CoRoT (Convection, Rotation and planetary Transits) é uma missão espacial liderada pela Agência Espacial Francesa (CNES) em associação com diversos parceiros internacionais, entre eles o Brasil. Seus objetivos principais são o estudo da sismologia estelar e a procura por planetas extra-solares (exoplanetas). Ambos os programas científicos baseiam-se em uma fotometria de altíssima precisão e requerem observações ininterruptas de longa duração, possíveis somente a partir do espaço. Uma revisão da literatura indica a existência de três técnicas principais para a realização de fotometria estelar a partir de imagens capturadas em CCDs: fotometria por máscara (por abertura), por ajuste de limiar (por threshold), e por ajuste da resposta impulsiva do sistema de aquisição de imagens. A fotometria por máscara, ou por abertura, apresenta maior precisão para o registro de estrelas brilhantes, em cenários de maior estabilidade de atitude do satélite (situação de baixo jitter), e é a solução adotada a bordo pelo satélite CoRoT, por ser um algoritmo determinístico. A fotometria por ajuste da resposta impulsiva, também chamada de função de espalhamento do ponto (point-spread function, PSF), por sua vez, por levar em conta a resposta do sistema a uma fonte pontual de luz, permite a restauração da imagem original através de processos de deconvolução; apresenta maior precisão para estrelas fracas, ou em um cenário degradado, com perturbações devidas a radiação externa (stray light), ou em que o jitter de atitude do satélite seja elevado. Tal robustez é uma característica desejada no processo de restauração de imagens. Já a fotometria por threshold é aplicada somente em casos de jitter muito elevado e pobre conhecimento da resposta impulsiva do sistema, de modo que não é utilizada no satélite CoRoT. Este trabalho visa consolidar e potencializar a participação brasileira no projeto CoRoT e contribuir com os esforços associados à redução de dados da missão, através de uma proposta inovadora de fotometria híbrida, que se utilizará dos conhecimentos da PSF modelada do instrumento e da alta relação sinal/ruído alcançada com a fotometria por máscara realizada a bordo, baseada e fundamentada em resultados preliminares que atestam o potencial desta metodologia. Tal algoritmo permite um ganho substancial de precisão fotométrica em relação à técnica de abertura, resultando em uma melhor exploração dos dados disponíveis, dada a sua robustez em caso de degradação dos dados de entrada. / CoRoT (Convection, Rotation and planetary Transits) is a high precision photometry experience dedicated to stellar seismology and the search for extrasolar planets. The mission is led by the French Space Agency (CNES) in association with several French laboratories and international partners in Austria, Belgium, Germany, Spain and Brazil. Both scientific programs require great instrumental stability and long, uninterrupted observation runs, which take place simultaneously on adjacent regions of the sky. An overview of the literature displays three main techniques to perform stellar photometry from space CCD images: aperture photometry, threshold photometry and PSF-fitting photometry. Aperture photometry defines a mask which represents the CCD pixels to be summed up in the computation of the collected photon flux for a given star. This method presents very high precision for isolated, bright stars and for stable satellite attitude (low jitter scenarios). It is the data reduction technique implemented on-board, due both to link capacity constraints (given the large number of targets simultaneously observed by the instrument) and to its deterministic algorithm. Fitting photometry allows restoration of degraded stellar images through deconvolution processes, using the point spread function (PSF) of the optical instrument itself. This technique presents better performance for crowded fields and for faint stars; it also presents robustness in the presence of disturbances such as stray light or high satellite attitude jitter. Finally, threshold photometry takes into account only those pixels whose values are above a given pre-computed level. This method is used only in scenarios with excessive satellite depointing due to attitude jitter, or in cases where the instrumental PSF is poorly known. Therefore, it is not used in the CoRoT mission. This work intends to consolidate and strengthen the Brazilian share in the CoRoT Project, contributing to the efforts associated to the ground-based reduction of scientific data, through an innovative, hybrid photometry technique, which will take advantage of a high-resolution instrumental PSF and of the high signal-to-noise-ratio obtained in the on-board aperture photometry. Studies here described show that this methodology, compared to the Aperture technique, achieves gains in photometric precision and in the operational duty cycle, enabling robust and accurate data exploitation.

