Submitted in fulfilment of the academic requirements for the Degree Master of Engineering: Electrical Engineering, Durban University of Technology. Durban. South Africa, 2015. / This dissertation describes the development and construction of the Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA) at the Durban University of Technology. The MITRA station consists of 2 antenna arrays separated by a baseline distance of 8 m. Each array consists of 8 Log-Periodic Dipole Antennas (LPDAs) operating from 200 MHz to 800 MHz. The design and construction of the LPDA antenna and receiver system is described. The receiver topology provides an equivalent noise temperature of 113.1 K and 55.1 dB of gain. The Intermediate Frequency (IF) stage was designed to produce a fixed IF frequency of 800 MHz. The digital Back-End and correlator were implemented using a low cost Software Defined Radio (SDR) platform and Gnu-Radio software. Gnu-Octave was used for data analysis to generate the relevant received signal parameters including total power, real, and imaginary, magnitude and phase components. Measured results show that interference fringes were successfully detected within the bandwidth of the receiver using a Radio Frequency (RF) generator as a simulated source. This research was presented at the IEEE Africon 2013 / URSI Session Mauritius, and published in the proceedings.

There are two topics in this dissertation: one is to develop new phase reduction algorithms for test interferograms especially of large optics and the other one is to find more accurate analytical expression of surface deflection due to gravity when the mirror is supported in the axial direction. Two new algorithms for generating phase maps from interferograms are developed. Both methods are sensitive to small-scale as well as large-scale surface errors. The first method is designed to generate phase from an interferogram that is sampled and digitized only along fringe centers, as in the case of manual digitization. A new interpolation algorithm uses the digitized data more efficiently than the fitting of Zernike polynomials, so the new method can detect small-scale surface error better than Zernike polynomial fitting. The second algorithm developed here is an automatic phase reduction process which works on test interferograms recorded by CCD camera and transferred digitally to a personal computer through a frame grabber. The interferogram results from interference of the test wavefront with a tilted reference wave-front. Phase is generated by assuming it to be proportional to the intensity of the interferogram, apart from changes of sign and offset occurring every half fringe so as to make the phase increase monotoically. The error of the new algorithm is less than 1/20 waves in the wavefront, which can be reduced further by averaging several phase maps which are generated by interferograms with random phase shifts. The new algorithm is quick and involves no smoothing, so it can detect surface errors on large mirrors on a scale of several centimeters. A new model is developed to calculate analytically the surface deflection of a mirror supported axially on multiple points. It is based on thin plate theory, but considerations of thickness variation of a curved mirror, lightweight honeycomb structure and shear are included. These additions improve the accuracy of the calculated surface deflection, giving results close to those obtained from the accurate but computer intensive finite element model.

Angles measurements from optical systems are the primary source of data for maintaining the orbits of high altitude satellites. Radar measurements are used primarily for low Earth orbit (LEO) satellites. Recently it has been shown that the accuracy of the orbit updates using only optical system angles-only data is just as good, if not better, than the performance from radar systems for LEO satellites. The purpose of this thesis is to investigate the use of optical angles data with and without laser ranging data in determining the trajectories of missiles. Analytical Graphics, Inc. Satellite Tool Kit is used to model the trajectory of a ballistic missile. Several scenarios are developed for determining the orbit when acquired by sensors providing various combinations of range, range rate and angles data. It is found that the combination of range, azimuth and elevation sensor data yields an orbit determination that has enough merit to be called accurate. The error of the orbit determined by the angles-only data is two orders of magnitude larger than the error of the range and angles measurement. Additionally completed was an analysis of what would happen if the sensors could only track to the maximum altitude of the orbit. As was assumed, the known position of the object drifts ranged from minimal to significant predicated on the final known position. This is indicated by the error ellipsoid. It was again found that the combination of range, azimuth and elevation sensor data until the maximum altitude yields an orbit determination that has enough merit to be called accurate. Also considered was the addition of a second sensor that had the capacity to always track range, azimuth and elevation to increase the time that is afforded to track the object, increasing the overall accuracy of the orbit determination. It is found that the addition of a second sensor increases the fidelity of the angles-only measurement such that the combination of azimuth and elevation sensor data yields an orbit determination that has enough merit to be called accurate.

