Satellite panicum mosaic virus (SPMV) depends on its helper Panicum mosaic virus (PMV) for replication and movement in host plants. The positive-sense single-stranded genomic RNA of SPMV encodes a 17-kDa capsid protein (CP) to form 16-nm virions. Previous studies showed that SPMV CP has multiple functions during infection including encapsidation, symptom exacerbation, inhibiting the accumulation of SPMV DIs, and facilitating systemic movement. This dissertation confirms and extends the results of our previous reports with new biological and biochemical evidence. For example, the dosage effect of SPMV CP on symptom severity supports its function as a pathogenicity factor. Biological assays also demonstrate compensatory effects of SPMV CP on virus mutants defective in systemic movement. In addition, it is shown for the first time that SPMV CP is involved in cellto- cell movement of SPMV RNA and associated with the cell wall and membranes, a signature property of plant virus movement proteins. However, SPMV CP in the cytosol exists exclusively as virions and is dispensable for symptom exacerbation. SPMV CP contains a distinctive N-terminal arginine-rich motif (N-ARM), which is required for the in vitro binding of SPMV and PMV genomic RNAs by SPMV CP. Mutations of this region impair all known functions of SPMV CP. Interestingly, manipulation of the C-terminus of SPMV CP resulted in the same phenotypes as alterations in the N-ARM except that this does not affect the RNA binding activity of SPMV CP. Biological experiments demonstrate that virions are not required for the properties of SPMV CP to facilitate local and systemic movement and inhibit the accumulation of SPMV DIs, suggesting that SPMV CP and RNA form alternative complexes for these purposes. This dissertation study reveals the nucleolar localization of SPMV CP and its interaction with PMV CP in the form of virions. The identification of distinct functional domains of SPMV CP and its complex subcellular localization profile resulted in the proposal of a tentative model on how the functions of SPMV CP are coordinated for a robust infection. This dissertation provides a foundation for further understanding of the complex interactions among host plants, helper viruses, and satellites.

Abstract On September 24, 1999, the first high-resolution commercial nature resource satellite, IKONOS-2, had been successfully launched. This started a new era to the applications of remote sensing. The best resolution of the IKONOS imageries is 0.82m. This imagery provides more detail spatial information than previous satellites. Many high spatial resolution satellites with hyper-spectral imageries will be launched successively by the year of 2002. When the time comes, the application of remotely sensed images in the area of land and sea will certainly be more widespread. Those imageries will be the fundamental data source for digital earth. The main purpose of this paper is to apply the IKONOS multi-spectral satellite imageries to derive the shallow water depth. Two key studies will be included as follows. The first is to discuss the high-resolution characteristics of IKONOS images and its precise geometrically correction. The other is applying the multi-spectral images to calculate water depth by regression with few field-measured bathymetry. It is anticipated that the high-resolution remote sensing technology will be an alternative tool to the shallow water bathymetric surveying. The rugged terrain imageries of CARTERRA Geo level in Taipei County were selected and the bundle adjustment was used for precise images geometrically correction. The positioning accuracy is approximate 1.83m for east-west direction, 1.35m for north-south direction, and 1.6m for elevation. If the orthophoto is been rectified by using bundle adjustment method, the horizontal position accuracy of the check points is about 2.04m. In accordance with these results, using bundle adjustment in the CARTERRA Geo level imagery rectification has proved feasible. In the study of using muti-spectral images to derive the shallow water depth, both simulated data, IKONOS and SPOT satellite images of South Bay in KenTing are used to verify the influence of wave effect in the satellite imageries. By means of the concept of multi-resolution analysis in wavelet theory, the Daubechies D4 coefficients is tried to filter out the wave effect. Significant improvement on the shallow water depth calculation after filtering wave effect is shown in the result. The accuracy of water depth derivation using high resolution is about 30cm for the water depth shallower than 10m. This research proves that derivation of shallow water depth by using high-resolution satellite imagery is feasibility.

Thesis--School of Advanced Airpower Studies, Maxwell Air Force Base, Ala., 1991-92. / Title from title screen (viewed Oct. 28, 2003). "October 1995." Includes bibliographical references.