CoRoT (Convection, Rotation and planetary Transits) é uma missão espacial liderada pela Agência Espacial Francesa (CNES) em associação com diversos parceiros internacionais, entre eles o Brasil. Seus objetivos principais são o estudo da sismologia estelar e a procura por planetas extra-solares (exoplanetas). Ambos os programas científicos baseiam-se em uma fotometria de altíssima precisão e requerem observações ininterruptas de longa duração, possíveis somente a partir do espaço. Uma revisão da literatura indica a existência de três técnicas principais para a realização de fotometria estelar a partir de imagens capturadas em CCDs: fotometria por máscara (por abertura), por ajuste de limiar (por threshold), e por ajuste da resposta impulsiva do sistema de aquisição de imagens. A fotometria por máscara, ou por abertura, apresenta maior precisão para o registro de estrelas brilhantes, em cenários de maior estabilidade de atitude do satélite (situação de baixo jitter), e é a solução adotada a bordo pelo satélite CoRoT, por ser um algoritmo determinístico. A fotometria por ajuste da resposta impulsiva, também chamada de função de espalhamento do ponto (point-spread function, PSF), por sua vez, por levar em conta a resposta do sistema a uma fonte pontual de luz, permite a restauração da imagem original através de processos de deconvolução; apresenta maior precisão para estrelas fracas, ou em um cenário degradado, com perturbações devidas a radiação externa (stray light), ou em que o jitter de atitude do satélite seja elevado. Tal robustez é uma característica desejada no processo de restauração de imagens. Já a fotometria por threshold é aplicada somente em casos de jitter muito elevado e pobre conhecimento da resposta impulsiva do sistema, de modo que não é utilizada no satélite CoRoT. Este trabalho visa consolidar e potencializar a participação brasileira no projeto CoRoT e contribuir com os esforços associados à redução de dados da missão, através de uma proposta inovadora de fotometria híbrida, que se utilizará dos conhecimentos da PSF modelada do instrumento e da alta relação sinal/ruído alcançada com a fotometria por máscara realizada a bordo, baseada e fundamentada em resultados preliminares que atestam o potencial desta metodologia. Tal algoritmo permite um ganho substancial de precisão fotométrica em relação à técnica de abertura, resultando em uma melhor exploração dos dados disponíveis, dada a sua robustez em caso de degradação dos dados de entrada. / CoRoT (Convection, Rotation and planetary Transits) is a high precision photometry experience dedicated to stellar seismology and the search for extrasolar planets. The mission is led by the French Space Agency (CNES) in association with several French laboratories and international partners in Austria, Belgium, Germany, Spain and Brazil. Both scientific programs require great instrumental stability and long, uninterrupted observation runs, which take place simultaneously on adjacent regions of the sky. An overview of the literature displays three main techniques to perform stellar photometry from space CCD images: aperture photometry, threshold photometry and PSF-fitting photometry. Aperture photometry defines a mask which represents the CCD pixels to be summed up in the computation of the collected photon flux for a given star. This method presents very high precision for isolated, bright stars and for stable satellite attitude (low jitter scenarios). It is the data reduction technique implemented on-board, due both to link capacity constraints (given the large number of targets simultaneously observed by the instrument) and to its deterministic algorithm. Fitting photometry allows restoration of degraded stellar images through deconvolution processes, using the point spread function (PSF) of the optical instrument itself. This technique presents better performance for crowded fields and for faint stars; it also presents robustness in the presence of disturbances such as stray light or high satellite attitude jitter. Finally, threshold photometry takes into account only those pixels whose values are above a given pre-computed level. This method is used only in scenarios with excessive satellite depointing due to attitude jitter, or in cases where the instrumental PSF is poorly known. Therefore, it is not used in the CoRoT mission. This work intends to consolidate and strengthen the Brazilian share in the CoRoT Project, contributing to the efforts associated to the ground-based reduction of scientific data, through an innovative, hybrid photometry technique, which will take advantage of a high-resolution instrumental PSF and of the high signal-to-noise-ratio obtained in the on-board aperture photometry. Studies here described show that this methodology, compared to the Aperture technique, achieves gains in photometric precision and in the operational duty cycle, enabling robust and accurate data exploitation.