Dissertationen zum Thema „Telescopes“

The Small Telescopes Installed at the Liverpool Telescope (STILT) have been in operation since March 2009, collecting wide field data from their position, at the Liverpool Telescope on La Palma. The system consists of a set of two wide field imaging cameras, known as SkycamT and SkycamZ. They provide fields of view of 21x210 and Ix 1 0, along with limits of 12th and 18th in R-band magnitude. The work in this thesis describes the methodology used to create an image analysis pipeline and database to store the photometric results contained in the images produced by these cameras. Such a database is capable of providing invaluable data for the study of many stellar and transient sources. The optimisation of the camera software, as well as modifications to the hardware of the cameras are presented, along with a discussion of the imaging methodologies used in the creation of the data pipeline, which involved specific setup for the case of wide field imaging. For the pipeline, the method for photometric calibration and the overall process structure will be presented along with the schema of the database, and the justifications for these choices. Work has also been carried out to define the performance of the system in a photometric, astrometric and computational sense. The resulting datasets contains: SkycamZ SkycamT Images processed 272,470 315,277 Unique Objects observed 6,290,935 21,453,608 Observations 332,735,320 904,033,139 Mean observations per object 53 42

A lo largo de toda nuestra historia, los seres humanos nos hemos esforzado por descifrar los misterios con los que el Universo nos desafía. En nuestros humildes comienzos, esta tarea era realizada con nuestros ojos desnudos, mirando las estrellas y los planetas y preguntándonos qué tan lejos estaban y cómo se movían en el cielo nocturno. Durante muchos siglos, sólo el Universo visible fue accesible para nosotros, pero se obtuvieron logros extraordinarios a pesar de las limitadas herramientas: descubrimos, por ejemplo, que nuestro planeta no era el centro del Universo, gracias a las observaciones de Nicolaus Copernicus y su modelo heliocéntrico. Desde la época de Copernicus hasta ahora, el desarrollo de nuevas tecnologías y el avance de nuestra propia comprensión del Cosmos, nos ha permitido desentrañar mucho enigmas. Afortunadamente, esta curiosidad natural que nos lleva a mejorar nunca termina, y nos enfretamos a nuevas preguntas que desafían nuestra capacidad como científicos. En la presente tesis, me centro en una pequeña fracción de esta ciencia: la astronomía de rayos gamma. Dentro de este campo, estudio la aceleraci ón de partículas y los mecanismos de producción de rayos gamma en los jets relativistas de los denominados microcuásares y en shocks producidos en pleriones. En la Parte I de la tesis, presento una introducción al Universo no térmico, profundizando en los mecanismos de producción y absorción que gobiernan la emisión de rayos gamma. También introduzco los telescopios MAGIC, de los cuales se obtiene la mayor parte de los resultados de esta tesis. Otras técnicas de detección, como las empleadas en el Observatorio HAWC o por el satélite Fermi-LAT, son igualmente presentadas dado que sus resultados son empleados en la discusión de fuentes galácticas incluidas en esta tesis. Los logros científicos están incluidos en la Parte II y Parte II. En el primera, discuto los resultados de los tres mejores candidatos microcuásares para emitir rayos gamma a muy altas energías: Cygnus X-1, Cygnus X-3 y V404 Cygni. Investigo todos ellos haciendo uso de los datos de MAGIC durante campañas observacionales de larga duración o durante periodos de alta actividad. Por otra parte, con el fin de complementar los resultados a energías más bajas, analizo los datos de Fermi-LAT de Cygnus X-1, lo cual condujo a la detección del sistema en el régime de altas energ ías. Esto constituye la primer detección firme de rayos gamma a altas energías de un sistema binario compuesto por un agujero negro. La Parte III se centra en el estudio de pleriones. Analizo cinco fuentes pertenecientes a esta clase y contextualizo los resultados dentro del estudio de población de pleriones realizado por la Colaboración H.E.S.S.. Haciendo uso de estos resultados, se discute la importancia de la densidad de fotones en el medio circundante junto con las características de los p´ulsares alojado por estos pleriones para la emisión de rayos gamma. En esta tesis, también presento el primer trabajo conjunto entre el Observatorio HAWC y MAGIC, que abre las puertas a futuros proyectos en sinergia. La Parte IV incluye el trabajo técnico realizado durante mi tesis con el futuro CTA. Este trabajo está centrado en el hardware de la cámara de los telescopios de gran tamaño (LST, por sus siglas en inglés) del futuro instrumento CTA, que incluye el control de calidad de varios subsistemas, entre los que descatan los fotomultiplicadores, las fuentes de alimentación y el sistema de trigger. Finalmente, resumo todos los anteriormente mencionados resultados en un capítulo de conclusiones. Todo el trabajo desarrollado durante mi tesis dio lugar a siete publicaciones en revistas científicas: dos ya publicadas, dos aceptadas por la correspondiente revista y tres actualmente bajo revisión de la Colaboración de MAGIC y otras colaboraciones implicadas.
Throughout our entire history, we humans have strived to unravel the mysteries with which the deep Universe challenges us. In our humble beginnings, this task was performed with our naked eyes, by gazing at the stars and planets and wondering how far away they were and how they moved in the night sky. For many centuries, only the visible Universe was reachable for us, but extraordinary achievements were accomplished despite the limited tools: we discovered, for example, that our planet was not the center of the Universe, owing to Nicolaus Copernicus’ observations and his heliocentric model. From Copernicus’ epoch up to now, the development of new technologies and the advancement of our own understanding of the Cosmos, allowed us to disentangle many riddles. Fortunately, this natural curiosity that leads us to improve never ends, and we face new questions that challenge our capacity as scientists. In the present thesis, I focus on a small fraction of this science: the gamma-ray astronomy. Within this field, I study particle acceleration and gamma-ray production mechanisms inside the relativistic jets displayed by the so-called microquasars and the shocks produced in Pulsar Wind Nebulae (PWNe). In Part I of the thesis I present an introduction to the non-thermal Universe, delving into the mechanisms of production and absorption that govern the gamma-ray emission. I also introduce the MAGIC telescopes, from which the bulk of results in this thesis are obtained. Other detection techniques, such as those used by the HAWC Observatory and the Fermi-LAT satellite, are also introduced as results from both of them are used in the discussion of galactic sources included in this thesis. The scientific achievements are encompassed in Part II and Part III. In the former, I discuss results from the three best microquasar candidates to emit Very-High-Energy (VHE) gamma rays: Cygnus X-1, Cygnus X-3 and V404 Cygni. I investigate them making use of MAGIC data during long-term campaigns or under flaring periods. Furthermore, in order to complement results at lower energies, I analyze Fermi-LAT data of Cygnus X-1, leading to the detection of the system in the High Energy (HE) regime. This constitutes the first firmly gamma-ray detection on a Black Hole (BH) binary system. Part III is focused on the study of PWNe. I analyze five sources of this type and set the results in the context of the TeV PWN population study performed by the High Energy Stereoscopic System (H.E.S.S.) Collaboration. Along with these results, I discuss the importance of the target photon field together with characteristic features of the pulsars hosted by these PWNe to emit gamma rays. In this thesis, I also present the first joint work between the HAWC Observatory and MAGIC, which opens the door to future synergy projects. In Part IV, I present the technical work performed during my thesis for the future Cherenkov Telescope Array (CTA) instrument. I focus on the camera hardware for the Large Size Telescope (LST), working on the Quality Control (QC) for several subsystems, among which the Photomultiplier Tubes (PMTs), power supplies and trigger mezzanines stand out. Finally, I summarize all the aforementioned results in a conclusion chapter. All the work developed during my thesis led to seven publications in scientific journals: two of them already published, two accepted by the corresponding journal and three currently under the revision of MAGIC and all implicated collaborations.

Philosophiae Doctor - PhD
The next generation of radio telescopes will revolutionize cosmology by providing large three-dimensional surveys of the universe. This work presents forecasts using the technique 21cm intensity mapping (IM) combined with results from the cosmic microwave background, or mock data of galaxy surveys. First, we discuss prospects of constraining curvature independently of the dark energy (DE) model, finding that the radio instrument HIRAX will reach percent-level accuracy even when an arbitrary DE equation of state is assumed. This is followed by a study of the potential of the multi-tracer technique to surpass the cosmic variance limit, a crucial method to probe primordial non-Gaussianity and large scale general relativistic e↵ects. Using full sky simulations for the Square Kilometre Array phase 1 (SKA 1 MID) and the Large Synoptic Survey Telescope (LSST), including foregrounds, we demonstrate that the cosmic variance contaminated scenario can be beaten even in the noise free case. Finally, we derive the signal to noise ratio for the cosmic magnification signal from foreground HI intensity maps combined with background galaxy count maps. Instruments like SKA1 MID and HIRAX are highly complementary and well suited for this measurement. Thanks to the powerful design of the planned radio instruments, all results confirm their potential and promise an exciting future for cosmology.

