations of satellites will be launched in each satellite series. The GCOM aims to monitor climate variability, focusing on the radiation budget, carbon cycle and water-energy cycle. Changes of cloud and aerosol and the radiative forcing are the major uncertainties in the climate modeling. Providing the information on carbon dioxide sources and sinks is necessary for complete understanding of the global warming. Cooperation with numerical prediction models will make the future climate change prediction more precise. This mission will contribute not only to more precise climate change prediction, but also to the efficient usage of the Earth observation data by the operational users, ex. metrological agency or fishery information service. For short-term weather forecasting, the satellite observation is becoming an indispensable data source to generate better initial values through data assimilation techniques.

GCOM-W1 (nicknamed “SHIZUKU”) and GCOM-C1 are the first generation of satellite series. Each one is a medium-size, polar-orbiting satellite with a single observing instrument. GCOM-W1 carries the Advanced Microwave Scanning Radiometer 2 (AMSR2) and GCOM-C1 is equipped with the Second-generation Global Imager (SGLI). AMSR2 follows the observation of AMSR-E on-board Aqua, which stopped the observation in October, 2011. AMSR2 is a multi-frequency, total-power microwave radiometer system with dual polarization channels for all frequency bands. The basic function is almost identical to that of AMSR-E. The frequency bands include 6.925, 7.3, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz. The 7.3 GHz channels are new channels to help to mitigate the radio-frequency interference from the ground in 6.925 GHz channels. The SGLI instrument consists of the Visible and Near-infrared Radiometer (VNR) and the Infrared Scanner (IRS). VNR has the unique features of 250 m spatial resolution for most of the visible channels and polarization/multidirectional observation capabilities. The 250 m spatial resolution will provide enhanced observation capability over land and coastal areas where the influences of human activity are most evident. The polarization observation will enable us to retrieve aerosol information over land. The IRS has 250/500m resolution for thermal channels. From the information gathered by the 19 channels of SGLI, considerable number of products will be produced.

GCOM-W1 was launched on May 18th (Japanese standard time), 2012 by H-IIA launch vehicle at Tanegashima Island. After launch GCOM-W1 deployed and rotated the solar paddles, deployed the antenna of AMSR2 and rotated it in 4 rpm, during about 1 day. The attitude control system and propulsion system were checked and then the maneuvers to enter the A-Train started on May 24th. The 6 maneuvers were performed and GCOM-W1 was successfully entered into the specified position of the A-Train, about 3 minutes earlier than Aqua. After entering the A-Train AMSR2 was spun up to 40 rpm and its observation started on July 3rd. In parallel the commissioning of the satellite system was performed and all satellite functions turned out to be normal. The satellite went forward from the commissioning phase to the steady operational phase on August 10th. The observation data was received at the Svalbard Station every 100 minutes in order to improve the data latency. The calibration and validation work is now on-going. The Level 1 products (brightness temperatures) and Level 2 products (8 geophysical products) are planned to be released in January and in May next year respectively. Then the observation data will be available to general researchers in the website of GCOM-W1 data provision service.

GCOM-C1 started the development in JFY (Japanese Fiscal Year) 2009 and is under critical design phase. Testing of the GCOM-C1 satellite mechanical and thermal models was finished. The instrument level test of SGLI EM is performed to confirm the electrical and optical performance after or during environmental tests. The critical design review of the satellite system will be held early next year at the target to launch in JFY 2015.

The international cooperation is inevitable to enhance the global Earth observation. Scientific cooperation of GCOM-W1 will be expanded among the A-Train satellites. The cooperation between GCOM and the Joint Polar Satellite System (JPSS) of the National Oceanic and Atmospheric Administration (NOAA) is on-going.