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1
Witzemann, Amadeus. "Cosmology with next generation radio telescopes". University of the Western Cape, 2019. http://hdl.handle.net/11394/6936.
Testo completoAbstract (sommario):
Philosophiae Doctor - PhDThe next generation of radio telescopes will revolutionize cosmology by providing large three-dimensional surveys of the universe. This work presents forecasts using the technique 21cm intensity mapping (IM) combined with results from the cosmic microwave background, or mock data of galaxy surveys. First, we discuss prospects of constraining curvature independently of the dark energy (DE) model, finding that the radio instrument HIRAX will reach percent-level accuracy even when an arbitrary DE equation of state is assumed. This is followed by a study of the potential of the multi-tracer technique to surpass the cosmic variance limit, a crucial method to probe primordial non-Gaussianity and large scale general relativistic e↵ects. Using full sky simulations for the Square Kilometre Array phase 1 (SKA 1 MID) and the Large Synoptic Survey Telescope (LSST), including foregrounds, we demonstrate that the cosmic variance contaminated scenario can be beaten even in the noise free case. Finally, we derive the signal to noise ratio for the cosmic magnification signal from foreground HI intensity maps combined with background galaxy count maps. Instruments like SKA1 MID and HIRAX are highly complementary and well suited for this measurement. Thanks to the powerful design of the planned radio instruments, all results confirm their potential and promise an exciting future for cosmology.
2
Leung, Martin. "A wideband feed for a cylindrical radio telescope". Phd thesis, School of Physics, 2008. http://hdl.handle.net/2123/5005.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Sydney, 2008.Includes graphs and tables. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Bibliography: p. 196-203. Also available in print form.
3
Mountfort, Peter Ian. "The observation of extended sources with the Hartebeesthoek radio telescope". Thesis, Rhodes University, 1990. http://hdl.handle.net/10962/d1005265.
Testo completoAbstract (sommario):
The Hartebeesthoek Radio Telescope is well suited to mapping large areas of sky at 2.3 GHz because of the stability and sensitivity of the noise-adding radiometer (Nicolson, 1970) and cryogenic amplifier used at this frequency, the relatively large 20' beam of the 26 m dish antenna, and its high-speed drive capability. Telescope control programs were written for the Observatory's online computer for automated mapping. Effort centred on removing the curved baseline or 'background' from each Declination (Dec) scan, due to atmospheric and ground radiation contributions varying as the antenna is scanned. Initially these backgrounds were measured over a wide range of Hour Angle (HA) for the Dec range of a map, and an interpolated curve subtracted from each on-source scan for its HA. A common base level was established by comparison with drift scans (observed with the antenna stationary). These different observations (on- and off-source Dec scans and drift scans) were combined into one in the Skymap system by performing Dec scans at a fixed starting HA for a period long enough to permit 'cold sky' and the source to drift through. A background formed by fitting a smooth curve through the lowest sample at each Dec provides a consistent relative base level for all the scans in an observation. A high scanning speed is used so that observations may fruitfully be repeated three times and interleaved to build a reliable, fully sampled map. As each observation has its own background removed, it may be made at any HA. For comparison, maps of Upper Scorpio produced by the earlier method (Baart et al., 1980) and the Magellanic Cloud region produced by Skymap (Mountfort et al., 1987) are shown. Skymap provides a simple and flexible mapping method which relies on the stability of the noise-adding radiometer and high-speed repeated scans to produce good maps of large or small extent with little computation. Correction for drift is more difficult than with systems which use intersecting scans, such as the 'nodding' scans used by Haslam et al. (1981) or the Azimuth scans of Reich (1982).
4
Zwart, Jonathan Tarquin Lawrence. "Preparing for blind surveys with the Arcminute Microkelvin Imager". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613300.
Testo completo
5
Kaneko, Takeshi. "The Arcminute Microkelvin Imager (AMI)". Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615182.
Testo completo
6
Holler, Christian Matthias. "Correlator and antenna design for the Arcminute Microkelvin Imager (AMI)". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619994.
Testo completo
7
Hurley-Walker, Natasha. "Targeted science observations with the Arcminute Microkelvin Imager (AMI)". Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608480.
Testo completo
8
Culverhouse, Thomas Louis. "Science targets for the Arcminute Microkelvin Imager". Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613801.
Testo completo
9
Tiplady, Adrian John. "Modeling and measurement of torqued procession in radio pulsars". Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1005260.
Testo completoAbstract (sommario):
The long term isolated pulsar monitoring program, which commenced in 1984 using the 26 m radio telescope at the Hartebeeshoek Radio Astronomy Observatory (HartRAO), has produced high resolution timing residual data over long timespans. This has enabled the analysis of observed spin down behaviour for 27 braking pulsars, most of which have dataspans longer than 14 years. The phenomenology of observed timing residuals of certain pulsars can be explained by pseudo periodic effects such as precession. Analytic and numerical models are developed to study the kinematic and dynamic behaviour of isolated but torqued precessing pulsars. The predicted timing residual behaviour of the models is characterised, and confronted with timing data from selected pulsars. Cyclic variations in the observed timing residuals of PSR B1642-03, PSR B1323-58 and PSR B1557-50 are fitted with a torqued precession model. The phenomenology of the observed timing behaviour of these pulsars can be explained by the precession models, but precise model fitting was not possible. This is not surprising given that the complexity of the pulsar systems is not completely described by the model. The extension of the pulsar monitoring program at HartRAO is used as motivation for the design and development of a new low cost, multi-purpose digital pulsar receiver. The instrument is implemented using a hybrid filterbank architecture, consisting of an analogue frontend and digital backend, to perform incoherent dedispersion. The design of a polyphase filtering system, which will consolidate multiple processing units into a single filtering solution, is discussed for future implementation.
10
Franke, Timothy Joseph. "Identification and Cancellation of Harmonic Disturbances in Radio Telescopes". Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1427897871.
Testo completo
11
Wong, Oiwei Ivy. "Star formation and galaxy evolution of the local universe based on HIPASS /". Connect to thesis, 2007. http://eprints.unimelb.edu.au/archive/00004069.
Testo completo
12
Manners, Paul John. "Measuring the RFI environment of the South African SKA site". Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1005259.
Testo completoAbstract (sommario):
The Square Kilometre Array (SKA) Project is an international effort to build the world’s largest radio telescope. It will be 100 times more sensitive than any other radio telescope currently in existence and will consist of thousands of dishes placed at baselines up to 3000 km. In addition to its increased sensitivity it will operate over a very wide frequency range (current specification is 100 MHz - 22 GHz) and will use frequency bands not primarily allocated to radio astronomy. Because of this the telescope needs to be located at a site with low levels of radio frequency interference (RFI). This implies a site that is remote and away from human activity. In bidding to host the SKA, South Africa was required to conduct an RFI survey at its proposed site for a period of 12 months. Apart from this core site, where more than half the SKA dishes may potentially be deployed, the measurement of remote sites in Southern Africa was also required. To conduct measurements at these sites, three mobile measurement systems were designed and built by the South African SKA Project. The design considerations, implementation and RFI measurements recorded during this campaign will be the focus for this dissertation.
13
Wiid, P. Gideon. "Lightning protection and radio frequency interference mitigation for the Karoo Array Telescope". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4009.
Testo completoAbstract (sommario):
Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: South Africa and Australia are now the two remaining countries bidding for the Square Kilometre Array (SKA), the biggest and most sensitive project ever undertaken in radio astronomy. The South African SKA is demonstrating its technology capabilities through the Karoo Array Telescope (KAT or MeerKAT). The development of KAT is taking place in stages to optimise design and minimise risks at each stage. An array of seven 12 m antennas will be complete by the end of 2009, called KAT-7. The following phase will see the construction of MeerKAT, which will lead to eighty arrayed dishes. Lightning and RFI studies for KAT-7 are the focus of this dissertation. Due to the extent and complexity of the South African demonstrator project, these studies have largely been conducted on a single structure. Parameters for the dish antenna and pedestal design changed throughout their development. To be effective, the doctoral research had to track these changes appropriately. A Method of Moments frequency domain computational electromagnetic code, FEKO, is used throughout the study. The consequences of direct and indirect lightning strikes are examined for the KAT-7 structure. Important FEKO model verification is achieved through measurement of physical scale models in an anechoic chamber. The microwave simulation code, CST, gives direct comparison of FEKO results by using a finite volume time domain method of calculation. Using frequency domain analysis on these models, the lightning down conductor design over the dish antenna bearings is optimised with cost-effectiveness as one driving parameter. RFI coupling levels for different designs are compared to each other to identify areas requiring RFI mitigation. Analysis of resonances enables evaluation of the mitigation at frequencies sensitive to radio astronomy. A Sommerfeld integral ground plane is used together with the computational model to investigate the use of the concrete foundation steel reinforcing as part of the lightning earthing electrode system. Different interconnections of the steel reinforcing elements are critically evaluated. The KAT-7 design incorporated clear lightning protection and RFI mitigation policies derived from recommendations contained within this dissertation.
