A major paradigm shift in the design of large telescopes is currently in progress. In order to increase the size of a telescope primary mirror, current designs use mirrors that are comprised of multiple segments instead of one monolithic piece. While this approach allows for larger primary mirrors than the monolithic approach, new challenges arise. One of the primary challenges is to accurately, rapidly, and cost-effectively test the multiple asphere segments. This dissertation provides a thorough design analysis and experimental validation on a novel method, proposed by Burge and Anderson, for measuring off-axis aspherical surfaces using test plate and computer-generated holograms. This new method is optimal for measuring segments of aspheric primary mirrors, and can be applied to any aspheric surface, convex or concave. It interferometrically compares the aspheric surface with a nearly matching spherical reference surface and uses CGH to compensate the aspherical departure. Like other Fizeau-type interferometric tests, high accuracy is achieved economically since the spherical reference is the only surface that directly affects the measurement. This technique is optimal for testing primary mirror segments where all the different off-axis pieces of the asphere can be measured with a single test plate, replacing only the smaller hologram. The most important property of this test for segmented mirrors is the fine control of the curvature provided by using a reference plate in close proximity to the aspherical surface being measured. This allows all the segments to be separately manufactured, assumes that they will fit together to form a single aspheric surface. In this dissertation, I examine, optimize, and validate this novel method, making it readily available for future telescope designers/manufacturers. First, the quantitative analysis on how segmentation tightens the testing requirements during fabrication and alignment provides valuable information in determining essential telescope parameters such as segment size, F/#, fabrication and alignment specifications. Secondly, the detailed optimization processes show how the test system can be designed and built to achieve high accuracy with maximum cost effectiveness. Lastly, the experimental data successfully validate the test and the method of design and analysis.

The terahertz (THz) frequency domain, located at the frontier of radio and light, is the last unexplored region of the electromagnetic spectrum. As technology becomes available, THz systems are finding applications to fields ranging all the way from astronomical and atmospheric remote sensing to space telecommunications, medical imaging, and security. In Astronomy the THz and far infrared (IR) portion of the electromagnetic spectrum (lambda = 300 to 10 mum) may hold the answers to countless questions regarding the origin and evolution of the Universe, galaxy, star and planet formation. Over the past decade, advances in telescope and detector technology have for the first time made this regime available to astronomers. Near THz frequencies, metallic hollow waveguide structures become so small, (typically much less than a millimeter), that conventional machining becomes extremely difficult, and in many cases, nearly impossible. Laser induced, micro-chemical etching is a promising new technology that can be used to fabricate three dimensional structures many millimeters across with micrometer accuracy. Laser micromachining of silicon possesses a significant edge over more conventional techniques. It does not require the use of masks and is not confined to crystal planes. A non-contact process, it eliminates tool wear and vibration problems associated with classical milling machines. At the University of Arizona we have constructed the first such laser micromachining system optimized for the fabrication of THz and far IR waveguide and quasi-optical components. The system can machine structures up to 50 mm in diameter, down to a few microns accuracy in a few minutes and with a remarkable surface finish. A variety of THz devices have been fabricated using this technique, their design, fabrication, assembly and theoretical performance is described in the chapters that follow.

An intensive observational program of Asymptotic Giant Branch (AGB) and post-AGB stars has been conducted in order to investigate the role of metal-containing compounds in the circumstellar envelopes surrounding these objects. The role of metal bearing molecules in the chemical evolution of these envelopes was also examined. These studies have led to the detection of a new interstellar molecule, AlNC, as well as the first identification of metal species in two new sources. Specifically, MgNC, AlF, NaCl, and NaCN were seen for the first time towards CRL 2688 and MgNC was also detected in CRL 618. These detections, and the non-detection of metal carbide or metal nitride species, indicate that metals preferentially form cyanide complexes in circumstellar clouds. The process of formation for these species is believed to be radiative association of a metal ion with a cyanopolyne chain followed by dissociative recombination. It has also been discovered that, as a star evolves, abundances of metal molecules in the inner circumstellar envelope decrease due to photo-destruction processes or adsorption onto dust grains. A new chemical code to study molecular abundances in the inner circumstellar envelope of AGB stars has also been developed. This new chemistry code is unique in that it is the first attempt to take a kinetic approach to the equilibrium problem. A system of reactions is used as a pathway to reach equilibrium at a specified temperature and density. This new technique allows the monitoring of abundance changes over time and can be used as a foundation for non-LTE calculations. The model results were consistent with previous work and older methods. The abundances of metal halides and NaCN in the AGB phase can be explained because of equilibrium processes at temperatures less than 1600 K for moderate to high densities. The model also demonstrated that AlNC could be produced in equilibrium conditions in amounts greater than the observed abundance of this molecule in IRC+10216. Chemical changes with time were monitored and it was shown that equilibrium processes occur on timescales larger than the typical pulsational period of an AGB star. Finally, abundance predictions were made for several potential new circumstellar metal-containing molecules.