Astronomy constantly pushes the limits of technology in order to decipher the workings of the Universe. There is a constant need for higher resolution observations across a wide range of wavelengths, at preferably a minimal cost. The terahertz regime (lambda=100 um to lambda=1000 um) covers a region of the electromagnetic spectrum that is blocked by Earth's atmosphere, which limits observations to high altitude plane and balloon telescopes and space telescopes. These current options limit the resolution achievable due to the size of telescopes that can be launched. This dissertation investigates a new approach, the Large Balloon Reflector (LBR), where a 20 meter diameter spherical balloon can be inflated and used as a 10 meter telescope inside a larger carrier balloon. Detailed in this dissertation are design considerations for the terahertz regime and a series of scaled versions of this balloon concept where I work to develop on-axis spherical corrector designs. Chapters 1 through 6 focus on the LBR designs and their variants, including investigations for a 3 meter rooftop proof of concept model, a 5 meter test flight model, and the final 20 meter LBR. The successful modeling and proof of concepts from the LBR studies then prompted an investigation into a Terahertz Space Telescope (TST), a proposed 20 meter inflatable telescope adapted from the LBR technology. Starting with Chapter7, this dissertation explores the application of using 1 meter diameter inflatable balloons as rapidly deployable communications satellites from standard CubeSats. The concept, design and test results of an electronically steerable line feed antenna array are presented which allows for instantaneous, non mechanical pointing of a 10 GHz signal within a 500 km ground footprint. Alternative uses of the 1 meter inflatable balloon CubeSat are also discussed, such as low cost astronomical galactic plane surveys.

En esta tesis se tratan diferentes aspectos de la acústica presente en un telescopio submarino de neutrinos, principalmente en dos vertientes: en el sistema de posicionamiento acústico utilizado para la monitorización de las posiciones de los módulos ópticos presentes a lo largo del detector, así como en sistemas para detección acústica de neutrinos, técnica que actualmente está en fase de estudio. Todos los estudios realizados están enmarcados dentro de dos colaboraciones europeas para el diseño, construcción y operación de telescopios submarinos de neutrinos: Antares (en fase de operación) y KM3NET (en fase de diseño). Objetivos. Los objetivos de este trabajo pueden resumirse en los siguientes aspectos: - Estudios y análisis del sistema de posicionamiento acústico de Antares. Desarrollo del software para la para la automatización del procesado de los datos de dicho sistema e incorporación de los resultados en la base de datos del experimento. Análisis de los datos proporcionados por dicho sistema con el fin de validar su correcto funcionamiento. - Diseño y desarrollo del sistema de posicionamiento acústico para KM3NeT, telescopio unas 20 veces más grande que Antares. - Estudios para la evaluación de la generación acústica paramétrica para el desarrollo de un calibrador compacto capaz de generar señales tipo neutrino útiles en sistemas de detección acústica. Elementos de la metodología a destacar. Cabe destacar aquí que el trabajo se ha desarrollado en el marco de dos colaboraciones internacionales: ANTARES y KM3NeT, financiados con fondos europeos y nacionales. Por su contexto y el carácter de las actividades realizadas ha sido necesaria la formación en distintos campos: telescopios de neutrinos y astropartículas, pero también en otras áreas como la acústica submarina. Además, se ha desarrollado diversas capacidades y destrezas en diversos ámbitos: en instrumentación, en aplicaciones informáticas, en análisis de datos, etc. Más concretamente, se ha trabajado en aplicaciones informáticas para los desarrollos y análisis en ANTARES.
Bou Cabo, M. (2011). Acoustics for underwater neutrino telescopes [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/10989
Palancia

Severement limite par la turbulence atmospherique, les grands telescopes au sol ne sont pas capables d'atteindre leur limite de resolution intrinseque de maniere directe. En fonctionnement normal, ils ne peuvent pas resoudre plus de details, aux longueurs d'ondes du visible et du proche infrarouge qu'un telescope de quelques decimetres de diametre. La technique d'optique adaptative decrite ici, offre l'avantage sur les autres techniques, d'un traitement du front d'onde avant la detection du signal. Lorsque la detection n'est pas limitee par le bruit propre du signal incident ce traitement permet d'ameliorer significativement le rapport signal sur bruit. La correction est realisee par un miroir deformable dont les comandes sont calculees a partir des mesures des perturbations de la surface d'onde. Les limitations de cette instrumentation sont donnees par le nombre d'actuateurs du miroir, la precision de la mesure du front d'onde, liee au flux disponible pour realiser la mesure, et a la bande passante de l'asservissement. Cette bande passante est surtout liee a la frequence d'echantillonnage du signal d'erreur, et a la vitesse de calcul dans la boucle d'asservissement. Nous donnons la description d'un instrument teste en observatoire au cours de l'automne 1989. Le front d'onde corrige au moyen d'un miroir deformable de 19 actuateurs, a permis d'obtenir en temps reel, des images limitees par la diffraction pour des longueurs d'onde superieures a 2,2 m, au foyer coude du telescope de 1,52 m de l'ohp. La mesure de la perturbation est realisee par un analyseur de shack-hartmann de 55 sous-pupilles pour echantillonner le signal a une frequence de 100 hz. La bande passante obtenue est de 9 hz en boucle ouverte a 0 db. Les resultats qui sont presentes illustrent l'interet de cette technique pour l'imagerie infrarouge en astronomie

Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of objects behind them. The effect enables observations of very distant supernovae, that otherwise would be too faint to be detected by existing telescopes, and allows studies of the frequency and properties of these rare phenomena when the universe was young. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their well known brightness can be used to determine the magnification, which can be used to understand the lensing systems. In this thesis, galaxy clusters are used as gravitational telescopes to search for lensed supernovae at high redshift. Ground-based, near-infrared and optical search campaigns are described of the massive clusters Abell 1689 and 370, which are among the most powerful gravitational telescopes known. The search resulted in the discovery of five photometrically classified, core-collapse supernovae at redshifts of 0.671<z<1.703 with significant magnification from the cluster. Owing to the power of the lensing cluster, the volumetric core-collapse supernova rates for 0.4 ≤ z < 2.9 were calculated, and found to be in good agreement with previous estimates and predictions from cosmic star formation history. During the survey, two Type Ia supernovae in A1689 cluster members were also discovered, which allowed the Type Ia explosion rate in galaxy clusters to be estimated. Furthermore, the expectations of finding lensed supernovae at high redshift in simulated search campaigns that can be conducted with upcoming ground- and space-based telescopes, are discussed. Magnification from a galaxy lens also allows for detailed studies of the supernova properties at high redshift that otherwise would not be possible. Spectroscopic observations of lensed high-redshift supernovae Type Ia are of special interest since they can be used to test for evolution of the standard candle nature of these objects. If systematic redshift-dependent properties are found, their utility for future surveys could be challenged. In the thesis it is shown that the strongly lensed and very distant supernova Type Ia PS1-10afx at z=1.4, does not deviate from the well-studied nearby and intermediate populations of normal supernovae Type Ia. In a different study, the discovery of the first resolved multiply-imaged gravitationally lensed supernova Type Ia is also reported.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Thesis (M.S. in Space Systems Operations)--Naval Postgraduate School, September 2005.
Thesis Advisor(s): Kyle T. Alfriend, Don A. Danielson. Includes bibliographical references (p. 33). Also available online.

A 2.7-meter Liquid Mirror Telescope (LMT) is currently under construction at the University of British Columbia. The stationary, parabolic primary mirror is formed by uniformly rotating the highly reflective liquid, metallic mercury. Compensation for the lack of mechanical tracking will be accomplished by using the Time Delay and Integrate (TDI) readout technique with our Ford 2048 x 2048 CCD detector. The ability to produce large, diffraction-limited mirrors in the laboratory has been previously demonstrated; this project, the first of its kind, is an investigation into their potential for astronomical survey-work, in a working observatory environment. A set of 40 intermediate-band filters, one filter to be used per "photometric" night, will facilitate the collection of Spectral Energy Distributions (SEDs) of all objects, to a limiting stellar V[symbol omitted] ~21, in the 83.0 deg² strip (1/3 deg wide) available to this telescope. A catalog of >10⁵ galaxy and ~3,000 quasar SEDs is expected, providing the largest database of its type to date. A detailed stress-tensor analysis of the mercury-loaded mirror cell is given. The maximum flexure of the cell (at the mirror rim) was found to be ≲0.32 mm. The high resonant frequency of the cell was designed to minimise the excitement of both gravity and capillary waves, surface phenomena which can degrade image quality. An analysis of the support structure indicated that its maximum deflection under wind loading (≲0.3µm) would be significantly less than the Ford CCD's physical pixel size of 15 µm. Temperature-sensitive autofocussing was needed to ensure that thermal expansion/ contraction of the support structure did not lead to defocussing. Star-trail curvature at non-zero latitudes and the discrete nature of the TDI readout mode leads to elongation of north-south (NS) and east-west (EW) image structure, respectively. Convolving stellar Point Spread Functions (e.g. Gaussian) with the CCD's pixel width showed image broadening of ~5% (EW) and ~9% (NS). While these effects are expected to be negligible for our instrument, quantifying them under on-site testing will be imperative before proceeding with the development of larger LMTs.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

Современную астрономию невозможно представить без зрительных труб (телескопов). Уже Галилей, первым применивший зрительную трубу для наблюдения небесных тел, сделал ряд важных открытий. Хотя его телескоп обладал увеличением всего в 30 раз и с нашей точки зрения давал весьма плохое качество изображения. Современные телескопы имеют огромные размеры и представляют собой весьма сложное сооружение.