AFRIKAANSE OPSOMMING: Suid-Afrika en Australie is nou die oorblywende twee lande wat bie vir die Vierkante Kilometer Reeks (SKA), die grootste en mees sensitiewe projek nog ooit in radio astronomie onderneem. Die Suid Afrikaanse SKA demonstreer sy tegnologiese bekwaamheid met die Karoo Reeks Teleskoop (KAT of MeerKAT). Die ontwikkeling van KAT vind plaas in fases om die ontwerp te optimaliseer en risikos te minimaliseer met elke fase. ’n Reeks van sewe 12 m antennas, genaamd KAT-7, sal teen die einde van 2009 klaar wees. Die volgende fase behels die konstruksie van MeerKAT, wat sal lei tot ’n tagtig-skottel reeks. Die fokus van hierdie proefskrif hanteer weerlig en radiofrekwensie steurings (RFS) vir KAT-7. As gevolg van die omvang en kompleksiteit van die Suid-Afrikaanse demonstreerder projek, is die studies hoofsaaklik op een struktuur gedoen. Parameters vir die antenna-skottel en -voetstuk ontwerp het met hul ontwikkeling deurgaans verander. Om effektief te wees, moes die doktorale navorsing hierdie veranderinge toepaslik volg. ’n Metode-van-Momente frekwensiedomein rekenaar elektromagnetiese kode, FEKO, is deurgaans met die studie gebruik. Die gevolge van direkte en indirekte weerligslae vir die KAT-7 struktuur is ondersoek. Belangrike FEKO model bevestiging is bereik met metings van skaalmodelle in ’n anego¨ıse kamer. Die mikrogolf-simulasie kode, CST, gee ’n direkte vergelyking met die FEKO resultate deur ’n eindige-volume-tyd-domein metode van berekening te gebruik. Met behulp van frekwensiedomein analise van hierdie modelle, is die weerligafleierontwerp oor die antenna-skottel laers ge-optimaliseer, met koste-effektiwiteit as een van die drywingsparameters. RFS koppelingsvlakke vir onderskeie ontwerpe is teen mekaar opgeweeg om areas te identifiseer wat RFS tempering benodig. Analise van resonansies stel die evaluering van die tempering in staat teen frekwensies wat sensitief is vir radio astronomie. ’n Sommerfeld integrale grondvlak word saam met die rekenaarmodel gebruik om die insluiting van die beton se staalversterking as deel van die aardingselektrodestelsel te ondersoek. Verskillende bindmetodes van die onderlinge staalversterkingselemente word krities ge¨evalueer. Die KAT-7 ontwerp inkorporeer duidelike weerligbeveiligings- en RFS temperingstrategie ¨e, komende van aanbevelings in hierdie proefskrif omskryf
14
Schammel, Michel Philippe. "Blind Sunyaev-Zel'dovich survey with the Arcminute Microkelvin Imager". Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648243.
Testo completo
15
Daniel-Tran, Philo Vinita. "A study of antenna design concepts for future large radio telescopes /". View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030930.163911/index.html.
Testo completo
16
Young, Andre. "Improving the direction-dependent gain calibration of reflector antenna radio telescopes". Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80915.
Testo completoAbstract (sommario):
Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Utilising future radio interferometer arrays, such as the Square Kilometre Array (SKA), to their full potential will require calibrating for various direction- dependent effects, including the radiation pattern (or primary beam in the parlance of radio astronomers) of each of the antennas in such an array. This requires an accurate characterisation of the radiation patterns at the time of observation, as changing operating conditions may cause substantial variation in these patterns. Furthermore, fundamental imaging limits, as well as practical time constraints, limit the amount of measurement data that can be used to perform such characterisation. Herein three techniques are presented which aim to address this requirement by providing pattern models that use the least amount of measurement data for an accurate characterisation of the radiation pattern. These methods are demonstrated through application to the MeerKAT Offset Gregorian (OG) dual-reflector antenna. The first technique is based on a novel application of the Jaco bi-Bessel series in which the expansion coefficients are solved directly from the secondary pattern. Improving the efficiency of this model in the desired application leads to the development of a different set of basis functions, as well as two constrained solution approaches which reduce the number of pattern measurements required to yield an accurate and unique solution. The second approach extends the application of the recently proposed Characteristic Basis Function Patterns (CBFPs) to compensate for non-linear pattern variations resulting from mechanical deformations in a reflector antenna system. The superior modelling capabilities of these numerical basis functions, which contain most of the pattern features of the given antenna design in a single term, over that of analytic basis functions are demonstrated. The final method focusses on an antenna employing a Phased Array Feed (PAF) in which multiple beam patterns are created through th e use of a beam-former. Calibration of such systems poses a difficult problem as the radiation pattern shape is susceptible to gain variations. Here we propose a solution which is based on using a Linearly Constrained Minimum Varia nce (LCMV) beamformer to conform the realised beam pattern to a physics-based analytic function. Results show that the LCMV beamformer successful ly produces circularly symmetric beams that are accurately characterised with a single-term analytic function over a wide FoV.
AFRIKAANSE OPSOMMING: Die volle benutting van toekomstige radio interferometersamestellings, soos die Square Kilometre Array (SKA), benodig die kalibrering van verskeie rigting-afhanklike effekte, insluitend die stralingspatroon (bekend as die primêre bundel onder radio astronome) van elke antenne in só ’n samestelling. Hierdie benodig ’n akkurate karakterisering van die stralingspatrone op die waarnemingstydstip, aangesien veranderende bedryfskarakteristieke ’n beduidende afwyking in hierdie patrone veroorsaak. Verder, weens fund amentele perke in beeldverwerking, asook praktiese tydbeperkinge, bestaan daar ’n limiet op die hoeveelheid gemeetde data wat benut kan word om die nodige karakterisering mee te doen. Hierin word drie tegnieke ten toon gestel wat gemik is daarop om aan hierdie behoefte te voorsien deur die gebruik van modelle wat ’n minimum hoeveelheid metingdata benodig om ’n akkurate beskrywing van die stralingspatroon te lewer. Die verskeie metodes word aangebied aan die hand van die MeerKAT afset-Gregorian dubbelreflektorantenne. Die eerste tegniek is gebasseer op ’n nuwe toepassing van die Jacobi- Besselreeks waarin die sekondêre stralingspatroon direk gebruik word om die uitsettingskoëffisiënte op te los. Die doelmatigheidsverbetering van hierdie model in die huidige toepassing lei na die ontwikkeling van ’n nuwe versameling van basisfunksies, asook twee voorwaardelike oplossings wat die nodige aantal metings vir ’n akkurate, unieke oplossing verminder. In die tweede tegniek word die toepassing van die onlangs voorgestelde Karakteristieke Basisfunksie Patrone uitgebrei om te vergoed vir die nie-lineêre stralingspatroonafwykings wat teweeggebring word deur meganiese vervormings in die reflektorantenne. Die superieure modelleringsvermoëns van hierdie numeriese basisfunksies, wat meeste van die patroonkenmerke vasvang in ’n enkele term, bo dié van analitiese basisfunksies word gedemonstreer. Die laaste metode fokus op die gebruik van ’n gefaseerde samestellingvoer waarin veelvoudige bundelpatrone geskep word deur die gebruik van ’n bundelvormer. Die kalibrering van sulke instrumente word bemoeilik daardeur dat die patroonvorm gevoelig is vir aanwinsafwykings. Hier stel ons ’n oplossing voor waarin ’n lineêrbegrensde minimumstrooiing bundelvormer gebruik word om die stralingspatroon te pas op ’n fisika-gebasseerde analitiese funksie. Resultate toon dat hierdie bundelvormer sirkelsimmetriese bundels kan skep wat akkuraat beskryf word deur ’n een-term analitiese funksie oor ’n wye gesigsveld.
17
Hickish, Jack. "Digital signal processing methods for large-N, low-frequency radio telescopes". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:7d983fb3-9411-4906-92cd-70e2c1040b54.
Testo completoAbstract (sommario):
Current attempts to make precision measurements of the HI power spectrum at high redshifts have led to the construction of several low-frequency, large-N, interferometric arrays. The computational demands of digital correlators required by these arrays present a significant challenge. These demands stem from the treatment of radio telescopes as collections of two-element interferometers, which results in the need to multiply O(N2) pairs of antenna signals in an N-element array. Given the unparalleled flexibility offered by modern digital processing systems, it is apt to consider whether a different way of treating the signals from antennas in an array might be fruitful in current and future radio telescopes. Such methods potentially avoid the unfavourable N2 scaling of computation rate with array size. In this thesis I examine the prospect of using direct-imaging methods to map the sky without first generating correlation matrices. These methods potentially provide great computational savings by creating images using efficient, FFT-based algorithms. This thesis details the design and deployment of such a system for the Basic Element of SKA Training II (BEST-2) array in Medicina, Italy. Here the 32-antenna BEST-2 array is used as a test bed for comparison of FX correlation and direct-imaging systems, and to provide a frontend for a real-time transient event detection pipeline. Even in the case of traditional O(N2) correlation methods, signal processing algorithms can be significantly optimized to deliver large performance gains. In this thesis I present a new mechanism for optimizing the cross-correlation operation on Field Programmable Gate Array (FPGA) hardware. This implementation is shown to achieve a 75% reduction in multiplier usage, and has a variety of benefits over existing optimization strategies. Finally, this thesis turns its focus towards The Square Kilometre Array (SKA). When constructed, the SKA will be the world's largest radio telescope and will comprise a variety of arrays targeting different observing frequencies and science goals. The low-frequency component of the SKA (SKA-low) will feature ~250,000 individual antennas, sub-divided into a number of stations. This thesis explores the impact of the station size on the computational requirements of SKA-low, investigating the optimal array configuration and signal processing realizations.
