Japan Aerospace Exploration Agency (JAXA) is proposing the Global Change Observation Mission (GCOM). The GCOM mission will take over the Advanced Earth Observing Satellite-II (ADEOS-II or Midori-II) mission and develop into long-term monitoring. The GCOM mission will consist of two series of medium size satellites: GCOM-W and GCOM-C (these names are provisional). Three consecutive generations of satellites with one year overlap will result in over 13 years observing period in total. Two observing instruments are proposed for the GCOM-W satellite: the Advanced Microwave Scanning Radiometer (AMSR) follow-on instrument and hopefully the scatterometer for measuring ocean vector winds like SeaWinds onboard Midori-II. To keep the continuous observation by AMSR-E on Aqua, the earliest launch date is desired by science community. Current proposed launch year is 2010. The AMSR follow-on instrument will be a multi frequency, dual polarized passive microwave radiometer that observes water-related geophysical parameters supporting the GCOM concept. To keep the earliest launch date, only minimum but essential modifications from AMSR-E are now being examined. Combination of AMSR follow-on instrument and the scatterometer will provide unique opportunity to generate a synergistic effect of the active and passive microwave measurement. This combination can provide some instrument-level advantages including attenuation and scattering correction for scatterometer. Furthermore, simultaneous measurements of water vapor, SST, precipitation, and sea surface winds are effective for investigating various time-space scale phenomena.
The mission objectives of ADEOS-II (Midori-II) are to improve satellite-based global earth observation system, and to obtain earth observation data for the contribution to better understanding and elucidation of global change mechanism relevant to earth environmental issues. To implement the objectives, five onboard earth observation sensors are selected based on the science requirement primarily focused on the quantitative estimation of geophysical parameters to describe important processes of the earth system such as water and energy cycle, carbon cycle, and changes in polar stratospheric ozone. This paper describes the present status of level-2 products derived from AMSR and GLI observation data after the launch, in the middle of operational observation / calibration and validation phase, as of the beginning of August, 2003 after four months from the beginning of calibration and validation phase on April 15, 2003.
The Advanced Microwave Scanning Radiometer (AMSR) is the multi-frequency, passive microwave radiometer on board the Advanced Earth Observing Satellite-II (ADEOS-II), currently called Midori-II. The instrument has eight-frequency channels with dual polarization (except 50-GHz band) covering frequencies between 6.925 and 89.0 GHz. Measurement of 50-GHz channels is the first attempt by this kind of conically scanning microwave radiometers. Basic concept of the instrument including hardware configuration and calibration method is almost the same as that of ASMR for EOS (AMSR-E), the modified version of AMSR. Its swath width of 1,600 km is wider than that of AMSR-E. In parallel with the calibration and data evaluation of AMSR-E instrument, almost identical calibration activities have been made for AMSR instrument. After finished the initial checkout phase, the instrument has been continuously obtaining the data in global basis. Time series of radiometer sensitivities and automatic gain control telemetry indicate the stable instrument performance. For the radiometric calibration, we are now trying to apply the same procedure that is being used for AMSR-E. This paper provides an overview of the instrument characteristics, instrument status, and preliminary results of calibration and data evaluation activities.
The ADEOS-II satellite was successfully launched with an H-IIA rocket from Tanegashima Space Center in southern Japan on December 14, 2002. Amongst the six remote sensing instruments on-board, the payload includes the Global Imager (GLI) - a 36-channel multi-spectral scanner developed by the National Space Development Agency of Japan (NASDA) for ocean, terrestrial, atmosphere and cryosphere applications. 30 bands operate with a 1 km spatial resolution, while the remaining six bands, primarily dedicated for terrestrial use, acquire data with 250 metres ground resolution at nadir. The cancellation of one of the two planned Data Relay Test Satellites (DRTS) required for data down-link however resulted in reduced acquisition capacity at 250 metre resolution and thus prompted the establishment of a dedicated 250-metre data observation strategy, which aims to optimise 250 m observations over land, and to provide spatially and temporally consistent, multi-seasonal global land coverage, on a repetitive basis during the life-time of the ADEOS-II satellite. Plans for 250 m data product generation are furthermore outlined briefly in this paper.
In recent years, the application of radar polarimetry for remote sensing of land cover types has attracted extensive interest. Numerous microwave scattering models have been developed and used to interpret the polarimetric SAR data. In this paper, existing L-band backscatter models were used to model land-cover types, such as smooth and slightly rough surfaces (single scattering), urban area and tree trunks (double-bounce scattering) and forested area (diffuse scattering). Using these models, it is possible to construct the amplitude scattering matrix, Mueller matrix, Stokes parameter, etc. for each target. However, a state- vector was created using the Stokes parameters, degree of unpolarization and the phase difference between the HH and VV polarizations. The angle between two state-vectors (the theoretical state-vector derived from the calculation using the existing models and the state-vector derived from the observation or image data) was calculated for each land cover-type. We found that there is a strong correlation between the model predicted and the observed state-vectors for the same land cover types. The angle between the calculated and observed state-vectors is very useful for contrast enhancement and classifying the polarimetric radar data. For this purpose, polarimetric L-band airborne SAR data acquired over a variety of geographic targets are analyzed with the support of field investigations of forest, bare land and smooth surface (or ground and water), urban and rough surfaces. The classification results were presented.
Advanced visible and near infrared radiometer type 2(AVNIR- 2) is a high resolution land observation sensor, which will be loaded on ALOS. AVNIR-2 is composed of a multispectral and panchromatic subsystem. THese former subsystem is recently named as AVNIR-2; same with the old instrument name. The latter subsystem is named PRISM. The multispectral subsystem has ground resolution of 10m and four spectral bands which have same spectral range with that of AVNIR loaded on ADEOS. PRISM has three line detectors and characteristics of B/H equals 1.0 and ground resolution of 2.5m. By means of these characteristics, topographic maps with contour of 5m elevation interval are planned to be produced from those panchromatic data. Because observing data rate of PRISM is very high, on-board lossy data compression will be applied in order to reduce down link data rate. In this report, influences of the on-board lossy compression for terrain elevation measurements are evaluated. As the results, it is clear that: (1) measurement error of terrain elevation does not increase by on-board lossy data compression, (2) measurement error of terrain elevation decreases by on-board lossy data compression under the condition of turbid atmosphere and (3) measurement error of terrain elevation decreases in spite of atmospheric conditions when block coding is used as a lossy compression method.