In accordance with the title, the present paper divides itself into two parts, of which the first wil1 be a brief resume of the planetary work done here, with a few details and announcements which have not heretofore been given to the public, and the second will present the writer's personal opinions of why it has been possible to reach these results. The latter must necessarily be more in the form of suggestions than facts, for to give facts one must have tried personally many widely separated localities over long periods of time.

Numerical methods have been used to predict the eigenperiods and eigenfunctions of the Earth’s Slichter modes, known as the Slichter triplets. In order to test the validity of our method, we have also computed the frequencies and displacement eigenfunctions of some of the inertial modes of the Earth’s fluid core. We use a Galerkin method to integrate the Three Potential Description (3PD) for a neutrally, stratified and rotating fluid core of a modified Preliminary Reference Earth Model (PREM). Moreover, the same mathematical tool is used for the computation of the frequencies and displacement amplitudes of the Slichter modes. In the Galerkin formulation of the 3PD, using the divergence theorem, we make use of the natural character of the boundary conditions to reduce the order of derivatives from second to first. To compute the frequencies of the Slichter modes, we solve simultaneously the equations of the inner core motion and the dynamics of the fluid core as described above. The results are compared to those in previous studies and it is shown that in the case of the inertial modes they agree well, which proves the validity of the approach. For the Slichter modes, however, it is shown that the results are significantly different from previous work for a similar Earth model. We have also plotted the displacement eigenfunctions for the motion of the fluid in the fluid core during the Slichter oscillations. It is shown that the pattern of motion is consistent with the motion of the inner core, which serves as a second test of the validity of our results. / x, 105 leaves : ill. ; 29 cm

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The primary objective of this thesis is to develop a framework to compare the performance of fixed-wing aircraft, airships, and the rotary-wing aircraft in the Martian environment and through that framework, determine which of these platforms is best suited to conduct a series of scientific investigations on Mars. Three Mars mission scenarios provide the context within which the performance of the platforms is evaluated. The mission scenarios are used to derive the performance requirements including the range and flight path to be covered, the altitude at which the platforms fly, and the scientific investigations to be performed along with the associated scientific instrumentation to be carried as payload. Existing platform designs are used for the purpose of this comparative study and are modified depending on specific mission requirements. A set of weighted performance metrics, including the gross takeoff mass, power required, manoeuvrability, and complexity, serves as a common basis for comparing the performance of the three aerial platforms. The results of this comparative study indicate that the airship is best suited for all mission scenarios considered due to its simplicity and high degree of manoeuvrability. However, it is important to note that a series of subjective design choices with respect to platform speed and available power were made that significantly impact the overall performance of the platforms. Altering these design choices as well as the mission requirements could result in a different platform being best suited for each Mars mission. For instance, increasing the cruising velocity of the fixed-wing aircraft may allow its dimensions to be scaled down thereby reducing the complexity and making it a more competitive platform for long-range missions. In addition, for short-range missions that do not require a high degree of manoeuvrability but where the gross takeoff mass and complexity are more important factors, the rotary-wing aircraft becomes the best option.

There are many observational methods for studying debris disks because of constraints imposed on observing their predominately infrared wavelength emission close to the host star. Two methods which are discussed here are ground-based high contrast imaging and space-based far-IR emission. The Gemini Planet Imager (GPI) is a high contrast near-IR instrument designed to directly image planets and debris disks around other stars by suppressing star light to bring out faint sources nearby. Because debris disks are intrinsically polarized, polarimetry offers a useful way to enhance the scattered light from them while suppressing the diffracted, unpolarized noise. I discuss the characterization of GPI's microlens point spread function (PSF) in polarization mode to try to improve the quality of the processed data cubes. I also develop an improved flux extraction method which takes advantage of an empirically derived high-resolution PSF for both spectral and polarization modes. To address the instrumental effects of flexure, which affect data quality, I develop methods to counteract the effect by using the science images themselves without having to take additional calibrations. By reducing the number of calibrations, the Gemini Planet Imager Exoplanet Survey (GPIES) can stand to gain ~66 hours of additional on-sky time, which can lead to the discovery of more exoplanetary systems. The Herschel Space Observatory offers another method for observing debris disks which is ideally suited to measure the peak dust emission in the far-IR. Through a careful analysis, we look at 100/160 μm excess emission around λ Boo stars, to differentiate whether the emission is from a debris disk or a bowshock with the interstellar medium. It has been proposed that the stars' unusual surface abundances are due to external accretion of gas from those sources. We find that the 3/8 stars observed are well resolved debris disks and the remaining 5/8 were inconsistent with bowshocks. To provide a causal explanation of the phenomenon based on what we now know of their debris disks, I explore Poynting-Robertson (PR) drag as a mechanism for secondary accretion via a debris disk. However, I find that the accretion rates are too low to cause the surface abundance anomaly. Further study into the debris disks in relation to stellar abundances and surfaces are required to rule out or explain the λ Boo phenomenon through external accretion. / Graduate / 0606 / zhd@uvic.ca

Spectroscopic measurements in the infrared have proven to be a valuable source of information about the Jovian atmosphere. However, numerous questions remain, many of which will be addressed by the Galileo μission, due to arrive at Jupiter in December, 1995. One of the instruments on Galileo is the Near-Infrared Mapping Spectrometer (NIMS), which will measure temperature structure, cheμical composition, and cloud properties. The objective of the work described in this thesis was to investigate the transmittance properties of the Jovian atmosphere and, in particular, to obtain transmittance functions of CH₄ for future use in the planning and interpretation of NIMS measurements. This thesis begins with a review of our current understanding of the Jovian atmosphere (Chapter 1), and a description of the Galileo μission and the design and objectives of NIMS (Chapter 2). It is then shown (Chapter 3) that absorption bands of CH₄ doμinate the nearinfrared spectrum of Jupiter, but that line data for CH₄ are currently inadequate over much of the NIMS spectral range (0.7-5.2 /μi). For the purposes of NIMS, which has a low resolution of 0.25 /μi, the spectrum of CH₄ can be characterised using band models of transmittance as a function of temperature, pressure, and abundance. The theory of band modelling is presented, and previous band-modelling studies of CH₄ are reviewed and are also shown to be inadequate for NIMS (Chapter 4). An experimental investigation was therefore undertaken to record CH₄ spectra under Jovian conditions of low temperature, large abundance, and H₂-broadening. The experimental resources used to obtain these spectra are described (Chapter 5), the generation of the transmittance spectra is discussed, and their quality is assessed (Chapter 6). The range of frequencies and laboratory conditions covered by these spectra (listed in Appendix A) makes them one of the most comprehensive data sets of this kind yet published. These spectra were subsequently used to derive transmittance functions for CH₄ (Chapter 7). A variety of models were fitted to the self-broadened CH₄ spectra, and the Goody and Malkmus random band models, using the Voigt lineshape, are shown to provide the best fits. These two models were then fitted to the combined set of self- and H₂-broadened CH₄ spectra. The parameters fitted with the Goody-Voigt model are included in this thesis (Appendices B and C). Finally, the application of these new band model fits to the problem of Jovian remote sounding is addressed (Chapter 8). This includes an assessment of the reliability of extrapolation to Jovian conditions, a calculation of the level in the Jovian atmosphere that will be sounded by observations of CH₄ absorption, and a calculation of how the uncertainties in the fitted band model will affect the retrieval of atmospheric parameters from NIMS spectra. This thesis concludes with a detailed summary, and with suggestions for future investigations which will help to maximise the return of information from NIMS.