QC 351 A7 no. 30 / This symposium was co- sponsored by the Kitt Peak National Observatory (Dr. D. L. Crawford) and the Optical Sciences Center and Steward Observatory of the University of Arizona (Dr. A. B. Meinel). The idea grew from the recognition of the many common problems that were being faced by national and international groups in the engineering of large telescopes. The divergences of opinions and designs in regard to the nature of large astronomical mirrors, and their mounting and testing, made it evident that an exchange of ideas would be profitable to all of the groups. The meeting was organized and chaired by D. L.Crawford and A. B. Meinel. Special commendation is also due to R. H. Noble of the Optical Sciences Center for managing the numerous arrangements that contributed to making this a well-attended and successful symposium. The original intent of the symposium was merely to provide a face-to-face exchange of ideas. In retrospect, however, it was realized that the meeting constituted a milestone in large telescope design, and it was decided to edit the recording tapes and publish the proceedings. The task of transcribing the tapes fell to Patricia Grames and Evelyn Brant, with assistance in technical content from Earl Pearson of Kitt Peak National Observatory. In several cases the presentations atthe symposium led to continuing discussion. In particular,the papers by Bleich and Schwesinger led to a spirited exchange in which considerable enlightenment resulted. We have decided not to include these supplemental contributions, both because they transpired outside the format of this meeting and in view of their intent to publish elsewhere. The editorial task undertaken by Martha Stockton was immense and was impeded by prior responsibilities of all the persons involved. We are pleased to now conclude the report. We hope that readers will find this volume a useful addition to the limited available works on the topic of the design and testing of large astronomical telescopes. A. B. Meinel D. L. Crawford

Adaptive optics or numerical restoration algorithms that restore high resolution imaging through atmospheric turbulence are subject to isoplanatic wave-front errors. Mitigating those errors requires that the wave-front aberrations be estimated within the 3D volume of the atmosphere. Present techniques rely on multiple beacons, either natural stars or laser guide stars, to probe the atmospheric aberration along different lines of sight, followed by tomographic projection of the measurements onto layers at defined ranges. In this paper we show that a three-dimensional estimate of the wave-front aberration can be recovered from measurements by a single guide star in the case where the aberration is stratified, provided that the telescope tracks across the sky with non-uniform angular velocity. This is generally the case for observations of artificial earth-orbiting satellites, and the new method is likely to find application in ground based telescopes used for space situational awareness.

Thesis. 1975. B.S. cn--Massachusetts Institute of Technology. Dept. of Physics. / MICROFICHE COPY AVAILABLE IN ARCHIVES. / Includes bibliographical references. / B.S.cn

No description available.

A thesis submitted to the Faculty of Science in fulfillment of the requirements of the degree of Doctor of Philosophy School of Computational and Applied Mathematics University of the Witwatersrand September 20, 2012 / In this thesis, we analyse reasons for poor image quality on the Southern African Large Telescope (SALT) and we analyse control methods of the segmented primary mirror. Errors in the control algorithm of SALT (circa 2007) are discovered. More powerful numerical procedures are developed and in particular, we show that singular value decomposition method is preferred over normal equations method as used on SALT. In addition, this method does not require physical constraints to some mirror parameters. Sufficiently accurate numerical procedures impose constraints on the precision of segment actuator displacements and edge sensors. We analyse the data filtering method on SALT and find that it is inadequate for control. We give a filtering method that achieves improved control. Finally, we give a new method (gradient flow) that gives acceptable control from arbitrary, imprecise initial alignment.

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.

"August 2001." Includes bibliographical references (p. 308-311). Describes the use of optical telescopes in the investigation of astronomical objects which have been discovered by earth-orbiting high-energy astronomical satellites.