The Small Telescopes at the Liverpool Telescope (STILT) is an almost decade old project to install a number of wide field optical instruments to the Liverpool Telescope, named Skycams, to monitor weather conditions and yield useful photometry on bright astronomical sources. The motivation behind this thesis is the development of algorithms and techniques which can automatically exploit the data generated during the first 1200 days of Skycam operation to catalogue variable sources in the La Palma sky. A previously developed pipeline reduces the Skycam images and produces photometric time-series data named light curves of millions of objects. 590,492 of these objects have 100 or more data points of sufficient quality to attempt a variability analysis. The large volume and relatively high noise of this data necessitated the use of Machine Learning and sophisticated optimisation techniques to successfully extract this information. The Skycam instruments have no control over the orientation and pointing of the Liverpool Telescope and therefore resample areas of the sky highly irregularly. The term used for this resampling in astronomy is ‘cadence’. The unusually irregular Skycam cadence places increased strain on the algorithms designed for the detection of periodicity in light curves. This thesis details the development of a period estimation method based on a novel implementation of a genetic algorithm combined with a generational clustering method. Named GRAPE (Genetic Routine for Astronomical Period Estimation), this algorithm deconstructs the space of possible periods for a light curve into regions in which the genetic population clusters. These regions are then fine-tuned using a k-means clustering algorithm to return a set of independent period candidates which are then analysed using a Vuong closeness test to discriminate between aliased and true periods. This thesis demonstrates the capability of GRAPE on a set of synthetic light curves built using traditional regular cadence sampling and Skycam style cadence for four different shapes of periodic light curve. The performance of GRAPE on these light curves is compared to a more traditional periodogram which returns a set of peaks and is then analysed using Vuong closeness tests. GRAPE obtains similar performance compared to the periodogram on all the light curve shapes but with less computational complexity allowing for more efficient light curve analysis. Automated classification of variable light curves has been explored over the last decade. Multiple features have been engineered to identify patterns in the light curves of different classes of variable star. Within the last few years deep learning has come to prominence as a method of automatically generating informative representations of the data for the solution of a desired problem, such as a classification task. A set of models using Random Forests, Support Vector Machines and Neural Networks were trained using a set of variable Skycam light curves of five classes. Using 16 features engineered from previous methods an Area under the Curve (AUC) of 0.8495 was obtained. Replacing these features with inputs from the pixel intensities from a 100 by 20 pixel image representation, produced an AUC of 0.6348, which improved to 0.7952 when provided with additional context to the dimensionality of the image. Despite the inferior performance, the importance of the different pixels produced relations in the trained models demonstrating that they had produced features based on well-understood patterns in the different classes of light curve. Using features produced by Richards et al. and Kim & Bailer-Jones et al., a set of features to train machine learning classification models was constructed. In addition to this set of features, a semi-supervised set of novel features was designed to describe the shape of light curves phased around the GRAPE candidate period. This thesis investigates the performance of the PolyFit algorithm of Prsa et al., a technique to fit four piecewise polynomials with discontinuous knots capable of connecting across the phase boundary at phases of zero and one. This method was designed to fit eclipsing binary phased light curves however were also described to be fully capable on other variable star types. The optimisation method used by PolyFit is replaced by a novel genetic algorithm optimisation routine to fit the model to Skycam data with substantial improvement in performance. The PolyFit model is applied to the candidate period and twice this period for every classified light curve. This interpolation produces novel features which describe similar statistics to the previously developed methods but which appear significantly more resilient to the Skycam noise and are often preferred by the trained models. In addition, Principal Component Analysis (PCA) is used to investigate a set of 6897 variable light curves and discover that the first ten principal components are sufficient to describe 95\% of the variance of the fitted models. This trained PCA model is retained and used to generate twenty novel shape features. Whilst these features are not dominant in their importance to the learned models, they have above average importance and help distinguish some objects in the light curve classification task. The second principal component in particular is an important feature in the discrimination of short period pulsating and eclipsing variables as it appears to be an automatically learned robust skewness measure. The method described in this thesis produces 112 features of the Skycam light curves, 38 variability indices which are quickly obtainable and 74 which require the computation of a candidate period using GRAPE. A number of machine learning classifiers are investigated to produce high-performance models for the detection and classification of variable light curves from the Skycam dataset. A Random Forest classifier uses a training set of 859 light curves of 12 object classes to produce a classifier with a multi-class F1 score of 0.533. It would be computationally infeasible to produce all the features for every Skycam light curve, therefore an automated pipeline has been developed which combines a Skycam trend removal pipeline, GRAPE and our machine learned classifiers. It initialises with a set of Skycam light curves from objects cross-matched from the American Association of Variable Star Observers (AAVSO) Variable Star Index (VSI), one of the most comprehensive catalogues of variable stars available. The learned models classify the full 112 features generated for these cross-matched light curves and confident matches are selected to produce a training set for a binary variability detection model. This model utilises only the 38 variability indices to identify variable light curves rapidly without the use of GRAPE. This variability model, trained using a random forest classifier, obtains an F1 score of 0.702. Applying this model to the 590,492 Skycam light curves yields 103,790 variable candidates of which 51,129 candidates have been classified and are available for further analysis.

The next generation of ground-based optical/infrared (IR) telescopes will have primary mirrors of up to 42 m. To take advantage of the large potential increase in angular resolution, adaptive optics will be essential to overcome the resolution limits set by atmospheric turbulence. Novel techniques such as Multi-Conjugate Adaptive Optics (MCAO) and Multi-Object Adaptive Optics (MOAO) are being developed to achieve near diffraction-limited images over large fields-of-view. This thesis concerns the development of MCAO and MOAO pathfinders. Specifically, the construction of CANARY, aMOAO demonstrator, and the on-sky performance and scientific exploitation of the Multi-conjugate Adaptive optics Demonstrator (MAD). CANARY is under construction for the William Herschel Telescope (WHT) in La Palma and contains a telescope simulator to allow testing of the set-up in the laboratory. The simulator contains a natural guide star emulator, turbulence phase screens, and telescope relay optics. The work presented here concerns the integration of the various components in relation to numerical models and the CANARY specifications. MAD was a near-IR imager on the Very Large Telescope (VLT) in Chile. Science demonstration observations were taken of R136, the young, massive cluster situated in the 30 Doradus star-forming region in the Large Magellanic Cloud. These data were used here to determine the MCAO performance across the ~1’x1’ field-of-view, for different pointings with respect to the guide stars, finding high Strehl ratios and relatively uniform corrections across the fields. The MAD data are then used to construct radial surface brightness profiles for R136, providing new insights into intriguing past results from the Hubble Space Telescope. The MAD data reveal that the profile is strongly asymmetric, removing the need for dramatic dynamical evolution of the cluster in the recent past, and highlighting the importance of considering asymmetries when analysing clusters further afield. The MAD data, combined with other near-IR imaging from the VLT, are then used to investigate the nature of candidate young stellar objects from recent observations with the Spitzer Space Telescope.

The Durham University Mk6 Ground Based Gamma Ray Telescope is a sensitive detector in the Very High Energy (VHE) band (~100GeV-10TeV). It is a 'composite' Cherenkov telescope consisting of three 42m(^2) mirrors, each of which is viewed by a Cherenkov photon detector. Together the three detectors provide the basis for a sophisticated coincidence trigger that gives the telescope its low energy threshold of ~300GeV. Analysis of high resolution Cherenkov images from the central detector allows gamma rays to be identified from the hadronic background. The Left and Right detectors also record two independent, medium resolution, Cherenkov images. This thesis has investigated the use of the images from the Left and Right detectors to provide extra gamma/hadron discrimination power. Two measurements, represented by the parameters dDist and LRconc, have been identified that are capable of improving current VHE source detection significance by 20-30%.In Chapter 1 some of the motivations behind the field of VHE gamma ray astronomy are discussed, along with brief explanations of VHE gamma ray production mechanisms. Potential astronomical sources of VHE photons are outlined in Chapter 2. In Chapter 3 the phenomenon of Cherenkov radiation emitted in the atmosphere from Extensive Air Showers (EAS) is introduced. The construction of Atmospheric Cherenkov Telescopes is considered in Chapter 4 and the Durham Mk6 telescope is detailed in Chapter 5. The moments method of analysing Cherenkov images is given in Chapter 6. Chapter 7 investigates the measurements that that could be made using data from the Left and Right detectors to identify gamma ray EAS from the hadron background. The effects on these measurements of various aspects of the Mk6 telescope's performance are also researched here and in further detail in Chapter 8. Finally a summary and some suggestions for future work are given in Chapter 9.

