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A primary objective of the effort reported here is to develop a radiometric instrument modeling environment to provide complete end-to-end numerical models of radiometric instruments, integrating the optical, electro-thermal, and electronic systems. The modeling environment consists of a Monte Carlo ray-trace (MCRT) model of the optical system coupled to a transient, three-dimensional finite-difference electrothermal model of the detector assembly with an analytic model of the signal-conditioning circuitry. The environment provides a complete simulation of the dynamic optical and electrothermal behavior of the instrument. The modeling environment is used to create an end-to-end model of the CERES scanning radiometer, and its performance is compared to the performance of an operational CERES total channel as a benchmark. A further objective of this effort is to formulate an efficient design environment for radiometric instruments. To this end, the modeling environment is then combined with evolutionary search algorithms known as genetic algorithms (GA's) to develop a methodology for optimal instrument design using high-level radiometric instrument models. GA's are applied to the design of the optical system and detector system separately and to both as an aggregate function with positive results. / Ph. D.

Light reflectance from plants can be used as a non-invasive predictor of health and yield for many cropping systems, and has been investigated to a lesser extent with managed turfgrass systems. The frequent agronomic inputs associated with maintaining golf course grasses allow for exceptional stand quality under harsh growing conditions, but often expend resources inefficiently, leading to either stand loss or unnecessary inputs in localized areas. Turfgrass researchers have adopted some basic principles of light reflectance formerly developed for cropping systems, but field radiometric-derived narrow-band algorithms for turfgrass-specific protocols are lacking. Research was conducted to expand the feasibility of using radiometry to detect various turfgrass stressors and improve speed and geographic specificity of turfgrass management. Methods were developed to detect applied turfgrass stress from herbicide five days before visible symptoms developed under normal field growing conditions. Soil volumetric water content was successfully estimated using a water band index of creeping bentgrass canopy reflectance. The spectral reflectance of turfgrass treated with conventional synthetic pigments was characterized and found to erroneously influence plant health interpretation of common vegetation indices because of near infrared interference by such pigments. Finally, reflectance data were used to estimate root zone temperatures and root depth of creeping bentgrass systems using a gradient of wind velocities created with turf fans. Collectively, these studies provide a fundamental understanding of several turfgrass-specific reflectance algorithms and support unique opportunities to detect stresses and more efficiently allocate resources to golf course turf. / Ph. D.

The objective of this research is to study the field of optical engineering and to combine this knowledge with radiation heat transfer analysis to create a radiometric imaging design tool. In particular, the tool is aimed at design of reflective radiometric imaging telescopes, capable of highly accurate heat flux measurements, to be used in space-borne satellite applications. A concise reference guide is provided to aid in the design of somewhat generic reflective radiometric imaging systems. Also developed is a Monte-Carlo virtual optical workbench that models one- and two-mirror reflective radiometric telescopes. The virtual optical workbench is capable of performing optical analyses and generating radiometric images based on temperatures of scene components and telescope structures. The workbench model allows simulation of surfaces with different absorptivities, along with simulation of surfaces that have diffuse as well as specular components of reflectivity. Results from the virtual optical workbench are presented to show the myriad of functions incorporated in this powerful new tool. / Master of Science

