Thèses : « Instrumentation for Astronomy »

1

Martindale, Adrian. « Novel X-ray instrumentation for astronomy ». Thesis, University of Leicester, 2008. http://hdl.handle.net/2381/3964.

Texte intégral

Résumé :

This thesis describes experimental and theoretical work and technology development directed towards the next generation of X-ray astronomical instrumentation. A great heritage exists of instruments which are sensitive to X-rays which operate on board space based observatories. The next generation of such telescopes will take advantage of the rapid technology advancement of the last four decades of more accurately observe the universe and give greater insight into the objects within it, how they formed and how they will evolve. Chapters 2 and 3 describe the investigation of extremely high speed microchannel plate detectors capable of counting individual photons with a timing accuracy of a few tens of picoseconds (1 ps = 10-12s)at extremely high spatial resolution. Although many early X-ray astronomical instruments were based on MCP detectors, it is only recent manufacturing improvements which have enabled the production of such small pore diameters, enabling the unparalleled temporal and spatial resolution. Prospects for future application exist in fields as diverse as X-ray and ultraviolet astronomy and the life sciences. Chapters 4 and 5 report the testing of Microchannel plates as low mass X-ray optics where the development of square pore geometrics has made true imaging MCP telescopes possible. Two flight programs are identified as areas where such optics will provide tangible benefits: These are BepiColombo, a European mission to the planet Mercury which will contain the first ever imaging X-raytelescope on a planetary science mission and Lobster-ISS, a wide field of view telescope for X-ray astronomy which will provide coverage of, almost, the whole sky every 90 minute orbit. Testing reported herein finds that the manufacturing techniques are maturing to a point where they can exceed the <5 arcmin resolution required for these missions. Chapters 6 and 7 comprise a description of a completely novel X-ray polarimeter. For the past three decades, little or now progress has been made in the field of X-ray astrophysical polarimetry owing to the lack of suitable instrumentation, this is despite intense scientific interest in such measurements. A simple optical design for a polarimeter is made possible using highly ordered materials which exhibit dichroism at fixed, narrow energy bands, for the first time allowing simultaneous measurement of ALL astronomically pertinent observables. The areas of science influenced by these three areas of instrument development are shown to be very broad, including; astrophysics and cosmology, planetary science, life sciences, nano-science and even fundamental chemistry.

Styles APA, Harvard, Vancouver, ISO, etc.

2

Lee, Aizeret, University of Western Sydney, of Science Technology and Environment College et School of Engineering and Industrial Design. « Radioastronomical instrumentation : the diagonal horn ». THESIS_CSTE_EID_Lee_A.xml, 2002. http://handle.uws.edu.au:8081/1959.7/699.

Texte intégral

Résumé :

The horn plays an elemental role in the make up of a radio-telescope. The focus of this research is on one particular type of horn – the diagonal horn. An analysis of the diagonal horn is made using the Fourier method. The analysis begins from Maxwell’s equations, as the basic building block, and describes the steps involved in developing the radiation pattern. Based on the theory, a program was written that produces the theoretical graphs referred to throughout the thesis. A diagonal horn was manufactured and the radiation patterns were measured. A comparison of these measured patterns is made against the theoretically generated patterns. Further research was carried out to demonstrate the effects on the radiation patterns when the horn is fitted with a dielectric plug. This practice may enhance the directivity of the horn at the cost of introducing new losses
Master of Engineering (Hons)

Styles APA, Harvard, Vancouver, ISO, etc.

3

Price, Daniel Charles. « Radio astronomy instrumentation for redshifted hydrogen line science ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:3185b622-9aba-4c0f-995b-eceb50a5a49c.

Texte intégral

Résumé :

This thesis presents instrumentation with which to measure the abundance of neutral hydrogen gas in the Universe. Measuring where the Universe’s hydrogen is, and tracing how its distribution evolves with time, holds the key to understanding how galaxies evolve, the nature of dark energy, and how the first cosmic structures formed. In particular, this thesis looks at instrumentation for 21-cm intensity mapping telescopes. In 21-cm intensity mapping, the collective emission of many galaxies is measured, without individual detections. This technique promises to allow detection of the baryonic acoustic oscillation peaks in the power spectrum of the Universe’s matter distribution. Such a detection would increase constraints on cosmological parameters. There are two main approaches to designing a 21-cm intensity mapping instruments: using a filled aperture instrument such as a single-dish telescope, or using a sparse aperture instrument such as an interferometric array of dipoles. This thesis investigates analogue components for a sparse aperture instrument operating at 1.0-1.5 GHz. As part of this work, a 16-element sparse aperture array was designed and constructed. To test the array’s performance, field testing was conducted; the results of which are presented here. In addition to this, I have designed a new digital spectrometer for redshifted hydrogen line science, named HISPEC. A copy of this spectrometer has been installed on the Parkes 64 m telescope, as a digital signal processor for the 21-cm multibeam receiver. HISPEC has increased instantaneous bandwidth, higher interchannel isolation, and improved quantization efficiency as compared to the existing backend, MBCORR. The HISPEC equipped multibeam receiver is an ideal instrument for 21-cm intensity mapping at redshifts z<0.2.

Styles APA, Harvard, Vancouver, ISO, etc.

4

McMahon, Peter Leonard. « Adventures in radio astronomy instrumentation and signal processing ». Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5165.

Texte intégral

Résumé :

Includes abstract.
Includes bibliographical references (leaves 117-119).
This thesis describes the design and implementation of several instruments for digitizing and processing analogue astronomical signals collected using radio telescopes. Modern radio telescopes have significant digital signal processing demands that are typically best met using custom processing engines implemented in Field Programmable Gate Arrays. These demands essentially stem from the ever-larger analogue bandwidths that astronomers wish to observe, resulting in large data volumes that need to be processed in real time. We focused on the development of spectrometers for enabling improved pulsar² science on the Allen Telescope Array, the Hartebeesthoek Radio Observatory telescope, the Nançay Radio Telescope, and the Parkes Radio Telescope. We also present work that we conducted on the development of real-time pulsar timing instrumentation.

Styles APA, Harvard, Vancouver, ISO, etc.

5

Zhang, Shuang Nan. « Instrumentation and data analysis for hard X-ray astronomy ». Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252689.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

6

Baron, Richard Leigh. « Occultation astronomy and instrumentation : studies of the Uranian upper atmosphere ». Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/51472.

Texte intégral

Résumé :

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.
Includes bibliographical references (leaves 207-208).
by Richard Leigh Baron.
Ph.D.

Styles APA, Harvard, Vancouver, ISO, etc.

7

Charalambous, Andrew. « Opto-mechanical design for large telescope instrumentation ». Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243313.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

8

Jovanovic, N., C. Schwab, O. Guyon, J. Lozi, N. Cvetojevic, F. Martinache, S. Leon-Saval et al. « Efficient injection from large telescopes into single-mode fibres : Enabling the era of ultra-precision astronomy ». EDP SCIENCES S A, 2017. http://hdl.handle.net/10150/625827.

Texte intégral

Résumé :

Photonic technologies off er numerous advantages for astronomical instruments such as spectrographs and interferometers owing to their small footprints and diverse range of functionalities. Operating at the diffraction-limit, it is notoriously difficult to efficiently couple such devices directly with large telescopes. We demonstrate that with careful control of both the non-ideal pupil geometry of a telescope and residual wavefront errors, efficient coupling with single-mode devices can indeed be realised. A fibre injection was built within the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument. Light was coupled into a single-mode fibre operating in the near-IR (J-H bands) which was downstream of the extreme adaptive optics system and the pupil apodising optics. A coupling efficiency of 86% of the theoretical maximum limit was achieved at 1550 nm for a diffraction-limited beam in the laboratory, and was linearly correlated with Strehl ratio. The coupling efficiency was constant to within <30% in the range 1250-1600 nm. Preliminary on-sky data with a Strehl ratio of 60% in the H-band produced a coupling efficiency into a single-mode fibre of similar to 50%, consistent with expectations. The coupling was >40% for 84% of the time and >50% for 41% of the time. The laboratory results allow us to forecast that extreme adaptive optics levels of correction (Strehl ratio >90% in H-band) would allow coupling of >67% (of the order of coupling to multimode fibres currently) while standard levels of wavefront correction (Strehl ratio >20% in H-band) would allow coupling of >18%. For Strehl ratios <20%, few-port photonic lanterns become a superior choice but the signal-to-noise, and pixel availability must be considered. These results illustrate a clear path to efficient on-sky coupling into a single-mode fibre, which could be used to realise modal-noise-free radial velocity machines, very-long-baseline optical/near-IR interferometers and/or simply exploit photonic technologies in future instrument design.

Styles APA, Harvard, Vancouver, ISO, etc.

9

Lee, Aizeret. « Radioastronomical instrumentation : the diagonal horn ». Thesis, View thesis, 2002. http://handle.uws.edu.au:8081/1959.7/699.

Texte intégral

Résumé :

The horn plays an elemental role in the make up of a radio-telescope. The focus of this research is on one particular type of horn – the diagonal horn. An analysis of the diagonal horn is made using the Fourier method. The analysis begins from Maxwell’s equations, as the basic building block, and describes the steps involved in developing the radiation pattern. Based on the theory, a program was written that produces the theoretical graphs referred to throughout the thesis. A diagonal horn was manufactured and the radiation patterns were measured. A comparison of these measured patterns is made against the theoretically generated patterns. Further research was carried out to demonstrate the effects on the radiation patterns when the horn is fitted with a dielectric plug. This practice may enhance the directivity of the horn at the cost of introducing new losses

Styles APA, Harvard, Vancouver, ISO, etc.

10

Lee, Hanshin. « Optical Alignment and Novel Instrumentation Techniques for Optical and Near-Infrared Astronomy ». Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504421.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

11

Deller, Adam Travis. « Precision VLBI astrometry instrumentation, algorithms and pulsar parallax determination / ». Swinburne Research Bank, 2009. http://hdl.handle.net/1959.3/48485.

Texte intégral

Résumé :

Thesis (PhD) - Faculty of Information and Communication Technology, Faculty of Life and Social Sciences, Swinburne University of Technology, 2009.
Submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy, Faculty of Information and Communication Technology, Swinburne University of Technology, 2009. Typescript. Bibliography: p. 165-186.

Styles APA, Harvard, Vancouver, ISO, etc.

12

Tillman, Richard Henry. « Absolute Flux Density Measurement and Associated Instrumentation for Radio Astronomy below 100 MHz ». Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/72289.

Texte intégral

Résumé :

This dissertation reports new measurements of the absolute flux densities of the brightest astrophysical sources visible from the northern hemisphere with O[10%] accuracy between 30-78 MHz. These measurements provide additional confidence in the existing understanding of the flux density spectra of these sources in this frequency range. This dissertation also reports new measurements of the antenna temperature due to the diffuse Galactic background between 30-78 MHz, addressing a paucity of existing measurements in this band. These measurements are relevant especially in the context of contemporary interest in radio astronomy and 21 cm cosmology in this frequency range. A new active antenna system and measurement technique were developed to facilitate these measurements. The antennas are simple, thin dipoles, allowing for accurate characterization. Amplification is preceded by notch filters to mitigate interference induced non-linearity. Previous efforts have used well matched antennas. The narrowband antennas and notch filters on the front end create large, frequency varying impedance mismatch that must be accounted for, and we demonstrate how this can be done. We present a novel in situ technique that uses the antenna temperature measurements to improve the calibration of the antennas and internal noise sources.
Ph. D.

Styles APA, Harvard, Vancouver, ISO, etc.

13

Cataldo, Giuseppe Ph D. Massachusetts Institute of Technology. « Development of ultracompact, high-sensitivity, space-based instrumentation for far-infrared and submillimeter astronomy ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98800.

