Keiji Imaoka

The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E), NASDA's contribution to the EOS for global energy and water cycle studies

The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) was developed and provided to the National Aeronautics and Space Administrations EOS Aqua satellite by the National Space Development Agency of Japan, as one of the indispensable instruments for Aquas mission. AMSR-E is a modified version of AMSR that was launched December 2002 aboard the Advanced Earth Observing Satellite-II (ADEOS-II). It is a six-frequency dual-polarized total-power passive microwave radiometer that observes water-related geophysical parameters supporting global change science and monitoring efforts. The hardware improvements over existing spaceborne microwave radiometers for Earth imaging include the largest main reflector of its kind and addition of 6.925-GHz channels. These improvements provide finer spatial resolution and the capability to retrieve sea surface temperature and soil moisture information on a global basis. This paper provides an overview of the instrument characteristics, mission objectives, and data products.

Global Change Observation Mission (GCOM) for Monitoring Carbon, Water Cycles, and Climate Change

The Japan Aerospace Exploration Agency (JAXA) is pursuing the Global Change Observation Mission (GCOM) that will inherit the Advanced Earth Observing Satellite-II (ADEOS-II) mission and develop into long-term monitoring. GCOM is not the name of a single satellite, but of a mission that consists of two series of medium-size satellites, GCOM-W (Water) and GCOM-C (Climate), and three generations of each satellite series to continue the observations for 10 to 15 years. The Advanced Microwave Scanning Radiometer-2 (AMSR2) will be the single instrument on the GCOM-W1 satellite, which is the first satellite of the GCOM series. The second satellite will be GCOM-C1, which will carry the Second-generation Global Imager (SGLI). GCOM-W will mainly contribute to the observations related to global water and energy circulation, while GCOM-C will contribute to the measurements related to the carbon cycle and radiation budget. Current target launch years are calendar year 2011 for GCOM-W1 and 2014 for C1.

Diurnal Variation of Precipitation over the Tropical Oceans Observed by TRMM/TMI Combined with SSM/I

Abstract The Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) data are used in this study as the first passive microwave information from a precessing orbit to reveal diurnal variations of precipitation over the tropical oceans (30°S–30°N). Data from three Special Sensor Microwave Imagers are combined to help alleviate the aliasing problem caused by the slow diurnal sampling of the TRMM satellite. Annual mean diurnal variations of rainfall in 1998 are presented for 10° latitude bands and six regions. The diurnal variation over all the tropical oceans exhibits an amplitude of about ±14% of the mean, and it peaks near dawn (approximately 0400–0700 LST). By latitude band, diurnal variation is most evident in the deep Tropics, while the ratio of the amplitude over the mean is relatively constant over most latitude bands. Other than in the early morning, there are no evident peaks exceeding the error bars for this analysis. By region, the coastal areas where the ITCZ intersects large continent...

AMSR/AMSR-E level 2 and 3 algorithm developments and data validation plans of NASDA

In 2002, two spaceborne microwave radiometers were launched to provide new observation data. One sensor is the Advanced Microwave Scanning Radiometer (AMSR), aboard the Advanced Earth Observing Satellite-II (ADEOS-II) of the National Space Development Agency of Japan (NASDA). The other is AMSR-E, aboard Aqua of the National Aeronautics and Space Administration (NASA). AMSR and AMSR-E are almost identical sensors, and have lower frequencies 6 and 10 GHz, in comparison with preceding sensors, such as the Special Sensor Microwave/Imager (SSM/I). In addition to geophysical products currently retrieved from the SSM/I, new products of sea surface temperature and soil moisture have been retrieved from AMSR and AMSR-E by using those lower frequencies. Eleven Principal Investigators were assigned by NASDA to develop algorithms to retrieve geophysical products, and their programs have been installed at the Earth Observation Research Center of NASDA. Geophysical products are currently being validated by several methods, such as using existing in situ data, employing instruments in field observations, and comparing data with other sensors data.

Status of AMSR2 instrument on GCOM-W1

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.