18
Долгушев, М. "Телескоп". Thesis, Сумский государственный университет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/38880.
Testo completoAbstract (sommario):
Современную астрономию невозможно представить без зрительных труб (телескопов). Уже Галилей, первым применивший зрительную трубу для наблюдения небесных тел, сделал ряд важных открытий. Хотя его телескоп обладал увеличением всего в 30 раз и с нашей точки зрения давал весьма плохое качество изображения. Современные телескопы имеют огромные размеры и представляют собой весьма сложное сооружение.
19
Lee, Aizeret, University of Western Sydney, of Science Technology and Environment College e 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.
Testo completoAbstract (sommario):
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 lossesMaster of Engineering (Hons)
20
Rodríguez, Gonzálvez Carmen. "Analysis of cosmic microwave background observations with the Arcminute Microkelvin Imager". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609911.
Testo completo
21
Liu, Kuo. "Exploring pulsar-black hole binaries using the next generation of radio telescopes". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/exploring-pulsarblack-hole-binaries-using-the-next-generation-of-radio-telescopes(90168fce-f8b9-4cea-a83d-773bf5368055).html.
Testo completoAbstract (sommario):
Binary pulsars are well known for their usefulness in testing gravitational theories. Pulsar-black hole (PSR-BH) binary systems, once discovered, will be the 'next generation of celestial laboratories' being able to both probe BH properties and test gravity especially General Relativity's cosmic censorship conjecture and no-hair theorem. The achievement of these prized goals requires highly precise pulsar timing observations, which are more readily achieved with the next generation of radio telescopes such as the Square Kilometre Array (SKA) and the Five-hundred-metre Aperture Spherical Radio Telescope (FAST). The purpose of work carried out in this thesis is to investigate the limits on precision timing and to explorethe potential for tests of theories of gravity by PSR-BH binaries with the future telescopes. Millisecond pulsars (MSPs) are more stable timers compared with normal pulsars. While the precision of MSP timing with present hardware is mainly limited by radiometer noise, for the brightest few MSPs one can already notice effects from other aspects, which can be separated into three categories: intrinsic noise from the pulsar, variations of the interstellar medium (ISM) effects, and instrumental artefacts. The case study based on the brightest MSP, PSR J0437-4715, demonstrates that most instrument-associated uncertainties in pulse time-of-arrival (TOA) measurement can be corrected by state-of-the-art techniques. The influence on TOAs by the interstellar medium (ISM) is shown to be unimportant for the source, and can potentially be corrected by approaches which are being developed. The TOA uncertainties for most MSPs observed with the next generation of radio telescopes, will mainly be limited by pulse jitter and radiometer noise. Based on this result, it is predicted that for normal-brightness MSPs a TOA precision of between 80 and 230 ns can be achieved at 1.4 GHz with 10-minute integrations by the SKA. With the current sensitivity, a further investigation on pulse jitter has been performed, regarding both the shape and central phase variability of several MSPs. No significant shape changes within a few hours observing time have been detected based on 10 to 100 s integrations. For PSR J0437-4715 the jitter parameter is quantified as f_J = 0.067+-0.002, based on timing on short timescales. Potential instrumental effects on this measurement have also been demonstrated. Jitter noise is found to be independent of observing frequency and bandwidth around 1.4 GHz on frequency scales of < 100 MHz, suggesting that the resulting uncertainty might not be mitigated by extending the observing bandwidth. Through detailed simulations, it has been found that timing a pulsar in orbit around a stellar mass BH (SBH) binary system with the next generation of radio telescopes can lead to a high precision determination of the BH mass and spin in ten years. Especially for MSPs, the measurements of mass and spin can be allowed for wide orbits of orbital period up to roughly ten days. The constrain on BH quadrupole moment is possible only with timing precisions achievable with MSPs, and for systems of either high-mass (e.g. ~80 solar mass) SBH or high orbital eccentricity. Meanwhile, timing a normal pulsar orbiting around the Galactic Centre BH, Sgr A*, with the SKA would lead to the extraction of the BH mass, spin and quadrupole moment within five years. Considering the perturbation from other stellar masses in the Galactic Centre region, these measurements could be converted to a test of the no-hair theorem with ~1% precision.
22
Lee, Aizeret. "Radioastronomical instrumentation : the diagonal horn". Thesis, View thesis, 2002. http://handle.uws.edu.au:8081/1959.7/699.
Testo completoAbstract (sommario):
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
23
Makhathini, Sphesihle. "Advanced radio interferometric simulation and data reduction techniques". Thesis, Rhodes University, 2018. http://hdl.handle.net/10962/57348.
Testo completoAbstract (sommario):
This work shows how legacy and novel radio Interferometry software packages and algorithms can be combined to produce high-quality reductions from modern telescopes, as well as end-to-end simulations for upcoming instruments such as the Square Kilometre Array (SKA) and its pathfinders. We first use a MeqTrees based simulations framework to quantify how artefacts due to direction-dependent effects accumulate with time, and the consequences of this accumulation when observing the same field multiple times in order to reach the survey depth. Our simulations suggest that a survey like LADUMA (Looking at the Distant Universe with MeerKAT Array), which aims to achieve its survey depth of 16 µJy/beam in a 72 kHz at 1.42 GHz by observing the same field for 1000 hours, will be able to reach its target depth in the presence of these artefacts. We also present stimela, a system agnostic scripting framework for simulating, processing and imaging radio interferometric data. This framework is then used to write an end-to-end simulation pipeline in order to quantify the resolution and sensitivity of the SKA1-MID telescope (the first phase of the SKA mid-frequency telescope) as a function of frequency, as well as the scale-dependent sensitivity of the telescope. Finally, a stimela-based reduction pipeline is used to process data of the field around the source 3C147, taken by the Karl G. Jansky Very Large Array (VLA). The reconstructed image from this reduction has a typical 1a noise level of 2.87 µJy/beam, and consequently a dynamic range of 8x106:1, given the 22.58 Jy/beam flux Density of the source 3C147.
24
Van, Tonder Vereese. "Beamforming for radio astronomy". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/96126.
Testo completoAbstract (sommario):
Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: Beamforming is a technique used to combine signals from an array of antennas to effectively synthesize a single aperture and beam. In the Radio Astronomy community the technique is used to obtain a desirable beam pattern as well as to electronically point the beam of an array. Next generation radio telescopes such as the Square Kilometre Array (SKA) surpass current technology and will extensively make use of beamforming techniques. Various factors determine the output of a beamformer; however, given an array with a fixed configuration only the weights applied to the incoming signals affect the synthesized aperture and beam. Furthermore, the incoming data must be processed in real-time, at a rate equal to the input-output rate of the processor. Both the weighting function and the real-time implementation of beamforming, are the primary subjects of this thesis. In this thesis various deterministic weighting functions are investigated. The algorithms are implemented in a matlab program, serving as a simulation tool for investigating the techniques. The program is verified by comparing the expected theoretical outcomes to the simulated output. For the program the following functionalities are included: a steering technique, spectral weighting, Dolph-Chebychev, and the Least Square Error algorithm. Applications of these techniques is investigated and their prominence in the Radio Astronomy community is established. For the real-time beamformer implementation, the UniBoard platform configured with beamformer firmware, is investigated. This is important as the UniBoard is an excellent example of a beamformer implementation within the Radio Astronomy community. The architecture is used to emulate a linear array by implementing a python control script, where the output corresponded accurately with the expected theoretical values. The thesis also constitutes the design and implementation of a digital frequency domain beamformer on the ROACH board. This processing board is employed by the Karoo Array Telescope (KAT-7) in South Africa. This work is therefore important as it demonstrates a beamformer implementation on an architecture in use by the Radio Astronomy community. An antenna array is designed and built for the verification of the beamformer design. Results with a good degree of accuracy were obtained and where errors exist they are discussed.