Texte intégral

Résumé :

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 111-131).
Far-infrared (IR) and submillimeter (15 [mu]m-1 mm) spectroscopy provides a powerful tool to probe a wide range of environments in the universe. In the past thirty years, many space-based observatories have opened the far-IR window to the universe, providing unique insights into several astrophysical processes related to the evolution of the early universe. Nonetheless, the size and cost of the cryogenic spectrometers required to carry out such measurements have been a limiting factor in our ability to fully explore this rich spectral region and answer questions regarding the very first moments of the universe. Among the key technologies required to enable this science are ultra-low-noise, far-IR, direct-detection spectrometers. In this thesis, Micro-Spec ([mu]-Spec) is proposed as a novel technology concept to enable a large range of flight missions that would otherwise be challenging due to the large size of current instruments and the required spectral resolution and sensitivity. [mu]-Spec is a direct-detection spectrometer operating in the 450-1000-[mu]m regime, which employs superconducting microstrip transmission lines to achieve a resolution (R >/= 1200) and be integrated on a ~10-cm² silicon chip. The objective of this thesis is to explore the feasibility of the [mu]-Spec technology. First, analytical models are developed for the dielectric function of silicon compounds to be used as substrates in the transmission lines. These materials represent the ultimate source of loss in the system. The models are used to analyze laboratory spectral data of silicon nitride and oxide films and provide information on the loss within a 4% accuracy. A design methodology is then developed for the spectrometer diffractive region given specific requirements on size and spectral range. This methodology is used to explore the design space and find the optimal solutions that maximize the instrument efficiency and minimize the phase error on the focal plane. Five designs are described with different requirements and performance. Finally, analysis and calibration techniques are developed to study the properties of the superconducting materials employed in the transmission lines and detectors. These techniques are applied to laboratory data of molybdenum nitride and niobium to extract their quality factors and kinetic inductance fraction within a 1% accuracy.
by Giuseppe Cataldo.
Ph. D.

Styles APA, Harvard, Vancouver, ISO, etc.

14

Isaak, Katherine Gudrun. « Low-noise instrumentation and astronomical observations of high-redshift objects in submillimetre wavelengths ». Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364389.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

15

SPINELLI, SEBASTIANO MAURO. « The use of optical coherence for instrumentation devoted to CMB experiments ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/7884.

Texte intégral

Résumé :

The thesis discusses the application of the concept of optical coherence to novel instrumentation dedicated to the study of CMB. The complex degree of mutual coherence is used to describe the performances of QUBIC (Q and U Bolometric Interferometer for Cosmology, http://www.qubic.org). An adding, single baseline, interferometer prototype, working in the WR10 waveguide band, has been tested to investigate the basic properties of mm-wavelength bolometric interferometry in a mm-wave laboratory. Moreover the performances of the optical combiner of the final instrument are investigated. The correct estimator (complex degree of mutual coherence) is defined and a simulation machine in ZEMAX to test systems is implemented and tested on a suitable system. Last part of the thesis focuses on the optical design of a Martin Pupplet Fourier transform spectrometer (where the complex degree of self coherence is measured) for the SAGACE ASI mission. A double coupled spectrometer is proposed, in order to increase its sensitivity compared to existing similar instruments, where half of the power is rejected.

Styles APA, Harvard, Vancouver, ISO, etc.

16

Bock, Douglas Carl-Johan. « Wide Field Aperture Synthesis Radio Astronomy ». University of Sydney. Physics, 1998. http://hdl.handle.net/2123/377.

Texte intégral

Résumé :

This thesis is focussed on the Molonglo Observatory Synthesis Telescope (MOST), reporting on two primary areas of investigation. Firstly, it describes the recent upgrade of the MOST to perform an imaging survey of the southern sky. Secondly, it presents a MOST survey of the Vela supernova remnant and follow-up multiwavelength studies. The MOST Wide Field upgrade is the most significant instrumental upgrade of the telescope since observations began in 1981. It has made possible the nightly observation of fields with area ~5 square degrees, while retaining the operating frequency of 843 MHz and the pre-existing sensitivity to point sources and extended structure. The MOST will now be used to make a sensitive (rms approximately 1 mJy/beam) imaging survey of the sky south of declination -30°. This survey consists of two components: an extragalactic survey, which will begin in the south polar region, and a Galactic survey of latitudes |b| < 10°. These are expected to take about ten years. The upgrade has necessitated the installation of 352 new preamplifiers and phasing circuits which are controlled by 88 distributed microcontrollers, networked using optic fibre. The thesis documents the upgrade and describes the new systems, including associated testing, installation and commissioning. The thesis continues by presenting a new high-resolution radio continuum survey of the Vela supernova remnant (SNR), made with the MOST before the completion of the Wide Field upgrade. This remnant is the closest and one of the brightest SNRs. The contrast between the structures in the central pulsar-powered nebula and the synchrotron radiation shell allows the remnant to be identified morphologically as a member of the composite class. The data are the first of a composite remnant at spatial scales comparable with those available for the Cygnus Loop and the Crab Nebula, and make possible a comparison of radio, optical and soft X-ray emission from the resolved shell filaments. The survey covers an area of 50 square degrees at a resolution of 43" x 60", while imaging structures on scales up to 30'. It has been used for comparison with Wide Field observations to evaluate the performance of the upgraded MOST. The central plerion of the Vela SNR (Vela X) contains a network of complex filamentary structures. The validity of the imaging of these filaments has been confirmed with Very Large Array (VLA) observations at 1.4 GHz. Unlike the situation in the Crab Nebula, the filaments are not well correlated with H-alpha emission. Within a few parsec of the Vela pulsar the emission is much more complex than previously seen: both very sharp edges and more diffuse emission are present. It has been postulated that one of the brightest filaments in Vela X is associated with the X-ray feature (called a `jet') which appears to be emanating from the region of the pulsar. However, an analysis of the MOST and VLA data shows that this radio filament has a flat spectral index similar to another more distant filament within the plerion, indicating that it is probably unrelated to the X-ray feature.

Styles APA, Harvard, Vancouver, ISO, etc.

17

Bock, Douglas Carl-Johan. « Wide Field Aperture Synthesis Radio Astronomy ». Thesis, The University of Sydney, 1997. http://hdl.handle.net/2123/377.

Texte intégral

Résumé :

This thesis is focussed on the Molonglo Observatory Synthesis Telescope (MOST), reporting on two primary areas of investigation. Firstly, it describes the recent upgrade of the MOST to perform an imaging survey of the southern sky. Secondly, it presents a MOST survey of the Vela supernova remnant and follow-up multiwavelength studies. The MOST Wide Field upgrade is the most significant instrumental upgrade of the telescope since observations began in 1981. It has made possible the nightly observation of fields with area ~5 square degrees, while retaining the operating frequency of 843 MHz and the pre-existing sensitivity to point sources and extended structure. The MOST will now be used to make a sensitive (rms approximately 1 mJy/beam) imaging survey of the sky south of declination -30°. This survey consists of two components: an extragalactic survey, which will begin in the south polar region, and a Galactic survey of latitudes |b| < 10°. These are expected to take about ten years. The upgrade has necessitated the installation of 352 new preamplifiers and phasing circuits which are controlled by 88 distributed microcontrollers, networked using optic fibre. The thesis documents the upgrade and describes the new systems, including associated testing, installation and commissioning. The thesis continues by presenting a new high-resolution radio continuum survey of the Vela supernova remnant (SNR), made with the MOST before the completion of the Wide Field upgrade. This remnant is the closest and one of the brightest SNRs. The contrast between the structures in the central pulsar-powered nebula and the synchrotron radiation shell allows the remnant to be identified morphologically as a member of the composite class. The data are the first of a composite remnant at spatial scales comparable with those available for the Cygnus Loop and the Crab Nebula, and make possible a comparison of radio, optical and soft X-ray emission from the resolved shell filaments. The survey covers an area of 50 square degrees at a resolution of 43" x 60", while imaging structures on scales up to 30'. It has been used for comparison with Wide Field observations to evaluate the performance of the upgraded MOST. The central plerion of the Vela SNR (Vela X) contains a network of complex filamentary structures. The validity of the imaging of these filaments has been confirmed with Very Large Array (VLA) observations at 1.4 GHz. Unlike the situation in the Crab Nebula, the filaments are not well correlated with H-alpha emission. Within a few parsec of the Vela pulsar the emission is much more complex than previously seen: both very sharp edges and more diffuse emission are present. It has been postulated that one of the brightest filaments in Vela X is associated with the X-ray feature (called a `jet') which appears to be emanating from the region of the pulsar. However, an analysis of the MOST and VLA data shows that this radio filament has a flat spectral index similar to another more distant filament within the plerion, indicating that it is probably unrelated to the X-ray feature.

Styles APA, Harvard, Vancouver, ISO, etc.

18

Bergomi, Maria. « Pyramid wavefront sensors for astronomy and for the human eye ». Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3426297.

Texte intégral

Résumé :

WaveFront Sensors (WFSs) may be defined as the heart of an adaptive optics system since they analyze the radiation coming from reference sources and allow to quantify the distortion of a wavefront. Among the varieties of existing WFSs, my PhD research thesis focuses especially on innovative optical systems taking advantage of the peculiarities of the Pyramid WFS. In my PhD project I have designed, implemented, characterized or studied three different applications characterized by the fact that one or multiple pyramid WFSs play a major role. They extend from WATERFALL, an application for the human eye (8 mm), to a Very-Linear (and very sensitive) WFS (VL-WFS), part of a concept for a 40 meter telescope adaptive optics, passing through a very complex system featuring more than 100 degrees of freedom, to be mounted on 8.4 m x 2 LBT telescope (Ground-layer WFS for LINC-NIRVANA). WATERFALL concerns the design and successful realization of a prototype for opthalmologic application for industrial commercialization to measure dioptric power of Intra-Ocular Lenses. GWS for NIRVANA works includes the definition of tolerances to be met and the detailed description of its alignment, integration phase and successful verification, leading it toward its on-sky commissioning phase in the Pathfinder experiment. The VL-WFS is in its very early phase, concepts and new ideas (mostly coming from our group) have to be organized in order to make a real proposal of a Global MCAO instrument for the E-ELT. The projects briefly presented are all based on the same optical concepts and if the ophthalmology application might at first sight look unrelated to astronomy, it is, in fact, representing a simple SCAO system applied to an optical system which is the eye, proving how the interaction between different research field can lead to successful results.
I sensori di fronte d'onda sono elementi chiave in un sistema di ottica adattiva, in quanto analizzano la radiazione proveniente da stelle guida e permettono di quantificare la deformazione di un fronte d'onda. Nell'ambito delle diverse tipologie di sensori esistenti, il presente lavoro di tesi si concentra su sistemi ottici innovativi che sfruttano le peculiarità del sensore a piramide. Durante il periodo di dottorato ho partecipato all'ideazione, realizzazione, caratterizzazione e approfondito lo studio di tre diverse applicazioni accomunate dal ruolo dominante occupato da uno o più sensori a piramide. I suddetti progetti spaziano da WATERFALL, applicazione destinata all'occhio umano (8 mm), ad un sensore estremamente lineare e molto sensibile (VL-WFS), parte dello studio di un concetto per un sensore da 40 metri di diametro, passando per un sistema molto complesso che presenta più di 100 gradi di libertà (il sensore di turbolenza a terra GWS di LINC-NIRVANA), che dovrà essere montato ad LBT, caratterizzato da 8.4 m x 2 di diametro. Il progetto WATERFALL riguarda il disegno, la successiva realizzazione e test di un prototipo per un'applicazione oftalmologica atta a misurare il potere diottrico di lenti intra-oculari, con obiettivo una possibile commercializzazione del sistema. Il lavoro svolto per il GWS di NIRVANA ha portato alla definizione di tolleranze da soddisfare ed in questo elaborato è contenuta la descrizione dettagliata delle varie procedure di allineamento e dei test svolti con successo, che hanno permesso il raggiungimento della fase di commissioning in cielo dello strumento nell'esperimento Pathfinder. Il progetto VL-WFS si trova ancora in una fase embrionale, dove concetti ed idee, prevalentemente provenienti dal nostro gruppo di Padova, devono essere organizzate per raggiungere il livello di una reale proposta per la realizzazione di uno strumento di MCAO globale per l'E-ELT. Tutti gli anzidetti progetti si basano sugli stessi concetti ottici e, anche se a prima vsita l'applicazione oftalmologica può essere vista come estranea all'astronomia, essa può essere in realtà qualificata come un semplice sistema SCAO applicato ad un sistema ottico che e' rappresentato dall'occhio umano, dimostrando come l'interazione tra diversi campi di ricerca possa portare a risultati di successo, anche in termini di applicazioni pratiche.

