DEVELOPMENT AND EVALUATION OF AUTOMATED RADAR SYSTEMS FOR MONITORING AND CHARACTERISING ECHOES FROM INSECT TARGETS by Timothy J. Dean BSc (Geophysics) (Hons), Curtin A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy 2007 I hereby declare that this submission is my own work and that to the best of my knowledge it contains no material previously published or written by another person, nor material which to a substantial extent has been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by colleagues, with whom I have worked at UNSW or elsewhere, during my candidature, is fully acknowledged. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project’s design and conception or in style, presentation and linguistic expression is acknowledged. Timothy J. Dean 18 March 2007 i ABSTRACT This thesis describes the construction of a mobile Insect Monitoring Radars (IMR) and investigations of: the reliability of IMRs for observing insect migration in inland Australia; possible biases in IMR migration estimates; the relation between an insect’s size and its radar properties; radar discrimination between insect species; the effect of weather on the migrations of Australian plague locusts and of moths; the scale of these migrations; and here IMRs are best located. The principles of entomological radar design, and the main features of insect migration in inland Australia, are reviewed. The main procedures used in the study are: calculation of radar performance and of insect radar cross sections (RCSs); reanalysis of a laboratory RCS dataset; statistical analysis of a four- year dataset of IMR and weather observations; and a field campaign using both two existing fixed IMRs and the new mobile unit. Statistical techniques used include correlation, multiple regression, discriminant analysis, and principal components analysis. The original results of this work include design details of the mobile IMR, extension of radar performance calculations to IMRs and evaluation of flight speed biases, a holistic approach to IMR design, the relation of insect RCS magnitudes and polarization patterns to morphological variables, an estimate of the accuracy of the retrieved parameters, evaluations of three approaches (one- parameter, theory-based, and a novel two-stage method) to target identification, and verification of inferred target identities using results from nearby light traps. Possible sites for future IMRs are identified. The major conclusions are that: a mobile IMR can be built with a performance equal to that of a fixed IMR but at half the cost; significant biases in the signal processing results arise from insect speed; locusts and moths can be distinguished if all RCS parameters are used; IMRs can be designed to match particular requirements; weather has a significant effect on insect migration, the best single predictor of insect numbers being temperature;moonlight has no effect; the spatial correlation of migration properties falls to 50% at a separation of 300 km; and migrating insects can be carried by the wind for 500 km in a single night. ii CONTENTS LIST OF TABLES..................................................................... VIII LIST OF FIGURES................................................................... XIV PRINCIPAL SHORT NAMES AND ABBREVIATIONS ............................................................................................... XXXIII ACKNOWLEDGEMENTS.................................................XXXIV 1 INTRODUCTION – RADAR, INSECTS, WEATHER, AND AIM OF STUDY..............................................................................1 1.1 Preface: Radar, Insects, Study Area.................................................. 1 1.2 Aim of the Present Study .................................................................... 3 1.3 Monitoring Insect Flight Using Radar .............................................. 5 1.3.1 The Origins of Radar Entomology.................................................. 5 1.3.2 Vertical-Beam Radars..................................................................... 8 1.3.3 Airborne, Doppler and Harmonic Radars..................................... 10 1.3.4 Entomological Radars in Australia............................................... 11 1.4 Radar Principles and Processing ..................................................... 13 1.4.1 Pulse Operation............................................................................. 13 1.4.2 Radar Frequencies......................................................................... 14 1.4.3 Radar Identification of Insect Species .......................................... 15 1.4.4 Processing of Entomological Radar Signals................................. 15 1.5 Effects of Weather on Insect Migration .......................................... 16 1.5.1 Distance and Types of Migration.................................................. 17 1.5.2 The Effect of Wind on Insect Migration....................................... 18 1.5.3 Effect of Temperature on Insect Migration .................................. 22 1.5.4 Effect of Humidity and Rainfall on Insect Migration................... 27 1.5.5 Orientation During Insect Migration ............................................ 28 1.6 Insects Studied in the Present Work................................................ 32 1.6.1 Australian Plague Locust.............................................................. 32 1.6.2 Spring Moths................................................................................. 40 1.7 Climate................................................................................................ 45 1.7.1 Climate of the Source Area........................................................... 45 1.7.2 The Study Area ............................................................................. 48 2 INSECT MONITORING RADARS......................................49 2.1 Development of the Fixed IMRs....................................................... 49 2.2 Radar Configuration of the Fixed IMRs......................................... 53 2.3 Equipment Modules of the Fixed IMRs .......................................... 54 2.4 Reasons For Developing a Mobile IMR........................................... 55 2.5 Specifications of the IMRs ................................................................ 55 2.6 Design of the Mobile IMR................................................................. 57 2.7 Construction of the Mobile IMR...................................................... 60 2.8 Equipment Modules of the Mobile IMR ......................................... 61 2.8.1 Control and Data-Acquisition Module ......................................... 63 iii 2.8.2 Microwave and Antenna Module ................................................. 66 2.8.3 Breakdown of Costs...................................................................... 69 2.9 Calibration of the IMRs.................................................................... 69 2.9.1 Measurement of Transmitter Power ............................................. 70 2.9.2 Measurement of Receiver Sensitivity........................................... 72 2.9.3 Estimated performance ................................................................. 73 2.10 Locations of the Mobile IMR............................................................ 74 2.11 Reliability of the IMRs...................................................................... 74 3 IMR PERFORMANCE, DESIGN, AND SIGNAL PROCESSING...............................................................................77 3.1 Introduction ....................................................................................... 77 3.2 Calculation of IMR Performance..................................................... 79 3.2.1 Parameters required for Calculating IMR Performance ............... 79 3.2.2 Power Received From the Target ................................................. 81 3.2.3 Sensitivity of Maximum Altitude r0 to Changes in Parameters.... 85 3.3 Component Modulations of the Reflected Signal ........................... 86 3.3.1 Signal Strength of Basic Components .......................................... 86 3.3.2 Modulation Due to Target Distance from the Beam Axis............ 88 3.3.3 Modulation due to Beam Offset.................................................... 89 3.3.4 Modulation by RCS due to Beam Rotation .................................. 90 3.4 Constraints on the Received Signal.................................................. 91 3.4.1 Constraints Due to the Visibility Factor Vf.................................. 91 3.4.2 Envelope Width Across Which a Target Can Be Detected .......... 92 3.4.3 Constraints Due to Target Speed .................................................. 95 3.5 Calculated Performance of the Four Radars................................ 102 3.6 Designing IMRs With a Specified Performance........................... 105 3.6.1 Distribution of Insects in the Air ................................................ 105 3.6.2 Maximum Altitude...................................................................... 118 3.6.3 Beamwidth.................................................................................. 119 3.6.4 Antenna Size vs. Transmitter Power..........................................