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Assembly of a Large Common Mount Astronomical InterferometerKim, Jihun January 2013 (has links)
A large multi-aperture telescope has the potential to reach the diffraction limit corresponding to its baseline. To do so, Adaptive Optics (AO) and beam combination are critical to good performance. Operation as an interferometer is a complicated mode for the telescope. The system now has much tighter tolerances and is difficult to align. The alignment process needs to be planned in multiple steps, and tolerance and sensitivity analysis needs to be performed for each step. Alignment tools can be prepared based on the resolution found in the sensitivity analysis in each step. Random fluctuation is another critical factor that reduces system performance. If noise sources near the telescope are characterized and identified, image quality can be improved by post-image processing. Measuring the outer scale of atmosphere is also helpful for understanding the system performance. The fringe tracking method in the Large Binocular Telescope Interferometer (LBTI) system provides optical path difference (OPD) variation, and the power spectral density of the OPD variation is used to estimate the size of the outer scale. However, this method is limited by the baseline of the LBTI by 5√3 B, where B is the baseline, and by this equation the outer scale size which is able to be estimated should be more than 125 m. AO simulation can provide an understanding of new AO system concepts and parameter variations before they are applied to the real system. In this dissertation study, we simulated an LBTI system with structural vibration of 10 Hz and 20 Hz and with various amplitudes. From the simulation, we learned that the slower bandwidth of piston-correcting systems allows stars as faint as ~13the magnitude to be observed. If there is significant vibration on the structure, the increased bandwidth will limit the phasing stars to 10~11th magnitudes. This demonstrates the limits of the LBTI system regarding structural vibration. An alternative phasing sensor for the LBTI system, the pseudo phasing sensor, can be used for more than 1000 m of outer scale of atmosphere. If the direct phasing sensor embedded in the LBTI system cannot be used for a very faint star, the pseudo phasing sensor, which approximately estimates the phase difference by AO wavefront sensor, can be useful for atmospheric conditions with estimated outer scale of about 1000 m. The analyses in this dissertation provide a partial guide for developing large-scale telescopes and astronomical instruments.
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Application of laser tracker technology for measuring optical surfacesZobrist, Tom L. January 2009 (has links)
The pages of this dissertation detail the development of an advanced metrology instrument for measuring large optical surfaces. The system is designed to accurately guide the fabrication of the Giant Magellan Telescope and future telescopes through loose-abrasive grinding. The instrument couples a commercial laser tracker with an advanced calibration technique and a set of external references to mitigate a number of error sources. The system is also required to work as a verification test for the GMT principal optical interferometric test of the polished mirror segment to corroborate the measurements in several low-order aberrations. A set of system performance goals were developed to ensure that the system will achieve these purposes. The design, analysis, calibration results, and measurement performance of the Laser Tracker Plus system are presented in this dissertation.
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Lives of White Dwarf StarsRicher, Harvey 17 March 2008 (has links)
White dwarf stars are the burnt out remnants that remain after a
star like the Sun has completed its nuclear evolution. In such a
star there are no remaining nuclear energy sources, so the star
evolves by simply radiating its stored thermal energy out into
space. This may seem rather uninteresting, but in fact there is a
wealth of physical phenomena that occur during this part of a
star's life - from getting kicked at birth, to neutrino emission
in early life, to some interesting high density physics, through
to functioning as precise clocks that can provide an age for some
of the oldest know stars in the Universe. Some of these phases
will be illustrated with detailed observations taken recently with
the Hubble Space Telescope.
