Global distribution characteristics of atmospheric effects in the thermal infrared region are important for investigators developing atmospheric correction algorithms. In the present article, global maps of the atmospheric effect parameters (transmittance, path radiance and sky radiance) for AVHRR channel 4 are created by the radiative transfer calculations combined with the NCEP Global Data Assimilation System (GDAS) products for July and January, and their statistical characteristics are evaluated.
Firstly, it is mentioned based on a general view of the global maps that the atmospheric effect parameters are not so different between July and January in the Southern Hemisphere, whereas they are much different in the Northern Hemisphere. And then, it is shown that the global distributions of these parameters can be approximately expressed as a composition of two different distributions ; one is related with the Inter-Tropical Convergence Zone (ITCZ), and another is related with the other zones. The global distributions are, therefore, divided to five zones based on the latitude ; the ITCZ, two transition zones of both Hemispheres, and two high latitude zones of both Hemispheres. The results demonstrate that the spatial variations of the atmospheric effect parameters are very small in the high latitude zones but very large in the ITCZ. This fact means that a local atmospheric correction algorithm is better than a global algorithm for the high latitude zones and we should consider such large spatial variations of the atmospheric effect parameters in developing an atmospheric correction algorithm used for the ITCZ.
In the final part of this article, it is mentioned that we need to evaluate how advantageous the approach using global algorithms is in comparing with the approach using a linkage of local algorithms.

View full abstract

In this paper, the dynamical characteristics of ASTER Ground Data System (ASTER GDS) were modeled for the study of the system construction. The data flow system of ASTER high rate science data including the imagery and engineering data was modeled by a system dynamics analysis tool, which has "Stocks" and "Flows" in the block diagrams as the fundamental elements. "Stocks" represent data accumulation and "Flows" represent data transfer. The modeled data flow system covered the scope from the observation on the spacecraft to the distribution of the processed data products. The following four partitioning scheme proved to be effective : EOS-AMI Sector, EOSDIS Sector, ASTER GDS Sector, USER Sector. ASTER data observed in EOS-AMI Sector are transmitted to EOSDIS Sector, where they are processed and transported to ASTER GDS Sector. The various products are generated in this sector, then transferred to USER Sector to distribute the products to the world. The effectiveness of system dynamical approach is demonstrated for the analysis of dynamical behavier of the ground data systems.

View full abstract

RPG (Radiometer Physics GmbH) has developed a 7 channel radiometer (18.7 GHz vertical and horizontal polarization, 23.8 GHz vertical polarization, 36.5 GHz vertical and horizontal polarization, 90 GHz vertical and horizontal polarization) for environmental research with a high absolute stability of 0.5 K and a sensitivity of better than 0.2 K rms. The system uses an internal radiometric autocalibration technique to precisely adjust for overall gain and system noise temperature variations without the need for external calibration loads or inaccurate sky tip calibration procedures. In addition nonlinearity errors caused by the non ideal responses of detector diodes which are always present in radiometers are eliminated by using a four point fit noise injection method. The radiometer's housing is mounted to a positioner system and can be accurately scanned in elevation (±90°) and azimuth (0-360°) for atmospheric or ground observations. The antenna beams have a FWHM (Full Width at Half Power Maximum) of 10°with a -40 dB sidelobe level. The system is designed to be used under outdoor conditions (rain protected, temp. range : -20^°C to 40^°C). Data aquisition, calibration, system diagnostics, position scanning etc. are automatically controlled by a versatile computer software.

View full abstract

It is very important to provide Earth observation satellite data and the related information for users timely. However, it takes a long time to disseminate Earth observation data to users because a volume of earth observation data is huge and Internet bandwidth is not enough to carry it.
Recently, APAN (Asia Pacific Advanced Network) and the other high end research and education network such as NREN (NASA Research and Education Network), NSF/VBNS, etc. are established and have been operated. NASDA and NASA implemented some pilot projects to study a feasibility of utilization of such high end network to exchange data and information in cooperation with AIT (Asian Institute of Technology) and APAN. In March 22, 1999, STA/NASDA and NOAA/NASA organized GOIN99 (Global Observation Information Network) workshop in University Hawaii. In this GOIN99 workshop, NASA and NASDA demonstrated some pilot projects including team collaboration and data exchange successfully.

View full abstract