Styles APA, Harvard, Vancouver, ISO, etc.

19

Bailey, Vanessa Perry. « Adaptive Optics for Directly Imaging Planetary Systems ». Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/577514.

Texte intégral

Résumé :

In this dissertation I present the results from five papers (including one in preparation) on giant planets, brown dwarfs, and their environments, as well as on the commissioning and optimization of the Adaptive Optics system for the Large Binocular Telescope Interferometer. The first three Chapters cover direct imaging results on several distantly-orbiting planets and brown dwarf companions. The boundary between giant planets and brown dwarf companions in wide orbits is a blurry one. In Chapter 2, I use 3–5 μm imaging of several brown dwarf companions, combined with mid-infrared photometry for each system to constrain the circum-substellar disks around the brown dwarfs. I then use this information to discuss limits on scattering events versus in situ formation. In Chapters 3 and 4, I present results from an adaptive optics imaging survey for giant planets, where the target stars were selected based on the properties of their circumstellar debris disks. Specifically, we targeted systems with debris disks whose SEDs indicated gaps, clearings, or truncations; these features may possibly be sculpted by planets. I discuss in detail one planet-mass companion discovered as part of this survey, HD 106906 b. At a projected separation of 650 AU and weighing in at 11 Jupiter masses, a companion such as this is not a common outcome of any planet or binary star formation model. In the remaining three Chapters, I discuss pre-commissioning, on-sky results, and planned work on the Large Binocular Telescope Interferometer Adaptive Optics system. Before construction of the LBT AO system was complete, I tested a prototype of LBTI's pyramid wavefront sensor unit at the MMT with synthetically-generated calibration files. I present the methodology and MMT on-sky tests in Chapter 5. In Chapter 6, I present the commissioned performance of LBTIAO. Optical imperfections within LBTI limited the quality of the science images, and I describe a simple method to use the adaptive optics system to correct for the science camera's optical aberrations. Finally, in Chapter 7, I discuss the status of a more sophisticated method for correcting these optical aberrations in LBTI.

Styles APA, Harvard, Vancouver, ISO, etc.

20

Rossoni, Mattos Diego. « Design and characterization of an 8gsps flash analog-to-digital converter for radio astronomy and cosmology applications ». Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14653/document.

Texte intégral

Résumé :

Un Convertisseur Analogique-Numérique (CAN) pour les applications spatiales en astrophysique et cosmologie a été développé au cours de cette thèse. Cette catégorie de circuits demande des bandes passantes très larges, de très hautes fréquences d'échantillonnage et une faible résolution. L’architecture flash a été retenue pour sa rapidité et sa bande passante. La fréquence d’échantillonnage est de 8GHz. La technologie utilisée est la CMOS 65 nm de chez STMicroeletronics. La conception a été faite en deux phases. Une première qui a amené à un prototype d'un échantillonneur-bloqueur et une deuxième qui a amené au CAN. Les deux prototypes ont été caractérisés et à partir de ces résultats des perspectives d'amélioration pour les nouvelles implémentations ont été retrouvées.Pour atteindre l'objectif final du CAN multi-bits (6-bit sont visés) il a été décidé de dessiner une première version du CAN avec la moitié de la résolution initialement prévue (on passe de 6-bit à 3-bit). L'objectif est de nous permettre d’analyser le comportement des blocs fonctionnels intégrés et ensuite passer à une deuxième voire troisième version pour remplir le cahier des charges initial
An Analog-to-Digital Converter (ADC) has been developed for astrophysical and cosmological applications. This class of circuits demands, especially in the millimeter wavelength domain, ultra wide bandwidths, ultra high sampling frequencies and a low resolution. The “flash” architecture has been chosen for its speed and bandwidth. This ADC samples at 8Gsps and it has been fabricated in 65nm CMOS technology from STMicroelectornics.The design has been done in two steps. The first was the prototype of a track-and-hold circuit. The second was the ADC. Both circuits have been characterized and from these results some perspectives for further improvements have been proposed.In order to achieve the final goal of the multi-bit ADC (6-bit resolution) we have decided to design a first prototype with half the final resolution, namely a 3-bit resolution ADC. Our idea was, with this first prototype, to conduct a first analysis of the behavior of the integrated functional blocks and, consequently, find the correct improvements required for the ADC final version

Styles APA, Harvard, Vancouver, ISO, etc.

21

Diebold, Sebastian [Verfasser], et Klaus [Akademischer Betreuer] Werner. « Development and Testing of Instrumentation for Space-Based Ultraviolet and X-Ray Astronomy / Sebastian Diebold ; Betreuer : Klaus Werner ». Tübingen : Universitätsbibliothek Tübingen, 2015. http://d-nb.info/116339713X/34.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

22

Saridakis, Voula. « Converging Elements in the Development of Late Seventeenth-Century Disciplinary Astronomy : Instrumentation, Education, and the Hevelius-Hooke Controversy ». Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29611.

Texte intégral

Résumé :

In this dissertation, I examine astronomical practice in the second half of the seventeenth century by analyzing the nature of observation and instrumentation within an institutional and social context. I argue that astronomical practice was transformed by the convergence of several overlapping factors including the deployment of new instruments, the mathematical and astronomical education of practitioners, the gradual assimilation of new ideas, and the rise of scientific societies and networks. More specifically, I argue that the 1670's controversy between Johannes Hevelius and Robert Hooke and the ensuing debate that involved a larger circle of practitioners, helped establish a new foundation for the discipline of astronomy. In forcing practitioners to take sides, the controversy prompted them to define the precise nature of astronomical practice as well as the necessary qualifications for its practitioners. In Chapter 1, I discuss sixteenth and seventeenth-century astronomical instruments, and I provide a history of instrumentation from the use of positional measuring instruments in the late sixteenth century to the more widespread use of micrometers and telescopically-mounted positional measuring instruments in the late seventeenth century. Proceeding from the instruments to the people involved, in Chapters 2 and 3 I discuss the mathematical and astronomical community of the late sixteenth to late seventeenth centuries. The "community" included those individuals working both within and outside the universities. In Chapter 4, I discuss the Hevelius-Hooke controversy over the relative merits of naked-eye versus telescopic sights as the watershed in positional astronomy that defined the role of astronomers, shaped their methods of observation, and directed future research. In the final chapter of this study, Chapter 5, I discuss the work of Cassini at the Paris Observatory and Flamsteed at the Greenwich Observatory, and how their efforts were shaped by the Hevelius-Hooke controversy.
Ph. D.

Styles APA, Harvard, Vancouver, ISO, etc.

23

Ceraudo, Francesco. « Caractérisation et optimisation des performances du plan focal du télescope X de la mission d’astronomie spatiale SVOM ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS595.

Texte intégral

Résumé :

SVOM est une mission Franco-Chinoise prévue pour fin 2021, pour l'étude des sursauts gamma (GRBs). SVOM sera composée par un réseau de télescopes au sol, ainsi que d'un satellite. À bord de celui-ci, le Télescope X à Micro-canaux (MXT) étudiera l’émission rémanente des GRBs dans la bande 0.2-10 keV et localisera les sources avec une précision de 2 arcmin. Au plan focal d’optiques à œil de langouste, MXT montera un Charge Coupled Device en silicium complétement dépleté et basé sur jonctions pn (pnCCD), hérité de XMM-Newton et eROSITA. Dans ce travail, les premiers essais de laboratoire sur le détecteur de MXT sont présentés. Une attention particulière est portée à l'étalonnage spectral par des méthodes instrumentales et d'analyse permettant une caractérisation rapide et fiable du détecteur, au sol et en vol. L’évolution des performances est critique en raison de l'environnement radiatif sévère de l’orbite terrestre basse auquel le détecteur sera exposé. Ceci fait l’objet de simulations Monte Carlo approfondies, amenant aux prédictions des performances à la fin de la mission, ainsi que à la planification d’une campagne d’essais d’irradiation de protons dans un accélérateur de particules pour une validation expérimentale des prédictions
SVOM is a Chinese-French astronomy mission due to launch at the end of 2021 for the study of Gamma-Ray Bursts (GRBs). SVOM will be composed of a network of ground telescopes along with a satellite. On board, the Micro-channel X-ray Telescope (MXT) will study the afterglow emission of GRBs in the 0.2-10 keV range and provide source localization within a 2 arcmin precision. At the focal plane of lobster-eye optics, MXT will mount a back-illuminated fully-depleted frame-store Charge Coupled Device based on silicon pn-junctions (pnCCD), heritage of XMM-Newton and eROSITA. In this work, the first laboratory tests on the MXT detector are presented. Special attention is dedicated to energy calibration, in terms of algorithms and setups for fast and reliable characterization of the detector, both on ground and in orbit. The evolution of the performance is of critical concern because of the harsh radiation environment of the low Earth orbit to which the detector will be exposed. This is the object of extensive Monte Carlo simulations, leading to predictions of the end-of-life performances as well as the planning of a proton irradiation campaign at a particle accelerator for the experimental validation of the predictions

Styles APA, Harvard, Vancouver, ISO, etc.

24

Belleval, Christophe. « Robust Statistics Applied to Radio Astronomy : Radio Frequency Interference Mitigation and Automated Spectral Line Detection for Broadband Surveys ». Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEO009.

Texte intégral

Résumé :

La nouvelle génération de radiotélescopes couplée avec les outils de numérisation à haute performance offrent des opportunités sans précédent en matière d'étude de l'environnement galactique et extragalactique. L'énorme quantité de données produites pose un certain nombre de défis, parmi lesquels : enregistrer des flux de données à très haut débit, en stocker temporairement des quantités considérables, adapter les logiciels à un traitement de masse, et fournir aux chercheurs des outils pratiques d'analyse.J'ai écrit cette thèse autour de deux thèmes. Premièrement la gestion des interférences électromagnétiques, et deuxièmement la mise au point de méthodes de détection automatique en aveugle de raies spectrales. Les algorithmes que je décris ont été développé à partir d'observations effectuées au radiotélescope décimétrique de Nanc{c}ay et enregistrées avec le spectromètre à large bande et haute fréquence d'échantillonnage WIBAR. Contrairement à l'analyse spectrale classique, ces algorithmes traitent les séries temporelles de densité de flux. Dans le but d'éliminer les interférences électromagnétiques et de détecter automatiquement des raies spectrales, j'ai choisi d'appliquer à ces séries temporelles des procédés issus des statistiques robustes, à savoir des paramètres de position, d'échelle, et de régression non linéaire qui sont insensibles aux données aberrantes.Dans la première partie, je présente les bases de la statistique appliquée à la radioastronomie, et plus spécifiquement des statistiques robustes appliquées à ce projet. Je décris les propriétés de différents paramètres de position, d'échelle et de régression, et en discute les avantages et inconvénients. Dans la seconde partie, après avoir présenté les caractéristiques du spectromètre WIBAR, j'expose les paradigmes et choix fondamentaux qui m'ont guidé dans le développement à cet effet du logiciel RObust Elusive Line detection (ROBEL). Dans la troisième partie, je présente et discute les résultats d'une part d'observations de radiosources effectuées avec WIBAR et traitées par ROBEL, d'autre part de la détection et de l'élimination de différents types d'interférences électromagnétiques. Je conclus en présentant les perspectives de développement, en particulier l'adaptation de tels procédés aux interféromètres dans le cadre de SKA
The advent of a new generation of radio telescopes coupled with digital processing hardware have provided tremendous new opportunities for extensive studies of the Galactic and extra galactic environment. In parallel, the nowadays huge amount of data produced has generated specific challenges. Among others: to secure high-speed data capture, to temporarily store huge quantities of raw data, to upgrade processing to this new data profile, and to provide researchers practical tools of analysis.In this thesis I have focused on two issues. Firstly the mitigation of radio frequency interference (RFI), and secondly practical methods for automated blind detection of spectral lines. The algorithms I present have been developed using observational data from the decimetric 100m-class single-dish Nanc{c}ay Radio Telescope (France) acquired with the WIBAR broadband and high sampling rate spectrometer. Contrary to classical spectral data analysis, The algorithms I have developed take into account time-series of flux-density. In order to excise RFI and detect spectral lines, I chose to apply robust statistics to these time-series, i.e., estimators of location and scale as well as regression which are immune to statistical outliers.In the first part, I lay down the basics of robust statistics applied to radio astronomy, used for this project: after having recalled basics of classical statistics in the context of radio astronomy, I discuss the pros and cons of several robust estimators of location and scale, followed by an evaluation of options for robust regression pertaining to the aims of this project. In the second part, I first describe the technical properties of the WIBAR broadband receiver, and then the fundamental assumptions and choices I have made to setup the architecture of the RObust Elusive Line detection (ROBEL) post-processing software I have developed for this matter. In the third part, I present results first from observations of different sources with WIBAR, and second related to RFI mitigation. After having discussed current issues, I conclude with possible future developments in interferometry in the SKA context

Styles APA, Harvard, Vancouver, ISO, etc.

