Showing papers by "Neil Gordon published in 2014"

Toward a New Generation of Photonic Humidity Sensors

Abstract: This review offers new perspectives on the subject and highlights an area in need of further research. It includes an analysis of current scientific literature mainly covering the last decade and examines the trends in the development of electronic, acoustic and optical-fiber humidity sensors over this period. The major findings indicate that a new generation of sensor technology based on optical fibers is emerging. The current trends suggest that electronic humidity sensors could soon be replaced by sensors that are based on photonic structures. Recent scientific advances are expected to allow dedicated systems to avoid the relatively high price of interrogation modules that is currently a major disadvantage of fiber-based sensors.

Optimization of Erbium-Doped Actively Q-Switched Fiber Laser Implemented in Symmetric Configuration

Abstract: We report the results of an experimental study aimed at improving the performance of actively Q-switched fiber lasers. Unlike generic design schemes employing photonic crystal fibers, large modal diameter fibers or double-clad fibers, we demonstrate a high-power, actively Q-switched laser based on standard communication erbium doped fibers with peak irradiance beyond the state-of-the-art at 3.1 GW/cm 2. The laser had 2.2 kW peak power, 15.5 ns pulse duration and 36.8 μJ pulse energy. We have also investigated the dynamics of pulse generation and have successfully suppressed pulse instabilities caused by backscattered laser emission reaching the pump laser diodes.

A Comparison of JPDA and Belief Propagation for Data Association in SSA

Abstract: : The process of initial orbit determination, or catalogue maintenance, using a set of unlabelled observations requires a method of choosing which observation was due to which object. Realities of imperfect sensors mean that the association must be made in the presence of missed detections, false alarms and previously undetected objects. Data association is not only essential to processing observations, it can also be one of the most significant computational bottlenecks. The constrained admissible region multiple hypothesis filter (CAR-MHF) is an algorithm for initial orbit determination using short-arc, optical (angles only), observations of space objects. CAR-MHF uses joint probabilistic data association (JPDA), a well-established approach to multi-target data association. A recent development in the target tracking literature is the use of graphical models to formulate data association problems. Using an approximate inference algorithm, belief propagation (BP), on the graphical model results in an algorithm that is both computationally efficient and accurate. This paper compares association performance on a set of deep-space objects with CAR-MHF using JPDA and BP. The results of the analysis show that by using the BP algorithm there are significant gains in computational load, with negligible loss in accuracy in the calculation of association probabilities.

Joint UK-Australian Space Surveillance Target Tracking, Cueing and Sensor Data Fusion Experiment

Abstract: N. M. Harwood, R. P. Donnelly, A. Ash Air and Weapons Systems, Defence Science and Technology Laboratory, UK M. Rutten, N. Gordon, T. Bessell NSID, Defence Science and Technology Organisation, Australia J. D. Eastment, D. N. Ladd, C. J. Walden Science and Technology Facilities Council, Chilbolton Observatory, UK C. Smith, J. C. Bennett * , I. Ritchie Electro-Optic Space Systems, Mount Stromlo, Australia * The SPACE Research Centre, School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Australia