AFRIKKANSE OPSOMMING: Bundelvorming is ’n tegniek waarmee die seine van ’n antenna samestelling gekombineer word om ’n enkele effektiewe stralingsvlak en stralingspatroon te sintiseer. In die Radio Astronomie gemeenskap word die tegniek gebruik om ’n gewenste stralingspatroon te sintiseer sowel as om die rigting van die patroon elektronies te beheer. Die Square Kilometre Array (SKA) is ’n toekomstige radioteleskoop en sal grootliks gebruik maak van bundelvorming tegnieke. Die uitset van bundelvormers word geaffekteer deur verskeie faktore, maar vir ’n gegewe samestelling is dit net die gewigsfunksies wat toegepas word op die inkomende seine wat die gesintiseerde patroon kan beheer. Verder moet die inkomende data verwerk word teen ’n tempo gelykstaande aan die inset-en-uitsetkoers van die verwerker. Die gewigsfunksie so wel as die implementasie van die bundelvormer is albei primêre onderwerpe van die tesis. ’n Verskeindenheid van deterministiese bundelvormingstegnieke sal ondersoek word in hierdie tesis. Die algoritmes is in ’n matlab program geïmplementeer vir simulasie doeleindes. Die program is geverifieër deur die uitset te vergelyk met die verwagte teoretiese waardes. Die program sluit die volgende funksies in: ’n rigting beheer algoritme, spektraalgewigte, Dolph-Chebychev, en die minste vierkantsfout algoritme. Hierdie tegnieke is van belang weens hul toepassing in die Radio Astronomie gemeenskap. Vir die implementasie van ’n bundelvormer is die UniBoard hardeware, geprogrameer in ’n bundelvormings modus, van gebruik gemaak. Hierdie aspek is belangrik omdat die Uni- Board ’n goeie voorbeeld van ’n geïmplementeerde bundelvormer in die Radio Astronomie gemeenskap is. Die UniBoard word gebruik om ’n lineêre samestelling te emuleer deur in python ’n beheer skrip te skryf, waar die uitset van die emuleerder akkuraat ooreenstem met die verwagte waardes. Die tesis behels ook die ontwerp en implementasie van ’n digitale frekwensiegebied bundelvormer op die ROACH platform. Hierdie verwerker word tans gebruik in die Karoo Array Telescope (KAT-7) in Suid-Afrika. Hierdie werk is dus belangrik omdat dit die implementasie van ’n bundelvormer op tegnologie wat huidiglik in die Radio Astronomie gemeenskap gebruik word demonstreer. Daarbenewens is ’n antenna samestelling ontwerp en gebou om die bundelvormer te verifieër. Die resultate is akkuraat tot ’n redelike mate. Waar daar ’n fout onstaan het word dit in die tesis bespreek.
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Angioni, Roberto. "High-energy view of radio galaxies: prospects for the new generation of Cherenkov telescopes". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8834/.
Testo completoAbstract (sommario):
I Nuclei Galattici Attivi (AGN) sono sorgenti luminose e compatte alimentate dall'accrescimento di materia sul buco nero supermassiccio al centro di una galassia. Una frazione di AGN, detta "radio-loud", emette fortemente nel radio grazie a getti relativistici accelerati dal buco nero.
I Misaligned AGN (MAGN) sono sorgenti radio-loud il cui getto non è allineato con la nostra linea di vista (radiogalassie e SSRQ). La grande maggioranza delle sorgenti extragalattiche osservate in banda gamma sono blazar, mentre, in particolare in banda TeV, abbiamo solo 4 MAGN osservati. Lo scopo di questa tesi è valutare l'impatto del Cherenkov Telescope Array (CTA), il nuovo strumento TeV, sugli studi di MAGN.
Dopo aver studiato le proprietà dei 4 MAGN TeV usando dati MeV-GeV dal telescopio Fermi e dati TeV dalla letteratura, abbiamo assunto come candidati TeV i MAGN osservati da Fermi. Abbiamo quindi simulato 50 ore di osservazioni CTA per ogni sorgente e calcolato la loro significatività.
Assumendo una estrapolazione diretta dello spettro Fermi, prevediamo la scoperta di 9 nuovi MAGN TeV con il CTA, tutte sorgenti locali di tipo FR I. Applicando un cutoff esponenziale a 100 GeV, come forma spettrale più realistica secondo i dati osservativi, prevediamo la scoperta di 2-3 nuovi MAGN TeV.
Per quanto riguarda l'analisi spettrale con il CTA, secondo i nostri studi sarà possibile ottenere uno spettro per 5 nuove sorgenti con tempi osservativi dell'ordine di 250 ore.
In entrambi i casi, i candidati migliori risultano essere sempre sorgenti locali (z<0.1) e con spettro Fermi piatto (Gamma<2.2).
La migliore strategia osservativa per ottenere questi risultati non corrisponde con i piani attuali per il CTA che prevedono una survey non puntata, in quanto queste sorgenti sono deboli, e necessitano di lunghe osservazioni puntate per essere rilevate (almeno 50 ore per studi di flusso integrato e 250 per studi spettrali).
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Martinez, Jose Guadalupe [Verfasser]. "Pulsar Searching and Timing with the Arecibo and Effelsberg Radio Telescopes / Jose Guadalupe Martinez". Bonn : Universitäts- und Landesbibliothek Bonn, 2019. http://d-nb.info/1194464866/34.
Testo completo
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Lee, Aizeret. "Radioastronomical instrumentation : the diagonal horn /". View thesis, 2002. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20031003.112749/index.html.
Testo completo
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Hungwe, Faith. "Variability analysis of a sample of potential southern calibration sources". Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1005281.
Testo completoAbstract (sommario):
A considerable number of Very Long Baseline Interferometry (VLBI) surveys have been conducted in the northern hemisphere and very few in the southern hemisphere mostly because of a lack of telescopes and therefore adequate baseline coverage. Thus there is a deficit of calibrator sources in the southern hemisphere. Further, some of the most interesting astronomical objects eg. the galactic centre and the nearest galaxies (the small and large Magellanic Clouds) lie in the southern hemisphere and these require high resolution studies. With a major expansion of radio astronomy observing capability on its way in the southern hemisphere (with the two SKA (Square Kilometre Array) precursors, meerKAT (Karoo Array Telescope) and ASKAP (Australian SKA Pathfinder), leading to the SKA itself) it is clear that interferometry and VLBI in the southern hemisphere need a dense network of calibration sources at different resolutions and a range of frequencies. This work seeks to help redress this problem by presenting an analysis of 31 southern sources to help fill the gaps in the southern hemisphere calibrator distribution. We have developed a multi-parameter method of classifying these sources as calibrators. From our sample of 31 sources, we have 2 class A sources (Excellent calibrators), 16 class B sources (Good calibrators), 9 class C sources (Poor calibrators) and 4 class D sources (Unsuitable calibrators).
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Black, Richard Allen. "Digital Back End Development and Interference Mitigation Methods for Radio Telescopes with Phased-Array Feeds". BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4233.
Testo completoAbstract (sommario):
The Brigham Young University (BYU) Radio Astronomy group, in collaboration with Cornell University, the University of Massachusetts, and the National Radio Astronomy Observatory (NRAO), have in recent years developed and deployed PAF systems that demonstrated the advantages of PAFs for astronomy. However, these systems lacked the necessary bandwidth and acquisition times to be scientifically viable. This thesis outlines the development of a 20-MHz bandwidth system that can acquire for much longer periods of time and across much larger bandwidths than previous BYU systems. A report of the deployment of this system on the 305-meter reflector at the Arecibo Observatory in Puerto Rico is also summarized.The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is currently constructing a PAF-equipped synthesis imaging array named the Australian Square Kilometre Array Pathfinder (ASKAP) that offers great promise for widening FOVs and enhancing RFI mitigation techniques. Previous work in RFI mitigation has demonstrated effective cancellation for synthesis imaging arrays under the assumption that the processing bandwidth is narrowband and correlator dump times are short. However, these assumptions do not necessarily reflect real-world instrument limitations. This thesis explores simulated adaptive array cancellation algorithm effectiveness as applied on the ASKAP instrument given realistic bandwidths and correlator dump times. The results demonstrate that active RFI mitigation performed across long baselines is largely ineffectual.
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Janse, van Vuuren Frank. "Design of a hexapod mount for a radio telescope". Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6693.
Testo completoAbstract (sommario):
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011.ENGLISH ABSTRACT: The world's astronomy community is working together to build the largest and most sensitive radio telescope in the world namely: the SKA (Square Kilometre Array). It will consist of approximately three thousand dishes which will each require accurate positioning. The Square Kilometer Array has a testbed called the Phased Experimental Demonstrator (PED) in Observatory, Cape Town. A hexapod positioning mechanism is required to position a 3.7 m radio telescope which forms part of an array of seven radio telescopes. This thesis details the design process of the hexapod system. The design consists of the mechanical design of the joints and linear actuators, a kinematic and dynamic model, a controller and a user interface. In order to verify the design for the PED hexapod a scaled prototype was designed, built and tested. The hexapod's repeatability as well as ability to track a path was tested using an inclinometer. The tests confirmed the design feasibility of the PED hexapod and also highlight issues that require care when constructing the full scale hexapod, such as the amount of play in the platform joints. The designed full scale hexapod will have an error angle less than 0.13°, a payload capacity of 45 kg, withstand wind speeds of 110 km/h and cost R160 000.