Spectral line observations are of vital importance in astrophysics. Hydrogen recombination lines are a uniquely powerful tracer of ionised gas in the Galaxy, and of star formation and gas kinematics in other galaxies. Improvements in receiver performance at ~GHz frequencies has generated renewed interest in recombination lines from other galaxies. The 76m Lovell Telescope should be sensitive enough to detect recombination lines from new galaxies in 10-100 hrs. Jodrell Bank Observatory has been without a dedicated spectral line backend for more than 15 years. The advancement of digital technology means a step-change in bandwidth and resolution capability is now possible. A ROACH2 board was configured as a spectrometer with up to ≈15kHz resolution in two polarisations across 512MHz bandwidth and up to ≈62.5kHz resolution across 2GHz bandwidth in one polarisation. Signal transport systems were developed to allow observation of signals from the MkII and Lovell telescopes by the spectrometer. The 2GHz primary system was found to be dominated by correlated noise, introduced by the e-MERLIN frequency conversion system. Initial observations of the H96-103α recombination line were found to be dominated by the band shape, which will limit calibration accuracy. The MkII telescope was commissioned for use in spectral line observations. The C-band receiver showed good performance. f_knee≈17mHz across 250kHz was found, scaling with bandwidth as expected. The telescope pointing accuracy was found to be a limiting factor, with offsets up to ~50% of the half-power beam width observed. Nevertheless hourly corrections demonstrated that sources could be tracked with ≲10% incremental offsets required. A 1hr observation of the calibrator NGC 7027 indicated ≈6% increase in the effective system noise, indicating long observations are well-represented by the radiometer equation. The RFI environment at Jodrell Bank was examined. C-band was found to be largely available for observation. The range of H96-103αRRLs were reliably observable. L-band is densely populated with ~10⁹ Jy signals. The protected band was observed over a four-week period using the Lovell Telescope. A strong correlation is found between human activity and the presence of RFI in the protected band, indicating that even where parts of L-band appear free from coherent RFI, sensitive total-power observations must take place at night. The future of RRL studies from Jodrell Bank is in C-band Galactic plane surveys using the MkII; extragalactic RRL work is unfeasible. The Galactic anti-centre is sparsely observed. The MkII is capable of a fully-sampled survey of 10-20 square degrees with T_rms ~1mK sensitivity in ~ 100 days observing time.

Observing the dynamic interaction between stars and their close stellar neighbors is key to establishing the stars’ orbits, masses, and other properties. Our ability to visually discriminate nearby stars is limited by the power of our telescopes, posing a challenge to astronomers at small observatories that contribute to binary star surveys. Masks placed at the telescope aperture promise to augment the resolving power of telescopes of all sizes, but many of these masks must be manually and repetitively reoriented about the optical axis to achieve their full benefits. This paper introduces a design concept for a mask rotation mechanism that can be adapted to telescopes of different types and proportions, focusing on an implementation for a Celestron C11 Schmidt–Cassegrain optical tube assembly. Mask concepts were first evaluated using diffraction simulation programs, later manufactured, and finally tested on close double stars using a C11. An electronic rotation mechanism was designed, produced, and evaluated. Results show that applying a properly shaped and oriented mask to a C11 enhances contrast in images of double star systems relative to images captured with the unmasked telescope, and they show that the rotation mechanism accurately and repeatably places masks at target orientations with minimal manual effort. Detail drawings of the mask rotation mechanism and code for the software interface are included.

Un banc test, composé d’ une cuve à eau et d’ un hodoscope, a été optimisé et utilisé pour la caractérisation des Modules Optiques (OMs) des expériences ANTARES et KM3NeT. La comparaison entre le flux attendu de muons atmosphériques et le flux mesuré a permis l’ estimation de l’ efficacité de l’ hodoscope.Dans un premier temps, des mesures effectuées avec un OM ANTARES ont permis de valider le système d’ acquisition et de caractériser l’ étalonnage temporel du banc test. Un Module Optique Digital (DOM) a ensuite pu être installé dans la cuve pour être testé. De nombreux points cruciaux pour les télescopes sous-marins à neutrino ont été mentionnés et une description détaillée de l’ étalonnage en charge et du réglage du détecteur a été présentée. La dégradation, observée expérimentalement, de l’ efficacité de détection des OMs ANTARES a été confrontée aux résultats obtenus en simulant la formation d’ une couche de sédimentation. L’ impact de différents profils de sédimentation a été étudié et les résultats de l’ analyse Monte Carlo ont été détaillés. Ce travail a permis de rejeter certains profils de sédimentation en désaccord avec les données
A test bench, comprised of a water tank and a hodoscope, was optimized and operated for the characterization of ANTARES and KM3NeT OpticalModules (OMs). A calculation of the expected atmospheric muon flux and the comparisonto the detected flux is made for the evaluation of the hodoscope efficiency.Measurements were initially made with an ANTARES OM for the evaluation of thetest bench potential and the consequent time correlation analysis. The results wereconsidered satisfying for proceeding to the characterization of a KM3NeT DigitalOM (DOM). This was the first time a DOM was investigated with known muontracks and the analysis lead to original and insightful results. Many key aspectsfor an undersea neutrino telescope are outlined and a detailed description of chargecalibration and the tuning sequence for the ANTARES detector are presented. Theobservation that the OM efficiencies for ANTARES are deteriorating in the courseof time has been compared to simulations of a sedimentation layer on the OMÕsglass sphere. Different profiles for this sedimentation impact are considered and thecombined analysis of monte carlo results with detector data is described. This workpermitted to reject extreme cases of biofouling profiles that are inconsistent withthe data

Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2006.
Thesis Advisor(s): Kyle T. Alfriend, Don A. Danielson. "December 2006." Includes bibliographical references (p. 57). Also available in print.

A real-time discrete-event simulation model is built to emulate the functional operations of the Thaw telescope of the Allegheny Observatory and its attached scientific instrument. The OASIS software system is used to communicate with the simulation model. This simulation model, written in Ada, consists of three major parts. The Command Receiver and the Data Transmitter are software written to service the incoming telecommands and outgoing telemetry, the Command Processor is the actual simulator itself consisting of a Command Retriever, a Scanner, a Parser, a Command Interpreter, and the actual Thaw telescope simulation. The motivation for our simulation model and discussion of design issues are presented in chapters 1 and 2. The details of the model are documented in chapters 3, 4, and 5. The final two chapters include examples, questions, thoughts for future work, and conclusions.

The Richard F. Caris Mirror Lab at the University of Arizona is responsible for production of the eight 8.4 m segments for the primary mirror of the Giant Magellan Telescope, including one spare off-axis segment. We report on the successful casting of Segment 4, the center segment. Prior to generating the optical surface of Segment 2, we carried out a major upgrade of our 8.4 m Large Optical Generator. The upgrade includes new hardware and software to improve accuracy, safety, reliability and ease of use. We are currently carrying out an upgrade of our 8.4 m polishing machine that includes improved orbital polishing capabilities. We added and modified several components of the optical tests during the manufacture of Segment 1, and we have continued to improve the systems in preparation for Segments 2-8. We completed two projects that were prior commitments before GMT Segment 2: casting and polishing the combined primary and tertiary mirrors for the LSST, and casting and generating a 6.5 m mirror for the Tokyo Atacama Observatory.

