L-Shaped Array for Multi-frequency Interferometry Telescope

L-Shaped set off for Multi-frequency Interferometry cathode-ray oscilloscopeAbstractAn represent of eight antennas with different configuration, more precisely an L- shaped ordinate has been make for the Multi-frequency Interferometry Telescope for radio receiver Astronomy (MITRA) project. It consists of quite newly designed triple Polarised Log nightly Dipole Antennas (DPLPDA).The first stage of the project was to seek the existing array of DPLPDA antennas in a parallelconfiguration in the North South direction and to bring forward different improvements. Also, comparision of data was done with the Durban University of Technology (DUT) at Durban RSA where a similar array was constructed.Next, UV coverage of different arrays were simulated. by and by that, the DPLPDA were constructed.After setting up the array, the antenna response of all(prenominal) antenna was tested and the results obtained was interpreted. The closing test was to test the complete array after combining all the antennas.CHAPTER 1Introduction and Overview1.1Introduction1.1.1Radio AstronomyRadio astronomy is the study of celestial objects that respire piano tuner waves.In the 1930s, Karl Jansky (1905-1950), working for the Bell Laboratories, was trying to determine the origin of the source of noise interfering with radio voice transmissions. He reinforced a steerable antenna designed to receive radio waves at a frequency of 20.5 MHz. From the observations, he found that the period of the earths rotation relative to the radio source was 23 hours and 56 minutes instead of 24 hours. Hence, he concluded that the source was follwing sidereal time. He also observed that the strongest radiation was advance from the centre of our Milky Way galaxy.Inspired by Janskys work, Grote Reber (1911-2002) built a parabolic radio compass of diameter 9m in his back yard, in 1937. After several trials, Reber successfully detected radio emission from the Milky Way, in 1938, confirming Janskys discov ery. This led to the discovery of a range of celestial objects, such as radio galaxies, quasars, and pulsars with radio emission with various types of antennas. 11.1.2.1 Radio InterferometryRadio interferometry argon arrays of radio antennas that are utilize inastronomicalobservations simultaneously to simulate singletelescopesof very largeapertures and are used to make measurements of fine angular detail in the radio emission. Radio interferometry enable measurement of the position of radio sources with accuracy to allow identification of different objects detected in the electromagnetic spectrum. Michelson and Pease made the discovery of the interferometric techniques in 1921. They were able to obtain sufficiently fine angular blockage to measure the diameters of some of the warm stars such as Arcturus and Betelgeuse. 21.1.2.2 Aperture SynthesisAperture Synthesis or Synthesis Imaging is a type of interferometry that correlates radio signals obtained from a collection of telesc opes or antennas to produce images. These images ask the same angular resolution as that of the size of a single and a much larger telescope or antenna. Aperture synthesis was first ascertained by Sir Martin Ryle (27 September 1918 14 October 1984) and coworkers from the Radio Astronomy Group at Cambridge University at radio wavelengths. In 1974, Martin Ryle was the first astronomer awarded a Nobel Prize. 3Very massive Baseline Interferometry(VLBI) also makes use of radio interferometric techniques. TypicallyVLBIrefers to experiments that do not process their data in real time, but record it for latercorrelation to produce the resulting image. It achieves ultra-high angular resolution and is a multi-disciplinary technique. VLBIis used in measuring pulsar parallaxes andproper motion, resolving the cores of radio galaxies and fets from supermassive black holes, among others. 14Some of the comm moreover used radio interferometers arethe Very Large Array (VLA) in Socorro, New Mexico, USAIt consists of 27 radio antennas, each of diameter 25 metres, along tether arms of a Y-shaped configuration spread over ternary 21 kilometres tracks providing 351 baselines. 4the Multi-Element Radio Linked Interferometer interlocking (pigeon hawk), operated by Jordrell Bank ObservatoryIt is an array of 7 radio telescopes spread across Britain with separation up to 217 kilometres operating(a) at frequencies between 151 MHz and 24 GHz. 5the Australia Telescope Compact Array (ATCA) in Narrabri, NSW, Australia.The telescope is an array of six identical 22 metres diameter dishes with louvre movable dishes along a 3 kilometres railway track and the sixth one is 3 kilometres west at the end of the principal(prenominal) track. The level best baseline length is 2.7 kilometres and the observing frequencies are from 300 MHz to 8 GHz.6the Giant Metrewave Radio Telescope (GMRT) in Narayangaon,Pune, India.It consists of 30 steerable parabolic dish each of diameter 45 metres opertaing at six different frequency bands and where 14 dishes are arranged in a central square and remaining 6 in a three arm Y-shaped array giving a baseline of about 25 kilometers . 