AFRIKAANSE OPSOMMING: Die wêreld se sterrekundige gemeenskap is besig om saam te werk om die grootste en mees sensitiewe radioteleskoop in die wêreld te bou, naamlik: die SKA (Square Kilometre Array). Dit sal uit ongeveer drie duisend skottels bestaan wat elkeen akkurate posisionering benodig. Die SKA het 'n toetssentrum, genaamd die “Phased Experimental Demonstrator” in Observatory, Kaapstad. 'n Sespoot posisionering meganisme word benodig om die 3.7 m radioteleskoop te posisioneer, wat deel vorm van 'n stelsel van sewe radioteleskope. Hierdie tesis beskryf die proses om die sespoot stelsel te ontwerp. Die ontwerp bestaan uit die meganiese komponent van die koppelings en lineêre aktueerders, 'n kinematiese en dinamiese model, 'n beheerder, asook 'n gebruikersintervlak. 'n Geskaleerde prototipe is ontwerp, gebou en getoets om die ontwerp te verifieer. Die platform se herhaalbaarheid sowel as akkuraatheid om 'n pad te volg was getoets met 'n oriëntasie sensor. Die toetse het probleme uitgelig wat versigtig hanteer moet word gedurende die konstruksie van die volskaalse sespoot, veral die hoeveelheid speling in die koppelings. Die volskaalse sespoot ontwerp het 'n hoek fout van minder as 0.13°, 'n ladingsvermoë van 45 kg en kan 'n windspoed van 110 km/h weerstaan en kos R160 000.
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Thompson, Nicholas Christopher. "RFI mitigation in radio astronomy". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86637.
Testo completoAbstract (sommario):
Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Technical advances in electromagnetics, signal processing and processing power have led to a significant increase in sensitivity and accuracy in radio telescopes. With this increase in sensitivity, radio frequency interference (RFI) has become a much larger problem. The notable growth in wireless communication as well as self generated RFI has further escalated this problem. In order to utilise the full capabilities of modern radio telescopes, RFI mitigation is required on the captured signals. With the enormous data rates of modern radio telescopes, managing RFI has become increasingly difficult, and in order to utilise the full captured radio spectrum, more accurate RFI mitigation strategies will be necessary. The use of different RFI mitigation strategies is studied in the form of online and offline techniques. This includes Spectral Kurtosis, Spectral Flatness and the Var/SumThreshold method. The special case for RFI mitigation in timing pulsars will also be studied. These techniques are well known in the radio astronomy community; here, spectral kurtosis and spectral flatness will be implemented on the raw data as well as the post correlated data. System speed and accuracy will be the deciding factors when testing these methods as possible solutions to this problem.
AFRIKAANSE OPSOMMING: ‘n Toename in die sensitiwiteit van hedendagse radioteleskope kan toegedra word aan die tegniese bevordering in elktromagnetika en seinverwerking. Die toename in sensitiwiteit het egter tot die gevolg dat radiofrekwensiesteuring ‘n groter rol speel in hedendaagse radioteleskope. Die groei in die gebruik van radioverbindings asook die gevolge van self gei¨nduseerde radiofrekwensiesteuring dra ook verder by tot hierdie probleem. Radiofrekwensiesteuring matiging word toegepas op die opgevangde seine, om sodoende gebruik te maak van die volle kapasiteit van moderne radioteleskope. Die bestuur van radiofrekwensiesteuring word bemoeilik deur die groot hoeveelheid intydse data van die radioteleskope. Meer akurate radiofrekwensiesteuring matigingstegnieke word vereis om die bandwydte ten volle te hanteer. Daar word op ‘n aantal verskillende matingstegnieke gefokus. Hierdie tegenieke kan in twee kategorieë verdeel word, naamlik aanlyn- en aflyntegenieke. Onderafdelings van hierdie kategorieë sluit in: spektrale kurtose, spektrale matheid en “Var/SumThreshold”. Daar word ook na ‘n spesiale geval van radiofrekwensiesteuring matiging gekyk, in die opmeeting van tydsberekening-pulsars. Alhoewel hierdie tegnieke bekend is in die radioastronomie gemeenskap, word spektrale kurtose en spektrale matheid egter toegepas op die rou data sowel as postgekorreleerde data. Daar sal op stelsel spoed en akuratheid gefokus word, om vas te stel of hierdie metodes wel moontlike oplossings bied tot die probleem bespreek.
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McAlpine, Kim. "The SKA's the limit : on the nature of faint radio sources". Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1007271.
Testo completoAbstract (sommario):
From abstract: Within the next few years a large number of new and vastly more sensitive radio astronomy facilities are scheduled to come online. These new facilities will map large areas of the sky to unprecedented depths and transform radio astronomy into the leading technique for investigating the complex processes which govern the formation and evolution of galaxies. This thesis combines multi-wavelength techniques, highly relevant to future deep radio surveys, to study the evolution and properties of faint radio sources.TeX
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Caneva, Gessica De. "Studies of active galactic nuclei with the MAGIC telescopes". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17179.
Testo completoAbstract (sommario):
Schwerpunkt dieser Arbeit ist die Emission von hochenergetischer Gammastrahlung aus Aktiven Galaxienkernen, anhand von Beobachtungen mit den MAGIC Teleskopen. Aktive Galaxien entstehen durch die Freisetzung von Gravitationsenergie der Stellarmaterie, die in das zentrale Schwarze Loch fällt. Zwei diametral entgegengesetzte Jets strömen aus dem Kern. Falls einer von diesen Jets zum Beobachter zeigt, wird der aktive Galaxienkern als Blazar bezeichnet. In dieser Doktorarbeit wird die Analyse der MAGIC Beobachtungen von drei Blazaren präsentiert: der bisher unbekannte hochenergetische Blazar 1ES 1727+502 und die bekannten Objekte 3C 279 und PKS 1510-089. Die Quelle 1ES 1727+502 gehört zu der Unterklasse der BL Lac Objekte, die die zahlenmässig größte Klasse an extragalaktischen hochenergetische Objekten ist. Diese Entdeckung beweist, wie wichtig es ist, mehrere und verschiedene Kriterien für die Auswahl von Objekten zu benutzen. Der Blazar 1ES 1727+502 wurde aus einem X-ray Katalog ausgesucht, die Datennahme war unabhängig von dem Aktivitätsstatus der anderen Energiebänder. Die Blazare 3C 279 und PKS 1510-089 gehören zu der Unterklasse des Flat Spectrum Radio Quasars. Es gibt nur drei bekannte Flat Spectrum Radio Quasare. Die Entdeckung von Flat Spectrum Radio Quasaren ist schwierig, weil im leisen Zustand der hochenergetische Fluss niedrig ist. Während eines Flares steigt der Fluss in sehr kurzer Zeit um mehrere Größenordnungen an, deswegen ist die Beobachtung eines Flares schwer zu realisieren aber physikalisch äußerst interessant. Die MAGIC Beobachtungen sind mit Messungen aus anderen Energiebändern kombiniert. Mögliche Interpretationen des beobachteten Verhaltens werden diskutiert. Die Ergebnisse werden erläutert und mit historischen Beobachtungen verglichen. Die offenen Fragen und Probleme, die Ziel zukünftiger Studien sein sollen, werden am Schluss hervorgehoben.This PhD thesis addresses the problem of understanding the very high energy emission from active galactic nuclei as detected with the MAGIC telescopes. Active galactic nuclei are galaxies powered by the release of gravitational energy of stellar material falling into a black hole, located in their core. Two opposed jets extend from the central region outwards, if one of the them points towards the observer, the source is called a blazar. In this thesis the analysis of MAGIC observations of three different blazars is presented: the newly discovered very high energy blazar 1ES 1727+502, and the two known objects 3C 279 and PKS 1510-089. The source 1ES 1727+502 belongs to the subclass of BL Lac objects, the most numerous class of extragalactic very high energy emitters. This source was selected for observations from an X-ray catalogue and was observed even if no high activity states were reported at lower energies. For this reason, this discovery proves the importance of using several criteria for the selection of very high energy observation targets. The other two objects, 3C 279 and PKS 1510-089, belong to the subclass of flat spectrum radio quasars. We count only three representatives of this class in the very high energy domain. Their detection is critical because during quiescent states they have low flux levels at very high energies. During flaring states, flat spectrum radio quasars exhibit flux enhancements of orders of magnitudes and short time scales. Observations during such states, difficult to catch, are interesting because extreme processes are taking place. Very high energy observations of these three objects are complemented with measurements at lower energies and interpretations of the observed behaviours are discussed. The results are compared with historical observations, highlighting open questions and problems which should be addressed by future studies.