The Hartebeesthoek Radio Telescope is well suited to mapping large areas of sky at 2.3 GHz because of the stability and sensitivity of the noise-adding radiometer (Nicolson, 1970) and cryogenic amplifier used at this frequency, the relatively large 20' beam of the 26 m dish antenna, and its high-speed drive capability. Telescope control programs were written for the Observatory's online computer for automated mapping. Effort centred on removing the curved baseline or 'background' from each Declination (Dec) scan, due to atmospheric and ground radiation contributions varying as the antenna is scanned. Initially these backgrounds were measured over a wide range of Hour Angle (HA) for the Dec range of a map, and an interpolated curve subtracted from each on-source scan for its HA. A common base level was established by comparison with drift scans (observed with the antenna stationary). These different observations (on- and off-source Dec scans and drift scans) were combined into one in the Skymap system by performing Dec scans at a fixed starting HA for a period long enough to permit 'cold sky' and the source to drift through. A background formed by fitting a smooth curve through the lowest sample at each Dec provides a consistent relative base level for all the scans in an observation. A high scanning speed is used so that observations may fruitfully be repeated three times and interleaved to build a reliable, fully sampled map. As each observation has its own background removed, it may be made at any HA. For comparison, maps of Upper Scorpio produced by the earlier method (Baart et al., 1980) and the Magellanic Cloud region produced by Skymap (Mountfort et al., 1987) are shown. Skymap provides a simple and flexible mapping method which relies on the stability of the noise-adding radiometer and high-speed repeated scans to produce good maps of large or small extent with little computation. Correction for drift is more difficult than with systems which use intersecting scans, such as the 'nodding' scans used by Haslam et al. (1981) or the Azimuth scans of Reich (1982).

Thesis (Ph. D.)--University of Sydney, 2008.
Includes graphs and tables. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Bibliography: p. 196-203. Also available in print form.

Research has been carried out on three major difficulties in designing efficient and economic telescopes with 8m f/1 lightweight mirrors. These problems are polishing f/1 aspherics, thermal distortion of borosilicate glass mirror and mirror seeing. Viable solutions to all three have been developed. Solving the fundamental problems allows future very large telescopes to use such mirrors as the basic elements in the design which will reduce the cost. Accurate mirror figure together with good pointing stability given by the short focal length will enable the telescope to form images as sharp as that permitted by nature on the ground. A new technology of polishing f/1 aspherics with a computer controlled stressed lap will give very accurate figure because the lap is changed accurately to adapt the desired figure. Design parameters and performance specifications for a 0.6m aluminum stressed lap for polishing a spun cast 1.8m f/1 borosilicate glass honeycomb mirror have been developed. These can be readily scaled up for polishing 8m f/1 mirrors. Stressed lap polishing also requires accurate material removal over the entire mirror surface. An optimization algorithm using the theory of material wear has been developed to search for the polishing strokes suited for uniform or other desired removal rates. Direct casting of lightweight mirrors requires that the glass be borosilicate. The figure distortion caused by the expansion of borosilicate glass requires the mirror be isothermal to less than 0.1°C for image degradation not to exceed 0.1 arcsecond. The problem of thermal interference by air and the environment has been investigated. A method of injecting well controlled air into the cells that forces the mirror to be isothermal to within 0.1°C has been discovered. Mirror seeing caused by temperature difference between the mirror and ambient air can degrade the telescope performance, but can be reduced by careful thermal design. A simple theoretical thermal model is used to select the glass thickness of a honeycomb structure mirror. Under air ventilation thermal control, the mirror responds to changing air temperature in less than an hour, reducing mirror seeing also to 0.1 arcsecond for telescopes at good seeing sites.

In this thesis we want to acknowledge one of the topics developed in his vast work by Guido Horn d’Arturo, the Director of the Bologna University Astronomical Observatory for large part of the 20th century. The topic addressed is of great international relevance in astronomy, even if it is unknown to most researchers. This thesis wants to be an in-depth analysis of the work started in 1999 for the inauguration of the new location of the Department of Astronomy and, mostly, the dedication of the Library to Guido Horn d’Arturo. A booklet printed in that occasion collects the most important papers on the instrument that the astronomer first conceived and realised: a telescope with a tessellated mirror. Thanks to the donation of Horn’s private correspondence to the Department Historical Archives, done by the Horn’s descendant, it has been possible to reconstruct the history, the evolution of the project, the efforts and the experiments that have led to the realization of the tessellated telescope, an attempt to obtain a patent included. This project occupied a great part of his life. The astronomer’s activities came to a standstill owing to historical events. Being Horn a Jew, he was obliged to leave his high position at Bologna University because of racial laws. He could resume his office at University and continue to work hard on his telescope only at the end of World War II. He continued to work on his project developing it more and more. In 1978, Luigi Jacchia - a Horn’s pupil and friend, then at the Smithsonian Astrophysical Observatory - was the first to call attention to the link between the project of Horn’s tessellated mirror and the then under construction Multiple Mirror Telescope in his paper “Forefathers of the MMT”. In conclusion, with this thesis we would like to enhance and spread the ingenious work done by this astronomer who succeeded in overcoming the large number of scientific, technical, economic, and environmental difficulties of his time.