Das Ziel dieser Dissertation ist das Schließen der radiometrischen Lücke zwischen der klassischen Radiometrie und der Radiometrie im Bereich weniger und einzelner Photonen. In dieser Arbeit wurden dazu zwei wesentliche Themen bearbeitet. Erstens, die Charakterisierung und Validierung eines neuen radiometrischen Detektorprimärnormals für den Wellenlängenbereich von 400 nm bis 800 nm basierend auf Silizium-Photodioden. Dieses neuartige Primärnormal kann sowohl in der Radiometrie im Bereich weniger Photonen als auch in der klassischen Radiometrie eingesetzt werden, der sogenannte “Predictable Quantum Efficient Detector” (PQED). Der PQED wurde im Rahmen dieser Arbeit charakterisiert und experimentell validiert. Für die Validierung war es nötig, die relativen Unsicherheiten der klassischen Radiometrie und insbesondere der Kryoradiometrie, deutlich zu verringern. Mit der Inbetriebnahme eines neuen Kryoradiometers wurde das Ziel, in den Unsicherheitsbereich von ca. 10E−5 vorzudringen, erreicht. Zweitens, es wurde eine Kalibriermethode für Einzelphotonendetektoren eingesetzt, rückgeführt auf das internationale Einheitensystem, die auf den einzigartigen Eigenschaften von Synchrotronstrahlung basiert. Diese Methode kann benutzt werden um sowohl Freistrahl- als auch fasergekoppelte Einzelphotonendetektoren bei praktisch jeder gewünschten Wellenlänge zu kalibrieren und erreicht im Moment die weltweit geringsten Messunsicherheiten. Mit dem neuen Kryoradiometer, dem PQED und dem auf Synchrotronstrahlung basierenden Kalibrierverfahren sind die erreichbaren Messunsicherheiten in der Radiometrie im Bereich von wenigen Photonen bis zu Strahlungsleistungen im Milliwattbereich deutlich reduziert worden. / This thesis addresses the bridging of the radiometric gap in the transition from classical radiometry to the few and single photon radiometry. In this context, two main tasks were emphasised. First: A new radiometric primary detector standard for wavelengths between 400 nm and 800 nm, suitable for classical and few photon radiometry, the so-called “Predictable Quantum Efficient Detector” (PQED) was characterised and validated. For the validation of the PQED, the relative uncertainties achievable in classical radiometry and, in particular, with cryogenic radiometers had to be reduced to a level of 10E−5 with the commissioning of a new cryogenic radiometer facility. Second: A calibration method for single photon detectors in the visible and NIR has been used which is based on the unique properties of synchrotron radiation. This calibration method allows radiometric single photon detector calibrations with the lowest uncertainties reported so far. This method can be used to calibrate free space and fibre-coupled single photon detectors traceable to the international system of units at practically every desired optical wavelength. With the new cryogenic radiometer, the PQED, and the calibration method based on synchrotron radiation, the uncertainties in radiometry have been significantly reduced in the range from milliwatts of radiant power down to attowatts corresponding to a few photons per second.

The C-Band All-Sky Survey (C-BASS) is a 1 GHz bandwidth survey of the radio sky in both intensity and polarization at a frequency of 5 GHz and with a resolution of 0.8. Northern and Southern sky coverage is provided by antennas located at the Owen’s Valley Radio Observatory (OVRO) in California, and the MeerKAT support base in South Africa, respectively. The primary science goal of C-BASS is to provide a highly sensitive C-Band all sky intensity and polarization map to augment the WMAP/Planck surveys. Removal of foregound contamination will place a limit on the success of Cosmic Microwave Background (CMB) experiments that attempt to detect the B-Mode polarization of the CMB. We will provide a HEALPix map (N_side=128) with an r.m.s. noise of 0.13 mK/pixel in Stokes Q and Stokes U, and a confusion limited r.m.s. noise of 0.8 mK/pixel in Stokes I. Removal of foregrounds at the higher frequency CMB surveys will be significantly improved by this lower frequency constraint. This thesis describes the development of the C-BASS gain-stabilized receiver capable of making sensitive measurements of both galactic total intensity and polarization. The receiver features a novel digital backend to provide spectral detail across the frequency band of interest. The analog signal conditioning uses a double sideband mixer to mix the RF frequencies to a DC–1000 MHz baseband for digitization. By changing the mixer frequency and/ or duplicating the signal conditioning and digital hardware, the RF frequency coverage can be modified for other projects. I also describe the process of converting a 7.6 m telecommunications dish to a high performance radio astronomy platform. The discussion includes dish surface measurements, optical design, and the development of an inexpensive telescope servo controller. The antenna conversion process and receiver design can be used to significantly reduce capital costs of future experiments, which is especially useful for short timescale experiments. The African VLBI (Nordling, 2012) is currently following a similar route to repurpose antennas across the African continent.

