- Concept & its Background
- Goals of ALOS Research Plan
- Calibration and Validation of Each Sensor and Related Basic Studies
- General Goals
- Strategic Goals
We define development of specific data products and algorithms for promoting the other scientific researches as "strategic goals." These are selected considering the relevance to the ALOS mission and the goals of this plan, resource limitations, etc.
4.1.1 Global High-resolution DEM and Orthophoto image (PRISM, AVNIR-2, and PALSAR):
These data products form the basis of many fields of research and practical applications. They are provided by only ALOS at the moment. However, resources required to generate these data are so large that the accuracy and resolution may change according to the objective area. Global coverage will be pursued by coordinating with other data node organizations.
4.1.2 Global Biomass density dataset (PALSAR and AVNIR-2):
Biomass is not only one of the most important parameters for estimating the carbon cycle, but also provides a basis for forestry management. However, it is difficult to measure on the ground and there is no data covering a large area. Since only ALOS is equipped with L-band, which favors biomass observation, it is expected that biomass density data will be generated using PALSAR images along with AVNIR-2 images and high resolution DEMs. These activities will allow us to conduct time series analysis with Global Forest Mapping (GFM) datasets from JERS-1 SAR data.
4.1.3 Land surface deformation dataset (Earthquake-prone areas only):
The distribution of deformed land surfaces can be extracted by interferometric measurement. Monitoring diastrophism is essential in the Pacific Rim area, including Japan, which is always threatened by earthquakes. Land surface deformation data will be collected by periodic satellite observation and continuous ground observation.
4.2.1 Automated generation of high-resolution DEM and orthophoto image:
A large computing capability is usually required to generate high-resolution DEMs and orthophoto images, and the quality of these products is affected strongly by the performance of the algorithms used. Algorithms for automated generation of high-resolution DEMs and orthophoto (including an algorithm to estimate satellite position and altitude) need to be developed.
4.2.2 Accuracy improvement of biomass measurement method:
Development of algorithms using DEMs and AVNIR-2 images together with other satellite images for measuring global biomass distribution with higher accuracy is solicited.
Calibration and validation of each sensor is necessary for improving the quality of the data products such as high-resolution DEMs and biomass density data. In addition, basic studies on calibration and validation for improving the accuracy of each sensor should also be pursued as strategic goals.
4.3.1 Calibration and validation for optical Sensors
To generate high-quality products from optical sensors, AVNIR-2 and PRISM, basic study for very accurately evaluating radiance characteristics, geometric characteristics, spatial resolution, system noises, and other factors. is considered to be one of the strategic objectives.
(1) Accuracy improvement of radiance and brightness calibration
The radiance and brightness of optical sensors will be calibrated by using pre-flight test data, internal calibration source data, and external calibration data after launch. The main output of this study is to estimate absolute calibration coefficients. In particular, an important challenge will be the improvement of stability characteristics with ground-based experiments with calibration after launch and development of the radiative transfer model with high accuracy.
(2) Accuracy improvement of DEM
Algorithms for automatically evaluating and correcting registration and pointing accuracy, and for automatically producing high-resolution DEMs using stereo matching images will be developed.
(3) Atmospheric correction
Algorithm should be improved to estimate the surface albedo on a heterogeneous surface using optical sensors data, taking into account the effect of multi-scattering in the atmosphere, especially spatial and temporal changes of aerosols.
4.3.2 Calibration and validation for PALSAR system
A basic study for achieving high radiometric accuracy of the PALSAR system is considered to be one of the strategic objectives.
(1) Accurate estimation of normalized radar cross section
The relation between the digital number and the normalized backscattering coefficient for PALSAR standard products will be determined by using the pre-flight test data, internal calibration source data, and external calibration data. The main outputs of this study are the estimated in-orbit antenna elevation patterns and the absolute calibration coefficients.
(2) Accuracy improvement of interferometric SAR data
In order to derive accurate digital elevation models as well as crustal movements, a study on achieving an accurate phase difference will be done by using repeat-pass interferometric datasets acquired by the PALSAR system.
(3) Accuracy improvement of polarimetric SAR data
PALSAR's polarimetric observation mode is currently an experimental mode. However, this observation mode will be the main operation mode in future SAR systems. In order to prepare for the practical use of fully polarimetric data, polarimetric calibration with the data acquired from PALSAR polarimetric observation mode should be studied. The methodology to derive phase correction, cross talk, and gain imbalance will be developed and investigated.