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CRANFIELD UNIVERSITY FAYE ANDREWS DESIGN OF A COTS MST DISTRIBUTED SENSOR SUITE SYSTEM FOR PLANETARY SURFACE EXPLORATION. SCHOOL OF ENGINEERING EngD. THESIS CRANFIELD UNIVERSITY SCHOOL OF ENGINEERING EngD. THESIS Academic Year 2005 FAYE ANDREWS Design of a COTS MST distributed Sensor Suite System for planetary surface exploration. Supervisors: Dr. Stephen Hobbs Dr. Ian Honstvet Dr. Robin Lane This thesis is submitted in partial fulfilment of the requirements for the degree of Engineering Doctorate. © Cranfield University 2005. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. ABSTRACT The aim of this project is To bring together current commercially available technology and relevant Microsystems Technology (MST) into a small, standardised spacecraft primary systems architecture, multiple units of which can demonstrate collaboration… Distributed “lab-on-a-chip” sensor networks are a possible option for the surface exploration of both Earth and Mars, and as such have been chosen as a model small spacecraft architecture. This project presents a systems approach to the design of a collection of collaborative MST sensor suites for use in a variety of environments. Based on a set of derived objectives, the main features of the study are: What are the fundamental limits to miniaturisation? What are the hardware issues raised using both standard and MST components? What is the optimum deployment pattern of the network to locate various shaped targets? What are the strategic and economic challenges of MST and the development of a sensor suite network? In general, there are few fundamental physical laws that limit the size of the sensor system. Limits tend to be driven by other factors including user requirements and the external environment. A simple breadboard model of the sensor suite consisting current COTS MST components raised practical issues such as circuit layouts, power requirements and packaging. A grid illustrating features of the Martian surface was created. Various patterns of target and sensor clusters were simulated. Overall, for larger target areas, clusters of sensors produced the best “hit rate”. The overall system utilises both wired and wireless communications methods. The I2C protocol has been investigated for intersuite communications. A link has been made between bacteria pools found on Glaciers (Cryoconites) and the possible conditions for life at the Polar Ice Caps of Mars. The investigation of Arctic Cryoconites has been selected as a representative case study that will incorporate all aspects of the project and demonstrate the system design. A comprehensive mission baseline based on this application has been produced, however the system has been designed to enable its use in a variety of situations whilst requiring only minimal modification to the overall design. Acknowledgements I wish to thank all the people who have supported and encouraged me throughout this project and my time at Cranfield. Particular thanks goes to Dr Steve Hobbs and the staff at Cranfield Space Research Centre for their continuing guidance, understanding and valued friendship. I would also like to thank those at Astrium who have helped me during this project, especially Ian Honstvet, Martyn Snelling Arnaud Lecuyot and Steve Eckersley, and the staff at the School of Management, in particular Robin Lane. Many people have touched my life during my research period. I’d like to offer my heartfelt thanks to the friends I have made, especially my fellow Research students with whom I have shared many memorable experiences, both good and not so good. In particular, huge thanks goes to Angie for always being there when I needed a walk and a friendly ear, to Patrick for being a Paint master, a great friend and for brightening my life and Jenny, my writing-up buddy. I would also like to thank Red 1 (Pete, Peter, Linda, Sam and Mayan), my Learning team during my MBA year. Without them I never would have known what a balanced score card is or how badly a group of project managers could manage a simulated warehouse exercise! Finally and most importantly, I would like to thank my family – in particular my Mum and Dad. Their love and encouragement have helped me realise my dreams and I will always be thankful for that. I dedicate this Thesis to the memory of my Father, James Andrews. I hope I make him proud. TABLE OF CONTENTS ABSTRACT Acknowledgements Table of Contents Table of Figures Table of Tables Definition of Acronyms 1. Introduction 1 1.1 Introduction 1 1.2 Project Aim 1 1.3 Project Objectives 1 1.4 Approach for Achieving Objectives 2 1.5 Research Rationale 4 1.6 Thesis Overview 5 2 Background and Review of Literature 7 2.1 Introduction 7 2.2 Distributed Sensor Networks 7 2.2.1 What is a Distributed Sensor Network? 