Target classification in multimodal video

The presented thesis focuses on enhancing scene segmentation and target recognition methodologies via the mobilisation of contextual information. The algorithms developed to achieve this goal utilise multi-modal sensor information collected across varying scenarios, from controlled indoor sequences to challenging rural locations. Sensors are chiefly colour band and long wave infrared (LWIR), enabling persistent surveillance capabilities across all environments. In the drive to develop effectual algorithms towards the outlined goals, key obstacles are identified and examined: the recovery of background scene structure from foreground object ’clutter’, employing contextual foreground knowledge to circumvent training a classifier when labeled data is not readily available, creating a labeled LWIR dataset to train a convolutional neural network (CNN) based object classifier and the viability of spatial context to address long range target classification when big data solutions are not enough. For an environment displaying frequent foreground clutter, such as a busy train station, we propose an algorithm exploiting foreground object presence to segment underlying scene structure that is not often visible. If such a location is outdoors and surveyed by an infra-red (IR) and visible band camera set-up, scene context and contextual knowledge transfer allows reasonable class predictions for thermal signatures within the scene to be determined. Furthermore, a labeled LWIR image corpus is created to train an infrared object classifier, using a CNN approach. The trained network demonstrates effective classification accuracy of 95% over 6 object classes. However, performance is not sustainable for IR targets acquired at long range due to low signal quality and classification accuracy drops. This is addressed by mobilising spatial context to affect network class scores, restoring robust classification capability

Imaging polarimetry of pre- and post- main sequence objects

In the first part of this thesis an automated polarimeter is described, and details are given of a dedicated CCD camera system based on a personal computer. The quality of the data produced by these instruments is demonstrated by the results presented in the succeeding chapters. Polarimetric observations of nebulae associated with two pre-MS objects, HH83/Rel7 and GL2591, and two post-MS objects, IRAS 07131-0147 and OH 231.8+4.2, are presented and discussed with reference to previous observations. In each case the location of the exciting source is determined and a simple model is described which explains the observed characteristics of the system. Both HH83/Rel7 and GL2591 are shown to be illuminated by nearby IRAS sources which have no optical counterparts. The nebula associated with HH83/Rel7 is caused by the reflection of radiation off the insides of the walls of a cavity excavated in the dark cloud by outflows from the IRS, and is crossed by a narrow unpolarised jet seen in emission-line radiation. The nebula associated with GL2591 is illuminated at optical wavelengths by both the IRS and a second, visible, source, and is composed of material ejected by the IRS in a discrete period of mass loss. IRAS 07131-0147 and OH 231.8+4.2 are shown to be stars which have evolved off the AGB and which will soon become the central stars of planetary nebulae. The protoplanetary nebulae which have formed as a result of the action of the fast stellar wind on the extended RGE around each star are bipolar and axially symmetric. The fast wind is shown to have ceased in the case of IRAS 07131-0147, but that related to OH 231.8+4.2 is still carrying material away from the star in a highly collimated fashion, producing narrow dusty filaments along the axes of the cavities. High levels of polarisation are measured in both nebulae, which indicates that the scattering particles are much smaller than those in the ISM.A brief comparison of the pre- and post-MS nebulae shows that the two phases of stellar evolution are linked by a number of observationally similar characteristics, and it is thought that similar processes may occur at opposite ends of the evolutionary track. Most notably, circumstellar discs appear to be common at various stages in the stellar life-cycle

Optimising the NAOMI adaptive optics real-time control system

This thesis describes the author's research in the field of Real-Time Control (RTC) for Adaptive Optics (AO) instrumentation. The research encompasses experiences and knowledge gained working in the area of RTC on astronomical instrumentation projects whilst at the Optical Science Laboratories (OSL), University College London (UCL), the Isaac Newton Groups of Telescopes (ING) and the Centre for Advanced Instrumentation (СfAI), Durham University. It begins by providing an extensive introduction to the field of Astronomical Adaptive Optics covering Image Correction Theory, Atmospheric Theory, Control Theory and Adaptive Optics Component Theory. The following chapter contains a review of the current state of world wide AO instruments and facilities. The Nasmyth Adaptive Optics Multi-purpose Instrument (NAOMI), the common user AO facility at the 4.2 William Herschel Telescope (WHT), is subsequently described. Results of NAOMI component characterisation experiments are detailed to provide a system understanding of the improvement optimisation could offer. The final chapter investigates how upgrading the RTCS could increase NAOMI'S spatial and temporal performance and examines the RTCS in the context of Extremely Large Telescope (ELT) class telescopes