Thesis (PhD (Physics))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Radioactivity is well known and well understood, but its usefulness in industrial applications to optimise processes or increase economic viability is not yet fully utilised by many industries. This study focuses on the measurement of natural radioactivity and its application in heavy mineral separation and vineyard soil classification. The gamma radiometry set-up consisted of a high purity germanium detector, a Marinelli beaker as sample container and associated electronics. It was calibrated for laboratorybased measurements by minimising the background radiation with the use of lead castle and energy and resolution calibrations. Furthermore, detection parameters were optimised; these included the counting time, the selection of gamma rays used for analysis of a sample, the peak area calculation for the detector dead time and the detector efficiency. Given that the samples had different densities and volumes, the detector efficiency had to be corrected for volume and density effects. After implementation of the corrections and optimisations the detection system was tested and found able to accurately measure radioactivity concentrations. The systematic measurement errors for 238U were 5.1 % in the case of the heavy mineral sands and 34.3 % for the vineyard soils, 4.5 % for the 232Th concentrations and 4.7 % for 40K concentrations. Statistical errors were kept below 2 %. The application of radiometry has not been done before at any South African heavy mineral separation plant. For this reason radiometry is suggested as an easier, faster and cheaper alternative to X-ray fluorescence (XRF) for effective implementation of grade control for zircon to improve the cost benefit of the heavy mineral separation process. Zircon is an example of a heavy mineral that is worldwide in demand with a consumption of more than a million tonnes per year. It is used in a wide range of industrial applications and products that include tiles, sanitary ware and plasma displays. South Africa is the second largest producer of zircon in the world and also has the second largest reserve of available zircon, making this mineral a viable source of income for several years to come. Radioactivity, in the form of uranium and thorium, and other impurities such as iron oxide and titanium oxide are found in the crystal lattice of zircon. For it to be a sellable product, the sum of the uranium and thorium concentrations must be less than 500 parts per million for prime or first grade zircon and less than 1000 parts per million for second grade zircon. At present the concentrations of uranium and thorium in zircon concentrates are measured on a whole rock basis by XRF during and at the end of the processing cycle before the final products are ready to be shipped. This is not an ideal situation as the grab samples are taken periodically and are not necessarily representative of the stream or final assignment and has resulted in significant losses by the producer. The solution is to accurately measure the uranium and thorium concentrations fast or immediately, preferably the measurements must be made online and in real time so that processing decisions can be implemented quickly to optimise the final product. Heavy mineral sand samples were obtained from the various separation processes in a Mineral Separation Plant and their 238U and 232Th concentrations determined. The results indicated that the samples’ uranium to thorium ratios together with their total concentrations can be used to differentiate between the samples (i.e. separation processes). The measurement results were compared with those obtained with XRF. The correlations with radiometry were excellent for the uranium (r2 = 0.992), thorium (r2 = 0.998) and total concentrations (r2 = 0.998). Radiometric measurements were also conducted by decreasing the counting time from 3600 s to 1 s to investigate its effect on the accuracy of the results. Correlations between the different times and 3600 s ranged from excellent to good. The obtained results are then used to recommend that radiometry is used in a Mineral Separation Plant to verify that the zircon and zirkwa meet the specifications, to optimise the entrance feed and the other separation processes and to monitor the tailings streams. Finally the practical aspects of the implementation of radiometry are discussed. As a second application was radiometry applied in an agricultural pilot study to demonstrate the applicability of radiometry as a possible useful tool in soil classification. The creation of a vineyard is a long term and expensive investment and its yield and quality will be influenced by many factors such as the type of soil, viticultural preparations and climate. Information on the different soil types in a vineyard is therefore indispensable for the optimisation