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / This student paper was produced as part of the team design competition in the University of Arizona course ECE 485, Radiowaves and Telemetry. It presents a telemetering system proposed for UASat, a small satellite being designed for launch in the year 2004. The overall system architecture is described, including the transducers used by each subsystem, the command and telemetry packet formats, the antennas and modulation schemes, the link budget, and some hardware recommendations. A discussion of the data analysis is also included.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Daylighting is fast emerging globally as a popular clean energy technology to compliment artificial electrical lighting. Unlike traditional artificial lighting, however, the variability of the sun due to geographical, geometrical and climatic variations presents a major challenge to engineers and architects involved in daylighting system design, particularly for critical tasks such as reading. This project evolved out of the need to be able to fully describe the performance of daylighting applications in order to aid and validate the design, improvement and installation of such systems. The primary focus of the project was to design, develop and test a system that is able to record and convey the variability of light, within an interior space, in terms of the spatial and time domains for the monitoring of daylighting applications, at a fraction of the cost of similar commercially available systems. Several potential sensors underwent stringent selection and testing procedures to determine which would meet the project requirements. The selected Sharp GA1A2S100LY sensing device proved to be the most suitable and was developed and included in a microcontroller based system to record illumination levels at multiple locations simultaneously. The sensor was selected and developed to match the spectral sensitivity of the human eye within the range of 0-1500 lux. The PIC18F8722 Explorer Demonstration Board manufactured by Microchip was selected to control all system operations. The board interfaces with each illuminance sensor and records the measured data, in text format in a .txt file on an SD card, in the PICtail daughter board SD card module. The system was able to record data from 64 sensors, simultaneously, at predefined time intervals and to store it for later processing. The data was then refined and used to generate easy to interpret visual representations of the illumination characteristics of the measured area as a function of time. The data is imported from the SD card text file to Microsoft Excel where a constant, predetermined, correction factor is applied to the data. A MATLAB program was developed to read the corrected data from the Excel spreadsheet and give an animated display of the progression of the illumination characteristics over the period for which the measurements were taken. Testing conducted with the system was done in an area supplied with daylight from two passive zenithal light pipes. The use of the system, under these conditions, proved effective with the system able to accurately convey the hourly, daily and seasonal variability of light within the measured area over a period of time. / AFRIKAANSE OPSOMMING: Dagbeligting ontwikkel teen 'n hoë pas wêreldwyd as 'n gewilde vorm van skoon energie tegnologie. Die doel van dagbeligting is om kunsmatige elektriese beligting aan te vul. In teenstelling met tradisionele kunsmatige beligting, bied die die son 'n verskeidenheid van groot uitdagings vir ingenieurs en argitekte betrokke in die ontwerp van 'n dagbeligting stelsel, veral vir take van kritieke belang insluitend die vermoë om te kan lees. Uitdagings sluit in: Geografiese-, geometriese-, asook klimaatstoestand veranderlikes. Hierdie projek het ontwikkel vanuit die behoefte om ten volle die werksverrigting van dagbeligting toepassings te kan beskryf om sodoende die ontwerp, bevordering en