Astrometry of mutual approximations between natural satellites. Application to the Galilean moons

Typically we can deliver astrometric positions of natural satellites with errors in the 50-150 mas range. Apparent distances from mutual phenomena, have much smaller errors, less than 10 mas. However, this method can only be applied during the equinox of the planets. We developed a method that can provide accurate astrometric data for natural satellites -- the mutual approximations. The method can be applied when any two satellites pass close by each other in the apparent sky plane. The fundamental parameter is the central instant $t_0$ of the passage when the distances reach a minimum. We applied the method for the Galilean moons. All observations were made with a 0.6 m telescope with a narrow-band filter centred at 889 nm with width of 15 nm which attenuated Jupiter's scattered light. We obtained central instants for 14 mutual approximations observed in 2014-2015. We determined $t_0$ with an average precision of 3.42 mas (10.43 km). For comparison, we also applied the method for 5 occultations in the 2009 mutual phenomena campaign and for 22 occultations in the 2014-2015 campaign. The comparisons of $t_0$ determined by our method with the results from mutual phenomena show an agreement by less than 1-sigma error in $t_0$, typically less than 10 mas. This new method is particularly suitable for observations by small telescopes.Comment: 13 pages, 11 figures and 8 tables. Based on observations made at the Laborat\'orio Nacional de Astrof\'isica (LNA), Itajub\'a-MG, Brazi

Astrometry of the main satellites of Uranus: 18 years of observations

We determine accurate positions of the main satellites of Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. Positions of Uranus, as derived from those of these satellites, are also determined. The observational period spans from 1992 to 2011. All runs were made at the Pico dos Dias Observatory, Brazil. We used the software called Platform for Reduction of Astronomical Images Automatically (PRAIA) to minimise (digital coronography) the influence of the scattered light of Uranus on the astrometric measurements and to determine accurate positions of the main satellites. The positions of Uranus were then indirectly determined by computing the mean differences between the observed and ephemeris positions of these satellites. A series of numerical filters was applied to filter out spurious data. These filters are mostly based on the comparison between the positions of Oberon with those of the other satellites and on the offsets as given by the differences between the observed and ephemeris positions of all satellites. We have, for the overall offsets of the five satellites, -29 (+/-63) mas in right ascension and -27 (+/-46) mas in declination. For the overall difference between the offsets of Oberon and those of the other satellites, we have +3 (+/-30) mas in right ascension and -2 (+/-28) mas in declination. Ephemeris positions for the satellites were determined from DE432+ura111. Comparisons using other modern ephemerides for the solar system -INPOP13c- and for the motion of the satellites -NOE-7-2013- were also made. They confirm that the largest contribution to the offsets we find comes from the motion of the barycenter of the Uranus system around the barycenter of the solar system, as given by the planetary ephemerides. Catalogues with the observed positions are provided.Comment: 13 pages, 21 figure

Mapeamento da contribuição de terraços agrícolas na redução da erosão do solo em sub-bacias do noroeste do Estado de São Paulo

O objetivo deste trabalho foi mapear a distribuição espacial do fator de práticas conservacionistas do solo (fator P) da Equação Universal de Perda de Solo Revisada (Revised Universal Soil Loss Equation, Rusle) em áreas terraceadas em sub-bacias do projeto GeoHevea, para posteriormente estimar a perda de solos dessas áreas. Foi considerado que o fator P da Rusle varia de acordo com o espaçamento horizontal entre terraços (EH). O EH foi calculado por equações e tabelas desenvolvidas para condições brasileiras e varia em função da declividade do terreno, do tipo de solo e dos tipos de uso e manejo do solo. O mapeamento das áreas terraceadas foi feito a partir da interpretação visual de imagens de satélite de alta resolução espacial. Para mostrar a variabilidade do fator P no espaço, os valores de EH foram obtidos de forma espacializada a partir do mapa digital de declividades e do mapa de solos em formato matricial (raster). O mapa digital de declividades foi obtido usando um modelo digital de elevação gerado a partir de dados de altimetria provenientes de cartas topográficas. As ferramentas do sistema de informações geográficas (SIG) mostraram-se úteis para o método, ao possibilitarem cálculos matemáticos envolvendo células de arquivos matriciais georreferenciados que representavam a distribuição espacial da declividade do terreno e de índices relacionados ao tipo de solo. A ferramenta de reclassificação do SIG também foi útil para atribuir um valor de P para cada célula do raster de EH, o que gerou o raster com a espacialização do fator P

Estação de monta em rebanhos de gado de corte.