The field of adaptive optics (AO) and laser-beacon AO has been successfully implemented in the last part of the 20th century. Adaptive optics greatly improves the resolution capabilities of ground-based telescopes by correcting for atmospheric turbulence. The initial implementation of laser-beacon AO was done on relatively small telescopes, on the order of 1.5 m. However, with larger aperture telescopes being built, such as the 8-m class Gemini telescopes, there is much room for improvement. Errors resulting from laser-beacon AO, such as focus anisoplanatism, become worse with an increase in aperture diameter. Tilt anisoplanatism is also a problem, regardless of the size of telescope, and also needs to be reduced to enhance the resolution of the objects being observed. This dissertation investigates alternate laser-beacon AO configurations, to reduce the effects of focus and tilt anisoplanatism for larger aperture telescopes. The configurations investigated include single and multiple laser beacons at single altitudes and single and multiple laser beacons at multiple altitudes. These second configurations are referred to as hybrid beacon systems and consist of Rayleigh beacons at altitudes of 10 to 20 km and sodium beacons at about 90 km, the location of the sodium layer. Hybrid systems are shown to reduce both focus and tilt anisoplanatism as opposed to the first configurations which only aid in reducing focus anisoplanatism. An addition to the hybrid systems with multiple beacons, the use of multiple deformable mirrors (DM's) is investigated. These additional DM's are placed conjugate to atmospheric altitudes with predominant turbulence, beyond the traditional conjugate location of the primary mirror. They correct for turbulence at these atmospheric layers and are referred to as multi-conjugate adaptive optical (MCAO) systems. The purpose of MCAO configurations is to increase the corrected field of view. For the types of systems investigated in this dissertation, radiometric characteristics are calculated. These include the optimum range-gate at the minimum noise equivalent angle (NEA) for several laser pulse energies, wavefront sensor sampling rate as a function of bandwidth, and the optimum system bandwidth for several laser powers. These characteristics can be used to further define a practical AO system that will enhance performance.

Impact cratering is a complex process which is not yet fully understood, especially in the cases of large planetary events. Most of the observations of impact craters created by such events are limited to remote sensing of their surface morphology; although there are large terrestrial craters whose sub-surface structures can be studied, most have been modified by subsequent geologic activity. Laboratory experiments are necessarily limited to very small impacts so their results need to be extrapolated over many orders of magnitude to compare to the largest terrestrial craters (>100 km in diameter). So, in order to study the formation of large craters it is useful to employ numerical simulations. Finite-element modeling is a numerical method that can accommodate complex structures and a variety of rheologies and can perform simulations at any scale. It is, therefore, useful for simulating impact crater collapse and I have used it to investigate different aspects of this process. In collaboration, E. Pierazzo and I used both hydrocode and finite-element modeling to recreate the formation of the Vredefort structure in order to predict where the pressure of an impact-generated shock wave would have been sufficient to form shatter cones and planar deformation features and to follow their subsequent displacement during crater excavation and collapse. By comparing the results of simulations of impacts by projectiles of various sizes to the observed locations of the shock features around Vredefort we constrained the projectile diameter to be 10-14 km. This corresponds to a final crater diameter of 120-200 km. I used finite-element models of crater collapse to investigate the ring-tectonic theory of multiple ring crater formation. The results of these models indicate that the ring-tectonic theory is consistent with the formation of circumferential faults around large terrestrial impact craters such as Chicxulub. The final project described in this dissertation uses the morphologies of impact craters on the icy Jovian satellite Europa to probe its lithospheric structure. Comparisons of simulated stress fields to the observed fracture patterns around Europan craters suggest that the elastic lithosphere in which the crater formed was at least 12 km thick.