The work presented in this Thesis has been carried out for the MAGIC experiment during three years of PhD student-ship at the University of Padova, Department of Physics G. Galilei, in association with the Padova section of National Institute of Nuclear Physics (Istituto Nazionale di Fisica Nucleare, INFN), under the supervision of Professor M. Mariotti, PhD Michele Doro and PhD Villi Scalzotto. The two MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, located in the Canary Island of La Palma (Spain), are a stereoscopic system based on the IAC (Imaging Atmospheric Cherenkov) technique and detect Cherenkov light emitted by atmospheric showers of charged particles that originate in the Earth’s atmosphere. These showers are predominantly generated by charged primary cosmic rays, such as protons and light isotopes, which impinge the Earth’s atmosphere isotropically, and by a percentage of gamma–rays, whose direction points back to the region of the cosmic emission. Thanks to sophisticated data reduction algorithms it is possible to efficiently extract the gamma–ray signal of the observed sources from the hadronic background in the energy range between ∼50 GeV and ∼20 TeV, allowing studies in different scientific fields such as galactic and extragalactic high energy Astrophysics, Cosmology and Particle Physics. The scientific activities of the MAGIC experiment are carried out in synergy and complementarity with satellite experiments, like AGILE and FERMI, and ground-based experiments, like H.E.S.S., VERITAS, and Milagro. The MAGIC telescopes, operated by a collaboration of about 150 physicists in more than 20 institutes, spread in several European countries, belong to the second generation of Cherenkov telescopes and have innovative features compared to previous IAC experiments related for example to the size of the reflecting surface area (about 250 square meters), to the lower energy threshold (below 100 GeV) and to the tracking velocity in case of observations of transient phenomena such as the Gamma Ray Bursts. In particular, the start of the operations of the second telescope MAGIC-II and the possibility to perform stereoscopic observations allow a lower energy threshold and a better sensitivity (by a factor ∼2) compared to the single MAGIC-I telescope observations. Currently, the MAGIC telescopes represent the more sensitive world-wide ground-based detector for gamma-rays in the energy range between ∼50 GeV and ∼150 GeV. During the PhD student-ship, my research activity focused on two principal occupations. The first one, orientated on technical issues, concerned the upgrade of a specific part of the software of the MAGIC experiment required for the stereoscopic data taking (which started since fall 2009), i.e. the calculation of the Effective Collection Area. The second one, more focused on scientific topics, was addressed to the possible indirect detection of dark matter with the MAGIC-I telescope. In particular, I contributed to the analysis data and to the related publications of the observations of interesting sources for possible detection of gamma–ray signal from self-annihilation processes of dark matter, like the dwarf spheroidal galaxies (satellite of the Milky Way) Draco and Willman 1 and the galaxy cluster Perseus. During the three years of PhD student-ship, I spent, on a whole, 4 months in the site of the MAGIC telescopes, as data taking operator and shift leader. I also contributed in June 2009 to the commissioning of the second telescope MAGIC-II for a period of 4 weeks. This Thesis is divided into eight chapters. Chapter 1 will be dedicated to a brief introduction on the physics of cosmic–rays and of astrophysical gamma-rays, on the current experimental methods for their detection, on the main mechanisms active in the Universe for the production of very high energy gamma-rays and on the main astronomical objects known as gamma-ray emitters. In chapter 2, a description of the main physical characteristics of the hadronic and electromagnetic atmospheric showers, the subsequent Cherenkov light emission and the Imaging Atmospheric Cherenkov technique will be given. In chapter 3, the main hardware components of the MAGIC telescopes will be illustrated, together with the main innovations introduced for the second telescope. In chapter 4, the standard analysis chain of the MAGIC-I telescope finalized to the extraction of the physical quantities of main interest, such as the significance and the gamma-ray flux of a given source, will be described. Subsequently, the new tools required for the stereo analysis of the MAGIC telescopes data will be introduced. The current performance of the stereoscopic system (whose commissioning phase was successfully accomplished during 2009) will be also shown. Chapter 5 will be dedicated to the alt-azimuth dependence of one of the main quantities which characterize the detection of Cherenkov light by the MAGIC telescopes, i.e. the Effective Collection Area. Indeed, while the Zenith effect on this quantity is well known and related to the increased atmospheric depth the atmospheric showers must pass through for increasing Zenith angles of observation, a possible Azimuth dependence is associated to the geomagnetic effects induced to the development of the showers and to the particular geometric configuration of the two telescopes system. The fixed direction between them, in fact, breaks the circular symmetry typical for the observations performed with a single telescope. In view of the start of the operations of the second MAGIC telescope and of the stereoscopic observations, the introduction of the Azimuth dependence of the Effective Collection Area has been therefore systematically taken into account and successfully implemented in the analysis software of the experiment. The results of tests performed on both Monte Carlo simulated data and real data will be shown. In chapter 6, a brief introduction on the dark matter topic will be reported: the main experimental evidences and some of the models and candidates proposed in literature to describe the dark matter nature will be discussed. In particular, the attention will be focused on the indirect dark matter search which is based on the possibility for MAGIC to detect gamma–rays as a result of annihilation or decay of dark matter particles. Gamma–ray signals are searched for in places where dark matter is concentrated, like, for example, the dwarf spheroidal galaxies satellite of the Milky Way. Chapter 7 will be dedicated to the data analysis of the observation carried out by the MAGIC-I telescope of Segue 1, a source considered to be a dwarf spheroidal galaxy satellite of the Milky Way, whose stellar kinematics seems to indicate a high mass–to–light ratio, making this celestial object extremely interesting from the point of view of indirect dark matter searches. The data of this source required particular cares due to the fact that a 3.5 apparent magnitude star was present in the field of view of the source during the whole survey. The adopted techniques used to face the problems related to the light of that star will be illustrated. This analysis allowed to determine, for energies above 100 GeV, upper limits on the flux emission derived form different assumed power law spectra. A paper on Segue 1 observation carried out by the MAGIC-I telescope, based on the results achieved by this analysis, is in preparation. Finally, in chapter 8, the general conclusions of the work presented in this Thesis will be given.
Il lavoro presentato in questa Tesi è stato svolto nell’ambito dell’esperimento MAGIC durante i tre anni di Scuola di Dottorato all’Università degli Studi di Padova, Dipartimento di Fisica G. Galilei, in associazione con l’Instituto Nazionale di Fisica Nucleare, sezione di Padova, sotto la supervisione del Professor M. Mariotti, del Dott. Michele Doro e del Dott. Villi Scalzotto. Il sistema stereoscopico di due telescopi MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov), situato nell’isola canaria di La Palma (Spagna), è basato sulla tecnica IAC (Imaging Atmospheric Cherenkov) per la rivelazione della luce Cherenkov emessa da cascate di particelle cariche che si originano nell’atmosfera terrestre. Tali cascate atmosferiche sono generate preminentemente dai raggi cosmici carichi, quali protoni e isotopi leggeri, che entrano isotropicamente nell’atmosfera terrestre, e da una percentuale di raggi gamma, la cui direzione di provenienza punta direttamente alla regione cosmica di emissione. Grazie a sofisticati algoritmi di riduzione dei dati è possibile estrarre efficacemente il segnale di natura gamma dal quello di natura adronica per energie comprese tra ∼50 GeV e ∼20 TeV, permettendo studi in diversi settori scientifici quali l’Astrofisica galattica ed extragalattica delle alte energie, la Cosmologia e la Fisica delle Particelle Elementari. Le attività scientifiche dell’esperimento MAGIC vengono portate avanti in sinergia e complementarità con gli esperimenti gamma posti su satellite, quali AGILE e FERMI, e quelli posti a terra, quali H.E.S.S., VERITAS eMilagro. I telescopi MAGIC, realizzati da una collaborazione internazionale di circa 150 fisici appartenenti ad una ventina di istituzioni di diversi paesi della comunità europea, rientrano nella seconda generazione di telescopi Cherenkov e presentano rispetto ai precedenti delle caratteristiche innovative legate per esempio alla grandezza della superficie riflettente (circa 250 metri quadri), all’abbassamento della soglia energetica al di sotto dei 100 GeV e alla velocità di puntamento nel caso dell’osservazione di fenomeni improvvisi, come ad esempio l’esplosione di raggi gamma (Gamma Ray Bursts). In particolare, la messa in opera del secondo telescopio MAGIC-II e la possibilità di condurre osservazioni stereoscopiche permettono un abbassamento della soglia energetica ed una sensibilità di circa un fattore 2 superiore a quella ottenuta con il singolo telescopio MAGIC-I. Attualmente, i telescopi MAGIC rappresentano il rivelatore posto a terra più sensibile al mondo per raggi gamma di energie comprese tra ∼50 GeV e ∼150 GeV. Durante il lavoro di dottorato ho svolto la mia ricerca in due principali attività. La prima, di tipo tecnico, ha riguardato l’aggiornamento di una specifica parte del software dell’esperimento MAGIC necessario in vista della presa dati stereoscopica dei telescopi MAGIC (iniziata alla fine del 2009), ovvero il calcolo dell’area efficace collettrice. La seconda, di tipo più prettamente scientifico, è stata rivolta alla possibile rivelazione indiretta di materia oscura con il telescopio MAGIC-I. In particolare, ho contribuito all’analisi dati e alle relative pubblicazioni delle sorgenti osservate dal telescopio MAGIC-I candidate per la ricerca di possibili segnali gamma dovuti ad auto annichilazione di materia oscura, quali le galassie nane satelliti della Via Lattea Draco e Willman 1 e il cluster galattico Perseus. Durante i tre anni di dottorato ho passato complessivamente 4 mesi a La Palma, nel sito dei telescopi MAGIC, come operatore di presa dati. Inoltre nel mese di Giugno del 2009 ho partecipato per 4 settimane alla fase di commissioning del secondo telescopio MAGIC-II. Questo lavoro di Tesi è suddiviso in otto capitoli. Nel capitolo 1 verranno brevemente introdotti la fisica dei raggi cosmici e dei raggi gamma di natura astrofisica, gli attuali metodi sperimentali per la loro rivelazione, i meccanismi attivi nell’Universo per la produzione di raggi gamma di alte energie e le principali sorgenti cosmiche note di raggi gamma. Il capitolo 2 sarà dedicato alla descrizione delle principali caratteristiche fisiche degli sciami atmosferici di natura adronica ed elettromagnetica, alla susseguente emissione di luce Cherenkov prodotta da essi e alla tecnica di rivelazione IAC, su cui i telescopi MAGIC sono basati. Nel capitolo 3 verranno descritte le principali componenti hardware dei due telescopi MAGIC e le innovazioni introdotte per il secondo telescopio. Nel capitolo 4 si discuterà la catena di analisi standard del telescopio MAGIC-I per l’estrazione delle principali quantità fisiche di interesse, quali la significanza del segnale proveniente da una data sorgente e il suo flusso. Successivamente verranno brevemente descritte le principali novità introdotte per la corrente analisi delle sorgenti osservate stereoscopicamente. Le attuali performance del sistema stereoscopico (la cui fase di commissioning è stata portata a termine con successo durante il 2009) saranno inoltre presentate. Nel capitolo 5 verrà introdotta la tematica riguardante la dipendenza alt-azimutale di una delle principali quantità che caratterizzano la rivelazione di luce Cherenkov da parte dei telescopi MAGIC ovvero l’area efficace collettrice. Infatti, se da un lato l’effetto zenitale su tale quantità è ben noto e correlato alla maggiore profondità atmosferica che gli sciami percorrono nel loro sviluppo per angoli zenitali via via maggiori, una possibile dipendenza azimutale è associata agli effetti che il campo geomagnetico induce sullo sviluppo degli sciami stessi e alla particolare configurazione geometrica del sistema di telescopi. La direzione fissa tra di essi, infatti, rompe la simmetria circolare di osservazione tipica delle osservazioni effettuate con un singolo telescopio. Alla luce della messa in funzione del secondo telescopio MAGIC-II e della osservazione stereoscopica delle sorgenti, l’introduzione della dipendenza azimutale dell’area efficace colletrice è stata dunque presa sistematicamente in considerazione e implementata efficacemente nel software di analisi dati dell’esperimento. Saranno riportati inoltre i risultati di test effettuati su campioni di dati Monte Carlo e di dati reali. Nel capitolo 6 verrà fatta una breve introduzione sulla materia oscura: saranno discusse le principali evidenze sperimentali, alcuni modelli che la descrivono e i principali candidati proposti in letteratura per spiegarne la natura. L’attenzione sarà focalizzata sulla ricerca indiretta di materia oscura che si basa sulla possibilità per i telescopi MAGIC di poter rivelare segnali indiretti sotto forma di raggi gamma, provenienti da annichilazione o decadimento di particelle di materia oscura, da parte di sorgenti caratterizzate da alte densità di tale tipo di materia quali, per esempio, galassie nane sferoidali satelliti della Via Lattea. Il capitolo 7 sarà dedicato all’analisi dati dell’osservazione effettuata da parte del telescopio MAGIC-I della sorgente Segue 1, ritenuta essere una galassia nana sferoidale satellite della Via Lattea, la cui cinematica stellare sembra indicare un elevato rapporto massa–luminosità, rendendo tale oggetto celeste estremamente interessante dal punto di vista della recerca indiretta di materia oscura. I dati di tale sorgente hanno richiesto particolare attenzione dovuta al fatto della presenza di una stella di magnitudo apparente 3.5 nel campo di vista della sorgente durante l’intera osservazione. Le tecniche adottate per trattare i problemi legati alla presenza di tale stella saranno illustrati. L’analisi ha permesso di determinare, per energie maggiori di 100 GeV, limiti superiori sul flusso della sorgente assumendo diversi generici spettri di potenza. Un articolo sull’osservazione della sorgente Segue 1 condotta dal telescopio MAGIC-I, basato sui risultati di questa analisi, è in fase di preparazione. Infine, nel capitolo 8, verranno riportate le conclusioni generali su questo lavoro di Tesi.

