The closest star to Earth is the Sun. The difference between our Sun and other stars is that the dynamics are observable with telescopes. A complex and strange part of our Sun is the chromosphere which is a part of the solar atmosphere. The chromosphere is located between the corona and photosphere where the temperature increases very rapidly within a short distance. A wavelength suited for observing this region is millimetre wavelength. A millimetre observing radio telescope suited to be pointed at the Sun is Atacama Large millimetres/submillimeter Array (ALMA). ALMA is using smaller telescopes to synthesis a larger aperture by correlating the difference between antenna pairs. This technique is called interferometry. When sampling a larger telescope, the projected distance between the smaller telescopes determines the sampling points in Fourier space. When the distance between the antennas increases, they will experience different noise due to Earth's atmosphere. This difference in noise is because the signal travels a different path through the Earth's atmosphere. Different Precipitable Water Vapour (PWV) levels in this path play a major role in this disturbance[1]. To acquire further knowledge of how different seeing effects affect ALMA it is important to enhance the understanding of what could be expected from actual observation. Realistic simulated observations can be a useful tool to extend this knowledge and is investigated in this report. This is done with the CASA (Common Astronomy Software Applications) package and simalma and the simulator tool. The simulator tool gives the possibility to include phase noise from Earth's atmosphere. This noise is calculated with atmospheric transmission at microwaves model and the aatm library [2]. This phase noise is simulated as a fluctuating PWV screen over that array that blows at specific wind speed[3].  Traditionally only thermal noise has been implemented when simulating an observation with the CASA task simalma and simobserve. Initial results indicate a big difference between traditional thermal noise and phase noise. Phase noises generate a greatly increased error as a function of radius compared to a noise free simulated observation. This effect is enhanced for higher PWV levels. This behaviour is due to that the antennas are more sensitive in the centre. This tool shows great potential since more realistic simulations give the possibility to investigate different phenomena in a controlled environment. One could optimize the reconstruction algorithm for noisy observations and investigate how physical phenomena could be affected by different seeing effects. There are a large variety of cases where this type of simulation could be used. Optimization of PWV fluctuating for specific cadences should be done first. This is important because the atmosphere is expected to behave differently at a different cadence because of different movement and averaging. However, optimization and comparison for 1.1 s cadence is doable with data generated from cosmological observations with ALMA[1].

Le Radiohéliographe de Nançay est le seul instrument dédié à l'imagerie du soleil en ondes décimétriques-métriques. Il fonctionne sur le principe de l'interférométrie, en utilisant 47 antennes essentiellement réparties sur des axes est-ouest (3,2 km) et nord-sud (2,5 km). Cette étude a pour but d'explorer un nouveau concept de numérisation propre à la radioastronomie du futur, appliquée ici à l'interférométrie solaire. Elle porte sur la numérisation rapide d'un système synchronisé en sortie d'antennes. Ces aspects "numérisation rapide" et "synchronisation" sont d'une importance capitale pour les prochains radiotélescopes du futur. Ils permettent de simplifier les chaînes de réception radiofréquence et de diminuer la consommation électrique ainsi que les coûts d'entretien et de la maintenance. L'application à l'observation du soleil comporte cependant des contraintes originales, comme la grande dynamique des signaux, qui ne sont pas prises en compte actuellement dans les études en cours pour les radiotélescopes du futur. Le radiohéliographe actuel a une chaîne de réception analogique avec une numérisation centralisée. La commutation entre les différentes fréquences dans la bande 150-450~MHz est réalisée d'une façon analogique et temporelle. Ceci nécessite beaucoup de calibrations analogiques et oblige de figer la gamme des fréquences (10 fréquences de largeur 1~MHz). De plus, en interférométrie métrique, les très grandes longueurs de câbles coaxiales sont onéreuses. Les signaux transmis des antennes au récepteur sont toujours sources d'erreurs et des fluctuations importantes réduisent l'information radiofréquence. Toutefois, apporter une numérisation complète de la bande (300~MHz) permet d'avoir de la souplesse dans le traitement et l'analyse des données (résolution fréquentielle et la possibilité d'observer plusieurs bandes simultanément, traitement des parasites). Ceci engendre la nécessité d'avoir une très grande précision des horloges (0,7~ps d'erreur de phase) pour cadencer des ADC (Analog-to-Digital-Converter) large bande (1~GHz d'horloge). L'objectif principal de la thèse est d'étudier la synchronisation pour l'application à un réseau d'antennes multi-réparties. Le saut technologique ainsi induit et les concepts étudiés sont un enjeu grandissant dans les grands projets européens et internationaux. / The Nançay Radioheliograph is the only instrument dedicated to the solar corona imaging in the 150-450 MHz frequency band. It operates on the principle of interferometry, using 47 antennas essentially distributed on the east-west (3.2 km) and north-south (2.5 km) axes. This study aims to explore a new technical concept for future radio astronomy, applied to solar interferometer. It deals with the rapid digitization of a synchronized system at the antenna sides. High speed digitization and high accuracy synchronization are the most important aspects for future radio telescopes. They make it possible to simplify radiofrequency reception chains and reduce their power consumption, as well as maintenance costs and complexity. The application to the observation of the sun, however, has some original constraints, such as the great dynamics of the signals, which are not taken into account in the current studies for future radio telescopes. The current radio telescope has an analog receiver with a centralized digitization. The switching time between each frequency (10 frequencies of 1 MHz width) in 150-450 MHz band analyzed introduce latency in solar images processing, also decrease the signal-to-noise ratio. In addition, in metric interferometry, the several lengths of coaxial cables in which the signal is transported from the antennas to the receiver always cause significant errors and fluctuations in the radiofrequency reception chains. Providing full digitization of the band (300 MHz) allows more flexibility in data processing and analyzing (frequency resolution and the ability to observe multiple bands simultaneously). This required high clock accuracy (0.7 ps of jitter) for ADCs clocks (1 GHz clock). Therefore, the main objective of this thesis is to reach a sub-ns global time synchronization of distributed networks such as radio interferometer array as the Nançay Radioheliograph. The technological leap thus induced is a growing challenge in major European and international projects.

