A method is developed for calculating integrated magnitudes of faint galaxies using I COSMOS mapping mode measurements of U&STU Schmidt photographs. The intensity calibration is provided by the step filters and the zero point of the magnitude scale is taken from the photoelectric sky brightness at the time of the exposure. Tests carried out on both star and galaxy images are described. The galaxy magnitudes are isophotal, the limiting isophote being about 28 mag arcsec 2. The errors range from ±O O8 at the bright limit of m - 18 to iOm43 at the faint limit of m - 22. The magnitudes from several hundred galaxies calculated from COSMOS mapping measurements are calibrated against the logarithm of the image area obtained from COSMOS coarse measurements. Using this calibration the magnitudes of galaxies in three areas near the south galactic pole are calculated. The total area of the survey is about 11 arcdeg2 and there are some 83,000 galaxies. The limits of the sample are discussed in detail. The log N(m) relation is compared with standard Friedman cosmological models. Some of these models are modified to take account of selection effects. An excess of observed faint galaxies is found which can be attributed to the effects of evolution or inhomogeneity of the universe. The effect of galaxy evolution is investigated assuming that the luminosity decreases linearly with time. The observations can be explained if, on average, the intrinsic luminosity of a galaxy decreases at the rate of about one magnitude per 1010 yr.

The results from deep <i>K</i> –band imaging of the most luminous known radio galaxies at <i>z</i> ~ 2 and the brightest known submillimeter sources in the 8-mJy survey are presented. The luminosities of the submillimeter galaxies are found to be ~ 1.5 magnitudes brighter than Lyman-break galaxies at comparable redshifts, indicating that submillimeter galaxies are significantly more massive. Finally, surface mass densities for both source types are found to be consistent with quiescent elliptical galaxies at high redshift, and not star-forming or Lyman-break galaxies. The results are presented of a study that uses the 3CRR sample of radio-loud active galactic nuclei to investigate the evolution of the black-hole:spheroid mass ratio in the most massive early-type galaxies from 0 < <i>z</i> < 2. Radio-loud unification is exploited to obtain virial (linewidth) black hole mass estimates from the 3CRR quasars, and stellar mass estimates from the 3CRR radio galaxies, thereby providing black hole and stellar mass estimates for a single population of early-type galaxies. The detection of evolution in the 3CRR black-hole:spheroid mass ratio further strengthens the evidence that, at least for massive early-type galaxies, the growth of the central supermassive black hole may be completed before that of the host spheroid. The results from an ongoing project to constrain the evolution of the black-hole:spheroid mass ratio at <i>z</i> = 3&4 are presented. At these redshifts quasars and their hosts provide a unique window on this evolution, as the only class of object in which both galaxy and black hole masses can be directly measured. These pilot data represent the first attempt to constrain the black-hole:spheroid mass ratio as part of a statistically significant sample at <i>z</i> = 3&4, a crucial epoch of galaxy formation and evolution.

This thesis describes the first search for star formation in primeval galaxies (PGs) at redshifts <I>z</I> ≥ 7. Our method was to undertake deep near-infrared imaging in the J window (~ 1.0 - 1.5<I>μ</I>m) using four narrowband filters of 2% FWHM. Over an area of sky of 3.0<SUP>?1</SUP>, no emission line object was found to a sensitivity limit of ≈ 10<SUP>-18</SUP> Wm<SUP>-2</SUP>. Interpreting this limit in terms of a limit on Lyα emission, it has been possible to place the first constraints on star formation at redshifts 7≤ <I>z</I> ≤ 9. The search is also sensitive to other emission lines at lower redshifts, of particular interest are the constraints placed on Hα emission. This line is a direct tracer of star formation (Kennicutt et al., 1987) and, at the wavelengths of the narrowband filter, it probes redshifts 0.5 ≤ <I>z</I> ≤ 0.9. Constraints on the star formation rate at these redshifts are of great interest in the interpretation of the excess of faint blue objects seen in number counts (Tyson 1988, Lilly et al. 1991, Metcalfe et al. 1991, Jones et al., 1991). By assuming that there is no evolution in the comoving number density of galaxies out to <I>z = 9, </I>and that the luminosity function of objects at these redshifts can be represented by a Schechter function, it is possible to use the limits of the IRCAM search to place constraints on the characteristic Lyα luminosity <I>L</I>*(Lyα) of PGs. Two extremes for the bright phase Δ<I>t</I><SUB>bright</SUB> of each galaxy are considered. In Case 1, Δ<I>t</I><SUB>bright</SUB> spans the four narrowband filters (~ 10<SUP>8</SUP> years). In Case 2, the bright period is much shorter, and the specific case of the Partridge & Peebles (1966) model is considered (Δ<I>t</I><SUB>bright</SUB> = 3 X 10<SUP>7</SUP> years). The 95% confidence limits for Case 1 models constrain <I>L</I>*(Lyα) to less than 1.6 X 10<SUP>37</SUP> W - 4.2 X 10<SUP>37</SUP> W, depending on the cosmological model. These limits are consistent with the Case 1 predictions for Lyα luminosity.