Spin-scanning Cameras for Planetary Exploration: Imager Analysis and Simulation

In this thesis, a novel approach to spaceborne imaging is investigated, building upon the scan imaging technique in which camera motion is used to construct an image. This thesis investigates its use with wide-angle (≥90° field of view) optics mounted on spin stabilised probes for large-coverage imaging of planetary environments, and focusses on two instruments. Firstly, a descent camera concept for a planetary penetrator. The imaging geometry of the instrument is analysed. Image resolution is highest at the penetrator’s nadir and lowest at the horizon, whilst any point on the surface is imaged with highest possible resolution when the camera’s altitude is equal to that point’s radius from nadir. Image simulation is used to demonstrate the camera’s images and investigate analysis techniques. A study of stereophotogrammetric measurement of surface topography using pairs of descent images is conducted. Measurement accuracies and optimum stereo geometries are presented. Secondly, the thesis investigates the EnVisS (Entire Visible Sky) instrument, under development for the Comet Interceptor mission. The camera’s imaging geometry, coverage and exposure times are calculated, and used to model the expected signal and noise in EnVisS observations. It is found that the camera’s images will suffer from low signal, and four methods for mitigating this – binning, coaddition, time-delay integration and repeat sampling – are investigated and described. Use of these methods will be essential if images of sufficient signal are to be acquired, particularly for conducting polarimetry, the performance of which is modelled using Monte Carlo simulation. Methods of simulating planetary cameras’ images are developed to facilitate the study of both cameras. These methods enable the accurate simulation of planetary surfaces and cometary atmospheres, are based on Python libraries commonly used in planetary science, and are intended to be readily modified and expanded for facilitating the study of a variety of planetary cameras

Solar science with the Atacama Large Millimeter/submillimeter Array - A new view of our Sun

The Atacama Large Millimeter/submillimeter Array (ALMA) is a new powerful tool for observing the Sun at high spatial, temporal, and spectral resolution. These capabilities can address a broad range of fundamental scientific questions in solar physics. The radiation observed by ALMA originates mostly from the chromosphere - a complex and dynamic region between the photosphere and corona, which plays a crucial role in the transport of energy and matter and, ultimately, the heating of the outer layers of the solar atmosphere. Based on first solar test observations, strategies for regular solar campaigns are currently being developed. State-of-the-art numerical simulations of the solar atmosphere and modeling of instrumental effects can help constrain and optimize future observing modes for ALMA. Here we present a short technical description of ALMA and an overview of past efforts and future possibilities for solar observations at submillimeter and millimeter wavelengths. In addition, selected numerical simulations and observations at other wavelengths demonstrate ALMA's scientific potential for studying the Sun for a large range of science cases.Comment: 73 pages, 21 figures ; Space Science Reviews (accepted December 10th, 2015); accepted versio

Earth imaging with microsatellites: An investigation, design, implementation and in-orbit demonstration of electronic imaging systems for earth observation on-board low-cost microsatellites.

This research programme has studied the possibilities and difficulties of using 50 kg microsatellites to perform remote imaging of the Earth. The design constraints of these missions are quite different to those encountered in larger, conventional spacecraft. While the main attractions of microsatellites are low cost and fast response times, they present the following key limitations: Payload mass under 5 kg, Continuous payload power under 5 Watts, peak power up to 15 Watts, Narrow communications bandwidths (9.6 / 38.4 kbps), Attitude control to within 5°, No moving mechanics. The most significant factor is the limited attitude stability. Without sub-degree attitude control, conventional scanning imaging systems cannot preserve scene geometry, and are therefore poorly suited to current microsatellite capabilities. The foremost conclusion of this thesis is that electronic cameras, which capture entire scenes in a single operation, must be used to overcome the effects of the satellite's motion. The potential applications of electronic cameras, including microsatellite remote sensing, have erupted with the recent availability of high sensitivity field-array CCD (charge-coupled device) image sensors. The research programme has established suitable techniques and architectures necessary for CCD sensors, cameras and entire imaging systems to fulfil scientific/commercial remote sensing despite the difficult conditions on microsatellites. The author has refined these theories by designing, building and exploiting in-orbit five generations of electronic cameras. The major objective of meteorological scale imaging was conclusively demonstrated by the Earth imaging camera flown on the UoSAT-5 spacecraft in 1991. Improved cameras have since been carried by the KITSAT-1 (1992) and PoSAT-1 (1993) microsatellites. PoSAT-1 also flies a medium resolution camera (200 metres) which (despite complete success) has highlighted certain limitations of microsatellites for high resolution remote sensing. A reworked, and extensively modularised, design has been developed for the four camera systems deployed on the FASat-Alfa mission (1995). Based on the success of these missions, this thesis presents many recommendations for the design of microsatellite imaging systems. The novelty of this research programme has been the principle of designing practical camera systems to fit on an existing, highly restrictive, satellite platform, rather than conceiving a fictitious small satellite to support a high performance scanning imager. This pragmatic approach has resulted in the first incontestable demonstrations of the feasibility of remote sensing of the Earth from inexpensive microsatellites

Working Papers: Astronomy and Astrophysics Panel Reports

The papers of the panels appointed by the Astronomy and Astrophysics survey Committee are compiled. These papers were advisory to the survey committee and represent the opinions of the members of each panel in the context of their individual charges. The following subject areas are covered: radio astronomy, infrared astronomy, optical/IR from ground, UV-optical from space, interferometry, high energy from space, particle astrophysics, theory and laboratory astrophysics, solar astronomy, planetary astronomy, computing and data processing, policy opportunities, benefits to the nation from astronomy and astrophysics, status of the profession, and science opportunities