GCOM-W1: Global Change Observation Mission 1st - Water

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May 17, 2013 Updated

SHIZUKU to provide geophysical quantity products

On May 17, 2013, JAXA started offering eight kinds of products whose physical quantity concerning water on the Earth, including precipitable water in the atmosphere and sea surface temperature, is calculated based on the observation data acquired by the Advanced Microwave Scanning Radiometer 2 (AMSR2) aboard the Global Change Observation Mission 1st-Water “SHIZUKU” (GCOM-W1).
These products will contribute to capture environmental changes on a global scale such as the El Nino and La Nina Phenomena. In addition, they can also be utilized for other various fields both in Japan and overseas including weather and precipitation forecasts, efficiently finding fishing points, and enhancing measures against floods.
JAXA has already started providing “brightness temperature products,” which indicate the strength of radio waves in a specific frequency emitted from the ground and in the atmosphere.

Overview

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Observing All Environmental Changes on Earth for Present and Future Generations

The "Global Change Observation Mission" (GCOM) aims to construct, use, and verify systems that enable continuous global-scale observations (for 10 to 15 years) of effective geophysical parameters for elucidating global climate change and water circulation mechanisms.
The GCOM mission is a two series of satellites, GCOM-W for observing water circulation changes and GCOM-C for climate changes. The GCOM-W with a microwave radiometer onboard will observe precipitation, vapor amounts, wind velocity above the ocean, sea water temperature, water levels on land areas, and snow depths.
The GCOM-W1 is the first satellite for the GCOM-W series.


World's Largest Revolving Space Antenna AMSR2

The Advanced Microwave Scanning Radiometer 2 (AMSR2,) which will be loaded onto the GCOM-W1, is a sensor to observe radiometers, or microwaves emitted naturally from the ground, sea surface and atmosphere, using six different frequency bands ranging from 7 GHz to 89 GHz. The strength of a natural microwave is determined by its characteristics and moisture, including the surface condition and temperature of the material. Although it depends on the frequency, the microwave is very weak. AMSR2 will detect such weak microwaves at an altitude of 700 kilometers and measure the strength of them with a very high accuracy. For example, by measuring the strength of a microwave emitted from the sea surface with the AMSR2, we can understand the water temperature of the sea surface to an accuracy of 0.5 degrees Celsius.
The antenna of the AMSR2, which receives microwaves from the ground, arc scans the ground surface at a ratio of one turn every 1.5 seconds and observes an area approximately 1,450 kilometers wide in one scan. Using this scanning method, the AMSR2 can observe over 99 percent of the Earth's area in just 2 days. The diameter of the antenna is about 2 meters, making it the world's largest observation sensor aboard a satellite. The height of the rotating part is about 2.7 meters and the weight is about 250 kilograms. The AMSR2 can keep rotating such a large and heavy antenna at a speed of one turn per 1.5 seconds for 24 hours a day and more than five years without a minute of rest.