25

Quint, Bruno Corrêa. « Modelagem numérica de alto nível de filtros do tipo Fabry-Pérot e de redes de difração holográficas para o instrumento BTFI ». Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-18102010-195658/.

Texte intégral

Résumé :

O trabalho apresentado nesta dissertação foi motivado essencialmente pelo projeto de construção de um novo instrumento a ser instalado no telescópio SOAR, no Chile. Este instrumento, chamado de \\textit{Brazilian Tunable Filter Imager} - BTFI, conta com várias novidades dentro da área de instrumentação astronômica. Uma delas envolve a utilização de duas redes de difração em série de modo a atuarem como um filtro espectral com uma resolução mais baixa. Aqui é mostrado o estudo realizado envolvendo dois diferentes modelos encontrados na literatura para simular numericamente a eficiência destas redes. Com estas simulações foi possível escolher um conjunto de redes a serem utilizadas no instrumento visando cobrir todo o espectro óptico com diferentes resoluções espectrais. Outra ferramenta estudada foi o filtro espectral do tipo Fabry-Pérot. Partindo de uma revisão teórica de interferência de raios múltiplos, apresenta-se também algumas características encontradas nos cubos de dados obtidos ao fazer uso de filtros deste tipo. Por fim, é descrito o software que foi criado buscando fornecer cubos de dados sintéticos para o desenvolvimento de novos pacotes numéricos para trabalhar com dados obtidos com um interferômetro Fabry-Pérot, além de auxiliar na compreensão de obtenção destes cubos.
The work presented in this dissertation was motivated primarily by the construction project of a new instrument to be installed on the SOAR telescope in Chile. This instrument, called \\textit {Brazilian Tunable Filter Imager} - BTFI, features several innovations within the area of astronomical instrumentation. One of them involves the use of two diffraction gratings in series in order to act as a spectral filter with a lower resolution. It is shown here the study involving two different models found in the literature to simulate the efficiency of these gratings. With these simulations it was possible to choose a set of gratings to be used in the instrument in order to cover the entire optical spectrum with different spectral resolutions. Another tool studied was the filter spectral type Fabry-Pérot. Starting from a theoretical review of interference of multiple beams, it is presented some features found in the data cubes obtained by making use of filters of this type. Finally, we describe the software that was created to provide synthetic data cubes for developing new packages for working with numerical data obtained with a Fabry-Perot interferometer, in addition to helping to raise understanding of these cubes.

Styles APA, Harvard, Vancouver, ISO, etc.

26

Andrade, Denis Furtado de. « Sistema embarcado para aquisição de imagens astronômicas ». Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-04042011-123639/.

Texte intégral

Résumé :

Neste trabalho são apresentados os resultados obtidos no desenvolvimento de um sistema eletrônico embarcado dedicado à aquisição de imagens astronômicas. Este sistema é composto principalmente por uma câmera científica astronômica, que abriga um detector de imagem do tipo EMCCD, e por um controlador eletrônico utilizado para a operação e leitura do detector de imagem. São detalhados os estágios que formam o sistema embarcado específico para um instrumento astronômico instalado no telescópico internacional SOAR, no Chile. Cada um destes estágios: sensor, câmera, controlador eletrônico, placa de aquisição de imagens e software, será descrito detalhadamente, desde uma revisão das alternativas de solução até as técnicas de operação de sensores, além da manipulação de controladores eletrônicos. São analisados detalhes referentes ao projeto da câmera, bem como a influência desses detalhes em seu funcionamento. Alguns resultados científicos já alcançados com sistemas embarcados equivalentes são expostos. Também são apresentados os resultados dos ensaios e trabalhos realizados em laboratório para este projeto, e os resultados atingidos com o instrumento já em operação no telescópio.
This work presents the results obtained in the development of an embedded electronic system dedicated to the acquisition of astronomical images. This system consists primarily of a scientific astronomical camera, which houses an imaging detector EMCCD, and an electronic controller used for operating and reading the imaging detector. The stages that constitute the embedded system specific to an astronomical instrument installed in the telescopic international SOAR, at Chile, are detailed. Each of these stages: sensor, camera, electronic controller, image acquisition board and software, is described in detail, from a review of alternative solutions to the technical operation of sensors, and manipulation of electronic controllers. Some details of the camera design are analyzed as well as its influence in the camera operation. Some scientific results already achieved with equivalent embedded systems are exposed. It also presents the results of laboratory tests and work done for this project, and the results achieved with the instrument already operating at the telescope.

Styles APA, Harvard, Vancouver, ISO, etc.

27

Austermann, Jason Edward. « The AzTEC Millimeter-wave Camera : Design, Integration, Performance, and the Characterization of the (sub-)millimeter Galaxy Population ». Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/open_access_dissertations/33/.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

28

Marshall, Jennifer L. « Mapping the Local Galactic Halo and An Image Motion Compensation System for the Multi-Object Double Spectrograph ». The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1155646690.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

29

Lanthermann, Cyprien. « Mise en oeuvre de détecteurs à avalanche pour l’interférométrie astronomique en proche infra-rouge : application à la multiplicité des étoiles massives ». Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY060.

Texte intégral

Résumé :

De par leur interaction avec leur environnement, les étoiles massives contribuent significativement à l'évolution de leur galaxie hôte. Cependant leur processus de formation est encore méconnu. Pour mieux contraindre les modèles de formation de ces étoiles, l'étude de leur multiplicité est essentielle. Alors que la photométrie et la spectroscopie permettent d'étudier les systèmes multiples séparés de quelques millisecondes d'angle (mas) et que l'imagerie directe permet de sonder les séparations supérieures à 50 mas, l'intervalle entre quelques mas et 50 mas de séparation ne pouvait être sondé jusqu'à récemment. Cet intervalle peut être résolu par l'interférométrie optique à longue ligne de base (OLBI), mais cette technique était limitée en sensibilité et ne pouvait observer qu'une dizaine d'étoiles massives jusqu'à il y a peu. Mener une étude statistique de la multiplicité des étoiles massives nécessite d'observer un bien plus grand nombre d'objets.L'objectif de cette thèse est l'amélioration de la sensibilité de la technique OLBI afin de réaliser un relevé de la multiplicité des étoiles massives de l'hémisphère Nord.J'ai tout d'abord participé activement à l'implémentation de deux caméras C-RED ONE dans les instruments interférométriques MIRC-X et MYSTIC pour le réseau CHARA à l’observatoire du mont Wilson, en Californie. Ces caméras, basées sur la technologie des photodiodes à avalanche (APD), ne sont utilisées en astrophysique que depuis quelques années ; notre connaissance sur leur fonctionnement est donc encore limitée. Durant ma thèse, j'ai mené une caractérisation complète de ces caméras. J'ai créé un modèle de distribution du signal des détecteurs APD afin de mieux comprendre les résultats obtenus. Ce modèle et les méthodes classiques de caractérisation ont mis en évidence des différences significatives entre les valeurs de gain et de facteur d'excès de bruit mesurées et celles fournies par le fabricant. Même si cela rend le comptage de photons individuels impossible, les caractéristiques de ces caméras restent exceptionnelles, avec un bruit total inférieur à l'électron pour des cadences de lecture allant jusqu'au kiloHertz, ce qui est fondamental pour s'affranchir au mieux des effets de la turbulence atmosphérique.Ces performances permettent un gain en sensibilité conséquent : MIRC-X atteint une magnitude limite de H = 7.5, comparé à H = 5 pour son prédécesseur MIRC. Cette magnitude limite est confirmée par le relevé de démonstration sur 44 étoiles massives. Lors de ce relevé, j'ai pu observer de manière routinière plusieurs cibles de magnitude H = 7.5, et jusqu'à une magnitude H = 8.1 avec des conditions atmosphériques très favorables. Dans ces observations, j'ai détecté 27 compagnons pour un total de 21 systèmes multiples, ayant des séparations comprises entre 0.5 et 50 mas. Ce relevé de démonstration permet de confirmer la possibilité d'utiliser MIRC-X pour rechercher des compagnons dans l'intervalle non couvert par les autres techniques d'observation, et cela sur un grand nombre d'étoiles massives (>100).Ce relevé de démonstration correspond à la première phase du grand relevé des étoiles massives de l'hémisphère nord ayant une magnitude H < 7.5 que j'ai préparé. J'ai ainsi sélectionné 120 systèmes observables avec le réseau CHARA, ce qui permettra une analyse statistique de la multiplicité des étoiles massives, complémentaire au relevé SMASH+ réalisé dans l'hémisphère sud. Ce type de relevés est essentiel pour contraindre les modèles de formation de ces étoiles
From their interaction with their environment, the massive stars contribute significantly to the evolution of their host galaxy. However, their formation process is still unknown. To better constrain the formation models of those stars, the study of their multiplicity is essential. While photometry and spectroscopy allow studying the multiple systems separated from a few milliarcseconds (mas), and direct imaging allows to probe the separations above 50 mas, the range between a few mas and 50 mas of separation could not be probed until recently. This range can be resolved by the optical long baseline interferometry (OLBI), but this technique was limited in sensitivity and was able to observe only a dozen of massive stars a few years ago. Performing a statistical study on the multiplicity of massive stars requires to observe a larger number of objects.The goal of this thesis is to improve the sensitivity of the OLBI technique to conduct a survey on the multiplicity of Northern hemisphere massive stars.First, I actively participated in the implementation of two C-RED ONE cameras in the interferometric instruments MIRC-X and MYSTIC for the CHARA array of the Mount Wilson Observatory, in California. These cameras, based on the avalanche photodiode (APD) technology, have been used in astrophysics only for a few years; our knowledge on how they work is quite limited. During my thesis, I performed a full characterization of these cameras. I built a model of the signal distribution of the APD detectors to better understand the obtained results. This model and the classical characterization methods highlighted significant differences between the gain and excess noise factor that I measured and those provided by the manufacturer. Even if this makes individual photon counting impossible, the characteristics of these cameras remain exceptional, with a total noise below the electron for a frame rate up to kilohertz, which is fundamental to get rid at best of the atmospheric turbulence.These performance lead to a consequent sensitivity improvement: MIRC-X reaches a limiting magnitude of H = 7.5, to be compared with H = 5 for its predecessor MIRC. This limiting magnitude is confirmed by the demonstration survey on 44 massive stars. During this survey, I could observe routinely several targets with magnitudes of H = 7.5, and up to H = 8.1 with really favorable atmospheric conditions. In these observations, I detected 27 companions for a total of 21 multiple systems, with separations between 0.5 and 50 mas. This demonstration survey confirms the possibility to use MIRC-X to look for companions in the range of separation not covered by the other observational techniques, and this on a large number of massive stars (> 100).This demonstration survey corresponds to the first phase of the large survey on Northern hemisphere massive stars with a magnitude H < 7.5 that I prepared. I have thus selected 120 systems that are observable with the CHARA array, which will allow a statistical analysis of the massive stars multiplicity, as a complement of the SMASH+ survey in the Southern hemisphere. This kind of surveys is essential to constrain the formation models of those stars

Styles APA, Harvard, Vancouver, ISO, etc.