Focal plane corrected Cassegrain type optical systems have been widely used in various fields. The axial alignment of complex optical systems is not easy and a practical alignment method is needed for such systems. Tilts, decenters and axial motion of elements or group of elements in the system are the typical alignment parameters. Interferometric measurement is an effective way to see the errors caused by the misalignment of each element in an optical system. In this thesis, alignment of a Cassegrain type telescope will be examined by using interferometric measurements and modulation transfer function simulations.

Future generations of space-based telescopes will require increasingly large primary reflectors, with very tight optical-quality tolerances. However, as their size grow, it becomes more and more difficult to meet the requirements, due to the manufacturing complexity and the associated costs. Chapters 2 and 3 propose two concepts of Adaptive Optics deformable mirrors, intended to be used as secondary corrector to compensate for manufacturing errors, gravity release and thermal distortion of large lightweight primary mirrors of space telescopes: (i) A scalable segmented bimorph mirror, based on independent PZT patches glued on Silicon wafers, providing a large number of degrees of freedom, a low mass while overcoming the problem of a low resonance mode; and (ii) A monolithic bimorph mirror, controlled by an array of independent electrodes, done by laser ablation on a single PZT patch. The modelling, the control strategy and the technological aspects are described. The performances of the manufactured prototypes are demonstrated experimentally. These prototypes have been developed in the framework of the ESA project, Bimorph Adaptive Large Optical Mirror Demonstrator (BIALOM). Chapter 4 introduces alternative designs, allowing to face the thermal distortion inherent to the bimorph architecture. They are compared in terms of stroke, voltage budget and first resonance frequency. These designs are required to be controlled in both directions using only positive voltages. Finally, the last chapter explores the feasibility of the shape control of a small size active thin shell reflector (with double curvature). The prototype is intended to be a technology demonstrator of a future large and very light active primary reflector. The behavior of the shell is studied through numerical simulations, and a preliminary design is proposed. This investigation is carried out in the framework of the ESA project: Multilayer Adaptive Thin Shell Reflectors (MATS).
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

A large fleet (in the hundreds) of high quality telescopes are used for tracking and imaging of launch vehicles during ascent from Cape Canaveral Air Force Station and Kennedy Space Center. A maintenance tool has been development for use with these telescopes. The tool requires rankings of telescope condition in terms of the ability to generate useful imagery. It is thus a case of ranking telescope conditions on the basis of the perceptual image quality of their imagery. Perceptual image quality metrics that are well-correlated to observer opinions of image quality have been available for several decades. However, these are quite limited in their applications, not being designed to compare various optical systems. The perceptual correlation of the metrics implies that a constant image quality curve (such as the boundary between two qualitative categories labeled as excellent and good) would have a constant value of the metric. This is not the case if the optical system parameters (such as object distance or aperture diameter) are varied. No published data on such direct variation is available and this dissertation presents an investigation made into the perceptual metric responses as system parameters are varied. This investigation leads to some non-intuitive conclusions. The perceptual metrics are reviewed as well as more common metrics and their inability to perform in the necessary manner for the research of interest. Perceptual test methods are also reviewed, as is the human visual system. Image formation theory is presented in a non-traditional form, yielding the surprising result that perceptual image quality is invariant under changes in focal length if the final displayed image remains constant. Experimental results are presented of changes in perceived image quality as aperture diameter is varied. Results are analyzed and shortcomings in the process and metrics are discussed.; Using the test results, predictions are made about the form of the metric response to object distance variations, and subsequent testing was conducted to validate the predictions. The utility of the results, limitations of applicability, and the immediate ability to further generalize the results is presented.
ID: 030423279; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 151-155).
Ph.D.
Doctorate
Center for Research and Education in Optics and Lasers
Optics and Photonics

This thesis is concerned with some of the limitations concerned with the imaging properties of astronomical telescopes of large apertures. These arise from the atmosphere, the diffracting aperture, the residual errors in the optically worked surfaces and the characteristics of the detection devices. Methods of Fourier optics are used to determine modulation transfer functions and associated point spread function. They are applied to three problems. The first of these is a comparison of the diffraction patterns that are expected from the multi-mirror telescopes. These are made either of separated individual mirrors or of segmented mirrors shaped to an overall parabolic shape. The effect of the dilution of the aperture in the former and the effect of misalignment in the latter is investigated. In the second study, the factors contributing to the imaging of the UK Schmidt telescope are considered and design studies of this and other two variants are examined. In particular the limiting effect of the atmosphere and of the detecting photographic emulsion is noted. Thirdly the overall limitation of the atmospheric seeing is considered experimentally. The Durham Polaris seeing monitor has been designed and built with a shear interferometer. It has been tested at local ground level where local measurements of seeing have been made. In the near future it will be taken and used at La Palma.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 171-178).
Timing and system parameters were measured for seven transiting exoplanets: OGLETR- 56b (11 transits), OGLE-TR-132b (7), OGLE-TR-111b (6), OGLE-TR-113b (6), CoRoT-2b (3), OGLE-TR-10b (3), and XO-2b (2). Ground-based observations of 38 transits were made using three new frame-transfer instruments: POETS and MagICe2v on the 6.5m Magellan telescopes, and MORIS on the 3m IRTF. For each planet, all transit light curves including available literature data were jointly fit using a Monte Carlo Markov Chain method, providing accurate new values for the planetary radius and other parameters. Transit ephemerides have been updated and transit midtimes have been investigated for potential transit timing variations (TTVs) caused by other planets or moons. Our transit midtime analysis contradicts a claimed TTV for OGLE-TR-111b (Diaz et al., 2008), finding no evidence in data from 2005-2009. The radius, 1.019 + 0.026 Rj, is intermediate to previous values (Winn et al., 2007; Diaz et al., 2008). We confirm the radius of OGLE-TR-56b, which previously had only one light curve (Pont et al., 2007), as 1.332 ± 0.063 Rj, but find a longer duration by 15 minutes, while the orbital period, 1.2119094 ± 0.0000024, is unchanged. Times for OGLE-TR-10b are consistent with the ephemeris of Holman et al. (2007), though two literature transits show large deviations (586 ± 86 s; Pont et al., 2007) and (-612 ± 26 s; Bentley et al., 2009). Times for four planets (OGLE-TR-113b, OGLE-TR-132b, CoRoT-2b, and XO-2b), with midtime errors as small as 9 s, agree with published ephemerides and show no signs of TTVs. The orbital period of OGLE-TR-113b derived from new data from 2007-2009, however, is shorter by 0.24 ± 0.12 s compared to the period calculated for literature data from 2002 and 2005. If confirmed, this would be the first detection of a change in the orbital period of an exoplanet, which could be caused by orbital decay as the planet falls onto its star.
by Elisabeth Rose Adams.
Ph.D.

This work characterises PIRATE’s primary camera, the SBIG STX-16803, as well as assessing the usefulness and impact of a small-aperture semi-autonomous facility in Mallorca for exoplanet studies and studies of transient sources. Additionally, a method for exploring the Roche lobe of an exoplanet and the effects this has on the shape and density of the planet is also described. PIRATE is a small aperture photometric facility that can be operated remotely or autonomously, is constructed from commercially available hardware and utilised by The Open University for research, education and outreach. The camera gain measurements are within the manufacturer specifications while the read noise deviates quite significantly. The camera shutter is also verified to evenly illuminate the CCD which may be suffering from a form of residual image. Regarding exoplanets, PIRATE has helped to identify 108 false positives as well as 24 real and plausible planets. Combined, this is 67% of PIRATE’s total exoplanet candidate observations. Several of these targets are explored in further detail. Still on the subject of exoplanets, Roche calculations are applied to 207 known exoplanets and highlight that WASP-12b, WASP-19b and WASP-103b are likely to have strong distortions from a spherical shape. Look-up charts were also generated for mass ratios of 10^-6 through to 10^-1. These look-up charts are intended to provide a quick reference volume correction to exoplanets (or any other system of similar mass ratios). As part of the Gaia transient preparatory and to demonstrate the capabilities of PIRATE, SN 2014J is provided as an example. A peak B apparent magnitude, Bmax of 11.80 +/- 0.14 mag is observed at a tmax of 56690.79 +/- 0.01 MJD and provides Dm15 = 0.98 +/- 0.20 mag. A peak E(B-V) extinction of 1.24 +/- 0.16 mag (E(B-V)host = 1.19 +/- 0.16 mag) is determined.

