No description available.

This thesis describes both round-pore microchannel plates (MCPs) used in energetic pho¬ton and particle detectors and their square-pore offspring, micropore optics (MPOs), used to focus x-rays. A Monte Carlo electron raytracing software package is described that is used to predict the energy and angular distribution of electrons (EDOE and ADOE) in a microchannel electron multiplier's output charge cloud, including saturated operation. The model is shown to agree with experimental evidence. The addition of a micromachined electrostatic lens to the end of a microchannel is modelled and found to have no beneficial effects upon the EDOE and ADOE of the channel. The current state of the art planar and slumped 'lobster eye' square-packed MPOs are evaluated. The best focus (5' FWHM) from a large format (61mm x 56mm), small chan¬nel (10μm side length) planar MPO is reported, together with the observation of high energy (~50keV →65keV) x-ray focusing from large (500:1) aspect ratio channels. The alignment of many small lobster eye MPOs to create a large optic for the Lobster-ISS instrument is discussed and the alignment jig constructed for this purpose is used to measure the bias angles of a Lobster specification MPO. The bias angle is found to be 4 ± 1.5'. The concept of the microchannel conic approximation to the Wolter type I and II x- ray lenses is reviewed. A radially-packed twin MPO Wolter approximation is then tested, which while of poor quality, demonstrates true Wolter II imaging with a peak gain greater than unity. Currently proposed (UK) astronomical instruments that employ MPOs are then discussed in the light of the results from the current generation of MPOs.

<p> One of the most important scientific discoveries to be had this century is the spectroscopic characterization of Earth-like exoplanets to determine the occurrence rate of worlds capable of supporting life and to potentially answer: are we alone in the universe? To accomplish these lofty goals requires an advancement in the technology to separate the overwhelming starlight from that of the exoplanet. I believe starshades are the key technology that will enable these discoveries within our lifetime. This dissertation work is a contribution to the advancement of starshade technology to put us on the path towards discovery.</p><p> In this dissertation I present a number of suborbital methods developed for testing small-scale starshades, which include a Vertical Takeoff Vertical Landing rocket, the surface of a dry lake bed, and the heliostat of a solar telescope. The results from our high contrast observations are used to validate the optical model I developed to conduct tolerance analyses that will drive future starshade designs. The results from testing a formation flying sensor on the VTVL rocket demonstrate the rocket&rsquo;s potential for conducting starshade experiments in the stratosphere.</p><p> This dissertation (along with [Novicki, et al. (2016)]) presents the first astronomical observations with a starshade that provide photometric measurements of stars, previously unobserved in the visible spectrum, in the proximity of Vega. These observations led to the development of a visual feedback system for the heliostat that allows us to push farther in separation and inner working angle. These high contrast observations were made using a starshade in the most flight-like configuration (in terms of Fresnel number, inner working angle, and resolution) to date.</p><p> The results of this dissertation have helped demonstrate the effectiveness and practicality of starshades for starlight suppression and have outlined a path forward to further advance starshade technology through optical testing and high contrast astronomy.</p>

Thesis (M.A.)--Boston University This item was digitized by the Internet Archive.

This thesis describes the design, calibration and analysis of data from two experiments flown on Skylark sounding rockets to observe X-rays from celestial sources. The first experiment, SL 904, was flown in November 1970 from woomera, and carried a large-area X-ray proportional detector, sensitive over 1-14 Kev. The objectives were to observe the X-ray background radiation as well as the source M87 and sources in Centaurus. Measurement of the degree of uniformity of the X-ray background is a valuable clue to its origin since if this is in discrete sources then, on a sufficiently small scale, spatial variations in the flux will be observable. Three scans were made with the instrument over an area lacking known sources, resulting in a lower limit of 7 x 104 for the number of sources which could produce the observed uniformity. The background spectrum over the range 1-10 KeV mas measured with a precision equal to previous results and mas in agreement. The second experiment, SL 1002, was carried out in September 1971, to obtain the position of the X-ray source GX 3+1 accurately, in one dimension, by observing the occultation of the source by the moon. The observation resulted in the source error box being reduced to 1.6 arc sec by 3 arc min (1). However, no optical object was identifiable with the X-ray source, although the error box of a possible radio source overlapped. In conjunction with higher energy measurements, the source is shown to be of thermal origin. No temporal fluctuations mere observed. Work on a focussing X-ray collector to observe low energy (0.1 - 1 KeV) X-radiation from sources is described. The characteristics of the mirror system are investigated and the calibration of the multi-mire detector is also described.

Astronomy is the oldest scientific field in human history. As such, it is linked heavily with Ancient History as a central part of understanding, scientific development and cultural appreciation in the world of antiquity. The goal of this thesis will be to investigate the importance of the ancient astronomers, their discoveries, the differences in cultural understandings of the universe due to environmental and political reasons, planets and the cosmos, and the impacts their discoveries had on the ancient world. Primary sources will be various writings and documents by ancient astronomers and philosophers such as Eratosthenes, Hipparchus, Plato and the Pythagorean concept. Also to be consulted will be ancient documents that explain the cosmos and nature of this universe from the cultural aspect of the Egyptian, Maya, Mesopotamian, and Hellenistic civilizations. Secondary sources will a variety of modern historical and scientific writings about the history of astronomy. These will include Astronomy of the Ancients by Kenneth Brecher and Michael Feirtag, Ancient Egyptian Science by Marshall Clagett, and A History of The Ancient Mathematical Astronomy by Neugebauer. Also included will be modern sources that explain astronomical events and notions.