Introdução; Duração e época; Vantagens; Seleção de matrizes e reprodutores; IA e IATF; Transição entre regimes de estação de monta; Doenças associadas à reprodução; Conclusão.bitstream/item/161736/1/Estacao-de-monta-em-rebanhos.pd

Astrometric positions for 18 irregular satellites of giant planets from 23 years of observations

The irregular satellites of the giant planets are believed to have been captured during the evolution of the solar system. Knowing their physical parameters, such as size, density, and albedo is important for constraining where they came from and how they were captured. The best way to obtain these parameters are observations in situ by spacecrafts or from stellar occultations by the objects. Both techniques demand that the orbits are well known. We aimed to obtain good astrometric positions of irregular satellites to improve their orbits and ephemeris. We identified and reduced observations of several irregular satellites from three databases containing more than 8000 images obtained between 1992 and 2014 at three sites (Observat\'orio do Pico dos Dias, Observatoire de Haute-Provence, and European Southern Observatory - La Silla). We used the software PRAIA (Platform for Reduction of Astronomical Images Automatically) to make the astrometric reduction of the CCD frames. The UCAC4 catalog represented the International Celestial Reference System in the reductions. Identification of the satellites in the frames was done through their ephemerides as determined from the SPICE/NAIF kernels. Some procedures were followed to overcome missing or incomplete information (coordinates, date), mostly for the older images. We managed to obtain more than 6000 positions for 18 irregular satellites: 12 of Jupiter, 4 of Saturn, 1 of Uranus (Sycorax), and 1 of Neptune (Nereid). For some satellites the number of obtained positions is more than 50\% of what was used in earlier orbital numerical integrations. Comparison of our positions with recent JPL ephemeris suggests there are systematic errors in the orbits for some of the irregular satellites. The most evident case was an error in the inclination of Carme.Comment: 9 pages, with 3 being online materia

Orbit determination of Transneptunian objects and Centaurs for the prediction of stellar occultations

The prediction of stellar occultations by Transneptunian objects and Centaurs is a difficult challenge that requires accuracy both in the occulted star position as for the object ephemeris. Until now, the most used method of prediction involving tens of TNOs/Centaurs was to consider a constant offset for the right ascension and for the declination with respect to a reference ephemeris. This offset is determined as the difference between the most recent observations of the TNO and the reference ephemeris. This method can be successfully applied when the offset remains constant with time. This paper presents an alternative method of prediction based on a new accurate orbit determination procedure, which uses all the available positions of the TNO from the Minor Planet Center database plus sets of new astrometric positions from unpublished observations. The orbit determination is performed through a numerical integration procedure (NIMA), in which we develop a specific weighting scheme. The NIMA method was applied for 51 selected TNOs/Centaurs. For this purpose, we have performed about 2900 new observations during 2007-2014. Using NIMA, we succeed in predicting the stellar occultations of 10 TNOs and 3 Centaurs between 2013 and 2015. By comparing the NIMA and JPL ephemerides, we highlighted the variation of the offset between them with time. Giving examples, we show that the constant offset method could not accurately predict 6 out of the 13 observed positive occultations successfully predicted by NIMA. The results indicate that NIMA is capable of efficiently refine the orbits of these bodies. Finally, we show that the astrometric positions given by positive occultations can help to further refine the orbit of the TNO and consequently the future predictions. We also provide the unpublished observations of the 51 selected TNOs and their ephemeris in a usable format by the SPICE library.Comment: 12 pages, 9 figures, accepted in A&

Alterações no uso e cobertura das terras no município de União Paulista, estado de São Paulo.

Alterações no uso e cobertura das terras foram investigadas pelo cruzamento de mapas de uso e cobertura das terras dos anos de 2006 e 2016 do município de União Paulista (SP), incluído na área de estudo do projeto GeoHevea, projeto de pesquisa que visa avaliar a sustentabilidade, competitividade e valoração de serviços ecossistêmicos da heveicultura. Os mapas foram elaborados para esse fim por meio da interpretação de imagens de satélite e de dados de campo. As áreas alteradas foram mapeadas, identificadas e quantificadas. O cultivo da cana-de-açúcar foi a principal forma de uso das terras nos anos estudados e apresentou percentuais superiores a 43% da área do município. Áreas com uso e cobertura inalterado na comparação entre os dois anos totalizaram 79,2% da área do município. Em 2016, os pastos e as seringueiras ocupavam, respectivamente, 17,57% e 6,73% da área municipal. Áreas com vegetação natural totalizavam 15,25% da área do município em 2016, percentual ligeiramente superior ao apresentado em 2006. Áreas de pasto sofreram redução de 46,35% entre 2006 e 2016, substituídas sobretudo pela cana-de-açúcar, cuja área cultivada apresentou crescimento de 30,58% no período. O percentual ocupado pelas seringueiras permaneceu praticamente constante no período, porém 24% das áreas com seringueira em 2006 foram substituídas por outras formas de uso em 2016, substituições compensadas pela expansão da heveicultura em outras áreas. Ainda foram observadas no município pequenas áreas com culturas anuais, eucalipto e citros, que, somadas, totalizaram área inferior a 2% da área municipal