The AlfaCrux CubeSat mission description and early results

On 1 April 2022, the AlfaCrux CubeSat was launched by the Falcon 9 Transporter-4 mission, the fourth SpaceX dedicated smallsat rideshare program mission, from Space Launch Complex 40 at Cape Canaveral Space Force Station in Florida into a Sun-synchronous orbit at 500 km. AlfaCrux is an amateur radio and educational mission to provide learning and scientific benefits in the context of small satellite missions. It is an opportunity for theoretical and practical learning about the technical management, systems design, communication, orbital mechanics, development, integration, and operation of small satellites. The AlfaCrux payload, a software-defined radio hardware, is responsible for two main services, which are a digital packet repeater and a store-and-forward system. In the ground segment, a cloud-computing-based command and control station has been developed, together with an open access online platform to access and visualize the main information of the AlfaCrux telemetry and user data and experiments. It also becomes an in-orbit database reference to be used for different studies concerned with, for instance, radio propagation, attitude reconstruction, data-driven calibration algorithms for satellite sensors, among others. In this context, this paper describes the AlfaCrux mission, its main subsystems, and the achievements obtained in the early orbit phase. Scientific and engineering assessments conducted with the spacecraft operations to tackle unexpected behaviors in the ground station and also to better understand the space environment are also presented and discussed.Fundação de Apoio à Pesquisa del Distrito Federal (FAPDF), Brasil | Ref. N/

Método solvotérmico assistido por micro-ondas aplicado à obtenção de nanocristais de ITO : deposição e caracterização de filmes de ITO

The formation of In1-xSnxO2 (ITO) nanocrystals through the conversion of radiant energy into heat has been studied by using an adapted domestic microwave oven. The formation of powder was obtained by heating the oven to 200 C using a heating rate of 50 C/min and soaking time of 30 min. The obtained powder by this method was characterized by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FEG-SEM), High Resolution Transmission Electron Microscope (HRTEM) and Selected Area Diffraction technique whose enable to distinguish possible crystalline phases, as well as the structure and morphology of the powder. Spherical particles with average size of 4, 8 and 12 nm were identified. This powder was characterized by sensing response against the presence or absence of oxygen gas. Finally, ITO powder was deposited on amorphous quartz or glass substrates by spin coating method. The films thus obtained were characterized by FEG-SEM, UVVIS and the electrical sheet resistance was measured using a four probe tips. Best results were obtained in the film whose particles were synthesized at pH 6,5. Optical transmittance at visible region of 98,5 % was observed and with an optical gap and resistance calculated to be 3,55 eV and 3,6.10-3 Ω.m respectively.Utilizando um forno micro-ondas doméstico adaptado como fonte de energia, estudou-se a formação de nanocristais de In1-xSnxO2 (ITO) por meio da conversão de energia radiante em térmica. O pó do material foi formado em uma temperatura de 200 ºC por tempo de 30 minutos, a razão de aquecimento do sistema foi de 50 ºC/min. Os pós obtidos por esse método foram caracterizadas por Difratometria de raios-X (DRX), Microscopia Eletrônica de Varredura com Campo Emissor de Elétrons (FEG-SEM), Microscopia Eletrônica de Transmissão de Alta Resolução (HRTEM) e Difração em Área Selecionada (SAD), essas técnicas possibilitaram a distinção das possíveis fases bem como a estrutura e morfologia do pó. Partículas esféricas e com tamanhos médios de 4, 8 e 13 nm foram identificadas. Os pós também foram caracterizados como sensores e suas respostas foram medidas na presença e ausência do gás oxigênio. Finalmente, o pó de ITO foi depositado sobre substrato de quartzo amorfo ou vidro pelo Método Spin Coating. Os filmes assim obtidos foram caracterizados por FEG-SEM, UV-VIS e a resistência elétrica superficial de cada um dos filmes foram medidas pelo método de quatro pontas. Os melhores resultados foram apresentados pelo filme cujas partículas foram sintetizadas em pH 6,5, sua transmitância é de 98,5%, gap óptico de 3,55 eV e resistividade de 3,6 10-3Ω.m

Influence of pH in Obtaining Indium Tin Oxide Nanoparticles by Microwave Assisted Solvothermal Method

<div><p>A systematic study about synthesis of In1-xSnxO2 (ITO) nanostructured crystals by microwave-assisted solvothermal method is reported. Different solutions using InCl3.4H2O and SnCl4.5H2O precursors in ethylene glycol solvent were prepared in distinct pHs (acid and basic ones). The syntheses were performed at 200 ºC using a heating rate of 50 ºC min-1 and soaking time of 30 minutes. All the synthesized powders were characterized by X-ray Diffraction (XRD) and Rietveld refinement to study the phase evolution as a function of pH. The materials synthesized in the pH ranging between 11.5 and 11.9 were further studied by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques. As ITO materials have many practical applications due to their transparency in the visible spectrum, UV-Vis spectroscopy analysis was performed to obtain the optical band gap and the respective optical window.</p></div

Território e sociedade

O livro Território e sociedade: as múltiplas faces da Brasília metropolitana vem integrar a Coleção Brasília da Editora UnB, que, desde a década de 1980, tem reunido pesquisadores de diferentes áreas do conhecimento, sob a liderança do professor emérito da Universidade de Brasília Aldo Paviani, para debater e proporcionar olhares complementares sobre esse território singular que abriga a capital federal. Na intenção de analisar e refletir sobre essas questões, os textos apresentados nesta obra abrangem desde temas mais amplos até aspectos mais específicos da integração/desintegração da Área Metropolitana de Brasília. As discussões passam por questões sobre desenvolvimento, economia, governança, política, patrimônio, cultura, vulnerabilidades e impactos dos marcadores de desigualdades ao longo do curso de vida dos grupos populacionais da cidade. O livro é organizado em quatro unidades: 1) desenvolvimento e integração metropolitana; 2) metropolização e governança; 3) patrimônio, cultura e território; e 4) o curso da vida e as desigualdades na metrópole