In recent years astronomers have been pushing to build larger ground-based telescopes with apertures greater than 5 m in order to see deeper into space and resolve smaller objects. Realistically, while a larger telescope aperture allows more light to be collected, atmospheric turbulence caused by thermal gradients in the atmosphere limits the achievable resolution to a level comparable with apertures on the order of half a meter or less. Adaptive optics (AO) can be used to counteract the degrading effects of the atmosphere in real time and recover diffraction-limited resolution. With the help of AO, better science can be done, and as more large ground-based telescopes are built, the need for reliable AO systems grows. The 6.5 m upgrade to the Multiple Mirror Telescope (MMT) on Mt. Hopkins is an example of a large telescope project. An infrared adaptive optics system for this telescope is currently under construction at Steward Observatory in the Center for Astronomical Adaptive Optics. This dissertation reports on the design, construction, and testing of various components of this AO system with which the author was involved. These components include the deformable secondary mirror, the wave front sensor, a laboratory testing system, and wavefront reconstruction algorithms.

This thesis contains complementary aspects of the Seyfert phenomenon, each of which is analysed to bring a better understanding of present unification theories. Observations of the nuclear regions of various types of Seyfert galaxies were mostly made at infrared wavelengths which allow the study of dusty environments and provide new information on the physical conditions of these objects. For example, near infrared spectroscopy of Seyfert 2 galaxies revealed that there is a subclass of type 2 Seyferts with hot IR excess at ∼3μm with broad IR emission lines suggesting that some Seyfert 2s do in fact contain a hidden Seyfert 1 nucleus. Additional spectropolarimetry showed that the scattering screens, postulated in the standard model, are not always present in Seyfert 2s. At mid infrared wavelengths, it was found that the 10μm nuclear emission of Seyferts with broad emission lines is intrinsically brighter than that of Seyferts with no broad lines. The extended 10mum emission shows that Seyfert 2 galaxies present enhanced star-formation when compared to Seyfert 1s. Both results pose obstacles for present unification ideas and I discuss possible interpretations to these observations. Seyfert galaxies were also observed at radio wavelengths to study their large scale emission of 1-0 CO. Surprisingly, this emission usually related with star formation activity was found to be similar in both types of Seyfert galaxies and therefore does not explain why Seyfert 2 galaxies have enhanced star formation as concluded in the 10mum study. A study of galaxy morphology and companions in this set of Seyferts shows at a significant statistical level that Seyfert 2s present a higher incidence of asymmetric morphologies compared to Seyfert 1s and field galaxies, and therefore are undergoing gravitational perturbations which may induce star formation. Near infrared spectroscopy of a large sample of Seyfert galaxies is analysed to study the excitation mechanisms of [FeII] and H₂ lines in the NLR of Seyfert galaxies, a subject which is in great debate at present. Here I present some results indicating that shock excitation is likely, but not always, the dominant mechanism that excites these IR lines.