of land use with respect to vine cultivar, wine quality and production. Soil samples were obtained from Kanonkop, Simonsig and Spier vineyards and their 238U, 232Th and 40K concentrations determined, assuming that fertilisers would have no effect on the results. The difference in 40K concentrations were related to the clay fraction of the soil and demonstrated that the Kanonkop and Simonsig soils are fine-grained and clay-rich compared to the sandy coarse-grained soils of Spier. The uranium and thorium concentrations were indicators of whether the mineralogy of the soil is the same as the underlying bedrock as well as soil maturity. The measurement results were compared with those obtained with XRF. The correlation with radiometry were poor for the uranium concentrations (r2 = 0.314), as many of the samples concentrations were below the XRF detection limit. The correlations were excellent for both thorium (r2 = 0.985) and potassium (r2 = 0.999). As a positive result from the findings of the study was an in-situ measurement performed by Newman et al. for the radiometric mapping of a Simonsig vineyard for soil classification. / AFRIKAANSE OPSOMMING: Radioaktiwiteit is wel bekend en word goed verstaan, tog is die gebruik daarvan in industriele toepassings om prosesses te optimiseer of winsgrense te verhoog nog nie deur baie industrië ten volle benut nie. Hierdie studie fokus op die meting van natuurlike radioaktiwiteit en die toepassing daarvan in swaar mineraal skeiding en wingerd grond klassifikasie. Die gamma radiometrie opstelling het bestaan uit ‘n hoë suiwerheid germanium detektor, 'n Marinelli beker as monster houer en verwante elektronika. Dit was gekalibreer vir laboratorium gebaseerde metings deur die vermindering van die agtergrondstraling met die gebruik van lood kasteel en energie en resolusie kalibrasies. Verder was deteksie parameters geoptimaliseer, dit sluit in die teltyd, die keuse van gammastrale wat gebruik word vir die ontleding van 'n monster, die piek area berekening, die korreksie vir die detektor se dooie tyd en die detektor doeltreffendheid. Gegee dat die monsters van mekaar verskil het in terme van dighteid en volume was dit nodig om die detektor doeltreffendheid te korrigeer vir volume en digtheid effekte. Na die implementering van die korreksies en optimalisasie was die detektor stelsel getoets en was gevind dat radioaktiwiteit konsentrasies akkuraat gelewer kan lewer. Die sistematiese meet foute vir 238U was 5.1 % vir die mineraal sand en 34.3 % vir wingerd grond, 4.5 % vir 232Th konsentrasies en 4.7 % vir 40K konsentrasies. Statistiese foute was onder 2 % gehou. Die toepassing van radiometrie was nog nie voorheen by enige Suid-Afrikaanse swaar mineraal skeidings aanleg gedoen nie. Vir die rede is radiometrie voorgestel as ‘n makliker, vinniger en goedkoper alternatief teenoor XSF vir effektiewe implementering van graad beheer vir zirkon om die koste voordeel van die swaar mineral skeiding proses te verbeter. Zirkon is ‘n voorbeeld van ‘n swaar mineraal wat wêreldwyd in aanvraag is met ‘n verbruik van meer as ‘n miljoen ton per jaar. Dit word in ‘n wye reeks van industriele toepassings en produkte gebruik onder andere teëls, sanitêre ware en plasma skerms. Suid Afrika is die tweede grootste vervaardiger van zirkon in die wêreld en het ook die tweede grootste reserwe van besikbare zirkon. Dit veroorsaak dat die mineraal ‘n lewensvatbare brom van inkomste is vir nog etlike jare. Radioaktiwiteit, in die vorm van uraan en thorium, word tesame met ander onsuiwerhede soos ysteroksied en titaanoksied in zirkon se kristal rooster gevind. Om ‘n verkoopbare produk te wees moet die som van die uraan en thorium konsentrasies minder wees as 500 dele per miljoen vir prima en eerste graad zirkon en minder wees as 1000 dele per miljoen vir tweede graadse zirkon. Huidiglik word die uraan en thorium konsentrasies in die zirkon konsentraat gemeet op ‘n heel gesteente basis met X-straal fluoroskopie (XSF) gedurende en op die einde van die prosesering siklus net voor die finale produk reg is om versend te word. Dit is nie die ideale situasie nie, want die monsters word periodies geneem en is nie noodwendig verteenwoordigend van die stroom of die finale produk nie en het al tot beduidende verliese deur die vervaardiger gelei. Die oplossing is om die uraan en thorium konsentrasies vinnig of onmiddelik te meet, verkieslik moet die metings inlyn en intyds gedoen word om verwerkings besluite vinnig geimplementeer kan word om die finale produk te optimaliseer. Swaar mineraal sand monsters was verkry van die verskeie skeidingsprosesse in ‘n Mineraal Skeidings Aanleg en hul 238U en 232Th konsentrasies bepaal. Die resultate het aangetoon dat die monsters se uraan en thorium verhoudings saam met hul totale konsentrasies gebruik kan word om te onderskei tussen die monsters (oftewel die skeiding prosesse). Die meting resultate