Thesis (MTech (Electrical Engineering))--Peninsula Technikon, 2002. / Word processed copy. Summary in English. Includes bibliographical references (p. 115-119). Also available online.

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The research objectives of this study were formulated to produce the soil spectral maps using spectral mixture analysis on the AVMS data of the Walnut Gulch Experimental Watershed, Tombstone, Arizona. To accomplish this objective the spectral characteristics of eight soils of this Watershed were determined considering the effect of the source of illumination/sensor viewing geometry, degree of wetness (dry vs wet), surface roughness, and the source of the spectra (field, sieved samples and lab) on the selection of image and reference endmembers. The scale effect of the source of spectra was also studied in connection with AVIRIS spectral response. The soils presented anisotropic behavior which varied inversely with the wavelength, and it was reduced under wet conditions. Loss of information occurred when moving from large scale data set (lab, sieved sample, and field spectra) to small scale data (AVIRIS). Cluster analysis and factor analysis were used to extract information about how soil reference endmembers are grouped in relation to viewing angles, degree of wetness and the source of the spectra. Factor analysis was applied to identify the key set of bands that carried most of the information. Soil spectral classes varied as a result of scale effects, soil conditions (wet or dry), and viewing angles. Factor analysis showed that with four unique bands (located at 0.410, 1.310, 0.650, and 2.400 p.m) it was possible to reconstruct the four basic soil spectral curves (Epitaph, Graham, McAllister, and Baboquivari) from the lab dataset. AVERT S image was modeled using mixture analysis on the basis of image endmembers and reference endmembers. Based on the four dimensions of the AVIRIS data image endmembers were defined by three soil spectra (McAllister, Stronghold-3, and Graham) and by one spectra of green vegetation. The shade fractions were separated from dark soils (Graham and Epitaph)on the basis of the spatial context The target test identified at least seven reference endmembers in the AVIRIS scene of the Watershed however; mixture analysis failed in obtaining fraction images from these reference endmembers. Mixture analysis was able to produce fraction images with a relatively high error for a small set (3) of reference endmembers (McAllister and Graham soils, and walnut leaf). However when applied to a subset of pixel extracted from the AVIRIS image mixture analysis identified the reference endmembers and quantified their proportions.

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Since 1975 McCarthy and Low have conducted a program of Michelson spatial interferometry at infrared wavelengths, measuring a large number of evolved stars and protostellar objects. This dissertation discusses the development of an infrared speckle interferometer which was used to extend those observations. This instrument uses a modified version of the technique pioneered by Sibille, Chelli, and Lena. The secondary mirror is used to scan the image across a narrow slit. Each scan is fourier transformed, and the modulii squared of many such transforms are coadded. Both the object of interest and a point source are observed. The square root of the ratio of their power spectra is the visibility as defined by Michelson. This system was assembled for the most part with existing equipment and the design should be readily adaptable to other observatories. Initial tests were made with the 154 cm telescope of the University of Arizona since it had a preexisting mechanism for scanning the secondary. However most of the observations were carried out with the University's 229 cm telescope. A new linear servo was added to the existing hard-stop chopper for this telescope's f/45 secondary. Three detector systems were used to provide wavelength coverage from 2 to 12 microns. An N₂ cooled InSb and a He cooled bolometer were available from the Michelson program. In addition a high sensitivity He cooled InSb detector from the Steward Observatory FTS was used. Slits with an angular size of λ/2D, where D is the telescope diameter were placed at the focal plane in the dewar. The narrow slit results in diffraction losses when used with conventional dewar optics. The loss could be eliminated with optics optimized for this application. However even with the loss, a large number of objects could be observed. Test results at 2 microns were obtained for a double star, the asteroids Vesta and Ceres, and the Galilean satellites Ganymede and Callisto, The protostellar objects W3 IRS 5, S140, and Mon R2 IRS 3 were resolved. The separation, orientation, and relative brightness of the two components IRS 5 were measured at 5 microns. The separation is 1.26" ±0.06 and the position angle is 37° ±5. The brightness ratio is approximately 0.59. S140 and Mon R2 IRS 3 were observed at 2 microns. S140 shows some indication of an extended region of greater than 1" contributing half the flux. IRS 3 has a size of approximately 1" but the data is too noisy for an exact fit. Upper size limits were determined for BN, GL 490, GL 2591, and NGC 2264 IRS. A large number of evolved stars were observed. The size of the shell around Alpha Ori was found to be ∼4" at 11 microns. Observations were obtained for IRC + 10216 at 2, 5, 8, and 11 microns which further define the asymmetrical shape of this object. Observations were also obtained for VY CMa. Upper size limits were established for Omicron Ceti, IRC + 10011, RX Boo, R Hyd, W Hyd, and CIT 6.