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Design and Implementation of the Tip/Tilt Compensation System for Raven, a Multi-Object Adaptive Optics SystemNash, Reston 22 April 2014 (has links)
Multi-Object Adaptive Optics promises to be a useful tool for the upcoming class of Extremely Large Telescopes. Like current adaptive optics systems, MOAO systems compensate optical aberrations caused by atmospheric turbulence, but with the added benefit of being able to compensate multiple portions of a telescope’s field at the same time. To ensure the success of the eventual MOAO systems built for the ELTs, several demonstrator instruments have been designed and tested on current telescopes. Raven is one of these demonstrators, designed by the University of Victoria Adaptive Optics Lab for the Subaru 8.2 meter telescope to feed the InfraRed Camera and Spectrograph. Raven corrects the light of two science targets using wavefront information from three natural guide stars, and a single laser guide star. The topic of this thesis is the design and implementation of Raven’s tip/tilt compensation system, used to stabilize the output image positions on IRCS’s 0.140” slit. Tip/tilt correction of the science targets is done using a combination of motorized pick-off arms, piezoelectric tip/tilt platforms, and deformable mirrors. Through digital filtering and calibration, it is shown that these actuators are able to collectively keep the output science images stationary during simulated laboratory observations. A performance reduction due to residual tip/tilt errors is expected to be less than 5%. Raven goes on-sky in mid-2014, and it will be the first MOAO instrument to attempt scientific observations. / Graduate / 0548 / 0606
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The Use of the Proper Orthogonal Decomposition for the Characterization of the Dynamic Response of Structures Due to Wind LoadingFlores Vera, Rafael 08 February 2011 (has links)
This thesis presents a study of the wind load forces and their influence on the response of structures. The study is based on the capacity of the Proper Orthogonal Decomposition method (POD) to identify and extract organized patterns that are hidden or embedded inside a complex field. Technically this complex field is defined as a multi-variate random process, which in wind engineering is represented by unsteady pressure signals recorded on multiple points of the surface of a structure. The POD method thus transforms the multi-variate random pressure field into a sequence of load shapes that are uncorrelated with each other. The effect of each uncorrelated load shape on the structural response is relatively easy to evaluate and the individual contributions can be added linearly afterwards. Additionally, since each uncorrelated load shape is associated with a percentage of the total energy involved in the loading process, it is possible to neglect those load shapes with low energy content. Furthermore, the load shapes obtained with the POD often reveal physical flow structures, like vortex shedding, oscillations of shear layers, etc. This later property can be used in conjunction with classical results in fluid mechanics to theorize about the physical nature of different flow mechanics and their interactions. The POD method is well suited to be used in conjunction with the classical modal analysis, not only to calculate the structural response for a given pressure field but to observe the details of the wind-structure interaction. A detailed and complete application is presented here but the methodology is very general since it can be applied to any recorded pressure field and for any type of structure.
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Cryogenic testing of an electromagnetic actuation system for low temperature slit masksFrancescutti, Paul 16 November 2009 (has links)
The James Web Space telescope will replace the aging Hubble in 2012. One instrument onboard will be the Near Infrared Spectroscope which will require a reconfigurable slit mask to control light incident upon it. One design for this device is called the Mechanically Actuated Reconfigurable Slit mask (MARS). The MARS uses several electromagnetic clamps to move shutters though the focal plane. The goal of this thesis is to develop a system to characterise these clamps at cryogenic temperatures. FEA simulations predicted clamp performance and aided in the development of a test apparatus. An apparatus which utilises the Lorentz force to force the clamp jaws open was developed, built and tested. The device was built inside a cryostat which operated at 30 K. It was found that the test apparatus performed as intended. The clamps themselves proved to be problematic. Small perturbations or misalignments caused significant inconsistencies in experimental results.
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Design and Implementation of the Tip/Tilt Compensation System for Raven, a Multi-Object Adaptive Optics SystemNash, Reston 22 April 2014 (has links)
Multi-Object Adaptive Optics promises to be a useful tool for the upcoming class of Extremely Large Telescopes. Like current adaptive optics systems, MOAO systems compensate optical aberrations caused by atmospheric turbulence, but with the added benefit of being able to compensate multiple portions of a telescope’s field at the same time. To ensure the success of the eventual MOAO systems built for the ELTs, several demonstrator instruments have been designed and tested on current telescopes. Raven is one of these demonstrators, designed by the University of Victoria Adaptive Optics Lab for the Subaru 8.2 meter telescope to feed the InfraRed Camera and Spectrograph. Raven corrects the light of two science targets using wavefront information from three natural guide stars, and a single laser guide star. The topic of this thesis is the design and implementation of Raven’s tip/tilt compensation system, used to stabilize the output image positions on IRCS’s 0.140” slit. Tip/tilt correction of the science targets is done using a combination of motorized pick-off arms, piezoelectric tip/tilt platforms, and deformable mirrors. Through digital filtering and calibration, it is shown that these actuators are able to collectively keep the output science images stationary during simulated laboratory observations. A performance reduction due to residual tip/tilt errors is expected to be less than 5%. Raven goes on-sky in mid-2014, and it will be the first MOAO instrument to attempt scientific observations. / Graduate / 0548 / 0606
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Distributed H∞ Control of Segmented Telescope MirrorsUlutas, Baris 12 August 2014 (has links)
Segmented mirrors are to be used in the next generation of the ground-based optical telescopes to increase the size of the primary mirrors. A larger primary mirror enables the collection of more light, which results in higher image resolutions. The main reason behind the choice of segmented mirrors over monolithic mirrors is to reduce manufacturing, transportation, and maintenance costs of the overall system. However, segmented mirrors bring new challenges to the telescope design and control problem. The large number of inputs and outputs make the computations for centralized control schemes intractable. Centralized controllers also result in systems that are vulnerable to a complete system failure due to a malfunction of the controller.