7Some of the new radio interferometers are utter Frequency Array (LoFAR) in north of Exloo, the Netherlands (core) and neighbouring countriesIt is a phased-array of radio telescopes of about 25,000 small antennas in at 48 larger post where 40 of these stations are distributed across the north of Netherlands, five stations in Germany, and one each in Great Britain, France and Sweden and has a low requency range from 10-240 MHz. 8Figure 1 The LoFAR ArrayAtacama Large Millimeter Array (ALMA) in llano de Chajnantar Observatory, Atacama Desert,ChileIt consists of sixty six 12 metres and 7 metres diameter radio telescopes observing at wavelengths of 0.3 to 9.6 millimetres . 9Murchison Widefield Array (MWA) in Murchison Radio Astronomy Observatory, Western AustraliaIt consists of 2048 dual-polarization dipole antenn as, each a 44 array of dipoles and operates at low radio frequencies, 80-300 MHz, with a processed bandwidth of 30.72 MHz for both(prenominal) linear polarisations, and consists of 128 aperture arrays (known as roofing tiles) distributed over close to 3- kilometres diameter cranial orbit. 10Figure 2 MWA Antenna tilesKAT7 MeerKAT in Northern Cape, South AfricaFigure 3 aery View of KAT7KAT-7 consist of 7 dishes of 12 metres in diameter each a Prime Focus Reflecting Telescopes having a minimum baseline of 26 meters and maximum baseline of 185 metres and have a frequency range of 1200 MHz 1950 MHz. KAT-7 is an engineering range of a function for the MeerKAT. KAT-7 is the worlds first radio telescope array with fiberglass dishes. . MeerKAT, which is still under verbalism and is slated for completion in 2016 , go out consist of 64 dishes of 13.5 meters in diameter having a minimum baseline of 29 metres and maximum baseline of 20 kilometres and it will operate at frequency rangin g from 580MHz 1.75 GHz and 8 15 Ghz.11,12e- MERLIN is an enhanced and upgraded array of the old MERLIN array.The e- MERLIN instrument is a high resolution radio interferometer connected by a new optical fibre network to Jodrell Bank Observatory. This new governance gives rise to a massive increase in esthesia and observational capabilities.13Figure 4 e-MERLIN arrayatomic number 63an VLBI Netwok (EVN) is an interferometric array of radio telescopes spread across Europe which also includes stations in far-East Asia , South Africa and Puerto Rico that conducts high resolution radio astronomical observations of radio sources. It is the most radiosensitive VLBI array in the world. It was socio-economic classed in 1980 and the administering body now comprises 14 institutes15.TheEVNalso routinely joins other networks, such as theVery Long Baseline Array (VLBA)and the Multi-Element Radio Linked Interferometer Network (MERLIN), to become a globalVLBIarray. The VLBA is spread throughout Mauna Kea , Hawaii and St Croix. It typically consists of 10 VLA radio antennas and as result it has a maximum baseline stupendous 8000 Km16.Some of the future African based new radio interferometers areAfrican VLBI Network (AVN)Multi-Frequency Interferometry Telescope for Radio Astronomy (MITRA)1.1.3 MITRA (Multi-frequency Interferometry Telescope for Radio Astronomy)1.1The MITRA is an transnational radio astronomy project which aims to do extremly all-embracing field of imaging with heterogenius non coplanar arrays. The acronym of MITRA means friend in Sanskrit. It is a low frequency array telescope jointly started by Girish Kumar Beeharry from University of Mauritius (UOM) nd Stuart David Macpherson and Gary Peter Janse Van Vuuren from the Durban University of Technolagy (DUT) in South Africa.The project is being simultaneously implemented at the Mauritius Radio Telescope (MRT), located at Bras DEau Mauritius, site and at the DUT campus site. The projects will then be expande d to the different SKA Africa partner countries and eventually to other African countries. selective information from each country will be combined to form an international aperture synthesis telescope using the techniques of Very Large Baseline Interferometry (VLBI). It is a sensitive high resolution multifrequency dual polarity instrument in the range of 200 to 800 MHz. The instrument chosen for this purpose are Dual Polarized Log Periodic Dipole Antennas (DPLPDA)17.1.1.4 African Long Baseline Interferometry Network (AVN)The African Very Long Baseline Interferometry Network (AVN) is an array of radio telescopes throughout Africa. It is planned to form part of the existing global VLBI networks . It will be associated with the European VLBI Network (EVN ). The latteris a consortium of major radio astronomy institutes in Europe and chinaware (Schilizzi). It has member and associated radio telescopes in Europe, China, South Africa (Hartebeesthoek0, Japan(Kashima) and Puerto Rico (Are cibo). The EVN is capable of providing an excellent angular resolution(from 5 to 0.15 milliarc seconds depending on observing frequency) and high sensitivity for VLBI observations. One of the main technological drivers has been the availability of telecommunication antennas all over Africa. Part of the scheme is to modify the existing dishes, of about at least 30 m in diameter, into radio telescopes. All these telescopes will be linked together, and to radio telescopes in South Africa, forming the African VLBI Network. This, in turn, would be connected to radio telescopes and arrays in Europe and elsewhere in the world, including North and South America, Asia and Australia. The conversion of a Ghana located dish into a radio telescopes has already been begun.The AVNs plans to convert three more dishes in Kenya, Zambia and Madagascar. It also aims to build four new radio telescopes in Namibia, Botswana, Mauritius and Mozambique. 