Global Navigation Satellite System-Reflectometry (GNSS-R) is an innovative technique for remote sensing. It uses reflected signals from the navigation constellations to determine properties of the Earth’s surface. The primary focus of this work is the remote sensing of the ocean by measurement of surface roughness. The most significant unresolved challenge in spaceborne GNSS-R is to verify the accuracy of surface roughness measurements. Existing remote sensing techniques have typically relied on extensive data-sets to validate satellite measurements with the ground truth. This thesis provides a receiver design for collection of the required validation data-sets which can then form part of an operational system for surface roughness measurement. New receiver approaches were investigated through the design of a software receiver to postprocess existing data from the GNSS-R experiment on the UK-DMC satellite. This forms the reflections into Delay-Doppler Maps (DDMs) from which the surface roughness can be determined. The software receiver improves on existing implementations by targeting all available specular reflections using open-loop tracking. A new approach called Stare processing is analysed, which controls the receiver to remain focused at a fixed point on the Earth’s surface as the satellites move. This improves the surface resolution over using the full DDM. Additionally it is shown to be a viable approach for surface roughness measurement through a scattering model and the first demonstration on data collected from space. GNSS-R research has primarily focused on the established GPS navigation system. This research extends the measurement concept to the new Galileo GNSS. A receiver that can target multiple GNSS constellations will allow greater remote sensing coverage. The primary differences between Galileo and GPS are analysed and an approach is developed leading to the first spaceborne demonstration of Galileo-like signals for remote sensing. The system design for the GNSS-R receiver presented in this thesis was carried out in the context of Surrey Satellite Technology Ltd developing a GNSS navigation receiver called the SGR-ReSI, to be launched on the UK Technology Demonstrations Satellite TDS-1. The critical areas identified in the GNSS-R system design were implemented and tested on this receiver. The design overcomes the challenging constraints of GNSS-R in a small satellite platform: principally the mass, power and data downlink capacity. To achieve these, on-board data compression was developed through real-time DDM processing and reflection tracking. An algorithm for real-time DDM processing within the mass and power constraints was designed and demonstrated within the receiver and combined with open-loop reflection tracking. A ground-based test set-up was developed to test the design on existing spaceborne data, from the UK-DMC experiment, before the TDS-1 satellite launch.

No description available.

No description available.

Many missions are now being proposed that make use of formations of satellites rather than just single platforms. While a small number of missions require no fixed formation geometry, the majority of missions use a well defined configuration of satellites. In this thesis I present a technique for modelling the motion of satellite formations in Low Earth Orbit (LEO). The relative motion model is based on an epicycle absolute orbit model, and avoids the linearisation problem by not relying on solution of the relative equations of motion. I present expressions for the relative motion and then show how they may be split up to describe the motion as a combination of the uniform motion of a formation origin, the motion of the formation as a whole about this origin and the motion of the individual satellites within the formation. I then show how this model may be used to determine properties of the formation such as its lifetime, and also to set properties of the formation, such as introducing a condition of no relative secular drift. I then invert the process of modelling the relative motion based on a given set of orbital parameters, and define a process for determining the orbital parameters required to produce a required relative motion. I consider a straightforward set of designs that rely on simple assumptions about the formation shape when planning the formation motion, and then more complex designs that consider the dynamics and configuration when determining the required orbital parameters. Finally, I present techniques for collision risk identification and mitigation, deriving the condition under which collisions occur in terms of the relative orbital parameters, and then showing how the risk may be mitigated with minimal change to the geometric properties of the formation.