Made available in DSpace on 2016-03-15T19:35:55Z (GMT). No. of bitstreams: 1 Amauri Shossei Kudaka.pdf: 14809012 bytes, checksum: 1dc60260bb5dcd12adfa496880fb2a7e (MD5) Previous issue date: 2015-08-20 / High cadence solar observations in infrared and H-α are important tools for the study of active regions during solar flaring events. The acquisition and analysis of these observational data associated with information in other frequency bands, can be helpful in the study of emission mechanisms during solar flares. Recently it was installed at the Universidade Presbiteriana Mackenzie, São Paulo, the Mackenzie Solar Observatory, with the objective to provide research opportunities in Solar Physics. Experimental tests carried out in the Observatory should provide advances in instrumentation, assembly and procedures to be implemented and operated in collaboration with others observatories, for solar observations from ground and space. In this work, the physical structure of the Solar Observatory Mackenzie is described in details.Operating procedures of instruments and data acquisition are proposed, as well as the systematization of simultaneous observations at infrared and H-α. Despite the short time of operation, records of some solar events have already been obtained. / Observações solares em infravermelho e H-α, em alta cadência, são importantes ferramentas para o estudo de regiões ativas durante eventos solares explosivos. A obtenção e a análise destes dados observacionais, associados com informações em outras faixas do espectro, podem auxiliar no estudo dos mecanismos de emissão durante explosões solares. Recentemente foi instalado na Universidade Presbiteriana Mackenzie, São Paulo, o Observatório Solar Mackenzie, com o objetivo de fornecer oportunidades de pesquisa na área de Física Solar. Ensaios experimentais realizados no Observatório deverão proporcionar avanços na instrumentação, montagem e procedimentos a serem implementados e operados em colaboração com outros observatórios, para observações solares a partir do solo e do espaço. Neste trabalho, a estrutura física do Observatório Solar Mackenzie é descrita em detalhes. Procedimentos de operação dos instrumentos e de aquisição de dados são propostos, bem como a sistematização das observações simultâneas em infravermelho e H-α. Apesar do pouco tempo de operação, registros de vários eventos solares já foram obtidos.

No / The Solar Feature Catalogues (SFCs) are created from digitized solar images using automated pattern recognition techniques developed in the European Grid of Solar Observation (EGSO) project. The techniques were applied for detection of sunspots, active regions and filaments in the automatically standardized full-disk solar images in Caii K1, Caii K3 and H¿ taken at the Meudon Observatory and white-light images and magnetograms from SOHO/MDI. The results of automated recognition are verified with the manual synoptic maps and available statistical data from other observatories that revealed high detection accuracy. A structured database of the Solar Feature Catalogues is built on the MySQL server for every feature from their recognized parameters and cross-referenced to the original observations. The SFCs are published on the Bradford University web site http://www.cyber.brad.ac.uk/egso/SFC/ with the pre-designed web pages for a search by time, size and location. The SFCs with 9 year coverage (1996¿2004) provide any possible information that can be extracted from full disk digital solar images. Thus information can be used for deeper investigation of the feature origin and association with other features for their automated classification and solar activity forecast.