The Global Change Observation Mission (GCOM) consists of two polar orbiting satellite observing systems, GCOM-W
(Water) and GCOM-C (Climate), and three generations to achieve global and long-term monitoring of the Earth. GCOM-W1, the first satellite of the GCOM-W series, was successfully launched on May 18, 2012 (Japan Standard
Time). The Advanced Microwave Scanning Radiometer-2 (AMSR2), which is a successor of AMSR on the Advanced
Earth Observing Satellite-II (ADEOS-II) and AMSR for EOS (AMSR-E) on NASA’s Aqua satellite, is a single mission
instrument on GCOM-W1. Basic characteristics of AMSR2 is similar to that of AMSR-E to continue the AMSR-E
observations, with several enhancements including larger main reflector (2.0 m), additional channels at the C-band frequency band, and improved calibration system. AMSR-E halted its observation on October 4, 2011 due to the increase
of antenna rotation torque, which is considered as the typical aging effect. Although all the efforts are being made to
resume the AMSR-E observation, early initiation of the AMSR2 observation has been highly desired. After the
completion of the orbit injection into the A-Train constellation, AMSR2 started rotating and initiated global observation.
During the initial calibration and validation phase, brightness temperatures will be evaluated and characterized through
methodologies such as the inter-calibration among similar microwave radiometers including the TRMM Microwave
Imager (TMI) and WindSat on Coriolis mission.