Abstract. 2D-spectroscopy in astronomy is defined as a technique where a spatially resolved electromagnetic spectrum is obtained over a two-dimensional field. In this paper the very basic principles of spectroscopy are briefly covered starting from the single slit concept via the Huygens principle and the Fraunhofer diffraction. The basic concept of a grating-based spectrograph is described. The connection between observed spectra, the chemical footprints and the underlying physical properties of the systems are briefly covered. The main IFU techniques used in the field of integral field spectroscopy are introduced. The basic ideas on how the data from the observed targets are produced and the wanted physical properties from the data are recovered are discussed. The work demonstrates the usage of 2D-spectroscopic data and its usefulness. The decay in the velocity dispersion profiles in the near central regions of galaxies known as sigma-drop is briefly introduced and a sample of 13 galaxies hosting a possible sigma-drop is analyzed via elliptical apertures. The radial profiles of each galaxy are extracted from given 2D-data connected to the kinematics of the sample galaxies. The radial profiles are then graphically presented with kinematic maps corresponding to the rotation velocity, the velocity dispersion, h₄ and h₃ profiles of the galaxy. Here the h₄ and h₃ are the amplitudes of the Gauss-Hermite series corresponding to the symmetric and asymmetric deviation from a Gaussian. The sample consists of only barred galaxies which could indicate star formation caused sigma-drops due to the bar-driven inflow of the gas to the central regions of the galaxies. Well-defined dust lanes are seen in ~70% of the sample showing a possible relation between the dust and the sigma-drops. There is no direct connection observed between the sigma-drops and the sizes of the galaxies.

This thesis investigates techniques and algorithms for mitigating radio frequency interference (RFI) affecting radio astronomy observations. In the past radio astronomy has generally been performed in radio-quiet geographical locations and unused parts of the radio spectrum, including small protected frequency bands. The increasing use of the entire spectrum and global transmitters such as satellites are forcing the astronomy community to begin implementing active interference cancelling. The amount of harmful interference affecting observations will also increase as future instruments such as the Square Kilometre Array (SKA) are required to use larger bandwidths to reach up to 100 times the current sensitivity levels, and as spectral line observations require observing in bands licensed to other spectrum users. Particular attention is paid to interference cancellation algorithms which make use of reference beams. This has proven to be successful in removing interference from the contaminated astronomical data. Reference antenna cancellers are closely analysed, leading to filters and techniques that can offer improved RFI excision for some important applications. It is shown that pre- and post-correlation reference antenna cancellers give similar results, and an important aspect of the cancellers is the use of a second reference signal when the reference interference-to-noise ratio is low. These modified filters can theoretically offer infinite interference suppression in the voltage domain, equivalent to that of post-correlation interference cancellers, and their internal structure can offer an understanding of the residual RFI and added receiver noise components of a variety of reference antenna techniques. The effect of variable geometric delays is also considered and various filters are compared as a function of the geometric fringe rate.

No description available.

The clouds of gas and dust that constitute the Interstellar Medium (ISM) within the Milky Way and other galaxies can be studied through the spectral lines of the atoms and molecules. The ISM follows a lifecycle in which each of its phases can be traced through spectral lines in the Terahertz (THz) portion of the electromagnetic spectrum, loosely defined as 0.3 - 3 THz. Using the high spectral resolution afforded by heterodyne instruments, astronomers can potentially disentangle the large-scale structure and kinematics within these clouds. In order to study the ISM over large size scales, large format THz heterodyne arrays are needed. The research presented in this dissertation focuses on the development of two heterodyne array receiver systems for ISM studies, SuperCam and a Super-THz (>3 THz) receiver. SuperCam is a 64-pixel heterodyne imaging array designed for use on ground-based submillimeter telescopes to observe the astrophysically important CO J=3-2 emission line at 345 GHz. The SuperCam focal plane stacks eight, 1x8 mixer subarrays. Each pixel in the array has its own integrated superconductor-insulator-superconductor (SIS) mixer and Low Noise Amplifier (LNA). In spring 2012, SuperCam was installed on the University of Arizona Submillimeter Telescope (SMT) for its first engineering run with 32 active pixels. A second observing run in May 2013 had 52 active pixels. With the outliers removed, the median double sideband receiver temperature was 104 K. The Super-THz receiver is designed to observe the astrophysically important neutral atomic oxygen line at 4.7448 THz. The local oscillator is a third-order distributed feedback Quantum Cascade Laser operating in continuous wave mode at 4.741 THz. A quasi-optical hot electron bolometer is used as the mixer. We record a double sideband receiver noise temperature of 815 K, which is ~7 times the quantum noise limit and an Allan variance time of 15 seconds at an effective noise fluctuation bandwidth of 18 MHz. Heterodyne performance is confirmed by measuring a methanol line spectrum. By combining knowledge of large array formats from SuperCam and quasi-optical mixers, initial tests and designs are presented to expand the single pixel 4.7 THz receiver into a quasi-optical 16-pixel array.