was vergelyk met dié verkry met XSF. Die korrelasies met radiometrie was uitstekend vir die uraan (r2 = 0.992), thorium (r2 = 0.998) en totale konsentrasies (r2 = 0.998). Radiometriese metings was ook uigevoer deur die teltyd te verminder van 3600 s tot 1 s om die uitwerking daarvan op die akkuraatheid van die resultate te ondersoek. Korrelasies tussen die verskillende tye en 3600 s het gewissel van uitstekend tot goed. Die bevindinge was dan gebruik om aan te beveel dat radiometrie in a Mineraal Skeidings Aanleg gebruik kan word om te verifeer dat daar aan die zirkon en zirkwa spesifikasies voldoen word, om die begin voer en ander skeidings prosesse te optimaliseer en ook die uitskot strome te monitor. Laastens is die praktiese aspekte van die implementering van radiometrie bespreek. Vir die tweede toepassing was radiometrie toepgepas in ‘n loods studie in die landbou om die toepaslikheid van radiometrie as ‘n moontlike nuttige instrument in grond klassifikasie te demonstreer. Die skepping van ‘n wingerd is ‘n lang termyn en duur belegging waarvan die opbrengs en kwaliteit beinvloed sal word deur vele faktore, onder andere die tipe grond, wynbou voorbereidings en die klimaat. Inligiting oor die verskillende grond tipes in ‘n wingerd is daarom onmisbaar vir die optimalisering van land gebruik in betrekking tot die wingerdstok kultivar, wyn kwaliteit en produksie. Radiometrie is toegepas om te demonstreer die toepaslikheid daaran as ‘n moontlike nuttige instrument in grond klassifikasie. Grondmonsters was verkry vanaf Kanonkop, Simonsig en Spier wingerde en hul 238U, 232Th en 40K konsentrasies bepaal met die aanname dat kunsmis nie ‘n uitwerking op die resultate sou hê nie. Die verskil in 40K konsentrasies was verwant aan die kleifraksie van die grond en het getoon dat die Kanonkop en Simonsig gronde is fyn korrelrig en kleiryk is in vergelyking met die sanderige growwe korrel grond van Spier. Die uraan en thorium konsentrasies het gedui op die samestelling van die grond en ook aangedui watter grond dieselfde is as die onderliggende rots. Die meting resultate was vergelyk met dié verkry met XSF. Die korrelasie met die radiometrie was sleg vir die uraan konsentrasies (r2 = 0.314) aangesien baie van die monster konsentrasies laer was as die XSF deteksie limiet. Die korrelasies was uitstekend vir beide thorium (r2 = 0.985) en kalium (r2 = 0.999). As ‘n positiewe resultaat van die studie se bevindinge was ‘n in-situ meting gedoen deur Newman et al. om ‘n Simonsig wingerd radiomeries te karteer vir grond klassifasie.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Dale J. Bremer / Jack Fry / Increasing water scarcity may result in greater irrigation restrictions for turfgrass. Drought tolerance and recovery of Kentucky bluegrasses (Poa. pratensis L.) (KBG) were evaluated during and after 88 and 60 day dry downs in 2010 and 2011, respectively, under a rainout shelter. Changes in green coverage were evaluated with digital images. Green coverage declined slowest during dry downs and increased fastest during recoveries in the cultivar ‘Apollo’, indicating it had superior drought tolerance. Electrolyte leakage, photosynthesis, and leaf water potential were evaluated in 7 KBG cultivars during and after the dry downs. Soil moisture at 5 and 20 cm was measured. There were generally no differences in physiological parameters among cultivars during or after dry down. The highest reduction in soil moisture at 5 and 20 cm was in Apollo, suggesting it had a better developed root system for mining water from the profile during drought. Weed prevention and turfgrass establishment of ‘Legacy’ buffalograss (Buchloe dactyloides [Nutt.] Engelm.) and ‘Chisholm’ zoysiagrass (Zoysia japonica Steud.) grown on turf reinforcement mats (TRM) was evaluated. ‘Chisholm’ zoysiagrass stolons grew under the TRM; as such, use of TRM for this cultivar is not practical. Buffalograss had 90% or greater coverage when established on TRM in 2010 and 65% or greater coverage in 2011; coverage was similar to that in oxadiazon-treated plots at the end of each year. ‘Legacy’ buffalograss plugs were established on TRM over plastic for 3 weeks, stored in TRM under tree shade for 7, 14, or 21 days, and evaluated for establishment after storage. In 2010, plugs on mats stored for 7 days had similar coverage to the control, but in 2011 displayed similar coverage to plugs stored on TRM for 14 or 21 day treatments. Green leaf are index (LAI) is an important indicator of turfgrass performance, but its measurement is time consuming and destructive. Measurements using hyperspectral radiometry were compared with destructive measurements of LAI. Results suggest spectral radiometry has potential to accurately predict LAI. The robustness of prediction models varied over the growing season. Finding one model to predict LAI across and entire growing season still seems unrealistic.