installering van dagbeligting stelsels te steun en te bevestig. Die hooffokus van die projek was om 'n stelsel te ontwerp, ontwikkel en te toets wat die vermoë het om die veranderlikheid van lig, binne 'n binneruimte, in terme van ruimtelike- en tydsdomeine op te neem en hierdie oor te dra vir die monitor van dagbeligting toepassings, teen 'n fraksie van die koste van 'n soortgelyke kommersieel beskikbare stelsel. Verskeie moontlike sensors het streng keuring- en toetsprosedures ondergaan om te bepaal watter sensors aan die projek vereistes sal voldoen. Die sensor wat gevind was as die mees toepaslike, bepaal deur die resultate verkry vanaf die keuring- en toetsprosedures, was die Sharp GA1A2S100LY sensor toestel. Hierdie toestel was ontwikkel en ingesluit in 'n mikroverwerker beheerstelsel om beligtingsvlakke by verskeie liggings terselfdertyd op te neem. Verder, was die sensor gekies en ontwikkel om die spektrale sensitiwiteit van die menslike oog te ewenaar, binne die reik van 0 – 1500 lux. Die PIC18F8722 Explore Demonstration Board vervaardig deur Microchip was gekies om alle stelsel bedrywighede te beheer. Die bord kommunikeer met elke illuminansievlaksensor en neem die gemete data op, in teks formaat in 'n .txt lêer wat dan op 'n SD kaart gestoor word, in die PICtail Daughter Board SD kaart module. Die stelsel kon data van 64 sensors, gelyktydig, opneem by voorafbepaalde tydsintervalle en dit dan stoor vir verdere verwerking later. Die data was dan verfyn en gebruik om maklik-om-te- interpreteer visuele voorstellings van die beligtingseienskappe van die gemete area as 'n funksie van tyd te genereer. Die data, gestoor as 'n .txt lêer, word ingevoer van die SD kaard in Microsoft Excel in waar 'n konstante, voorafbepaalde regstellingsfaktor op die data toegepas word. A MATLAB program was ontwikkel om die gekorrigeerde data te lees vanaf die Excel werkblad en 'n geanimeerde voorstelling, van die vordering van die beligtingseienskappe oor die tydperk waarvoor die lesings geneem was, terug te voer. Toetse uitgevoer met die stelsel was uitgevoer in 'n vertrek, voorsien met daglig van twee passiewe “zenithal” beligtingspype. Die gebruik van die stelsel, onder hierdie kondisies, blyk effektief. Die stelsel is in staat om akkuraat die uurlikse, daaglikse, asook die seisoensveranderlikheid van lig, binne die afgemete area oor ʼn tydperk van tyd, weer te gee.

Photometric data on the Kron-Cousins photometric system have been obtained for 118 new late K to middle M-type stars with known distances. These data have been used to obtain absolute red magnitudes, to construct a color-magnitude diagram, and to compute a polynomial function for disk dwarf stars in the color range 1.5 ≤ R-I < 2.0, which can be used to compute absolute red magnitudes to be used for photometric parallaxes. Such photometric parallaxes allow new stellar distance estimations that are essential when modeling the spatial distribution of stars in our Galaxy. This is especially important for M-type stars, as they make up more than half of the mass of the Milky Way. Intermediate-band CaH observations have also been obtained in an ongoing effort to distinguish stellar luminosity classes and populations; R-L and R-I colors are used to identify possible subdwarf stars. A total of seven possible new subdwarfs and three previously known subdwarfs have been identified with this method. / Department of Physics and Astronomy

ISIS is a program that specializes in detecting variable stars within clusters, both open and globular. ISIS has historically been used in surveys searching for variable stars. However, recent work has identified new uses for ISIS, such as the detection of exoplanet transits in clusters of stars. This thesis will evaluate ISIS, both how the program functions and for which objects it is most efficient and appropriate. I examined five clusters: three open, and two globular, for one night surveys. With this survey, I identified twenty-five variable stars. Twenty-two variables were previously known, and three variable stars were previously undiscovered. In total, from my short one night surveys, I confirmed twenty-five previously known variable stars and four unknown variable stars. Furthermore, ISIS has detected several δ Scuti stars whose amplitude of variation is on par with an exoplanet transit. These data suggest that ISIS can be used for the detection of exoplanet transits. / Department of Physics and Astronomy

No description available.