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Lord, Christopher John. "A low frequency array of simple radio telescopes for the detection of solar x-ray and radio flares and the study of the Ionosphere". Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/2102.
Testo completoAbstract (sommario):
The thesis: “A low frequency array of simple radio telescopes for the detection of solar X-ray and radio flares, and the study of the ionosphere”, describes the development of antennas, receivers and software for a radio telescope system that captures data from the 16 MHz to 30MHz radio spectrum to a personal computer. Three of these radio telescope systems were established at sites in Perth, Gingin and Learmonth, Western Australia.
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Tenenbaum, Emily Dale. "MILLIMETER WAVE STUDIES OF CIRCUMSTELLAR CHEMISTRY". Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194941.
Testo completoAbstract (sommario):
Millimeter wave studies of molecules in circumstellar envelopes and a planetary nebula have been conducted. Using the Submillimeter Telescope (SMT) of the Arizona Radio Observatory (ARO) on Mt. Graham, a comparative spectral survey from 215-285 GHz was carried out of the carbon-rich asymptotic giant branch star IRC +10216 and the oxygen-rich supergiant VY Canis Majoris. A total of 858 emission lines were observed in both objects, arising from 40 different molecules. In VY Canis Majoris, AlO, AlOH, and PO were detected for the first time in interstellar space. In IRC +10216, PH3 was detected for the first time beyond the solar system, and C3O, and CH2NH were found for the first time in a circumstellar envelope. Additionally, in the evolved planetary nebula, the Helix, H2CO, C2H, and cyclic-C3H2 were observed using the SMT and the Kitt Peak 12 m telescopes. The presence of these three molecules in the Helix suggests that relatively complex chemistry occurs in planetary nebulae, despite the harsh ultraviolet field. Overall, the research on molecules in circumstellar and planetary nebulae furthers our understanding of the nature of the material that is fed back into the interstellar medium from evolved stars. Besides telescope work, laboratory research was also conducted - the rotational spectrum of ZnCl was measured and its bond length and rotational constants were determined. Lastly, in partial fulfillment of a graduate certificate in entrepreneurial chemistry, the commercial applications of terahertz spectroscopy were explored through literature research.
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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.
Testo completoAbstract (sommario):
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.
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Bock, Douglas Carl-Johan. "Wide Field Aperture Synthesis Radio Astronomy". University of Sydney. Physics, 1998. http://hdl.handle.net/2123/377.
Testo completoAbstract (sommario):
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.
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Bock, Douglas Carl-Johan. "Wide Field Aperture Synthesis Radio Astronomy". Thesis, The University of Sydney, 1997. http://hdl.handle.net/2123/377.
Testo completoAbstract (sommario):
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.
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Volkmann, Mark Hans. "A superconducting software defined radio frontend with application to the Square Kilometre Array". Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85798.
Testo completoAbstract (sommario):
Thesis (PhD)-- Stellenbosch University, 2013.ENGLISH ABSTRACT: Superconducting electronics can make the Square Kilometre Array (SKA) a better instrument. The largest radio telescope in the world will consist of several arrays, the largest of which, consisting of more than 3000 dishes, will be situated primarily in South Africa. The ambitions of the SKA are grand and their realisation requires technology that does not exist today. Current plans see signals in the band of interest ampli ed, channelised, mixed down and then digitised. An all-digital frontend could simplify receiver structure and improve its performance. Semiconductor (analog-to-digital converters) ADCs continue to make great progress and will likely nd applications in the SKA, but superconductor ADCs bene t from higher clock speeds and quantum accurate quantisation. We propose a superconducting softwarede ned radio frontend. The key component of such a frontend is a superconducting ash ADC. We show that employing such an ADC, even a small- to moderately-sized one, will signi cantly improve the instantaneous bandwidth observable by the SKA, yet retain adequate signal-to-noise ratio so as to achieve a net improvement in sensitivity. This improvement could approach factor 2 when compared to conventional technologies (at least for continuum observations). We analyse key components of such an ADC analytically, numerically and experimentally and conclude that fabrication of such an ADC for SKA purposes is certainly possible and useful. Simultaneously, we address the power requirements of high-performance computing (HPC). HPC on a hitherto unprecedented scale is a necessity for processing the vast raw data output of the SKA. Utilising the ultra-low-energy switching events of superconducting switches (certain Josephson junctions), we develop rst demonstrators of the promising eSFQ logic family, achieving experimentally veri ed shift-registers and deserialisers with sub-aJ/bit energy requirements. We also propose and show by simulation how to expand the applicability of the eSFQ design concept to arbitrary (unclocked) gates.
AFRIKAANSE OPSOMMING: Supergeleier-elektronika kan 'n beter instrument maak van die \Square Kilometre Array" (SKA). Die wêreld se grootse radioteleskoop sal bestaan uit etlike skikkings, waarvan die grootste - met meer as 3 000 skottels - hoofsaaklik in Suid-Afrika gesetel sal wees. Die SKA is ambisieus en vereis tegnologie wat nog nie vandag bestaan nie. Volgens huidige planne sal seine in die band van belang versterk, gekanalisieer, afgemeng en dan versyfer word. 'n Heel-digitale kopstuk sal die ontvangerstruktuur kan vereenvoudig en sy prestasie kan verbeter. Halfgeleier analoog-na-digital omsetters (ADOs) verbeter voortdurend en sal waarskynlik toepassings in die SKA vind, maar supergeleier ADOs trek voordeel uit hoër klok spoed en kwantumakkurate kwantisering. Ons stel 'n supergeleier sagteware-gede nieerde radio kopstuk voor. Die sleutelkomponent van so 'n kopstuk is 'n supergeleier \ ash" ADO. Ons toon hoe die gebruik van so 'n ADO, selfs een van klein tot matige bisgrootte, die oombliklike bandwydte waarneembaar deur die SKA aansienlik sal verbeter en 'n voldoende sein-tot-ruis verhouding sal behou, en gevolglik 'n netto verbetering in sensitiwiteit sal bereik. Hierdie verbetering kan, vergeleke met konvensionele tegnologie, 'n faktor van 2 nader (ten minste vir kontinuum waarnemings). Ons analiseer belangrike komponente van so 'n ADO analities, numeries and eksperimenteel en lei af dat die vervaardiging van so 'n ADO vir SKA doeleindes beide moontlik en nuttig is. Terselfdertyd spreek ons die drywingsverkwisting van Hoë-verrigting rekenaars aan. Sulke rekenaars van 'n tot dusver ongekende skaal is 'n noodsaaklikheid vir die verwerking van die enorme rou data uitset van die SKA. Deur die gebruik van die ultra-lae-energie skakels van supergeleier skakelaars (sekere Josephson-vlakke), ontwikkel ons die eerste demonstratiewe hekke van die veelbelowende eSFQ logiese familie, en toon eksperimenteel bevestigte skuifregisters en deserieëliseerders met sub-aJ/bis energievereistes. Ons stel verder voor en wys met simulasies hoe om die toepaslikheid van die eSFQ ontwerpkonsep na arbitr^ere (ongeklokte) hekke uit te brei.
40
Baelemans, Rene Adrianus Cornelis. "Co-Design of Wideband Polarization-Agile Phased-Array Antennas and Low-Noise Amplifiers for the Next Generation Radio Telescopes". Thesis, Curtin University, 2022. http://hdl.handle.net/20.500.11937/89767.
Testo completoAbstract (sommario):
The next generation of radio-astronomy telescopes in the UHF or decimetre band require phased-array technologies which can provide a high sensitivity, large bandwidth, high polarization purity, and a large Field-of-View. To this end, this thesis will present and discuss the capacitively-connected dipole array including a novel small-scale intermediate experimental validation method and a comprehensive description of its performance as a radio-astronomy instrument.
41
Jew, Luke. "Measurements of diffuse galactic emission at 5 GHz with C-BASS". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:31f0227a-84be-421a-ae46-eebe9f422767.
Testo completoAbstract (sommario):
The C-Band All-Sky Survey (C-BASS) is a project to produce an all-sky map in intensity and polarization at a central frequency of 5 GHz with 1 GHz bandwidth and approximately 1 degree resolution. The central frequency is low enough for the map to be dominated by synchrotron and free-free emission but high enough so that Faraday rotation and depolarization are small across most of the sky. The C-BASS map will enable a more accurate removal of contaminating foregrounds from measurements of the cosmic microwave background, particularly in polarization where the B-mode signal from inflation is likely to be orders of magnitude weaker than the diffuse Galactic foreground emission. To produce an all-sky map from the ground requires two telescopes, one in the northern and one in the southern hemisphere. This thesis focuses on analysis of C-BASS North data. The noise properties of time-ordered data are characterised by fitting a noise model to periodograms. Using simulations, the errors introduced into the C-BASS maps by a destriping mapmaker are quantified and we reduce the signal error by masking the brightest pixels during baseline offset estimation. Jackknife tests are used to test the C-BASS data for systematics and to test the accuracy of the sensitivity maps. In total intensity, the spectral index of diffuse Galactic emission between 5 GHz and 408 MHz is measured using an extended T-T plot method and the results are compared to simulations. The spectral index of polarized diffuse Galactic emission between 5 GHz and 30 GHz is estimated in 55 arcminute pixels, modelling the polarized intensity as a Rician random variable.