30

Antier-Farfar, Sarah. « La détection des sursauts gamma par le télescope ECLAIRs pour la mission spatiale SVOM ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS467/document.

Texte intégral

Résumé :

Les sursauts gamma sont des événements fascinants de par leur origine longtemps restée mystérieuse, leur apparition imprévisible dans le ciel, et la formidable énergie qu'ils libèrent sous forme de bouffées de rayonnement gamma. Découverts fortuitement au début des années 1970, ils se traduisent par un intense flash de rayons gamma de brève durée (de quelques ms à quelques min), appelé émission prompte, suivi d'une émission longue, appelée rémanence, qui décroît rapidement, en émettant depuis les rayons X jusqu'au domaine radio. L'origine des sursauts gamma est encore largement discutée mais ces phénomènes extrêmes sont très vraisemblablement associés à la formation de nouveaux trous noirs stellaires. Mon sujet de thèse se situe au coeur de la mission sino-française SVOM dont le lancement du satellite est prévu en 2021, qui scrutera le ciel pour observer les sursauts avec une précision inégalée, associant observations spatiales et terrestres. Mon travail concerne l'instrument principal de la mission, le télescope spatial ECLAIRs. Il s'agit d'une caméra à masque codé sensible aux rayons X et gamma de basse énergie, en charge de la détection et de la localisation de l'émission prompte des sursauts. Durant mon travail de thèse, j'ai travaillé sur les performances scientifiques de l'instrument ECLAIRs et j'ai en particulier estimé le nombre de sursauts qui seront détectés et leurs caractéristiques. Pour cela, j'ai mis en place des simulations de performances utilisant les prototypes des algorithmes de détection embarqués combinés au modèle de l'instrument ECLAIRs. Les données en entrée des simulations comportent un bruit de fond simulé, et une population synthétique de sursauts gamma générée à partir de catalogues existants issus des observations des missions antérieures (CGRO, HETE-2, Swift et Fermi). Mon étude a permis d'estimer finement l'efficacité de détection d'ECLAIRs et prédit un taux de sursauts attendu par ECLAIRs entre 40 et 70 sursauts par an. Par ailleurs, mon travail a montré qu'ECLAIRs sera particulièrement sensible à une population de sursauts très riches en rayons X, population encore mal connue. Ma thèse présente plusieurs autres études complémentaires portant sur la performance de localisation, le taux de fausses alertes et les caractéristiques des déclenchements des algorithmes. Enfin, j'ai proposé deux nouvelles méthodes originales de détection de sursauts dont les résultats préliminaires présentés dans ma thèse sont très encourageants. Ils montrent que la sensibilité d'ECLAIRs aux sursauts courts (population d'intérêt particulier en raison de son lien attendu avec les ondes gravitationnelles) peut être encore améliorée
Discovered in the early 1970s, gamma-ray bursts (GRBs) are amazing cosmic phenomena appearing randomly on the sky and releasing large amounts of energy mainly through gamma-ray emission. Although their origin is still under debate, they are believed to be produced by some of the most violent explosions in the Universe leading to the formation of stellar black-holes. GRBs are detected by their prompt emission, an intense short burst of gamma-rays (from a few millisecondes to few minutes), and are followed by a lived-afterglow emission observed on longer timescales from the X-ray to the radio domain. My thesis participates to the developement of the SVOM mission, which a Chinese-French mission to be launched in 2021, devoted to the study of GRBs and involving space and ground instruments. My work is focussed on the main instrument ECLAIRs, a hard X-ray coded mask imaging camera, in charge of the near real-time detection and localization of the prompt emission of GRBs. During my thesis, I studied the scientific performances of ECLAIRs and in particular the number of GRBs expected to be detected by ECLAIRs and their characteristics. For this purpose, I performed simulations using the prototypes of the embedded trigger algorithms combined with the model of the ECLAIRs instrument. The input data of the simulations include a background model and a synthetic population of gamma-ray bursts generated from existing catalogs (CGRO, HETE-2, Fermi and Swift). As a result, I estimated precisely the ECLAIRs detection efficiency of the algorithms and I predicted the number of GRBs to be detected by ECLAIRs : 40 to 70 GRBs per year. Moreover, the study highlighted that ECLAIRs will be particularly sensitive to the X-ray rich GRB population. My thesis provided additional studies about the localization performance, the rate of false alarm and the characteristics of the triggers of the algorithms. Finally, I also proposed two new methods for the detection of GRBs.The preliminary results were very promising and demonstrate that the sensitivity of ECLAIRs to the short GRBs (an interesting population due to the predicted association with gravitational waves) could be improved further

Styles APA, Harvard, Vancouver, ISO, etc.

31

Ludovici, Dominic Alesio. « Radio wavelength studies of the Galactic Center source N3, spectroscopic instrumentation for robotic telescope systems, and developing active learning activities for astronomy laboratory courses ». Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5557.

Texte intégral

Résumé :

The mysterious radio source N3 appears to be located within the vicinity of the Radio Arc region of the Galactic Center. To investigate the nature of this source, we have conducted radio observations with the VLA and the VLBA. Continuum observations between 2 and 50 GHz reveal that N3 is an extremely compact and bright source with a non-thermal spectrum. Molecular line observations with the VLA reveal a compact molecular cloud adjacent to N3 in projection. The properties of this cloud are consistent with other galactic center clouds. We are able to rule out several hypotheses for the nature of N3, though a micro-blazar origin cannot be ruled out. Robotic Telescope systems are now seeing widespread deployment as both teaching and research instruments. While these systems have traditionally been able to produce high quality images, these systems have lacked the capability to conduct spectroscopic observations. To enable spectroscopic observations on the Iowa Robotic Observatory, we have developed a low cost (~ $500), low resolution (R ~ 300) spectrometer which mounts inside a modified filter wheel and a moderate cost (~ $5000), medium resolution (R ~ 8000) fiber-fed spectrometer. Software has been developed to operate both instruments robotically and calibration pipelines are being developed to automate calibration of the data. The University of Iowa offers several introductory astronomy laboratory courses taken by many hundreds of students each semester. To improve student learning in these laboratory courses, we have worked to integrate active learning into laboratory activities. We present the pedagogical approaches used to develop and update the laboratory activities and present an inventory of the current laboratory exercises. Using the inventory, we make observations of the strengths and weaknesses of the current exercises and provide suggestions for future refinement of the astronomy laboratory curriculum.

Styles APA, Harvard, Vancouver, ISO, etc.

32

Black, Richard Allen. « Phased-Array Feed Instrumentation and Processing for Astronomical Detection, Interference Mitigation, and Transient Parameter Estimation ». BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6627.

Texte intégral

Résumé :

Radio astronomy, the survey and study of naturally occurring astronomical radio signals, is a challenging field in terms of engineering requirements. The typical astronomical signal of interest is incredibly faint, resulting in very low signal-to-noise ratios (SNRs) on the order of -30 dB or lower. To detect such signals, one must have an uncommonly low and stable receiver noise temperature, high gain through large aperture reflectors, and state-of-the-art signal processing algorithms. One must also be able to mitigate the effects of interference, the presence of which, even if extremely weak, can completely mask the faint astronomical signals of interest. To this end, this work presents the development of and results from a new broadband phased array feed (PAF) named the Focal L-Band Array for the Green Bank Telescope (FLAG). This instrument is able to form multiple simultaneous beams to survey a large patch of sky instantaneously, and has a minimum system noise temperature (Tsys) of 16.83 K. This PAF also has the potential to use spatial filtering techniques to place pattern nulls in the direction of interfering signals through the use of an orthogonal projection. This work will also present an improved method for computing an orthogonal projection operator, which is able to place a spatially broad null in the direction of a moving RFI source. A formal derivation of some detection and estimation theory properties for astronomical radio transients is also presented, which formalization is lacking within the astronomical community. This includes maximum-likelihood detectors and estimators and a Cramér Rao bound (CRB) analysis of astronomical transient parameters.

Styles APA, Harvard, Vancouver, ISO, etc.

33

Andrade, Denis Furtado de. « Otimização das câmeras astronômicas do instrumento Brazilian Tunable Filter Imager ». Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-26082016-160404/.

Texte intégral

Résumé :

Este trabalho apresenta os resultados obtidos no processo de otimização realizado nas câmeras astronômicas do instrumento BTFI (Brazilan Tunable Filter Imager) instalado no telescópio SOAR, no Chile, para reduzir o ruído nos sinais. O instrumento BTFI opera com duas câmeras astronômicas de alto desempenho que utilizam detectores de imagens denominados EMCCDs. Esses detectores são sensores de imagem baseados em dispositivos de carga acoplada (CCDs) otimizados por um estágio integrado de multiplicação de elétrons por avalanche. Essa característica permite atingir ao mesmo tempo altas taxas de leitura (10 MHz) e níveis de ruído muito baixos (<1 elétron/pixel). Detectores CCD exigem temperaturas de operação da ordem de -100oC para operar com baixo ruído, o que demanda uma série de especificações técnicas quanto ao projeto da câmera. O trabalho aqui exposto fundamentou-se na otimização de aspectos mecânicos e eletrônicos de câmeras astronômicas com o intuito de se obter a melhor relação sinal-ruído, mostrando a importância do correto desenho mecânico (do ponto de vista térmico) e sua influência no comportamento eletrônico da câmera. São expostos os resultados obtidos com as duas câmeras em laboratório, os métodos e processos de caracterização utilizados, bem como as simulações térmicas e experimentos realizados em laboratório. Com as técnicas empregadas alcançou-se níveis de ruído total menores que 0,18 elétrons/pixel/segundo para exposições de 10 segundos. Os resultados atingidos foram observados nas duas câmeras do instrumento BTFI e foram validados em laboratório, onde demonstraram estabilidade durante 71 dias consecutivos. Por fim, é mostrada uma caracterização comparativa entre as duas câmeras quanto aos níveis de ruídos, ganho, estabilidade, eficiência quântica, linearidade e relação sinal-ruído.
This work presents results of the optimization performed in the astronomical cameras from the Brazilian Tunable Filter Imager (BTFI), instrument for the SOAR Telescope in Chile, in order to reduce the signals noise. The BTFI instrument has two highperformance cameras equipped with detectors named EMCCDs, which are image sensors based on charge-coupled devices (CCDs) optimized by an electron multiplication integrated stage. This feature enables to achieve high readout rates (10 MHz) and very low noise levels (<1 electron/pixel) at the same time. CCD detectors demand running temperatures of about -100,sup>oC for very low noise operation, which requires a series of technical specifications for the camera design. The work shown here is based in the optimization of the mechanical and electronic aspects for the astronomical cameras, in order to obtain the best signal to noise ratio, showing the importance of the correct mechanical design (from the thermal point of view) and its influence on the camera electronic behavior. The laboratory results obtained with the two cameras, the characterization procedures, as well as the thermal simulations and laboratory ratification experiments that allowed achieve the results presented are exposed. Using such techniques it was possible to achieve total noise levels lower than 0.18 electron/pixel/second for 10 seconds of exposure time. The results achieved were observed in both BTFI cameras and were validated in laboratory showing 71 consecutive days of stability. Finally it is shown a comparative characterization between both cameras in: noise and gain levels, stability, quantum efficiency, linearity and signal to noise ratio.