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In this project we have used Fourier transform infrared spectroscopy to study the photoresponse of two different types of quantum dot-in-a-well infrared photodetectors (DWELL QDIPs). The basic task was to compare the photoresponse of these two detectors, and to study the influence of external resonant laser pumping on the photoresponse. Series of measurements were done at 77K. In the first measurements we investigated the photoresponse for different applied voltages at 77K. In a second run of experiments, we used a 1064 nm infrared semiconductor laser to resonantly pump the fundamental transition of the quantum dots. The results show that by using this additional illumination the photoresponse was dramatically increased by creating additional charge carriers in the quantum dots. This could be used to increase the sensitivity of infrared detectors based on QDs.

The level of information provided by electrochemical measurements can be substantial as evident by the use of electrochemistry in varied disciplines spanning from materials research to cellular biochemistry. However, electrochemistry on its own does not provide direct information concerning redox induced changes in molecular structure. This information can only be elucidated by coupling spectroscopic and/or separation techniques with traditional electrochemical methodologies. In principle, infrared (IR) spectroelectrochemistry (SEC) is ideal for such studies but in practice coupling IR spectroscopy and electrochemistry are often experimentally incompatible. Since the inception of in-situ IR SEC techniques in the 1980’s, two competing methodologies (using either external- or internal- IR reflection geometries), were developed to deal with the two major challenges associated with IR SEC (strong infrared absorption of the electrolytes and weak analytical signals). The primary focus of this thesis is the successful advancement of IR SEC techniques through the implementation of synchrotron infrared radiation with ultramicroelectrodes (UMEs; electrode diameters < 25 µm) to study spectroelectrochemical processes on the microsecond time scale. Several examples using Surface Enhanced Infrared Absorption Spectroscopy (SEIRAS) are presented including the adsorption of dimethylaminopyridine (DMAP) on gold substrates and the proton-coupled electron-transfer (PCET) kinetics of electrochemically-active 1,4-benzoquinone terminated self-assembled monolayers (SAMs). These studies highlight the benefits of coupling electrochemistry and infrared spectroscopy. For instance, in-situ spectroscopic evidence shows that small amounts of DMAP’s conjugate acid (DMAPH+) adsorb on gold electrodes in acidic electrolytes and at negative potentials. This result was not forthcoming from previous electrochemical measurements and was only realized through in-situ SEIRAS. Finally, the largest contribution in advancing in-situ IR SEC methodologies was through the development of utilizing synchrotron infrared radiation on UMEs to study fast electrochemical processes. This work was technically very challenging and emphasized the interfacing of an electrochemical cell containing an UME with fast infrared data acquisition techniques (i.e. rapid scan and step-scan interferometry). The use of a prototypical electrochemical system, i.e. the mass-transport controlled reduction of ferricyanide, indicate that at short times the spectroscopic signal closely matches the electrochemical signal but at long time scales it deviates due to edge effects associated with the diffusion environment of the UME.

The Andromeda Galaxy (M31) is an ideal target for detailed studies of galaxy structure and tests of stellar population models. This thesis presents deep Canada-France-Hawaii Telescope WIRCam near-infrared J- and Ks-band photometric maps of M31. These near-infrared data alleviate the age-metallicity-dust degeneracy that plagues stellar population analysis of optical-only maps. For the sake of calibrating stellar population models, a detailed reconstruction of the M31 near-infrared surface brightness and a study of sky subtraction uncertainties is needed. The analysis of our 2007 and 2009 WIRCam data has revealed unexpected spatial variations in the sky background shapes over the width of the WIRCam fields. In order to solve for the offset caused by such fluctuations, we have used couplings between images. Scalar sky offsets are optimized to produce a mosaic that is seamless within 0.02% of the sky background. These offsets are solved hierarchically, to reduce the dimensionality of optimizations, and an adaptation of the Nelder Mead downhill simplex ensures a globally optimal solution. Variations in sky shape are well-characterised in median sky images built by nodding to a random ring of sky fields every 1.2 minutes. Sky shape appears consistent across the 3˚ ring of sky fields, while levels do change by ~2%, suggesting that the dominant sky structures extend beyond the M31 survey region. Planar sky offset optimization was tested and promises to significantly improve continuity across the outer disk of M31. Our near-infrared data are part of an effort to assemble a multi-wavelength data set for M31 to study a broad suite of topics in stellar and galaxy evolution. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-12-07 15:34:00.279