Distributed control is a viable alternative that requires the use of a network of simple individual segment controllers that can address two levels of coupling among segments and achieve the same performance objectives. Since segments share a common support structure, there exists a coupling among segments at the dynamics level. Any control action in one segment may excite the natural modes of the support structure and disturb other segments through this common support. In addition, the objective of maintaining a smooth mirror surface requires minimization of the relative displacements among neighbouring segment edges. This creates another level of coupling generally referred to as the objective coupling.
This dissertation investigates the distributed H∞ control of the segmented next generation telescope primary mirrors in the presence of wind disturbances. Three distributed H∞ control techniques are proposed and tested on three segmented primary mirror models: the dynamically uncoupled model, the dynamically coupled model and the finite element model of Thirty Meter Telescope (TMT) project. It is shown that the distributed H∞ controllers are able to satisfy the stringent imaging performance requirements. / Graduate / 0548
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The Balloon-borne Large Aperture Submillimeter Telescope and Its Rebirth as a PolarimeterThomas, Nicholas E 14 December 2011 (has links)
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a 1.8 meter Cassegrain telescope that operates in three bands (250, 350, and 500 μm), each with 30% bandwidth. The detection system is comprised of 280 silicon-nitride micromesh bolometers distributed on three focal plane arrays with 30”, 42”, and 60” FWHM (full width at half max) beam sizes, respectively. BLAST's goal is to study the evolutionary history and processes associated with star formation. Earth's atmosphere is opaque to submillimeter radiation and astronomical observations in this wavelength are best conducted at high altitudes. BLAST is designed to be flown above 99.5% of the atmosphere on a stratospheric balloon. BLAST has made three scientific flights and this thesis covers the last two. The second flight was made in 2006 from McMurdo, Antarctica and studied the evolutionary history and processes associated with star formation. For the third flight, BLAST was reconfigured as a polarimeter (BLAST-Pol) and was also launched from McMurdo in December 2010. BLAST-Pol's objective is to determine what role, if any, magnetic fields play in star formation. This thesis will describe the BLAST-Pol instrument and provide a summery of key observations made by the 2006 flight.
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Three-dimensional mapping of fine structure in the solar atmosphereHenriques, Vasco M. J. January 2013 (has links)
The effects on image formation through a tilted interference filter in a converging beam are investigated and an adequate compensation procedure is established. A method that compensates for small-scale seeing distortions is also developed with the aim of co-aligning non-simultaneous solar images from different passbands. These techniques are applied to data acquired with a narrow tiltable filter at the Swedish 1-meter Solar Telescope. Tilting provides a way to scan the wing of the Ca II H line. The resulting images are used to map the temperature stratification and vertical temperature gradients in a solar active region containing a sunspot at a resolution approaching 0''10. The data are compared with hydro-dynamical quiet sun models and magneto-hydrodynamic models of plage. The comparison gives credence to the observational techniques, the analysis methods, and the simulations. Vertical temperature gradients are lower in magnetic structures than in non-magnetic. Line-of-sight velocities and magnetic field properties in the penumbra of the same sunspot are estimated using the CRISP imaging spectropolarimeter and straylight compensation adequate for the data. These reveal a pattern of upflows and downflows throughout the entire penumbra including the interior penumbra. A correlation with intensity positively identifies these flows as convective in origin. The vertical convective signatures are observed everywhere, but the horizontal Evershed flow is observed to be confined to areas of nearly horizontal magnetic field. The relation between temperature gradient and total circular polarization in magnetically sensitive lines is investigated in different structures of the penumbra. Penumbral dark cores are prominent in total circular polarization and temperature gradient maps. These become longer and more contiguous with increasing height. Dark fibril structures over bright regions are observed in the Ca II H line core, above both the umbra and penumbra. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>
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