The determination of galaxy redshifts in the James Webb Space Telescope's (JWST) blank-field surveys will mostly rely on photometric estimates, based on the data provided by JWST's Near-Infrared Camera (NIRCam) at 0.6-5.0 mu m and Mid Infrared Instrument (MIRI) at lambda > 5.0 mm. In this work we analyze the impact of choosing different combinations of NIRCam and MIRI broadband filters (F070W to F770W), as well as having ancillary data at lambda < 0.6 mu m, on the derived photometric redshifts (z(phot)) of a total of 5921 real and simulated galaxies, with known input redshifts z = 0-10. We found that observations at lambda < 0.6 mm are necessary to control the contamination of high-z samples by low-z interlopers. Adding MIRI (F560W and F770W) photometry to the NIRCam data mitigates the absence of ancillary observations at l < 0.6 mm and improves the redshift estimation. At z = 7-10, accurate zphot can be obtained with the NIRCam broadbands alone when S/N >= 10, but the z(phot) quality significantly degrades atb S/N <= 5. Adding MIRI photometry with 1 mag brighter depth than the NIRCam depth allows for a redshift recovery of 83%-99%, depending on spectral energy distribution type, and its effect is particularly noteworthy for galaxies with nebular emission. The vast majority of NIRCam galaxies with [F150W] = 29. AB mag at z =7-10 will be detected with MIRI at [F560W, F770W] < 28 mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.

We present a study of photometric redshift accuracy in the 3D-HST photometric catalogs, using 3D-HST grism redshifts to quantify and dissect trends in redshift accuracy for galaxies brighter than JH(IR) > 24 with an unprecedented and representative high-redshift galaxy sample. We find an average scatter of 0.0197 +/- 0.0003(1 + z) in the Skelton et al. photometric redshifts. Photometric redshift accuracy decreases with magnitude and redshift, but does not vary monotonically with color or stellar mass. The 1 sigma scatter lies between 0.01 and 0.03 (1 + z) for galaxies of all masses and colors below z. <. 2.5 (for JH(IR) < 24), with the exception of a population of very red (U - V > 2), dusty star-forming galaxies for which the scatter increases to similar to 0.1 (1+ z). We find that photometric redshifts depend significantly on galaxy size; the largest galaxies at fixed magnitude have photo-zs with up to similar to 30% more scatter and similar to 5 times the outlier rate. Although the overall photometric redshift accuracy for quiescent galaxies is better than that for star-forming galaxies, scatter depends more strongly on magnitude and redshift than on galaxy type. We verify these trends using the redshift distributions of close pairs and extend the analysis to fainter objects, where photometric redshift errors further increase to similar to 0.046 (1 + z) at H-F160W = 26. We demonstrate that photometric redshift accuracy is strongly filter dependent and quantify the contribution of multiple filter combinations. We evaluate the widths of redshift probability distribution functions and find that error estimates are underestimated by a factor of similar to 1.1 - 1.6, but that uniformly broadening the distribution does not adequately account for fitting outliers. Finally, we suggest possible applications of these data in planning for current and future surveys and simulate photometric redshift performance in the Large Synoptic Survey Telescope, Dark Energy Survey (DES), and combined DES and Vista Hemisphere surveys.

We present an update to the ultraviolet-to-radio database of global broadband photometry for the 79 nearby galaxies that comprise the union of the KINGFISH (Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel) and SINGS (Spitzer Infrared Nearby Galaxies Survey) samples. The 34-band data set presented here includes contributions from observational work carried out with a variety of facilities including GALEX, SDSS, Pan-STARRS1, NOAO, 2MASS, Wide-Field Infrared Survey Explorer, Spitzer, Herschel, Planck, JCMT, and the VLA. Improvements of note include recalibrations of previously published SINGS BVRCIC and KINGFISH farinfrared/submillimeter photometry. Similar to previous results in the literature, an excess of submillimeter emission above model predictions is seen primarily for low-metallicity dwarf or irregular galaxies. This 33-band photometric data set for the combined KINGFISH+SINGS sample serves as an important multiwavelength reference for the variety of galaxies observed at low redshift. A thorough analysis of the observed spectral energy distributions is carried out in a companion paper.