191.1.5 Electronic Multi Beam Radio Astronomy ConcEpt(E MBRACE) and African European Radio Astronomy Aperture Array (AERA3 )The EMBRACE demonstrates the technical and scientific potential of the aperture array concept using a phased array station with the essential SKA. There are two stations, one in Nanay, France and the other one at the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands. These two stations are prototype arrays for the SKA MFAA. It consists of an antenna array organized in tiles of dual polarization antennas. A large number of antenna tiles forms the accumulation area. The signals from the radiating elements of the antenna from each tile are amplified and the initial analogue RF beam forming is applied. Generally, an EMBRACE is designed for a frequency range of 400-1500 MHz of single polarization, a collecting area of 100 m2 , system temperature of 100 K and has two fields of view with 8 digital beams . The idea of having multiple independent beams gives rise to the AERA3 because EMBRACE considers only two beams. AERA3 is similar to EMBRACE but this new aperture array will have a greater collecting area with will be approximately 2000 m2 varying with a frequency range of 400-1500 MHz with full polarization, two fields of view with 64 digital beams, system temperature of 50 K and bandwidth of little than 500 MHz. AERA3 will be used for intensity single-valued function, watchs of the whole sky and search for pulsars.20,21Figure 5 Embrace at Nancay, Paris1.1.6 The Square Kilometre array (SKA)The SKA will be a revolutionary radio telescope made of hundred of thousands of receptors. They will be linked together, forming a total collecting area of approximately one square kilometre. It will be the largest and most sensitive radio telescope ever built. It will be able to survey the sky faster than present instruments.In 2006, the African consortium and Australia were both shortlisted as potential sites fot building the SKA. In the 25th May 2012, the SKA organisation announced that SKA wou ld be shared between the African consortium and Australia on a 21 ratio basis. The African consortium would be undertaking the construction of the high and mid frequency arrays. The Australian would be in charge of the low frequency aperture array.The SKA consists of two phases wherePhase 1 is the construction of about 10% of the SKA. It will make use of the existing infrastructure and telescopes already being built by the two countries. That is, the South Africas precursor array the 64-dish MeerKAT telescope and the Australias 36-dish SKA Pathfinder (ASKAP). Additionally, there will be 50low-frequency 1.5 metre high antenna stations, 60mid-frequency 15 metre dishes built in Australia. Finally, 190mid-frequency 15 metres dishes will be built in South Africa.Phase 2 is the extension to a baseline of 3,000 Km or more in South Arica and African partners countries. These are namely, Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia, and Zambia. Also, a total of about th ree thousand dishes, with the highest concentration in the Northern Cape, South Africa, and some dishes in the other consortium countries will be built.In Australia, the telescope will extend over a baseline of200 km.It will operate with a frequency coverage from 70 MHz to 30 GHz. The SKA will use aperture synthesis, over a distance of more than 3000km to simulate a single giant radio telescope capable of extremely high sensitivity and angular resolution.The SKA will be able to observe the black holes, stars, galaxies and detect black holes11,22,23,24.Figure 6 SKA overview1.1.7 The Log Periodic Dipole AntennaA log periodic antenna, also referred to as a log periodic array, is an antenna that can operate on a wide frequency band. It was rst built in 1958 by Dwight Isbell at the University of Illinois, United States of America. LPDA is a directional antenna which possesses constant electrical characteristics such as gain, impedance and front-to-back ratio over the wide range of freque ncies. It varies periodically with the logarithmic. The antenna consists of a series of linear elements also known as dipoles and the individual elements connect with a transmission or contribute line such as coaxial cable. Each element is placed in an alternating configuration leading to a phase shift of 180o ( radians). 251.2 haveThe aim of this project is to construct a front-end system for radio astronomical observations in the frequency range 200 MHz to 800 MHz using the Dual Polarised Log Periodic Dipole Antenna model with bandwidth 200 MHz to 800 MHz. The front end system will consist of an L-shaped array of antennas. This L shaped array is the start of a matrix of an eight by eight antennas. It will be used as a prototype for Intensity mapping for large scale neutral hydrogen (HI) mapping. Several improvements to the existing antennas will be made and applied to new array configuration. Also along with the array, a shielded box will be constructed for electronic purposes. This work focuses on the longer baseline sparse mid frequency aperture array (MFAA), in descent to the dense aperture arrays like EMBRACE and the future AERA3.