This thesis describes the analysis, design, simulation, evaluation and implementation of an optimized network protocol and its software system for 'little LEO' satellite networks to support an efficient digital store and forward (S&F) global data deliyery service. Many protocols have been proposed for 'little LEO' satellite S&F communication net""orks. These protocols fall into two categories. One category is the protocols which have been implemented in the real world, such as MSG2 and P ACSA T. These protocols were designed under constrained conditions and concentrated more on real world implementation. Another category is the protocols which are still proposals, such as LAMSLM, LAMS-DLC, variable-length information frame-type random access scheme and so on. These protocols were designed under some idealized conditions and concentrated only on some aspects. All these protocols are evaluated on their capability to handle the dominating problems in a typical LEO satellite S&F communication system, such as message addressing, multiple access control, multiplexing, and error control. Some problems in the design of these protocols are identified from real world statistics and others by simulation or analysis. To solve the problems, an optimized network layer protocol (called LEONET) is developed. LEONET provides an optimized and integrated solution to the dominating problems in 'little LEO' satellite S&F networks. Several improvements over previous protocols have been achieved in LEONET. On the up-link, LEONET defines a ne"" multiple access control protocol which allocates the number of reservation time slots according to dynamic network requirements, and therefore reduces collisions and leaves more up-link resource to upload messages. On the down-link, LEONET adopts a new message addressing and multiplexing mechanism which eliminates the directory downloading and can dO\\lnload more messages. The message uploading and downloading are scheduled by a novel routing optimization algorithm which can further improve the network performance. Simulation models are built for both pervious protocol and proposed protocols to evaluate their performance. It shows that LEONET can better use the 'little LEO' satellite network resource and provide much better performance, especially when the offered load is heavy orland the user population is large. An object-oriented software model for the proposed protocol is built. A software system of the proposed protocol is generated from the model and verified by OPNET.

The objectives of the subject-matter of this thesis were to appraise some methods of solving non-singular optimal control problems by their degree of success in tackling four chosen problems and then to try the most promising methods on chosen singular problems. In Part I of this thesis, the chosen problems are attempted by quasilinearisation, two versions of shooting, Miels's method, differential dynamic programming and two versions of parameterisation . Conclusions on the various methods are given. NOC shooting, developed by the Numerical Optimisation Centre of The Hatfield Polytechnic, and constrained optimisation were found to be very useful for non-singular problems. In Part 11, the properties and calculation of possible singular controls are investigated, then the two chosen methods used. It was found that NOC shooting was again very useful, provided the solution structure is known and that constrained parameterisation was invaluable for determining the solution structure and when shooting is impossible. Contributions to knowledge as as follows. In Part I, the relative merits of various methods are displayed, additions are made to the theory of parameterisation, shooting and quasilinearisation, the best solutions known of the chosen problems are produced and choices of optimisation parameters for one chosen problem, the satellite problem, are compared. The satellite problem has dependent state variables and the Maximum Principle is extended in Appendix III to cover this case . In Part II, a thorough survey of the properties of singular controls is given, the calculation of possible singular controls clarified and extended, the utility of the two chosen methods is displayed, the best solutions known of the Goddard problem obtained with improved understanding of transitions in soluti on structures , Cl problem studied with control dependent on the costate variables and singular solution structures found.