Post-launch calibration and data evaluation of AMSR-E

The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) was developed and provided to NASAs EOS Aqua satellite by the National Space Development Agency of Japan (NASDA). AMSR-E is the modified version of AMSR onboard the Advanced Earth Orbiting Satellite-II (ADEOS-II, currently called the Midori-II). AMSR-E has been in operation since June 2002 and providing continuous data record. This paper presents the status of post-launch calibration and data evaluation of the instrument.

Intercalibration of Advanced Microwave Scanning Radiometer-2 (AMSR2) Brightness Temperature

Here, we describe the characteristics of brightness temperature (Tb) measured by the Advanced Microwave Scanning Radiometer-2 (AMSR2) onboard the Global Change Observation Mission 1st-Water (GCOM-W1). This mission aims to achieve long-term global monitoring of Earth using two polar-orbiting satellite observation systems with three consecutive generations. GCOM-W1, the first satellite of the GCOM-W (Water) series, was launched successfully on May 18, 2012. AMSR2 is a single-mission instrument onboard the GCOM-W1 satellite. The basic characteristics of AMSR2 are similar to those of its predecessor, AMSR-E; this allows the continuation of AMSR-E observations but with several improvements, including a larger main reflector (2.0-m diameter), additional channels at C-band frequency, an improved calibration system, and increased reliability imparted by the addition of a redundant momentum wheel. Since July 3, 2012, the instrument has functioned properly and has accumulated a data set of Tb measurements. During the initial calibration and validation period, Tb values are being evaluated and characterized according to various methodologies, including intercalibration between similar microwave radiometers [e.g., the Tropical Rainfall Measuring Mission Microwave Imager (TMI)] based on radiative transfer computations. The intercalibration results for the ocean area as the cold end and the rainforest area the as warm end demonstrate that Tb measured by AMSR2 exhibits no apparent seasonal variation, with a maximum calibration difference of approximately 5 K compared to TMI and AMSR-E. This calibration difference appears to depend on the Tb of the observed object.

POLDER-OCTS preflight cross-calibration experiment using round-robin radiometers

This joint article presents the POLDER-OCTS preflight cross-calibration procedure and data set. POLDER is a radiometer developed by CNES devoted to the measurement of the polarization and directionality of the Earths reflectances and OCTS is an ocean color and temperature scanner developed by NASDA. Both radiometers are onboard the ADEOS satellite to be launched in 1996. The preflight POLDER-OCTS cross-calibration experiment was carried out by NRLM, NASDA, and CNES from March to April in 1994 using round- robin radiometers. The cross-calibration results show the agreement between NRLM/NASDA and CNES radiometers better than 6% regarding POLDER integrating sphere at CNES in Toulouse and better than 5% regarding OCTS integrating sphere at NEC in Yokohama. Calbration of OCTS integrating sphere by NEC agreed with cross calibration by NRLM/NASDA within 3%. The calibration of CNES round-robin radiometer is guaranteed at 3.5%.

AMSR2 validation results

The Advanced Microwave Scanning Radiometer 2 (AMSR2) on board the Global Change Observation Mission - Water 1st (GCOM-W1 or “SHIZUKU”) was launched on May 18, 2012 (JST), and continuous its observation from the A-Train orbit more than one year successfully. Validation results of eight geophysical parameters of AMSR2 standard products show that all products satisfied required release accuracy, and JAXA has released AMSR2 geophysical parameters to public though the GCOM-W1 Data Providing Service System (https://gcom-w1.jaxa.jp) since May 17, 2013.

Instrument characteristics and calibration of AMSR and AMSR-E

The National Space Development Agency of Japan (NASDA) developed two spaceborne microwave radiometers: the Advanced Microwave Scanning Radiometer (AMSR) for NASDAs Advanced Earth Observing Satellite-II (ADEOS-II) and AMSR-E for NASAs Aqua satellite. Each instrument, as well as the combination of instruments, will provide valuable information for understanding the mechanism of global water and energy circulation. To accomplish the mission, it is necessary to provide reliable, well-calibrated data. Several post-launch calibration and validation activities are then planned in addition to two-point, on-board calibration of the instruments.