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We use Spitzer Space Telescop and Heinrich Hertz Telescope(HHT) observations to study the earliest stages of low--mass starformation. Using spatially resolved absorption features, termedshadows, we study the cold cloud cores where stars form.We study Barnard 335, a prototypical isolated Bok globule with anembedded Class 0 protostar. We discover an 8 micron shadow in theinner regions of the core; using this feature we measure the densecore structure and mass. Using HHT observations we detect a rotatingstructure, a flattened molecular core, with a diameter~ 10,000 AU. The flattened molecular core is likely to be thesame structure as that generating the 8 micron shadow, and isexpected from theoretical simulations. This structure has not beenrobustly detected in previous observations although there have beensome prior indications of its presence.We study dense starless core structure through longer wavelengthobservations of shadows; we present Spitzer observations of 8 micron,24 micron, and 70 micron\ shadows of 14 cores in total. Combined withHHT observations of 12CO 2--1 and 13CO 2--1, we derive core sizes,masses, study core structure, and investigate the collapse status ofeach core. Our study of starless core CB190 reveals that the core islikely to be stable against collapse if magnetic pressure is presentat a reasonable level in the core. Our study of the 70 micron shadowassociated with the starless core L429 reveals that this object isvery likely to be collapsing. Finally, we study a sample of 12starless cores selected to have prominent 24 micron shadows. We findthat about 2/3 of these sources are likely to be collapsing.Additionally, we find indications that 1/2 of the cores revealed to becollapse candidates show indications of having 70 micron shadows. Weconclude that all cores dense enough to produce 70 micron shadows arecollapse candidates, and that the presence of a shadow at 24 micronis an indicator that the core is likely (60% probability)to be collapsing.

The Rodessa Formation is one of the major oil and gas reservoirs in the East Texas Basin. In Van Field, the upper Rodessa Formation consists of interbedded biotic and abiotic mudstones to grainstones. The lower Rodessa is composed of interbedded sandstones, shales, and limestones called the Carlisle Member. Based on core and well log interpretation, the Rodessa Formation was deposited on a broad, restricted, shallow marine platform interpreted to be lagoonal, subtidal, and intertidal. Both Rodessa limestone and sandstone have been altered significantly by diagenetic processes that include micritization, cementation, dissolution, neomorphism and compaction. Dissolution is the main factor that resulted in enhanced porosity and permeability while cementation adversely affected porosity. Diagenesis is interpreted to have begun in the marine phreatic environment and continued through the freshwater phreatic and shallow burial environments. Two reservoir units have been identified from core and well log interpretations. The potential reservoir within the Rodessa Formation occurs in the Carlisle Member which is composed mainly of medium to coarse grained sandstone with porosities and permeabilities in ranges of 8 to 11 percent and 46 to 896 millidarcies, respectively. The water saturation analysis has also shown the reservoir to be hydrocarbon bearing, having water saturation below 46 percent.

Formation flying is a new paradigm in space mission design, aimed at replacing large satellites with multiple small satellites. Some of the proposed benefits of formation flying satellites are: (i) Reduced mission costs and (ii) Multi mission capabilities, achieved through the reconfiguration of formations. This dissertation addresses the problems of initiatialization, maintenance and reconfiguration of satellite formations in Earth orbits. Achieving the objectives of maintenance and reconfiguration, with the least amount of fuel is the key to the success of the mission. Therefore, understanding and utilizing the dynamics of relative motion, is of significant importance. The simplest known model for the relative motion between two satellites is described using the Hill-Clohessy-Wiltshire(HCW) equations. The HCW equations offer periodic solutions that are of particular interest to formation flying. However, these solutions may not be realistic. In this dissertation, bounded relative orbit solutions are obtained, for models, more sophisticated than that given by the HCW equations. The effect of the nonlinear terms, eccentricity of the reference orbit, and the oblate Earth perturbation, are analyzed in this dissertation, as a perturbation to the HCW solutions. A methodology is presented to obtain initial conditions for formation establishment that leads to minimal maintenance effort. A controller is required to stabilize the desired relative orbit solutions in the presence of disturbances and against initial condition errors. The tradeoff between stability and fuel optimality has been analyzed for different controllers. An innovative controller which drives the dynamics of relative motion to control-free natural solutions by matching the periods of the two satellites has been developed under the assumption of spherical Earth. A disturbance accommodating controller which significantly brings down the fuel consumption has been designed and implemented on a full fledged oblate Earth simulation. A formation rotation concept is introduced and implemented to homogenize the fuel consumption among different satellites in a formation. To achieve the various mission objectives it is necessary for a formation to reconfigure itself periodically. An analytical impulsive control scheme has been developed for this purpose. This control scheme has the distinct advantage of not requiring extensive online optimization and the cost incurred compares well with the cost incurred by the optimal schemes.

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