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.

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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.

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本小論文は,RPG社と共に環境条件を調査する事を目的に開発し製品化した,7チャンネルラジオメーターについて記したものである。
ラジオメーターにとって最も重要な事項は,より信頼性のある校正方法である。
本装置は,信頼性のある校正を自動的に行なう機能を備えている。
7チャンネルの内訳は,18.7GHz(垂直,水平両偏波),23.8GHz(垂直偏波),36.5GHz(垂直,水平両偏波),90GHz(垂直,水平両偏波)の,合計7チャンネルである。全てのチャンネルにおいて,絶対安定度は0.5K以下,0.2Krms以内の優れた感度を備えている。
本装置の特徴である自動校正は,他の装置に見られる様な外部絶対校正負荷や,天空の温度による校正等の方法を用いなくて済む。
アンテナ系は－40 dB以下のサイドローブ特性をもち,野外での計測に対応し,防雨対策が講じられ,－20～40度Cの環境下で使用出来る。ソフトウエアは,通常のPC(Window 95,98等)に対応,計測データーの表示,校正条件,システムのダイアグノステック,アジマス/エレベーションの正確な設定も自動的に行える。

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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.

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