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Submillimetre astronomyEve, W. D. January 1981 (has links)
No description available.
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Ancient astronomyMiddleton, Stephen Douglas January 1910 (has links)
No description available.
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Ancient astronomyMiddleton, Stephen Douglas January 1910 (has links)
No description available.
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AIRBORNE INFRARED ASTRONOMYAUMANN, HARTMUT HANS-GEORG January 1970 (has links)
No description available.
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RFI mitigation in radio astronomyThompson, Nicholas Christopher 04 1900 (has links)
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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Spectroscopic mode identification in a sample of non-radially pulsating stars : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Astronomy at the University of Canterbury /Wright, Duncan John. January 2008 (has links)
Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 190-195). Also available via the World Wide Web.
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Analysis of three close eclipsing binary systems : BP Velorum, V392 Carinae and V752 Centauri : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science, University of Canterbury /Schumacher, Hana Josephine. January 2008 (has links)
Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 66-68).
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Culprit and victim management RFI environment for a radio astronomy siteVan der Merwe, Carel 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A methodology is developed to manage the large number of RFI Culprits on a new Radio
Telescope location such as the South African site being developed in the Karoo, both during
construction and ongoing operations. The requirement for RFI control is presented, with brief
reference to the more traditional methods used by other Radio Telescope observatories. The new
approach is then presented, based on methods used in the engineering field of Logistic
Engineering. Three case studies are used to illustrate how the approach can be applied. Finally,
recommendations are made on how the approach can be implemented for new Radio Telescope
projects. / AFRIKAANSE OPSOMMING: ‘n Metodolgie word ontwikkel vir die beheer van die groot aantal Radiofrekwensiesteurings
oortreders by ‘n nuwe Radio Teleskoop terrein, soos die Suid Afrikaanse terrein wat huidiglik in die
Karoo ontwikkel word. Die metodolgie geld beide gedurende konstruksie en gedurende bedryf.
Die behoefte vir RFS beheer word aangebied, met kortlikse melding van die meer tradisionele
metodes wat ander Radio Teleskoop Sterrewagte gebruik. ‘n Nuwe aanslag, gebaseer op die
metodolgieë van Logistieke Ingenieurswese, word dan aangebied. Drie gevallestudies wys hoe
hierdie nuwe aanslag toegepas kan word. Laastens word aanbevelings gemaak om hierdie nuwe
aanslag met nuwe Radio Teleskoop projekte te implimenteer.
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Image reconstruction in radio astronomy with non-coplanar synthesis arraysGoodrick, Lee 03 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Traditional radio astronomy imaging techniques assume that the interferometric array is
coplanar, with a small field of view, and that the two-dimensional Fourier relationship
between brightness and visibility remains valid, allowing the Fast Fourier Transform to be
used. In practice, to acquire more accurate data, the non-coplanar baseline effects need
to be incorporated, as small height variations in the array plane introduces the w spatial
frequency component. This component adds an additional phase shift to the incoming signals.
There are two approaches to account for the non-coplanar baseline effects: either the full
three-dimensional brightness and visibility model can be used to reconstruct an image, or the
non-coplanar effects can be removed, reducing the three dimensional relationship to that of the
two-dimensional one.
This thesis describes and implements the w-projection and w-stacking algorithms. The aim of
these algorithms is to account for the phase error introduced by non-coplanar synthesis arrays
configurations, making the recovered visibilities more true to the actual brightness distribution
model. This is done by reducing the 3D visibilities to a 2D visibility model. The algorithms
also have the added benefit of wide-field imaging, although w-stacking supports a wider field
of view at the cost of more FFT bin support. For w-projection, the w-term is accounted for in
the visibility domain by convolving it out of the problem with a convolution kernel, allowing
the use of the two-dimensional Fast Fourier Transform. Similarly, the w-Stacking algorithm
applies a phase correction in the image domain to image layers to produce an intensity model
that accounts for the non-coplanar baseline effects.
This project considers the KAT7 array for simulation and analysis of the limitations and
advantages of both the algorithms. Additionally, a variant of the Högbom CLEAN algorithm
was used which employs contour trimming for extended source emission flagging. The CLEAN
algorithm is an iterative two-dimensional deconvolution method that can further improve image
fidelity by removing the effects of the point spread function which can obscure source data. / AFRIKAANSE OPSOMMING: Tradisionele beeldvormingstegnieke in radio-astronomie aanvaar dat die interferometriese
skikking samevlakkig is. Dit beteken dat die twee-dimensionele Fourier verhouding tussen
helderheid en sigbaarheid geldig bly en dat die Vinnige Fourier Transform aangewend kan
word. Klein hoogtevariasies in die skikkingsvlak bring die w-ruimtelike frekwensiekomponent
mee, wat ’n faseverskuiwing in die inkomende seine tot gevolg het. Dus, in praktyk, moet
die bydrae van die nie-samevlakkige basislyneffekte in ag geneem word om sodoende
die akkuraatheid van die data te verhoog. Twee benaderings kan gevolg word om die
nie-samevlakkige basislyneffekte in ag te neem: Metodes wat die volle drie dimensionele
helderheid en sigbaarheidsmodel gebruik kan toegepas word om ’n beeld te herbou, andersins
kan die nie-samevlakkige effekte verwyder word om sodoende die drie-dimensionele
verhouding te verminder tot ’n twee-dimensionele verhouding.
Hierdie tesis beskryf en implementeer die ‘w-projeksie’ en ‘w-stapel’ algoritmes. Die doel van
hierdie algoritmes is om die fasefout wat deur nie-samevlakkige sinteseskikkingskonfigurasies
veroorsaak word, reg te stel. Hierdie regstelling maak die herwinde sigbaarheid van die beeld
meer getrou aan die werklike helderheidsverspreidingsmodel. ’n Bykomende voordeel van
die algoritmes is beeldvorming van wye-veld ruimtewaarnemings. In ‘w-projection’ word die
w-term in die sigbaarheidsdomein in ag geneem deur die ruimtelike frekwensiekomponent met
behulp van ’n konvolusiekern vanuit die probleem te verwyder. Die twee-dimensionele Vinnige
Fourier Transform kan gevolglik toegepas word. Soortgelyk hieraan, wend die ‘w-Stacking’
algoritme ’n fasekorreksie aan tot ’n reeks beeldlae, om sodoende ’n beeld te verkry wat die
nie-samevlakkige basislyneffekte in ag neem.
Die KAT7 teleskoop is gebruik in die simulasie en analiese van die tekortkominge en voordele
van beide algoritmes. ’n Hibriede weergawe van die Högbom CLEAN algoritme is bykomend
oorweeg. Hierdie algoritme is ’n iteratiewe twee-dimensionele dekonvolusiemetode wat die
betroubaarheid van beelde verbeter deur die verskansingseffek van puntverspreidingsfunksies
te verwyder. Verder gebruik die Högbom CLEAN algoritme kontoersnoeiing om uitgebreide
bron-emisies te identifiseer.
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A survey for resolved Milky Way dwarf galaxy satellites /Willman, Beth. January 2003 (has links)
Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 161-167).
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