42
Nigro, Cosimo. "Study of Persistent and Flaring Gamma-Ray Emission from Active Galactic Nuclei with the MAGIC Telescopes and Prospects for Future Open Data Formats in Gamma-Ray Astronomy". Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/20582.
Testo completoAbstract (sommario):
Angetrieben durch die Akkretion von Materie in ein super massives Schwarzes Loch in ihrem Zentrum, stellen aktive Galaxien die stärksten und beständigsten Strahlungsquellen im Universum dar. Ihre elektromagnetische Emission kann sich bis in den Gammastrahlenbereich ausbreiten. Das Ziel dieser Arbeit ist, diese Mechanismen und die Orte jenseits der hoch energetischen Emission zu charakterisieren. Dafür werden die Observationen von zwei Aktiven Galaxien im Bereich von hunderten von GeV verwendet, welche mit den Cherenkov Teleskopen MAGIC aufgenommen wurden. Die physikalische Interpretation wird durch Beobachtungen mit dem Fermi Gamma-ray Space Teleskop und durch Multiwellenlängendaten unterstützt. Es werden zwei Aktive Galaxien mit Jet untersucht: PKS 1510-089 und NGC 1275. Die MAGIC Teleskope, welche PKS 1510-089 seit 2012 immer wieder beobachten, detektieren eine signifikante Emission über dutzende von Observationsstunden, was auf schwache aber kontinuierliche Gammastrahlung aus dieser Quelle hinweist. NGC 1275 zeigte in der Periode von September 2016 bis Februar 2017 einen großen Ausbruch im Gammerstrahlenbereich: MAGIC zeichnete eine Variabilität in der Größenordnung von wenigen Stunden und die erstmalige Emission von TeV Photonen. Aus beiden untersuchten Quellen ist ersichtlich, dass die Kombination von Daten aus verschiedenen Instrumenten die physische Diskussion entscheidend beeinflusst. Der Übergang zu zugänglichen und interoperablen Daten wird zu einem zwingenden Thema für Gammastrahlenastronomen, und diese Arbeit stellt das technische Bestreben dar, standardisierte hochrangige Daten für Gammastrahleninstrumente zu erzeugen. Ein Beispiel für eine zukünftige Analyse, die einheitliche High-Level-Daten von einem Gammastrahlensatelliten und vier Cherenkov-Teleskopen kombiniert, wird vorgestellt. Der neue Ansatz, der vorgeschlagen wird, führt die Datenanalyse durch und verbreitet die Ergebnisse, wobei nur Open-Source-Ressourcen verwendet werden.Powered by the accretion of matter to a supermassive black hole, active galactic nuclei constitute the most powerful and persistent sources of radiation in the universe, with emission extending in the gamma-ray domain. The aim of this work is to characterise the mechanisms and sites beyond this highly-energetic radiation employing observations of two galaxies at hundreds of GeV, conducted with the MAGIC imaging Cherenkov telescopes. The physical interpretation is supported with observations by the Fermi Gamma-ray Space Telescope and with multi-wavelength data. Two peculiar jetted galaxies are studied: PKS 1510-089 and NGC 1275. The first source, monitored by MAGIC since 2012, presents a significant emission over tens of observation hours, in what appears to be a low but persistent gamma-ray state. The second source has instead shown, in the period between September 2016 and February 2017, a major outburst in its gamma-ray activity with variability of the order of few hours and emission of TeV photons. The broad band emission of jetted galaxies is commonly modelled with the radiative processes of a population of electrons accelerated in the jet. While PKS 1510-089 conforms to this scenario, modelling the gamma-ray outburst of NGC 1275 requires placing the acceleration and radiation of electrons close to the event horizon of the black hole. From both the sources studied it is evident that the combination of data from different instruments critically drives the physical discussuion. Moving towards accessible and interoperable data becomes a compelling issue for gamma-ray astronomers and this thesis presents the technical endeavour to produce standardised high-level data for gamma-ray instruments. An example of a future analysis combining uniformed high-level data from a gamma-ray satellite and four Cherenkov telescopes is presented. The novel approach proposed performs the data analysis and disseminates the results making use only of open-source assets.
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Botha, Antheun. "Development of a real-time transient analyser for the SKA". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86462.
Testo completoAbstract (sommario):
Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The extension of the Karoo Array Telescope (KAT), MeerKAT, will be the most sensitive radio telescope in the southern hemisphere until it is superseded by the completion of the Square Kilometre Array (SKA). These instruments are to be constructed in the Karoo which is an area in South-Africa that is protected against Radio Frequency Interference (RFI) by the Astronomy Geographical Advantage (AGA) act. However, the telescope is also vulnerable to self-generated interference and specialised measurement systems are required to monitor RFI levels. The development of a ReAl Time Transient AnalYser (RATTY) is described and two Experimental Development Models (XDM) are compared. The first uses a mixing philosophy, and the second direct-sampling. The selection of these models was based on the evaluation of several analogue Front-End (FE) designs. A stripline-filter design process is presented along with the results obtained for custom filters developed for the FEs. Several analyses were compared to measurements performed with one of the devices and good agreement was shown between the system characteristics. Issues regarding the Spurious Free Dynamic Range (SFDR) of the FE designs were identified in the process and measurement-corrected simulations used to predict the achievable ranges. The outcome of the XDM comparison promotes the continued development of a direct-sampling strategy to fulfil the short-term goals of the project. A static calibration procedure is demonstrated for the mixing system and implemented to account for different FE configurations. An overview of the digital and software components of the RATTY system is given and Electromagnetic Compatibility (EMC) principles are applied during the construction of both systems.
AFRIKAANSE OPSOMMING: Die finale fase van die Karoo Reeks Teleskoop (KAT), MeerKAT, sal die sensitiefste radio teleskoop in die suidelike halfrond wees. Dit sal egter oortref word deur die vierkante kilometer reeks, wat die sensitiefste radio teleskoop ter wêreld sal word. Beide instrumente sal vatbaar wees vir radiofrekwensie steurings en sal opgerig word in ‘n wet-beskermde omgewing. Die teleskope is ook vatbaar vir radiofrekwensie steurings wat deur interne stelsels opgewek kan word. Dus word gespesialiseerde meetapparate benodig om die betrokke area en substelsels van die teleskope te monitor. Die ontwikkeling van ‘n meetinstrument vir die ontleding van kort-durasie tydseine (RATTY) word beskryf en twee eksperimentele ontwikkelings modelle word vergelyk. Hierdie modelle is gebaseer op die verfyning van voorafgaande ontwerpe vir die analoog substelsel van die instrument en hierdie proses word verduidelik. Die eerste model volg ‘n menger strategie waar die tweede model direkte-monstering implementeer. ‘n Dubbel-laag, mikrostrookfilter ontwerpsproses word beskryf en die gemete resultate vir die ontwikkelde filters word bespreek. Verskeie ontledings is aangewend en vergelyk met die gemete resultate van die stelsels. Hieruit word bevredigende ooreenkomste getref. Die beperkings van die modelle, weens interne distorsie, word geïdentifiseer in dié proses en verdere skattings word gemaak d.m.v. simulasies. Die eksperimentele modelle word vergelyk en die voorkeur van ‘n direkte-monsterings stelsel word gemotiveer. Die digitale en sagteware komponente word oorsigtelik behandel. Tydens die konstruksie van die modelle word die toepassing van elektromagnetiese verenigbaarheids beginsels verduidelik. Laastens word ‘n eenvoudige kalibrasie toegepas op die menger stelsel en ‘n toepassing daarvan word behandel.
44
Ranka, Trupti. "Disturbance Rejection Control for The Green Bank Telescope". Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1459556332.
Testo completo
45
Matthysen, Nardus. "Time domain metrology for MeerKAT systems". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95963.