Measurements made by the AVHRR (Advanced Very High Resolution Radiometer) on board of five NOAA polar orbiting satellites were used to retrieve cloud optical depth (τ) and cloud droplet effective radius (r[sub eff]) for marine boundary layer clouds over the Pacific Ocean west of California and over the Southern Ocean near Tasmania. Retrievals were obtained for 21 days of data acquired between 1987 and 1995 from which over 300 subscenes ~ 256 km x 256 km in size were extracted. On this spatial scale cloud fields were found to have mean τ between 8 and 32 and mean r[sub eff] between 6 and 17 μm. The frequency distribution of τ is well approximated by a two parameter gamma distribution. The gamma distribution also provides a good fit to the observed r[sub eff] distribution if the distribution is symmetric or positively skewed but fails for negatively skewed or bi-modal distributions of r[sub eff] which were also observed. The retrievals show a relationship between τ and r[sub eff] which is consistent with a simple "reference" cloud model with reff ~ r[sup 1 / 5]. The proportionality constant depends on cloud droplet number concentration N and cloud subadiabaticity β through the parameter N[sub sat] = N/ [sq rt. Β]. Departures from the reference behaviour occur in scenes with spatially coherent N[sub sat] regimes, separated by a sharp boundary. AVHRR imagery is able to separate two N[sub sat] regimes if they differ by at least 30% in most cases. Satellite retrievals of τ and r[sub eff] were compared with in situ aircraft measurement near Tasmania. The retrievals overestimated r[sub eff] by 0.7 to 3.6 μm on different flights, in agreement with results from earlier comparison studies. The r[sub eff] overestimation was found to be an offset independent of τ. The reference cloud model and the N[sub sat] retrieval were tested on aircraft data and yield results consistent with direct in situ measurements of N and 8. Spectral and multifractal analyses of the spatial structure of cloud visible radiance, τ and r[sub eff] fields in 34 satellite scenes revealed scale breaks at 3 to 2 km in all analysed scenes in agreement with some earlier observations (Davis et al. (1996a)) but in contrast with other work (Lovejoy et al. (1993)). The nonstationarity H(1) and intermittency C(1) parameters were computed for the 34 scenes, stratified using the reference cloud model and according to mean τ and r[sub eff]. Similar values of H(1) and C(1) were found in all these categories. These measurements of the frequency distribution and spatial variability of τ, r[sub eff], liquid water path (Iwp), and N[sub sat] can be used to place constraints on mesoscale models of layer clouds.

As the potential uses of nanosatellites become apparent, their numbers keep increasing. This is evident at the Space Flight Laboratory (SFL) located at the University of Toronto Institute for Aerospace Studies which has seen a rapid growth in satellite missions in recent years. By leveraging the use of the Generic Nanosatellite Bus developed at SFL, satellites can be rapidly developed to carry science payloads or demonstrate the capabilities of new technologies on orbit. Testing satellite systems in an Earth environment is an important step in qualifying them for space. This thesis describes the development of ground support equipment for testing SFL’s nanosatellite separation system, XPOD, and characterizing the performance of the propulsion system, CNAPS. Also, the thermal behaviour of a pressure regulator valve on CNAPS is examined for various flow conditions.

The work described in this thesis summarizes the author's contributions to the design, development, and testing of embedded systems for SFL spacecraft. The unique environment of space and the constraints it imposes on embedded systems is described, and the testing methodologies employed to qualify spacecraft hardware for this environment are presented. The implementation of an automated functional test framework for SFL's Generic Nanosatellite Bus satellites and the role it plays in the spacecraft development cycle is also discussed. Application software and device drivers in support of the BRITE mission were designed and developed. Finally, a controller was implemented for thermal control of the BRITE optical instrument. These contributions play an important role in the continual efforts to expand access to space and to prove the feasibility of the microspace approach in doing so.

As the potential uses of nanosatellites become apparent, their numbers keep increasing. This is evident at the Space Flight Laboratory (SFL) located at the University of Toronto Institute for Aerospace Studies which has seen a rapid growth in satellite missions in recent years. By leveraging the use of the Generic Nanosatellite Bus developed at SFL, satellites can be rapidly developed to carry science payloads or demonstrate the capabilities of new technologies on orbit. Testing satellite systems in an Earth environment is an important step in qualifying them for space. This thesis describes the development of ground support equipment for testing SFL’s nanosatellite separation system, XPOD, and characterizing the performance of the propulsion system, CNAPS. Also, the thermal behaviour of a pressure regulator valve on CNAPS is examined for various flow conditions.

The work described in this thesis summarizes the author's contributions to the design, development, and testing of embedded systems for SFL spacecraft. The unique environment of space and the constraints it imposes on embedded systems is described, and the testing methodologies employed to qualify spacecraft hardware for this environment are presented. The implementation of an automated functional test framework for SFL's Generic Nanosatellite Bus satellites and the role it plays in the spacecraft development cycle is also discussed. Application software and device drivers in support of the BRITE mission were designed and developed. Finally, a controller was implemented for thermal control of the BRITE optical instrument. These contributions play an important role in the continual efforts to expand access to space and to prove the feasibility of the microspace approach in doing so.