A paleotopographic reconstruction has revealed the potential existence of an ancient enormous drainage basin and productive regional aquifer system in the eastern part of the Tharsis region. The basin model addresses a fundamental question in martian paleohydrology: Where did the massive amount of water required to carve the catastrophic outflow channels come from? These gigantic channels are typified in the recently discovered northwestern slope valleys (NSVs). The paleohydrologic implications for the NSVs are enormous, as they represent: (1) previously undocumented Noachian and early Hesperian martian catastrophic floods, (2) a watershed to the northwest of Tharsis, possibly related to the early development of the circum-Chryse system of outflow channels, a watershed to the northeast that records flooding as recent as the early Amazonian, and (3) a potential source of water for a northern plains ocean and/or paleolakes. In addition to catastrophic outflows, Hesperian and Amazonian hydrological activity resulted in the formation of sapping valleys, such as Abus Vallis. An investigation of Wet Beaver Creek, Arizona, revealed geological, hydrogeological, and geomorphic similarities between Wet Beaver Creek and Abus Vallis, Mars. As such, one may infer lithological and hydrological similarities as well. Wet Beaver Creek represents geological and climatological conditions that result in rapid, sometimes dynamic, formation of sapping channels. Sapping channels that occur along the highland-lowland boundary scarp, such as Abus Vallis, may now also be explained in terms of rapid formation during short-term periods of global climatic change, as well as by hypersaline aquifers and hydrothermal processes. The dark slope streaks on Mars may represent yet another type of hydrogeomorphic process, different from the NSVs and Abus Vallis. In light of Mars Global Surveyor-based geographic, geologic, and morphologic considerations, spring discharge is a viable explanation for the formation of dark slope streaks. Such activity would indicate the existence of near-surface aquifers and, more importantly, hydrological processes acting upon the surface of the planet, making it the only other hydrogeomorphically-active planet in the solar system besides Earth.

In the 45 years since the dawn of the space age, there have only been two Mars lander camera designs to successfully operate on the Martian surface. Therefore information on Mars imager design and operation issues is limited. In addition, good examples of Mars lander imager calibration work are almost non-existent. This work presents instrument calibration results for a Mars lander camera originally designed to fly as an instrument onboard the 2001 Mars Surveyor lander as a robotic arm camera (RAC). Test procedures and results are described as well as techniques for improving the accuracy of the calibration data. In addition we describe camera algorithms and operations research results for optimizing imager operations on the Martian surface. Finally, the lessons learned from the 2001 RAC are applied to the preliminary design of a new Mars camera for the Artemis Mars Scout mission. The design utilizes a Bayer color mosaic filter, white light LED's and includes an optical system operating at f/13 with a maximum resolution of 0.11 mrad/pixel. It is capable of imaging in several modes including: stereo, microscopic and panoramic at a mass of 0.3 kg. It will provide planetary geologists with an unprecedented view of the Martian surface.

Chemistry in the interstellar medium is very different from the processes which take place in terrestrial settings. Environments such as circumstellar envelopes, molecular clouds, and comets contain diverse and complex chemical networks. The low temperatures (10-50 K) and densities (1-10⁶ cm⁻³) allow normally unstable molecules to exist in significant quantities. At these temperatures, the rotational energy levels of molecules are populated, and thus these species can be detected by millimeter-wave radio astronomy. The detection and quantification of interstellar molecules, including metal cyanides and molecular ions, is the basis of this dissertation work. While conducting observations of CN and ¹³CN to determine the ¹²C/¹³C ratio throughout the Galaxy, it was found that the ratios in photon-dominated regions (PDRs) were much higher than those in nearby molecular clouds. This can be explained by isotope-selective photodissociation, in which the ¹²CN molecules are self-shielded. However, the chemistry in these regions is poorly understood, and other processes may be occurring. In order to understand one of the chemical networks present in PDRs, observations of HCO⁺, HOC⁺, and CO⁺ were made toward several of these sources. Previous studies indicated that the HCO⁺/HOC⁺ ratio was much lower in PDRs, due to the presence of CO⁺. The new observations indicate that there is a strong correlation between CO⁺ and HOC⁺ abundances, which suggests that other molecular ions which have not been detected in molecular clouds may be present in PDRs. There is a significant obstacle to the detection of new interstellar molecular ions, however. The laboratory spectra are virtually unknown for many of these species, due to their inherent instability. Thus, techniques which can selectively detect ionic spectra must be utilized. One such method is velocity modulation, which incorporates an AC electrical discharge to produce and detect ions. Previously, velocity modulation spectroscopy was employed only at infrared wavelengths. The final phase of this dissertation work was to design, build and test a velocity modulation spectrometer which functions at millimeter/sub-mm wavelengths. This system was then used to measure the previously unknown pure rotational spectrum of SH⁺ (X3Σ⁻).