Testo completoAbstract (sommario):
Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: This work in this study covers a powerful technique to derive propagation and scattering information in an expedient fashion. Expedient because time-domain (TD) data gathers a broad spectrum in a single transmitted pulse. TD has been criticised because of a lack of dynamic range, which has now been overcome by the direct sampling system, RATTY and RTA. This study focuses on the investigation of a TD metrology system, to assist with the characterisation of MeerKAT systems. The elementary components of the system include a fast-rising impulse generator that was coupled with an impulse radiating antenna (IRA). The system was calibrated and tested before practical measurements and preliminary testing in the Karoo were done. For TDmetrology a larger bandwidth accelerates measurements without the loss of accuracy. The pulse generator’s (PG’s) fundamental components are an avalanche transistor and a step recovery diode (SRD), to sharpen the leading edge of the pulse. Improving the rise-time of a pulse increases its bandwidth in the spectrum. The external circuitry around these components is pivotal and it determines the shape, amplitude and rise-time of the pulse. In the course of the investigation, the general circuitry around the PG was improved to obtain the best possible pulse for measurements inside a reverberation chamber (RC) and for measurements in the Karoo. In light of this, a second and third PG source were obtained. For measurements in the Karoo, a larger amplitude pulse was required to increase the spectral content and this is essential for propagation measurements over distance and the shielding effectiveness (SE) of structures. Stacking avalanche transistors allow larger amplitude pulses and it improves the dynamic range of the spectrum. A PG incorporating stacked avalanche transistors, was designed, built and measured to assist with RC and small-scale field measurements in the Karoo. The third PG was bought for the practical measurements in the Karoo. The PG produces kilovolt pulses with pico-second rise-times that extend the spectral range of the current PGs at our disposal. With these PGs, an antenna is required for the radiation of impulse-like transients. The IRA is a high-gain large-bandwidth antenna. The IRA consists of a parabolic reflector, conical-plate transmission lines that are terminated through resistors onto the dish, and a feeding balun. The IRA design was thoroughly discussed and a first model for metrology was designed, measured and optimised. The IRA was also simulated with computation software code, FEKO. Before deployment of theTDsystem, calibration and characterisation measurements are required. The measuring devices used within this study were sampling oscilloscopes and direct sampling systems. The limitations of each device were explored and are discussed. The final measurements that were conducted contribute to work related to the SKA. This incorporated antenna pattern calibration, propagation over distance and the SE of a berm built from Karoo soil. The system investigated the propagation attenuation over the Karoo soil and vegetation, with great promise. A broad spectrum was measured over a few kilometres and compared to free-space loss. The SE of the berm covered the same spectral bandwidth. In this measurement, scattering effects and knife-edge diffraction were observed.
AFRIKAANSE OPSOMMING: Die werk in hierdie studie dek ’n kragtige tegniek wat gebruik kan word om die voortplanting en die verstrooiingsinligting van elektromagnetiese golwe op ’n voordelige manier af te lei. Dit is voordelig, want tydgebieddata versamel ’n wye spektrum in ’n enkele oordraagbare puls. Tydgebied is in die verlede baie gekritiseer omdat dit ’n dinamiese reikwydte kortkom en dit is nou oorwin deur die direkte steekproefnemingstelsel, RATTY en RTA. Hierdie studie fokus op die ondersoek van ’n tydgebiedmetingssisteem en dit help met die karakterisering van MeerKAT sisteme. Die elementêre komponente van die sisteem bestaan uit ’n vinnig-stygende impulsgenerator wat gekoppel is aan ’n impulsuitstralende-antenna (IRA). Die sisteem is gekalibreer en getoets voordat praktiese metings en toetse in die Karoo uitgevoer kon word. Vir tydgebiedmetings versnel ’n groter bandwydte die metings sonder om die akkuraatheid daarvan te beïnvloed. Die pulsgenerator se fundamentele komponente is ’n stortvloedtransistor en ’n stap-herstel diode (SRD) wat die voorpunt van die puls verskerp. Die eskterne stroombaan rondom hierdie komponente is noodsaaklik en dit bepaal die vorm, amplitude en die stygtyd van die puls. Deur die loop van hierdie ondersoek is die algemene stroombaan rondom die puls verbeter, om die beste moontlike puls vir metings binne in die weerkaatsingskamer en vir metings in die Karoo, te verkry. Na aanleiding van dit is ’n tweede en derde pulsgenerator bron verkry. Vir die metings in die Karoo is ’n puls met ’n groter amplitude vereis om die spektrale inhoud te vermeerder. Dit is noodsaaklik vir elektromagnetiese golf voortplantingsmetings oor afstand asook die beskermings effektiwiteit (SE) van die strukture. Stapel-stortvloed transistors skep pulse met groter amplitudes en dit verbeter die dinamiese reikwydte van die spektrum. ’n Pulsgenerator wat gestapelde stortvloedtransistors insluit is ontwerp, gebou en gemeet om te help met metings in die weerkaatsingskamer en kleinskaal veldmetings in die Karoo. Die derde pulsgenerator is gekoop vir praktiese metings in die Karoo. Die pulsgenerator vervaardig kilovolt pulse met pikosekond stygtye, wat die reikwydte van die spektrum van ons huidige puls uitbrei. Hierdie pulsgenerators vereis ’n antenna vir die uistraling van impulsagtige seine. Die IRA is ’n hoë-wins, groot-bandwydte antenna. Die IRA bestaan uit ’n paraboliese weerkaatser, konieseplaat transmissielyne wat deur weerstande op die skottel getermineer word, asook ’n voedings "balun". Die IRA ontwerp is deeglik bespreek en ’n model is ontwerp, gemeet en verbeter. Die IRA is ook gesimuleer met behulp van ’n rekenaarsagtewareprogram, FEKO. Voordat die tydgebiedsisteem benut kan word, moet dit gekalibreer word en karakteriseringsmetings moet ook daarmee uitgevoer word. Die meetinstrumente wat in hierdie studie gebruik is, is steekproefneming-ossilloskope en direkte steekproefneming-sisteme. Die tekortkominge van elke instrument is ondersoek en bespreek. Die finale meting wat uitgevoer is, dra by tot die werk wat geassosieer word met die SKA. Dit behels antennapatroonkalibrasie, voortplanting van elektromagnetiese golwe oor afstand en die SE van ’n "berm"wat gebou is uit Karoo-grond. Hierdie sisteem is gebruik om die voortplantings-verswakking oor die Karoo-grond en plantegroei te ondersoek en dit lyk baie belowend. ’nWye spektrumis oor ’n paar kilometer gemeet en dit is met wrywinglose ruimte vergelyk. Die SE van die "berm"het dieselfde spektrale bandwydte gedek. In hierdie meting is verstrooiingseffekte en mespunt-diffraksie waargeneem.
46
Mathys, Sebastian [Verfasser]. "Optimization of the AERA data at the Pierre Auger Observatory - Developing a new interface for data handling and improving the radio reconstruction based on data measured by fluorescence telescopes / Sebastian Mathys". Wuppertal : Universitätsbibliothek Wuppertal, 2019. http://d-nb.info/1186720883/34.
Testo completo
47
Lindén, Henrik. "Ångström Small Radio Telescope". Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-154732.
Testo completoAbstract (sommario):
For the Swedish Institute of Space Physics and Uppsala University, we have developed a working radio astronomy telescope capable of receiving the 21cm hydrogen line; the Ångström Small Radio Telescope. The work have resulted in a functional system for positioning the dish, with built in tracking of deep space objects and scanning functions, and signal reception with filtering, mixing and digital sampling. The system is controlled via a computer through an Internet connection.
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Feliachi, Rym. "Traitement spatial des interférences cyclostationnaires pour les radiotélescopes à réseau d'antennes phasé". Phd thesis, Université d'Orléans, 2010. http://tel.archives-ouvertes.fr/tel-00578950.
Testo completoAbstract (sommario):
Cette thèse est une contribution à l'amélioration des observations pour les radiotélescopes à réseaux phasés en présence d'interférences. L'originalité de cette thèse repose sur l'utilisation de la séparation spatiale entre les sources cosmiques et les brouilleurs issus des télécommunications en se basant sur la cyclostationnarité de ces derniers. Cette thèse s'inscrit dans le cadre du projet européen SKADS pour l'amélioration des techniques de suppression d'interférences en radioastronomie pour les futurs instruments d'observations.Nous avons proposé trois techniques de traitement d'interférences : la détection,l'estimation et la soustraction, et le filtrage spatial. Les performances des techniques proposées ont été évaluées à travers des simulations sur des données synthétiqueset/ou réelles, et comparées aux techniques existantes.
49
CIORBA, LORENZO. "UAV-based Far-Field and Near-Field Antenna Measurements". Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2972561.
Testo completo
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Zhang, Yan. "Patch Antenna for 1420MHz Radio Telescope". Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-1151.
Testo completoAbstract (sommario):
Patch antenna is one of the most rapidly popular topics in the antenna field in the past twenty years. In high-performance aircraft, spacecraft, satellite and missile applications, where size, weight, cost, performance, ease of installation, and aerodynamic profile are constraints, low profile antennas may be required. [7].
The project is to develop a single patch antenna operating on a specific frequency 1420MHz. The frequencies near to 1420MHz are worth to observe because the hydrogen in throughout of the space can be mapped by the observation of the 21 – cm wavelength line which is corresponding to 1420 MHz radiation. The final product antenna will be used in a radio telescope as a part of the signal receiving system.
The work within the project contains simulation, fabrication and test of final antenna. The simulation work was carried out in advanced design system which is developed by Agilent technologies, USA. The most different feature of the project is that, comparing to normal patch antenna, usually 50 ohms is selected as the matching impedance, while in this project we made it conjugate to the input impedance of the LNA. In this way we can save extra components, as well as energy consuming.