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The Brazilian National Institute for Space Research (INPE) is operating the Brazilian Environmental Data Collection System that currently amounts to a user community of around 100 organizations and more than 700 data collection platforms installed in Brazil. This system uses the SCD-1, SCD-2, and CBERS-2 low Earth orbit satellites to accomplish the data collection services. The main system applications are hydrology, meteorology, oceanography, water quality, and others. One of the functionalities offered by this system is the geographic localization of the data collection platforms by using Doppler shifts and a batch estimator based on least-squares technique. There is a growing demand to improve the quality of the geographical location of data collection platforms for animal tracking. This work presents an evaluation of the ionospheric and tropospheric effects on the Brazilian Environmental Data Collection System transmitter geographic location. Some models of the ionosphere and troposphere are presented to simulate their impacts and to evaluate performance of the platform location algorithm. The results of the Doppler shift measurements, using the SCD-2 satellite and the data collection platform (DCP) located in Cuiabá town, are presented and discussed.

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South America covers a large area of the globe and plays a fundamental function in its climate change, geographical features, and natural resources. However, it still is a developing area, and natural resource management and energy production are far from a sustainable framework, impacting the air quality of the area and needs much improvement in monitoring. There are significant activities regarding laser remote sensing of the atmosphere at different levels for different purposes. Among these activities, we can mention the mesospheric probing of sodium measurements and stratospheric monitoring of ozone, and the study of wind and gravity waves. Some of these activities are long-lasting and count on the support from the Latin American Lidar Network (LALINET). We intend to pinpoint the most significant scientific achievements and show the potential of carrying out remote sensing activities in the continent and show its correlations with other earth science connections and synergies. In Part I of this chapter, we will present an overview and significant results of lidar observations in the mesosphere and stratosphere. Part II will be dedicated to tropospheric observations.

In Part II of this chapter, we intend to show the significant advances and results concerning aerosols’ tropospheric monitoring in South America. The tropospheric lidar monitoring is also supported by the Latin American Lidar Network (LALINET). It is concerned about aerosols originating from urban pollution, biomass burning, desert dust, sea spray, and other primary sources. Cloud studies and their impact on radiative transfer using tropospheric lidar measurements are also presented.

ABSTRACT. The use of the Doppler shift measurements to locate a transmitter has been studied and tested within the Brazilian Environmental Data Collection System.To improve the location of Data Collection Platforms (DCPs) with their transmitters, some effects such as corrections due to the ionosphere and the troposphere have been considered in a previous work (Celestino et al., 2007) using simulated data and some initial error evaluation for one existing DCP. This work presents an evaluation of the impacts on the geographical location due to the ionospheric and the tropospheric effects, however using two meteorological DCPs and covering a longer test period (one year). The seasonal and day-night effects are also analyzed during this test period. The results of the analysis indicated that correction of the ionospheric and tropospheric effects can, on the average, reduce the location errors to the scale between ten and hundred meters for the test conditions independent of the DCP location that was used. Due to the complexity of modeling sources of errors in the location of a platform, still a considerable work need to be done to reduce location errors in the system. Initial analysis indicates that the knowledge of the satellite position can be another significant source of platform position error.Keywords: geographical location, Data Collection Platforms, Doppler shift, tropospheric and ionospheric effects. RESUMO. O uso de medidas do desvio Doppler para localizar um transmissor foi estudado e testado considerando o Sistema Brasileiro de Coleta de Dados Ambien-tais. Para melhorar a localização de plataformas de coleta de dados (PCDs), com os seus transmissores, alguns efeitos como a correção devidoà ionosfera eà troposfera, foram considerados no trabalho de Celestino et al. (2007) usando dados simulados e algumas avaliações dos erros iniciais de umaúnica PCD. Este trabalho apresenta uma avaliação dos impactos sobre a localização geográfica, devido aos efeitos da ionosfera e da troposfera, entretanto usando duas PCDs meteorológicas e cobrindo um período mais longo de testes (um ano). Os efeitos, sazonal e dia-noite, também são analisados durante este período experimental. Os resultados das análises indicam que a correção dos efeitos da ionosfera e da troposfera pode, em média, reduzir os erros de localizaçãoà escala entre dez e cem metros para as condições de testes independente da localização da PCD que foi utilizada. Devidoà complexidade da modelagem das fontes dos erros na localização de uma plataforma, um trabalho considerável ainda precisa ser feito para reduzir o erro de localização no sistema. A análise inicial indica que o conhecimento da posição do satélite pode ser outra fonte significativa do erro na posição da plataforma.Palavras-chave: localização geográfica, plataformas de coletas de dados, desvio Doppler, correção dos efeitos da ionosfera e da troposfera. INPE/DSE,

A água está presente na atmosfera na forma de vapor, indo desde o nível do solo até a estratosfera. Como principal componente do ciclo hidrológico, a variação em sua quantidade sobre uma região provoca alterações nas condições climáticas, afetando assim as condições de vida e econômicas da população local. O fotômetro solar permite monitorar a variação dessa coluna de vapor de água, ou coluna de água precipitável (PWC) utilizando a radiação solar na banda de 940 nm, que sofre uma forte absorção ao atravessar a atmosfera. Para a calibração do fotômetro solar desenvolvido nesse trabalho, foi investigado um sítio na região semiárida do estado do Rio Grande do Norte, próximo à cidade de Caicó. Foi aplicado o Método de Langley Modificado (MLM) que é uma variação do Método de Langley. Essa metodologia permite calibrar fotômetro solar em campo aberto, que sob a condição de estabilidade óptica da atmosfera, permite obter-se constantes de calibração com melhores índices de incerteza que em laboratório. Os resultados, durante o período estudado, mostraram que não ocorreu a esperada estabilidade óptica da atmosfera para permitir a calibração do equipamento.

The current Brazilian System of Environmental Data Collection is composed of several satellites (SCD-1 and 2, CBERS-2 and 2B), Data Collection Platforms (DCPs) spread mostly over the Brazilian territory, and ground reception stations located in Cuiabá and Alcântara. An essential functionality offered to the users is the geographic location of these DCPs. The location is computed by the in-house developed “GEOLOC” program which processes the onboard measured Doppler shifts suffered by the signal transmitted by the DCPs. These data are relayed and stored on ground when the satellite passes over the receiving stations. Another important input data to GEOLOC are the orbit ephemeris of the satellite corresponding to the Doppler data. In this work, the impact on the geographic location accuracy when using orbit ephemeris which can be obtained through several sources is assessed. First, this evaluation is performed by computer simulation of the Doppler data, corresponding to real existing satellite passes. Then real Doppler data are used to assess the performance of the location system. The results indicate that the use of precise ephemeris can improve the performance of GEOLOC by reducing the location errors, and such conclusion can then be extended to similar location systems.