This thesis investigates two problems concerned with contact binary stars: the mechanism of energy transfer and the evolutionary states in the W UMa-type contact binary systems. The observational and theoretical background is first reviewed. This highlights the importance of a proper treatment of energy transfer if W UMa stars are to be understood. Expressions for the ratio of the transferred luminosity to the primary's radiated and centrally generated luminosities are derived. An estimate of the size of the transfer rate in observed unevolved systems is determined. The implications of accurate mass-ratios are briefly discussed. The generalized transport equation is shown to contradict the requirements of the TRO theory. A more general formula is put forward. The sideways convection model is investigated critically and is found to work only in very deep A-type systems. The implications of this result on contact binaries' structure, stability and evolution are discussed. A variety of different energy transfer models are explored. Equilibrium circulation and turbulent conduction models require moderately deep A-type systems. The small- and large-scale models can, respectively, transfer enough energy in the shallow and moderately shallow W-type systems. Webbink's ideas of energy transfer are used to construct numerical contact binary models which for the first time use an explicit mechanism to represent the energy transfer process. The added complications caused by the implementation of such a mechanism rendered the procedure used to build numerical models ineffective. An alternative procedure is briefly discussed. Hazlehurst's dissipation mechanism is simulated numerically. We argue on the basis of our results that this mechanism is unworkable in its present form. We attribute this to a fundamental error in the formulation of the model and sketch a possible reformulation of the model in terms of the theory of thermals. The consequences of strict hydrostatic equilibrium for the overall structure of contact binaries are discussed. It is shown that imposition of strict hydrostatic equilibrium in the envelope requires (1) the observed anomalous M-L relation hold and (2) the contact phenomenon be considered as a single (severely distorted) configuration. A model is proposed which deviates markedly from hydrostatic equilibrium just below the envelope, with accelerating flow through the L, -point and a shock in the secondary component. A substantial amount of energy can be transferred, with conditions in the envelope remaining very close to hydrostatic equilibrium. The model works independently of the overlying envelope structure. We approach the second of our topics by investigating the evolutionary states in 9 A-type systems. Depending on their observed properties the systems are divided into two distinct groups. Group I members are evolved. Group II members belong to a distinct, still problematic category. The W-type system TX Cnc in Praesepe may be a pre-main sequence contact binary system. The implications of these results on the transfer mechanism are discussed.

No description available.

Hubble Space Telescope <i>R</i>-band images of a sample of 10 radio galaxies (RG), 10 radio-loud quasars (RLQ) and 13 radio-quiet quasars (RQQ) at redshift <i>z</i> 0.2 are presented. The sources comprising the radio-loud sub-samples have been selected to be indistinguishable in the <i>P</i>_{5<i>GHz </i>}- <i>z</i> plane. The two quasar sub-samples have been similarly selected to have indistinguishable distributions in the <i>V</i> - <i>z</i> plane. All three sub-samples have been analysed with two-dimensional modelling software, designed to accurately determine the host-galaxy parameters. The modelling results show all of the RG, and all of the quasars with M<i>_V</i> < -23, to have bulge-dominated host galaxies, excluding the hypothesis that host morphology is responsible for the radio-loudness dichotomy. Furthermore, the host galaxies are found to be essentially identical to a de Vaucouleurs (<i>b</i> = 0.25) law, with 30/33 objets having <i>b</i> parameters in the range 0.2 < <i>b</i> < 0.3. The hosts of all of the objects studied are found to be extremely luminous (<i>L </i>³ <i>L</i>_*), with 25/33 objects having <i>L</i> ³ 2L_*. The hosts of the RQQs are found to be typically 0.4 magnitudes fainter than their radio-loud counterparts. The host galaxies of all three sub-samples are found to be larger than average ellipticals (< <i>r_e</i>> = 10.5 kpc), with a trend found for the RQQ hosts to be some 20% smaller than those of the RLQs. For the first time it is demonstrated that the hosts of quasars, as well as RG, display a Kormendy relation basically identical to that of inactive ellipticals. In conclusion with the previous <i>K-</i>band modelling of this sample (Taylor <i>et al. </i>1996) the first set of reliable optical-infrared colours for a significant sample of AGN host galaxies has been determined. The <i>R - K</i> colours of the hosts in all three sub-samples are shown to be consistent with each other, with the close agreement of the median colour of <i>R - K</i>=2.5 with that expected from a ~ 14 Gyr-old stellar population implying that the host galaxies of both RG and quasars are consistent with having formed at high redshift (<i>z</i> ³ 3). The nuclear colours of the RGs are shown to be perfectly consistent with those of dust reddened RLQ nuclei. The combined luminosity, scalelength, Kormendy relation and <i>R - K</i> colour results for the RG and RLQ sub-samples clearly demonstrate that they are drawn from the same parent population, in strong support of the orientation-based unification scheme of Barthel (1989). The corresponding results for the full 33 objects sample show that, in terms of their global structural parameters, the hosts of powerful AGN are no different to normal massive ellipticals.