7 2.2.2 Communications Architectures for Sensor Networks 11 2.2.3 Sensor Nodes 12 2.2.4 Deployment strategies 15 2.2.5 Applications 17 2.2.5.1 Military 17 2.2.5.2 Environmental and Ecosystem Monitoring 18 2.2.5.3 Space Applications 19 2.2.5.4 Health Care 19 2.2.5.5 Disaster Monitoring 20 2.2.5.6 Commercial 20 2.2.5.7 Home Intelligence, Automation and Security 20 2.2.5.8 Other Applications 21 2.3 Existing Distributed Sensor Network Programmes 21 2.3.1.1 Sensor web 21 2.3.1.2 Microcluster 22 2.3.1.3 μAMPs 23 2.3.1.4 Smart Dust 23 2.3.1.5 WINS 23 2.3.1.6 Astrium micropack 24 2.4 MST for Space 24 2.5 Other Relevant Background 25 2.6 Positioning of this project 25 3 Fundamental Physical limits to the size of a Space sensing system 27 3.1 Introduction 27 3.2 Spacecraft systems functions 28 3.3 Limiting factors of functions 28 3.3.1 Sensing 29 3.3.1.1 Physical principles behind the operation of an accelerometer 29 3.3.1.2 Fundamental principles behind a pressure sensor 33 3.3.2 Information Processing 36 3.3.3 Communication 38 3.3.4 Secondary Functions 39 3.4 Other Constraints and Drivers 40 3.4.1 Material properties 41 3.4.2 Environmental 41 3.4.3 User requirements 42 3.5 Examples 43 3.5.1 The Molecular sensor system 43 3.5.2 A Simple Sensing System Example 44 3.5.2.1 Transducer – Photovoltaic cell photon detector 45 3.5.2.2 Digitiser - Capacitor System 49 3.5.2.3 Transmitter – LED 52 3.5.3 Comparison to existing spacecraft 52 3.6 Discussion 54 3.7 Conclusions 55 4. Management and Strategic Issues of the Space Industry 56 4.1 Introduction 56 4.2 Strategic Outline of the Space Industry 56 4.2.1 Background to the Space industry 56 4.2.2 Porter’s 5 Forces 60 4.2.3 PESTLE Analysis 61 4.2.4 Scenario planning and the implications of recent and future events 63 4.3 Capabilities of companies within the industry 67 4.4 Knowledge and Technology Transfer and the adoption of MST for Space 70 4.4.1 What is Knowledge Transfer? 70 4.4.2 Barriers and facilitation to the adoption of MST 71 4.5 Conclusions 72 5. Hardware 73 5.1 Introduction 73 5.2 Top Level requirements and selection criteria 73 5.2.1 Overall sensor suite top level requirements 73 5.2.2 Proposed mission scenarios 74 5.2.2.1 Mars Applications 74 5.2.2.2 Earth Applications 76 5.2.2.3 Other Space Applications 77 5.2.3 Selection criteria for components 78 5.3 Basic Environmental Sensor Suite Version 1 81 5.3.1 Initially selected sensors 82 5.3.1.1 Temperature 82 5.3.1.2 Pressure 84 5.3.1.3 Accelerometer 84 5.3.1.4 Light 85 5.3.2 Combined circuit diagram 86 5.3.3 Lessons from sensor board construction 88 5.4 Intersuite Communication (I2C) 89 5.4.1 What is I2C? 89 5.4.2 Practical I2C work 90 5.4.3 Key lessons 92 5.5 Processing – PIC Microcontroller 92 5.5.1 What is a PIC? 92 5.5.2 Choice of PIC for the sensor suite application 93 5.5.3 Issues raised with the PIC microcontroller 94 5.6 Conclusions drawn from the hardware investigations 95 6 Microsystems Technology 96 6.1 Introduction 96 6.2 Background – What is MST? 96 6.2.1 Definition 96 6.2.2 Background and common use of MST 97 6.2.3 European and Worldwide initiatives 98 6.2.4 University research 99 6.3 Currently available components 100 6.4 Examples for sensor suite design 104 6.4.1 Figures of Merit and sensor comparison 104 6.4.1.1 Accelerometers 105 6.4.1.2 Pressure Sensors 106 6.4.1.3 Temperature Sensor 107 6.4.1.4 Light/Radiation Sensor 108 6.4.2 Chosen MST sensors for sensor suite 109 6.5 MST issues raised and possible solutions 109 6.5.1 Standardisation 109 6.5.2 Packaging 110 6.5.3 Space-related issues 111 6.6 Full integration potential 113 6.7 Conclusions 115 7 Simulation of the Martian Surface Environment 116 7.1 Introduction 116 7.2 Background 116 7.2.1 Definition of Simulation 116 7.3 Martian Environment Simulation 118 7.3.1 Why Martian Environment? 118 7.3.2 Rock field creation 119 7.3.3 Rock Field Visual Basic Subroutine 122 7.4 Possible Deployment Patterns 123 7.4.1 Visual Basic subroutine creation for simulation of varying deployment patterns 123 7.4.2 Uniform 124 7.4.3 Random sensors 125 7.4.4 Cluster 126 7.4.6 Simulation of reduced reliability 129 7.5 Location of Target Resources 130 7.5.1 Visual Basic subroutine to simulate finding a specified target 131 7.5.2 Target 1 – block 131 7.5.3 Target 2 – L 132 7.5.4 Targets 3 and 4 – Horizontal and vertical lines 133 7.5.5 Target 5 – Individual cells 135 7.6 Effect of reliability and quantity on the deployment patterns and target location 137 7.6.1 Runs with different reliabilities and quantities 137 7.6.3 Histograms and Distribution plots 138 7.7 System Design issues raised by simulation 142 7.8 Conclusions 143 8 Prototype System Design 145 8.1 Introduction 145 8.2 Sensor Suite Architecture Design 145 8.2.1 Final Component Choice 145 8.2.1.1 Accelerometer 146 8.2.1.2 Pressure Sensor 147 8.2.1.3 Temperature Sensor 147 8.2.1.4 UV Photodetector 148 8.2.2 Processing and communications 149 8.2.3 Power 150 8.2.4 Sensor Suite Circuit Diagram 150 8.3 Demonstrator / MCMs 151 8.3.1 3D Multichip Modules 152 8.3.1.1 Stacked Chip-Scale package (CSP).