Styles APA, Harvard, Vancouver, ISO, etc.

34

Wade, G. A., C. Neiner, E. Alecian, H. H. Grunhunt, V. Petit, B. Batz, D. A. Bohlender et al. « The MiMeS Survey of Magnetism in Massive Stars : Introduction and Overview ». Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/2723.

Texte intégral

Résumé :

The MiMeS (Magnetism in Massive Stars) project is a large-scale, high-resolution, sensitive spectropolarimetric investigation of the magnetic properties of O- and early B-type stars. Initiated in 2008 and completed in 2013, the project was supported by three Large Program allocations, as well as various programmes initiated by independent principal investigators, and archival resources. Ultimately, over 4800 circularly polarized spectra of 560 O and B stars were collected with the instruments ESPaDOnS (Echelle SpectroPolarimetric Device for the Observation of Stars) at the Canada–France–Hawaii Telescope, Narval at the Télescope Bernard Lyot and HARPSpol at the European Southern Observatory La Silla 3.6 m telescope, making MiMeS by far the largest systematic investigation of massive star magnetism ever undertaken. In this paper, the first in a series reporting the general results of the survey, we introduce the scientific motivation and goals, describe the sample of targets, review the instrumentation and observational techniques used, explain the exposure time calculation designed to provide sensitivity to surface dipole fields above approximately 100 G, discuss the polarimetric performance, stability and uncertainty of the instrumentation, and summarize the previous and forthcoming publications.

Styles APA, Harvard, Vancouver, ISO, etc.

35

Cavalcanti, Luiz Eduardo Mendonça. « Sistema de controle para o filtro óptico sintonizável Fabry-Perot do instrumento BTFI ». Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-06042011-115126/.

Texte intégral

Résumé :

Este trabalho trata do desenvolvimento de um sistema de controle para um módulo do instrumento astronômico BTFI (Brazilian Tunable Filter Imager), um filtro óptico sintonizável altamente versátil que está instalado no telescópio SOAR, localizado no Chile. Será empregado neste instrumento um novo interferômetro Fabry-Perot, capaz de realizar observações em uma ampla faixa de resoluções espectrais. Para operar com resolução espectral variável, o Fabry-Perot proposto neste projeto terá uma faixa mais ampla de ajuste do vão entre suas placas refletivas, utilizando atuadores piezelétricos amplificados com grande capacidade de deslocamento e sensores capacitivos de alta precisão. O novo controlador apresenta uma malha de controle totalmente digital, implementada com um DSP (Digital Signal Processor) sintetizado num dispositivo FPGA (Field-programmable Gate Array). Na primeira etapa do desenvolvimento, trabalhou-se com um sistema de posicionamento nanométrico utilizando um protótipo simplificado com um canal composto por um sensor capacitivo de distância e um atuador piezelétrico. A partir dos bons resultados obtidos no sistema de um canal, realizou-se a expansão para um sistema de controle multi-malha de três canais com protótipo do Fabry-Perot, mas sem o uso das placas de vidro refletivas definitivas. O sistema permite controlar o posicionamento para cada canal individualmente ou os três em simultâneo, com desempenho adequado para os requisitos do filtro óptico sintonizável Fabry-Perot.
This work aims the development of a control system for a module of the BTFI astronomical instrument (Brazilian Tunable Filter Imager), a highly versatile optical tunable filter, deployed on the SOAR Telescope. The instrument will employ a new Fabry-Perot interferometer, which is able to provide observations in a wide range of spectral resolutions. In order to achieve variable spectral resolution, the new Fabry- Perot proposed in this project will present a larger range for adjusting the air gap between its reflective plates, using amplified piezoelectric actuators presenting high stroke capability and high precision capacitive sensors. The new controller presents a full digital control loop, implemented in a DSP (Digital Signal Processor) synthesized through a FPGA device (Field-programmable Gate Array). During the first phase of the development, it was used a nanometric positioning system using a single channel prototype comprising one capacitive sensor and one piezoelectric actuator. The good results obtained using the single channel prototype led to the expansion to a 3- channel multi-loop control system on a Fabry-Perot prototype which comprises dummy plates. The system allows controlling the position of each channel separately or simultaneously, presenting performance in accordance with the requirements of a Fabry-Perot optical tunable filter.

Styles APA, Harvard, Vancouver, ISO, etc.

36

Garrett, John. « A 230 GHz focal plane array using a wide IF bandwidth SIS receiver ». Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:d47fbf3b-1cf3-4e58-be97-767b9893066e.

Texte intégral

Résumé :

Superconductor-Insulator-Superconductor (SIS) mixers offer the best noise properties of any heterodyne mixing technique at millimetre wavelengths. In astronomy, they are used for sensitive spectroscopy, which is vital for understanding the properties of the cold interstellar medium, including regions of star formation activity. Modern SIS receivers have noise properties that are ∼3 times the quantum limit, and it is now becoming increasingly difficult to lower the noise properties any further. In this thesis, I investigate two techniques that extend the capability of SIS receivers. The first technique is extending the instantaneous bandwidth of the receivers, i.e., the intermediate frequency bandwidth (IFBW). For spectral line sources, wide IFBW expands the survey depth to allow multiple emission lines to be observed simultaneously. Here, I present a new SIS mixer device at 230 GHz. The planar circuit was minimised to reduce any parasitic capacitances that may limit the IFBW. Experimentally, the device provides excellent noise temperatures down to 36 K and an IFBW extending from approximately 0-11 GHz. Simulation software was developed to better understand the performance of this device, and it suggests that the IFBW can be extended to higher frequencies if the IF measurement chain is upgraded. The second technique that I investigate is increasing the number of receivers in the focal plane of the receiver, i.e., adding more pixels. There are many challenges involved in this task including how to fit multiple receivers into a small space, how to properly cool the receiver, and how to deliver the local-oscillator signal. Here, I present a new 1 Ã 4 focal plane array. This array is acting as a demonstrator for a new array architecture that can be expanded into many more pixels in the future. It uses cascaded waveguide power splitters to divide the local-oscillator signal, and then waveguide directional couplers to combine the LO with the astronomical signals. Finally, I present CO(J=1→0) measurements from 34 galaxies in the 5MUSES survey. These measurements trace the amount of cold molecular gas present in these galaxies. By comparing these measurements to other metrics that trace star formation activity (e.g., infrared luminosity), I was able to form empirical relationships between the observed quantities. I also combined these results with other star formation studies from nearby and high redshift galaxies to form scaling relationships spanning a large fraction of cosmic time.

Styles APA, Harvard, Vancouver, ISO, etc.

37

Eastman, Jason David. « DEMONEX : The DEdicated Monitor of EXotransits ». The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1312287607.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

38

Coker, Carl. « The Frequency of Binary Companions Around KELT Planet Host Stars ». The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu149978799487883.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

39

Athanasiou, Eleni. « Studies of the orbital background noise and the detector characteristics for the MeVCube mission ». Thesis, Luleå tekniska universitet, Rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80758.

Texte intégral

Résumé :

A space camera is a promising candidate to address the non-stop rising interest for astrophysics research in the Compton regime. The MeVCube mission is intended to be launched in 2022, hosting an on-board Compton Camera. To better support the development of the instrument in this early stage, a series of feasibility studies to assess two potential launch orbits were performed. The studies were composed by a series of mission analysis simulations which permitted the characterisation of the orbital environments for the two orbital options. Several sources of background noise to the instrument were identified. The population of trapped protons and trapped electrons were simulated for the periods of Solar Minimum and Solar Maximum, as well as the levels of Galactic Cosmic Ray (GCR) flux. The performance of trade-off studies concluded that an equatorial orbit is more preferable for reducing the influence of background noise. To better estimate the environment effects at the equatorial orbit, the number of particles which can penetrate the detector shielding were simulated. The next step was to perform a series secondary studies whose aim were to simulate the induced current on the electrodes, produced by the interactions occurring within the detector. The actualisation of these simulations required the study of photon interaction with matter, the various Cadmium-Zink-Telluride (CZT) types and the how they operate, and the use of a sophisticated software to perform the appropriate simulations. COMSOL, which allows the method of FEA, was chosen as the tool to perform the simulations. The geometry of the detector voxel was primarily designed in SIEMENS NX. The geometry was inserted into COMSOL, where a number of iterations were performed to finalise the appropriate mesh size, which ensured an accurate representation of the Electric field and the Weighting potential within the detector voxel. The induced current on the electrodes was decided to be calculated via MATLAB. As a verification step it was thought useful to firstly plot the weighting potential of the three electrodes under test; the chosen anode pixel, the steering grid and the cathode. The process revealed a series of numerical errors, most likely introduced by the type of mesh chosen or by the data manipulation process via MATLAB. Significant reduction of the numerical errors would lead to more accurate values for the induced current. Unfortunately, due to time constraints this was a task that was not completed. Solving this problem would be optimal for future studies with MATLAB, as the induced current on the electrodes can be correctly calculated based on charge transport within the detector bulk.
MeVCube, DESY

Styles APA, Harvard, Vancouver, ISO, etc.

40

Nickelt-Czycykowski, Iliya Peter. « Aktive Regionen der Sonnenoberfläche und ihre zeitliche Variation in zweidimensionaler Spektro-Polarimetrie ». Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/2552/.

Texte intégral

Résumé :

Die Arbeit beschreibt die Analyse von Beobachtungen zweier Sonnenflecken in zweidimensionaler Spektro-Polarimetrie. Die Daten wurden mit dem Fabry-Pérot-Interferometer der Universität Göttingen am Vakuum-Turm-Teleskop auf Teneriffa erfasst. Von der aktiven Region NOAA 9516 wurde der volle Stokes-Vektor des polarisierten Lichts in der Absorptionslinie bei 630,249 nm in Einzelaufnahmen beobachtet, und von der aktiven Region NOAA 9036 wurde bei 617,3 nm Wellenlänge eine 90-minütige Zeitserie des zirkular polarisierten Lichts aufgezeichnet. Aus den reduzierten Daten werden Ergebniswerte für Intensität, Geschwindigkeit in Beobachtungsrichtung, magnetische Feldstärke sowie verschiedene weitere Plasmaparameter abgeleitet. Mehrere Ansätze zur Inversion solarer Modellatmosphären werden angewendet und verglichen. Die teilweise erheblichen Fehlereinflüsse werden ausführlich diskutiert. Das Frequenzverhalten der Ergebnisse und Abhängigkeiten nach Ort und Zeit werden mit Hilfe der Fourier- und Wavelet-Transformation weiter analysiert. Als Resultat lässt sich die Existenz eines hochfrequenten Bandes für Geschwindigkeitsoszillationen mit einer zentralen Frequenz von 75 Sekunden (13 mHz) bestätigen. In größeren photosphärischen Höhen von etwa 500 km entstammt die Mehrheit der damit zusammenhängenden Schockwellen den dunklen Anteilen der Granulen, im Unterschied zu anderen Frequenzbereichen. Die 75-Sekunden-Oszillationen werden ebenfalls in der aktiven Region beobachtet, vor allem in der Lichtbrücke. In den identifizierten Bändern oszillatorischer Power der Geschwindigkeit sind in einer dunklen, penumbralen Struktur sowie in der Lichtbrücke ausgeprägte Strukturen erkennbar, die sich mit einer Horizontalgeschwindigkeit von 5-8 km/s in die ruhige Sonne bewegen. Diese zeigen einen deutlichen Anstieg der Power, vor allem im 5-Minuten-Band, und stehen möglicherweise in Zusammenhang mit dem Phänomen der „Evershed-clouds“. Eingeschränkt durch ein sehr geringes Signal-Rausch-Verhältnis und hohe Fehlereinflüsse werden auch Magnetfeldvariationen mit einer Periode von sechs Minuten am Übergang von Umbra zu Penumbra in der Nähe einer Lichtbrücke beobachtet. Um die beschriebenen Resultate zu erzielen, wurden bestehende Visualisierungsverfahren der Frequenzanalyse verbessert oder neu entwickelt, insbesondere für Ergebnisse der Wavelet-Transformation.
The publication describes the analysis of two sunspot observations in two-dimensional spectropolarimetry. The data was obtained with the Fabry-Pérot-interferometer of Göttingen University at the German Vacuum Tower Telescope on Tenerife. Of the active region NOAA 9516 the full Stokes vector of polarised light was observed in the absorption line at 630.249 nm in single scans. A ninety minute time series of circular polarised light of the active region NOAA 9036 was observed at 617.3 nm wavelength. From the reduced data results for intensity, line-of-sight velocity, magnetic field strength as well as several other plasma parameters are inferred. Different approaches to solar atmosphere model inversion are applied and compared. The significant influence of errors is discussed in detail. The frequency behaviour of the results and spatial and temporal dependencies are further analysed by Fourier and wavelet transformation. As a result the existence of a high frequency band of velocity oscillations with a central frequency of about 75-seconds (13 mHz) can be confirmed. In greater heights of about 500 km the majority of the corresponding shock waves are derived from darker parts of the granules in contrast to the dominant five-minute-oscillations. 75-second-oscillations can also be observed in the active region, especially in the light bridge. In the identified bands of oscillatory velocity power, distinct structures become visible in a penumbral dark structure as well as in the light bridge that move into the quiet sun with a horizontal speed of 5-8 km/s. They show an increase in power, mostly 5-minute-band, and may be related to the Evershed cloud phenomenon. Under the constraint of a very low signal-to-noise ratio and high error influence, magnetic field variations of a 6-minute period are also observed in an umbral-penumbral transition area close to a light bridge. To derive these results, existing visualisation methods for frequency analysis where improved or newly developed, especially so for wavelet transform results.

