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Thesis (Ph. D.) -- California Institute of Technology, 2010. / Title from home page (viewed 03/03/2010). Advisor and committee chair names found in the thesis' metadata record in the digital repository. Includes bibliographical references.

Thesis (Ph.D) - Pune University, 2000.

This thesis is a performance study of the paraboloidal antenna of the Dominion Radio Astrophysical Observatory and is an assessment of the quantity and distribution of radiation reaching the receiver input from all directions. This study deals first with the ideal reflector for which the radiation pattern is computed for small off-axis angles and for wide-angle radiation. The latter calculations make use of the stationary-phase principle in evaluating the radiation integrals. It has been found that the half-power beam-width is slightly more than 0.5° and the first side-lobe is at least 30 db down. In the following chapter, the surface imperfections of the reflector are considered, in addition to the radiation reaching the feed from the ground. The aperture field is divided into a number of zones perturbed slightly in phase so as to approximate the slowly-varying roughness of the reflector. The resulting increase in side-lobe level is then not only related to the surface tolerance, but to the average size of each zone. The radiation reaching the feed from the ground due to spillover, transmission through the reflector mesh and holes, and reflector surface loss, contributes about 16°K to the equivalent noise temperature of the antenna. The hollow dielectric spars supporting the feed horn are considered and are treated first as being infinite in length where the necessary boundary conditions are applied. The concept of scattering in cones about the cylinder axis is also developed. Then, for the finite cylinder, radiation is assumed to result from the same scattering width. Experimental studies are carried out and with Cassiopeia A as a source, the shape of the main beam is found to agree with the theoretical result, but the level of the first side-lobe is higher than expected. This discrepancy is believed to be due to reflector distortion. The sun is used as a source for detection of spar scattering and the presence of scattering cones is confirmed. An absolute temperature calibration is carried out with a resulting figure 27°K for the antenna pointed at the zenith. This temperature is measured at the input of a Dicke switch and is consistent with the theoretical 16°K presented to the input of the feed horn. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The National Radio Astronomy Observatory (NRAO) operates the Very Large Array (VLA) Radio Observatory in New Mexico, and the Very Long Baseline Array (VLBA) with 10 radio antenna in locations from Hawaii to St. Croix, as well as other radio telescopes at Green Bank, West Virginia, and the 12 meter radio antenna near Tucson, AZ. Although radio frequency (RF) bands have been set aside for passive use by these radio telescopes, harmful interference from increased demands on the radio spectrum is a growing problem for earth-based radio astronomy. For example, locating a radio observatory in a remote area is little defense from satellite downlink telemetry. This paper describes why the operation of the radio telescopes is susceptible to RF telemetry interference, what bands are particularly vulnerable and at what power levels, and how data collection and centralized control of the arrays are accomplished without RF telemetry.

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The behaviour of the radio source population at high redshift has been a major area of research in extragalactic radio astronomy during the past decade. In particular, the question of at what redshift the co-moving number density of radio sources reaches a peak, has been of considerable interest. Radio surveys are particularly good for yielding large numbers of distant radio galaxies and quasars but at the price of having the edshift of the individual sources very difficult to obtain. This thesis has examined the behaviour of faint radio sources at large redshift, in particular those objects showing the classical double structure as is commonly found in samples selected at low frequency. The first part of this thesis identifies the need for at least approximate redshift information for complete flux limited samples to properly address the behaviour of these sources at large redshift; known redshift indicators are shown to be inadequate for this purpose. A new method of obtaining the intrinsic radio luminosity and hence redshift for classical double radio sources from the bright 3C sample <i>from the radio data alone</i>, is introduced. The same relationship is shown to be applicable to similar sources found at larger redshifts when selected from fainter samples. The middle part of this work is concerned with the construction of two new faint radio samples selected at 151 MHz. In addition to VLA and 5km telescope mapping, a review of existing optical data together with new CCD imaging and some spectroscopy is given. Finally, by taking these two new samples together with the intermediate sample of Eales and the bright sample of LRL, the new method of deriving radio luminosity has been used to explore the shape of the evolution function and degree of linear size evolution required for double radio sources at a much larger redshift than has been previously possible.

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