This PhD work is focused on the study of transient sources, astrophysical events exhibiting short-time scale variability. In particular, Gamma-Ray Bursts (GRBs) and Gravitational Waves (GWs) counterparts were searched using the data of the MAGIC telescopes, two Cherenkov telescopes detecting gamma-rays in the energy range 50 GeV-10 TeV (very high energies, VHE) thanks to the Imaging Atmospheric Cherenkov Technique. GRBs are the most violent sources in the Universe, releasing a huge amount of energy in few seconds. They are characterized by a prompt emission, where the bulk of photons in the hard-X and gamma energy range are emitted, and an afterglow phase, which is a long-lasting but dimmer emission observable in some of other bands (optical, infrared, ultraviolet, radio, X, gamma). One of the current questions about GRBs regards their possible High Energy (HE, E<100 GeV) and VHE emissions. Several models were proposed but no clear signature of any of them was found yet. Detecting a GRB in the MAGIC energy range would help in clarifying the emission processes at play. For this purpose, a set of several GRBs observed by the MAGIC telescopes was analyzed searching for a possible gamma-ray signal. None of the GRBs showed any signal, so only upper limits (integral and differential) on the gamma-ray flux could be determined. Nonetheless, these upper limits can be used to test possible emission models in the VHE range. The second part of this work was dedicated to find a possible gamma-ray counterpart to GW candidate events detected by the LIGO/Virgo interferometers. MAGIC performed the follow-up of GW151226, the second detection of a GW signal from a binary black hole system. Since the uncertainty in the position of the event given by LIGO was too large compared to the MAGIC field of view (3.5 degrees), a new analysis method had to be implemented. Usually fluxes and spectra are computed at the nominal position of the source, but in the case of large error boxes the emission could be coming from any point of the field of view. For this reason a new tool built upon the existing MAGIC analysis software was developed in order to compute fluxes and upper limits in a wide region of the observed field of view. The method was used to produce "upper limits skymaps" of the four positions observed after the GW151226 trigger. No gamma-ray signal was found. The last part of the thesis was focused on a technical work on the MAGIC automatic system which receives and processes the transient alerts coming from the Gamma-ray Coordinate Network (GCN), called GSPOT (Gamma-ray Source POinting Target). As an extension to other astrophysical transients, the automatic response to neutrino alerts coming from IceCube was implemented in a similar way to what is currently done with GRB alerts. Preliminary tests performed remotely on GSPOT resulted in a correct processing of the neutrino alerts, with a correct calculation of the observability according to predefined criteria.

All future Extremely Large Telescopes (ELTs) will be segmented. However, as their size grows, they become increasingly sensitive to external disturbances, such as gravity, wind and temperature gradients and to internal vibration sources. Maintaining their optical quality will rely more and more on active control means. This thesis studies active optics of segmented primary mirrors, which aims at stabilizing the shape and ensuring the continuity of the surface formed by the segments in the face of external disturbances.

The modelling and the control strategy for active optics of segmented mirrors are examined. The model has a moderate size due to the separation of the quasi-static behavior of the mirror (primary response) from the dynamic response (secondary, or residual response). The control strategy considers explicitly the primary response of the telescope through a singular value controller. The control-structure interaction is addressed with the general robustness theory of multivariable feedback systems, where the secondary response is considered as uncertainty.

Scaling laws allowing the extrapolation of the results obtained with existing 10m telescopes to future ELTs and even future larger telescopes are addressed and the most relevant parameters are highlighted. The study is illustrated with a set of examples of increasing sizes, up to 200 segments. This numerical study confirms that scaling laws, originally developed with simple analytical models, can be used in confidence in the preliminary design of large segmented telescopes.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada
Astronomers now communicate over Internet with robotic astronomical telescopes using a specially designed instruction set. ATIS, Automatic Telescope Instruction Set, is designed to communicate specific, technical instructions to a robotic telescope, facilitate data retrieval and analysis, support a wide range of data formats, and also convey preference information that describe the astronomers general needs for data acquisition. Over a dozen telescopes now use ATIS and more are under construction.

Many astronomers require large amounts of observational data to solve astrophysical problems and to validate theoretical hypotheses. It is therefore imperative that both the observer and telescope work efficiently, maximising data collection whilst minimising object selection and acquisition time. One method in which this can be achieved is through telescope automation. The advent of cheap integrated process controllers enables the system designer to realise novel control system architectures which were previously prohibitive to all but the largest of sites. This thesis reviews the development of processor based control systems in the astronomical and industrial environment and compares distributed and centralised control system architecture. It describes the design and construction of one such distributed control system for the St Andrews Twin Photometric Telescope.

Thesis (Ph.D.)--Boston University
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This dissertation presents the legacy, theory, design, characterization, and application prospects of a fully symmetric monolithic nulling interferometer (nuller). A nuller's function is to destructively interfere light originating from a bright, on-axis, unresolved source in order to lower its contrast with faint, off-axis sources of light in the field of view. The primary application lies in astronomical instrumentation, serving as an enabling technology for directly imaging exoplanets and measuring exozodiacal dust and debris disks, the planetary system evolutionary components around nearby stars. Typical on-sky planet/star flux ratios are 1:109 or less in the visible. Mitigating this contrast is key to spectroscopic study of exoplanets, which aims to characterize exoplanetary atmospheres and potentially locate biosignatures on exo-Earths. Within the past decade, adaptive optics-equipped breadboard demonstrations of nullers and other coronagraphs have shown the capability to image nearby (< 30 lightyears) extrasolar analogs to Jupiter with a 0.5 meter diameter telescope in the visible. The quiet laboratory environments that have been produced to demonstrate this capability do not reflect those of typical ground-based observatories where thermal drifts perturb optical alignment and atmospheric turbulence perturbs the source wavefront. Space-based platforms circumvent the atmosphere problem, but are still subjected to thermal instabilities and their associated risks. Robust optical systems must be designed and flight-tested in order to address such risks and provide grounds for their inclusion in the design of future exo-Earth imaging satellites. Sub-orbital platforms such as sounding rockets and high-altitude balloons provide a rapid, lowcost means of providing heritage for such optical systems while also delivering significant scientific results. The primary risk inherent with these platforms are harsh transient environmental conditions, for which, similar to an orbital platform, robust optical systems are necessary. A novel feature of the nuller described in this work is its monolithic design, which greatly enhances optical stability, the primary obstacle plaguing all high-contrast imaging efforts. Additional design benefits include theoretical achromatic performance and an inner working angle that is 2-4 times smaller than other coronagraph designs, enabling its use with proportionally smaller telescopes.
2031-01-01

The purpose of this thesis is to investigate new instrument technology to enhance the capabilities of 8-m telescopes. This thesis first describes the theory, design, construction, and testing of an immersed grating. Immersed gratings can be used to provide R≥ 10(^4) with a multi-object and/or integral field spectrograph on an 8-m telescope. Immersed gratings allow high resolution to be achieved whilst maintaining the required pupil size at a level similar to that on 4-m telescopes. This thesis describes laboratory tests which verify that immersed gratings provide high resolution. The throughput penalty in using an immersed grating is shown to be small with losses due to air-glass reflections, which can be eliminated with antireflection coatings, and metal-dielectric losses. This work demonstrates that immersed gratings provide a good method to reach R=10(^4) (and above) with a multi-aperture spectrograph on an 8-m telescope. The second part of this thesis describes the construction of a microlens-fibre based integral field unit (IFU): the SMIRFS-IFU. This instrument provides a unique J and H-band integral field capability for use with the CGS4 spectrograph at UKIRT. The optical design, assembly, laboratory testing, and telescope commissioning of the SMIRFS-IFU are described. The microlens arrays for use with SMIRFS-IFU were tested in detail and found to provide excellent image quality but with some scattered light. The assembly of the SMIRFS-IFU was achieved with high precision. The overall performance of the SMIRFS-IFU was found to be high and close to theoretical expectations. This instrument demonstrates that the technology of microlenses linked to fibres does provide a means of constructing high performance (i.e. high throughput, high spatial and spectral resolution) IFUs. Integral field spectroscopy is even more important for 8-m telescopes to take advantage of their enormous fight gathering power. The SMIRFS-IFU is an important upgrade to CGS4 to perform high spatial resolution integral field spectroscopy.