Styles APA, Harvard, Vancouver, ISO, etc.

41

Lefranc, Valentin. « Recherche de matière noire, observation du centre galactique avec H.E.S.S.et modernisation des caméras de H.E.S.S. I ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS204/document.

Texte intégral

Résumé :

Le réseau de 5 télescopes Tcherenkov au sol H.E.S.S. (High Energy Stereoscopic System) permet de détecter des rayons gamma à très hautes énergies (E>50GeV) pour sonder les phénomènes non thermiques les plus violents de l'univers. Ces rayons gamma peuvent provenir de l'annihilation de particules de matière noire. L'astronomie gamma permet donc de rechercher les signatures de l'annihilation de particules de matière noire dans les régions denses de l'univers. Cette thèse est composée de trois parties. Après un bref rappel sur l'instrument H.E.S.S., sont présentés en premier lieu les tests de performance effectués pour l'étalonnage de la nouvelle électronique utilisée pour la modernisation des caméras des quatre télescopes CT1 à 4. L'analyse des premières données de la caméra CT1 modernisée montre la réduction du temps mort de lecture du réseau qui permettra de bénéficier pleinement de la stéréoscopie entre les 5 télescopes du réseau. La deuxième partie de la thèse traite des 10 ans d'observations de la région du Centre Galactique avec H.E.S.S. ainsi que les récentes observations obtenues avec l'ajout en 2012 du télescope de 28 mètres de diamètre (CT5) au centre du réseau. L'analyse des données de CT5 en direction de la source centrale HESS J1745-290 permet d'avoir accès aux événements aux plus basses énergies accessibles avec H.E.S.S. (100 GeV). Le spectre de la source centrale est en très bon accord avec celui de HESS J1745-290 mesuré avec CT1-4 et les données en dessous de 150 GeV permettent de raccorder ce dernier à celui de la source Fermi 3FGHL J1745.6-2859c.Dans la troisième partie, les 10 ans de données dans la région du Centre Galactique avec la première phase de H.E.S.S sont analysés pour rechercher un signal d'annihilation de matière noire à l'aide d'une méthode de vraisemblance utilisant les caractéristiques spectrale et spatiale du signal de matière noire par rapport à celles du bruit de fond. En l'absence de signal matière noire, les contraintes sont calculées sur la section efficace d'annihilation et, pour la première fois, un réseau de télescope Tcherenkov au sol est capable de sonder la section efficace d'annihilation thermique dans le cas d'un profil de matière noire piqué. La sensibilité sur la section efficace d'annihilation de l'instrument H.E.S.S. utilisant CT5 est ensuite présentée vers le Centre Galactique et la galaxie naine récemment découverte Reticulum II. La dernière partie de cette thèse étudie le potentiel du futur réseau de télescopes Tcherenkov CTA, (Cherenkov Telescope Array) pour la détection d'un signal d'annihilation de matière noire. Vers la région du Centre Galactique le signal de matière noire attendu est significativement augmenté par la contribution de rayons gamma produits par effet Compton inverse d'électrons et positrons énergétiques sur les champs de radiation ambiants. La sensibilité obtenue permet à CTA de sonder la section efficace d'annihilation thermique dans tous les canaux d'annihilation dans le cas d’un profil de matière noire piqué. L’impact sur la sensibilité de CTA des erreurs systématiques et de l’émission diffuse mesurée par Fermi est aussi montré. Dans le cas des galaxies naines satellites de la Voie Lactée, les performances de CTA permettent de les considérer comme des objets spatialement étendus, et d'obtenir une sensibilité compétitive avec celle du Centre Galactique dans le cas d’un profil à cœur de plusieurs kpc. Dans le cas d'un signal de matière noire de type ligne, CTA sera capable de contraindre fortement des modèles spécifiques de matière noire au TeV grâce à l'effet Sommerfeld, comme le Wino et le MDM-5plet
The ground-based Cherenkov telescope array H.E.S.S. (High Energy Stereoscopic System) is able to detect gamma rays at very high energies (E> 50GeV) to probe the most violent non-thermal phenomena in the universe. These gamma rays can also come from dark matter particle annihilation. Gamma-ray astronomy provides a promising avenue to search for signatures of these annihilations in overdense regions of the universe. This thesis is composed of three parts. After a brief reminder of the H.E.S.S. instrument, the performance tests to calibrate the new electronics used for the modernization of the four cameras CT1-4 telescopes are presented. The analysis of the upgraded camera raw data shows a reduction global array dead time allowing to maximize the benefit of the stereoscopy between the 5 telescopes. The second part of the thesis deals with 10 years of observations of the Galactic Center region with H.E.S.S. and recent observations taken with the 28-meter-diameter telescope (CT5) located at the center of the array. The data analysis towards the central source HESS J1745-290 provides access to events at lower energies (100 GeV). The spectrum of the central source is in very good agreement with the one of HESS J1745-290 measured with CT1-4 and data below 150 GeV enable to connect it to the Fermi 3FGHL J1745.6-2859c source spectrum. In the third part, the 10 years of data in the region of the Galactic Centre with the first phase of H.E.S.S. are scanned for a dark matter annihilation signal using a likelihood method using the spectral and spatial characteristics of the dark matter signal compared to background. No dark matter signal is detected. The constraints are calculated on the annihilation cross section and, for the first time, a ground-based Cherenkov telescope array is capable to probe the thermal cross section in the case of a cuspy dark matter profile. The sensitivity of the annihilation cross section of the H.E.S.S. instrument using CT5 is then presented toward the Galactic Center and the recently discovered dwarf galaxy Reticulum II. The last part of the thesis studies the potential of the future ground-based instrument CTA (Cherenkov Telescope Array) for the detection of dark matter annihilation signal. Towards the Galactic Center region, the expected dark matter signal is significantly increased by the contribution of gamma rays produced by inverse Compton process of energetic electrons and positrons on ambient radiation fields. The sensitivity obtained enables CTA to probe the thermal cross section in all annihilation channels for a cuspy dark matter profile. The impact on CTA sensitivity of systematic errors and diffuse emission measured by Fermi is also shown. In the case of dwarf galaxy satellites of the Milky Way, the CTA performances enable to consider them as extended objects and provide a competitive sensitivity with the Galactic Centre sensitivity for a kpc-core profile. In the case of a line signal, CTA will be able to strongly constrain specific TeV dark matter models through the Sommerfeld effect, as Wino and MDM-5plet

Styles APA, Harvard, Vancouver, ISO, etc.

42

Curiel, Luis R. III. « Investigation on the Use of Small Aperture Telescopes for LEO Satellite Orbit Determination ». DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2253.

Texte intégral

Résumé :

The following thesis regards the use of small aperture telescopes for space domain awareness efforts. The rapidly populating space domain was motivation for the development of a new operation scheme to conduct space domain awareness feasibility studies using small telescopes. Two 14-inch Schmidt-Cassegrain Telescopes at the California Polytechnic State University and the Air Force Research Lab in Kirtland AFB, NM, in conjunction with a dedicated CCD camera and a commercial DSLR camera, were utilized to conduct optical observations on satellites in Earth orbit. Satellites were imaged during August 2019, and from January 2020 to March 2020, resulting in the collection of 77 valid images of 16 unique satellites. These images were used to obtain celestial spherical coordinates, which were used in Gauss and Double-R angles-only initial orbit determination methods. Initial orbit determination methods successfully produced valid results, reaffirming the feasibility of using small aperture telescopes for such methods. These orbit determinations were used to propagate orbit states forward in time to determine the feasibility of future imaging of the targets with the same apparatus. Propagation results demonstrated that initial orbit determinations rapidly decayed in accuracy over distant times and are most accurate for immediate satellite passes. In addition, an attempt to combine multiple initial orbit determinations using Lambert’s problem solutions was made. Combination of these multiple initial orbit determinations resulted in either no orbit state accuracy improvement compared to individual initial orbit determinations, or a decrease in accuracy compared to these methods. Ultimately, efforts demonstrated that small telescope usage is feasible for orbit determination operations, however there may be a need for hardware and operational revisions to improve the ability of the apparatus.

Styles APA, Harvard, Vancouver, ISO, etc.

43

Ritchie, Douglas Allen. « Factors That Affect the Global Positioning System and Global Navigation Satellite System in an Urban and Forested Environment ». Digital Commons @ East Tennessee State University, 2007. https://dc.etsu.edu/etd/2089.

Texte intégral

Résumé :

The purpose of this study was to evaluate the accuracy in real time measurements acquired from GPS and GLONASS satellite observations using RTK techniques in an urban and forested environment. To determine this accuracy, 2 data sets of 3-dimensional coordinates were created and compared at 14 stations situated at East Tennessee State University. One data set included coordinates determined by conventional land survey methods; the second was solved by RTK GPS/GLONASS. Once the magnitude of any deviation in the coordinate positions was determined, the contributions to the accuracies from cycle slips, multipath, satellite availability, PDOP, and fixed or float solutions were evaluated. Three points in the urban environment varied from the conventional data set. Multipath was assumed to be the major bias in these points. Seven points in the forested environment varied from the conventional data set. The use of float solutions and high PDOP may have caused this bias.

Styles APA, Harvard, Vancouver, ISO, etc.

44

Thom, Christian. « Conception et realisation d'un appareil de traitement d'images interferometriques en comptage de photons ». Paris, ENMP, 1986. http://www.theses.fr/1986ENMP0004.

Texte intégral

Résumé :

Description de l'appareil tant au point de vue du materiel que du logiciel apres avoir rappele les bases theoriques de l'interferometrie et du traitement d'images en comptage de photons. Etude des principales applications de cet appareil en interferometrie des tanelures et en synthese d'ouverture optique, notamment avec un resultat original dans le domaine des etoiles chaudes a enveloppe: premiere mesure directe du diametre angulaire de l'enveloppe de l'etoile gamma cassiopee

Styles APA, Harvard, Vancouver, ISO, etc.

45

Jones, Mark. « Determining the Rotational and Orbital Velocities of Objects in the Solar System ». Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/585.

Texte intégral

Résumé :

Astronomers have been observing the night sky for many centuries to establish a better understanding for our universe and solar system. As part of their observations, astronomers characterize celestial bodies by fundamental properties such as mass, motion, and composition in order to provide further insight about the objects in question. As technology and science have evolved, the methods for measuring these properties have become more precise and accurate. One such methodology is known as spectroscopy, and it is a signiﬁcant tool for observational astronomy. In this paper, we shall describe how we used astronomical spectroscopy to determine orbital and rotational velocities for various objects in our solar system. This method was implemented speciﬁcally using the facilities of the Harry D. Powell Observatory on the campus of East Tennessee State University.

Styles APA, Harvard, Vancouver, ISO, etc.

46

Dagoneau, Nicolas. « Détection de sursauts gamma ultra-longs et traitement d'images embarqué pour le télescope spatial SVOM/ECLAIRs ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP040.

Texte intégral

Résumé :

Les sursauts gamma sont des phénomènes extragalactiques brefs, comptant parmi les plus énergétiques de l’Univers et résultant de la formation d’un trou noir stellaire. Ils sont caractérisés par une émission prompte de photons X et gamma, pouvant durer d’une fraction de seconde à quelques minutes, suivis d’une rémanence dans d’autres longueurs d’onde. La mission franco-chinoise SVOM qui est prévue d’entrer en opération après 2021 a pour objectif de détecter leur émission prompte et d’observer leur émission rémanente depuis l’espace et le sol. Le télescope à masque codé ECLAIRs embarqué à bord du satellite SVOM aura la charge de scruter le ciel à la recherche de l’émission prompte des sursauts gamma dans le domaine des rayons X durs et gamma mous, mais aussi d’observer d’autres sources connues rayonnant dans cette gamme d’énergie comme des binaires de rayons X hébergeant un trou noir ou une étoile à neutrons et une étoile compagnon. ECLAIRs est également sensible au bruit de fond cosmique de rayons X (CXB). Pendant ma thèse, j’ai étudié l’influence du CXB et des sources de rayons X connues sur les capacités de l’imagerie embarquée du télescope ECLAIRs. Le CXB et les sources connues dégradent la qualité des images produites par le logiciel embarqué, et donc réduisent les capacités de détection des sursauts gamma. Afin d’optimiser la détection de sources inconnues, j’ai étudié deux méthodes de traitement d’image détecteur avant reconstruction des images du ciel : une méthode d’ajustement d’un modèle prédéfini et une méthode à base d’ondelettes. Les sources brillantes connues risquant de perturber la détection des sursauts gamma seront corrigées par l’une de ces méthodes tandis que les moins brillantes seront exclues de la zone du ciel pour la recherche de nouvelles sources. Dans ce dernier cas, il sera possible de détecter avec le logiciel embarqué des éruptions de sources de rayons X connues. La stratégie de traitement des sources connues ainsi que la gestion de la détection d’éruptions reposent sur un catalogue qui fera partie du logiciel embarqué d’ECLAIRs et que j’ai construit à partir des données collectées par les instruments Swift/BAT et MAXI/GSC. De plus, je me suis aussi penché sur les sursauts gamma d’ultra-longue durée, dont l’émission en rayons X peut atteindre plus de 1000 secondes. La détection de ces sursauts pourrait bénéficier de l’imagerie à longue exposition d’ECLAIRs atteignant 20 minutes. J’ai simulé les quelques événements détectés à ce jour par l’instrument Swift/BAT avec un prototype du logiciel de déclenchement d’ECLAIRs et montré que ECLAIRs pourrait détecter au moins autant de sursauts ultra-longs que Swift
Abstract : Gamma-ray bursts (GRBs) are brief extragalactic phenomena, among the most energetic in the Universe, resulting from the formation of a stellar-mass black hole. They are characterised by a prompt emission of X and gamma-ray photons, which can last from a fraction of a second to a few minutes, followed by an afterglow in other wavelengths. The French-Chinese SVOM mission, expected to begin operations after 2021, aims to detect their prompt emission and to observe their afterglow from space but also from the ground. The ECLAIRs coded mask telescope onboard the SVOM satellite will scan the sky in search of the prompt emission of GRBs in the hard X-ray and soft gamma-ray band, but also observe other known sources emitting in this energy range, such as X-ray binaries hosting a black hole or a neutron star and a companion star. The ECLAIRs telescope is also sensitive to the Cosmic X-ray Background (CXB). During my thesis, I studied the influence of the CXB and the known X-ray sources on the onboard imaging capabilities of ECLAIRs. The CXB and known sources downgrade the quality of the images produced by the onboard software, and thus reduce the detection capabilities of GRBs. In order to enhance the detection of unknown sources, I studied two methods to correct the detector plane image prior to sky image reconstruction: a predefined model fitting method and a wavelet based method. Known bright sources that may disturb the detection of GRBs will be corrected by one of those methods, while the fainter ones will be excluded from the search region for new sources in the reconstructed sky. In the latter case, it will be possible to detect X-ray flares with the onboard software. The processing strategy for known sources and the management of flare detection are based on a catalogue which will be part of the ECLAIRs onboard software and which I have built from data collected by the Swift/BAT and MAXI/GSC instruments. In addition, I also studied ultra-long duration GRBs, whose X-ray emission can reach more than 1000 seconds. The detection of these bursts could benefit from long exposure imaging of ECLAIRs up to 20 minutes. I have simulated the few events detected so far by Swift/BAT with a prototype of the ECLAIRs triggering software and shown that ECLAIRs could detect at least as many ultra-long bursts as Swift

Styles APA, Harvard, Vancouver, ISO, etc.

47

Galata, Salvatore. « A time dependent search for neutrino emission from microquasars with the ANTARES telescope ». Phd thesis, Aix-Marseille Université, 2012. http://tel.archives-ouvertes.fr/tel-00782883.

Texte intégral

Résumé :

La Collaboration ANTARES exploite actuellement un détecteur sous-marin Cherenkov d édi é a l'astronomie neutrino de haute énergie. Le but principal de cette expérience est de d détecter les sources cosmiques de neutrinos, a n de r ev eler les sites de production des rayons cosmiques. Parmi les sources candidates gurent celles o u a lieu l'acc el eration de ces rayons cosmiques dans les jets relativistes, comme les noyaux actifs de galaxie, les sursauts gamma et les microquasars. Les microquasars sont des syst émes stellaires binaires form es par un objet compact accr étant la mati ere d'une étoile compagnon. Ce transfert de masse est responsable de l' emission de rayons X, tandis que les forces magn etiques du plasma d'accr étion peuvent causer la cr éation de jets relativistes qui sont observ es par des t télescopes radio grâce au rayonnement synchrotron non thermique émis par les particules charg ées acc el er ees dans ces jets. Dans certains syst emes, la corr élation entre les courbes de lumi ere des rayons X et les courbes radio indique une interaction forte entre accr etion et ejection. Certains microquasars emettent egalement des rayons gamma de haute et tr es haute energie (jusqu' a quelques dizaines de TeV). Dans ce travail de th ese, une recherche d' émission de neutrinos provenant de microquasars a ét é conduite avec une approche multi-messager (photon/neutrino). Les données des satellites RXTE/ASM et SWIFT/BAT, ainsi que du t elescope gamma FERMI/LAT ont et e etudi ées a n de s sélectionner les périodes dans lesquelles se produisent les jets relativistes. La restriction de l'analyse des neutrinos aux phases d' éjection permet de r réduire drastiquement le bruit de fond de neutrinos et de muons atmosph èriques et ainsi d'augmenter les chances de d écouverte d'une source cosmique de neutrinos. Les recherches ont et e effectué a partir des donn ées ANTARES obtenues entre 2007 et 2010. Une analyse statistique a et e faite en utilisant une m ethode \unbinned" bas ee sur le test du rapport de vraisemblance. Les coupures de s élection des év enements ont et e optimisés a partir de simulations Monte Carlo a n de maximiser les chances de ddécouverte. Comme aucun signal de neutrinos n'a et e observé en corrélation avec ces microquasars, des limites sup erieures sur les ux de neutrinos produits dans ces microquasars ont et e calcul ées et confront ées avec des modèles de production de neutrino dans ces objets.

Styles APA, Harvard, Vancouver, ISO, etc.

48

Bowsher, Emily Collins. « Measuring the Effective Wavelength of CHARA Classic ». Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/phy_astr_theses/8.

Texte intégral

Résumé :

This thesis presents an engineering project measuring the effective wavelength of the CHARA Classic beam combiner on the CHARA Array. Knowing the actual effective wavelength of light observed is very important because that value is necessary for determining astrophysical parameters of stars. Currently, the value used for CHARA Classic data comes from a model of the system and is based on numbers published by the manufacturer of the filter; it is not derived from measurements done on the system directly. We use two data collection methods to observe standard stars of different spectral types and calculate the wavelength of light recorded by the instrument for each star. We find the best estimate of the effective wavelength for the CHARA Classic K′-band configuration to be 2.138±0.003μm, a 0.56% decrease from the previously adopted value of 2.150μm. Our result establishes the first estimate of the uncertainty in the effective wavelength.

Styles APA, Harvard, Vancouver, ISO, etc.

49

Giebels, Berrie. « A contribution to gamma-ray astronomy of GeV-TeV Active Galaxies with Fermi and H.E.S.S ». Habilitation à diriger des recherches, Ecole Polytechnique X, 2011. http://tel.archives-ouvertes.fr/tel-00672596.

Texte intégral

Résumé :

L'astronomie des rayons g de haute (E > 100MeV, HE) et de très haute énergie (E 100GeV, VHE) ont effectué des progrès considérables en moins d'une décennie. Le nombre de sources émettrices dans ce régime d'énergie a augmenté de plus d'un ordre de grandeur, de nouvelles classes d'émetteurs ont été découvertes et des nouvelles sous-classes ont été établies basées sur l'émission gamma, et les sources connues sont à présent résolues à des échelles spatiales ou temporelles sans précédent révélant de nouvelles propriétés. Les noyaux actifs de galaxie (AGN) sont l'une des classes d'émetteurs les plus énergétiques, dont le pic de puissance émis dans le spectre électromagnétique peut dans certains cas dépasser la capacité de mesure des instruments actuels, et dont l'investigation requiert la maîtrise simultanée du ciel g HE et VHE qu'apportent les expériences Cerenkov au sol (atmospheric Cerenkov telescope, ou ACT) et le satellite Fermi.

Styles APA, Harvard, Vancouver, ISO, etc.

50

Artho-Bentz, Samuel S. « Telescope Parallel Actuator Mount : Control and Testing ». DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2242.

Texte intégral

Résumé :

This thesis approaches the task of designing a control system for the Parallel Actuator Mount developed by Dr. John Ridgely and Mr. Garrett Gudgel. It aims to create a base framework that directly controls the telescope and can be expanded to accept external command. It incorporates lower priced components and develops more easily approachable software with great functionality. An open-loop method for velocity control is established. Developing repeatable tests is a major focus. Testing finds the control methods developed result in velocity error of less than 5% and position error of less than 1.5% despite several mechanical issues and inaccuracies. Design guidelines are established that allow for the easy implementation of a Parallel Actuator Mount on other systems. This paper proves that the Parallel Actuator Mount is a potentially viable system for aiming a telescope when an astronomer does not require full sky coverage. The tests showed too much error to fully recommend the system as built and tested, but there are paths to increase accuracy of the system without greatly increasing the complexity or cost. The inclusion of a method of feedback, including a plate solver and an inertial measurement unit, would greatly improve the system. It may also be of use to modify the software to include a variable time step for the velocity control.

Styles APA, Harvard, Vancouver, ISO, etc.

Thèses sur le sujet « Instrumentation for Astronomy »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres