Eyes in the Sky

By Richard Smith

This book is a must read for anyone concerned with climate change and lack of Government action addressing this rapidly unfolding crisis. 

The authors, tell their story of introducing the new technology of observing Earth from Space into the WA Government, following the first images of Earth being sent back by man from spa

• Language: English
• Publisher: AllSaints Floreat Uniting Church
• Release date: Sep 14, 2021
• ISBN: 9781922629548

Richard Smith

Richard Smith wrote his PhD thesis on China’s economic reforms and has written extensively Chinese issues for New Left Review, Monthly Review, Real-World Economics Review, and Ecologist. He has also written essays collected in Green Capitalism: The God that Failed (2016) and in The Democracy Collaborative’s Next System Project (2017). Smith is also a founding member of the US-based group System Change Not Climate Change.

Book preview

EYES IN THE SKY

EYES IN THE SKY

SURVEILLANCE FOR SURVIVAL

Richard Smith and Henry Houghton

Copyright © 2020 by Richard Smith and Henry Houghton

All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law.

Smith, Richard (author)

Houghton, Henry (author)

Eyes in the Sky: Surveillance for Survival

ISBN: 978-1-922527-64-6 (paperback)

ISBN: 978-1-922629-54-8 (eBook)

TECHNOLOGY / Satellite Remote Sensing

ENVIRONMENT / Sustainability

Minion Pro 11pt/14pt

Cover and book design by Green Hill Publishing

All images reproduced by permission (No. 200219) of the Western Australian Land Information Authority

Himawari-8 weather satellite Source: Google Images

To our grandchildren and all those who are working to save the Earth.

Stand in awe of Nature and do what it requires of you,

for this is the whole duty of humankind.

For everything we do Nature will bring to judgement,

even everything hidden, whether it be good or evil.

Ecclesiastes c. 300BC

ACKNOWLEDGMENTS

Richard Smith and Henry Houghton acknowledge the input of many former colleagues: Frank Honey, Peter Hick, Alan Pearce, Peter Sanders, Mike Steber, Andrew Buchanan, Ron Craig, Peter Davidson, Richard Stovold, Ken Dawbin, Agnes Kristina, Carolyn McMillan (neé Browne), Stefan Maier, Adrian Allen, Sarfraz Khokhar, Simon Abbott, Matt Adams, Bonnie James (nee Stewart), Katherine Zdunic and many others from whom we sought information and answers to our questions.

As we proceeded, we received invaluable comments, editing and advice from

•Associate Professor Andrea Gaynor, Environmental Historian, UWA.

•Peter Newman, Professor of Sustainability, Curtin University who alerted us to his long-forgotten Western Australian State Sustainability Strategy and the need to focus on the future not just the past.

•Michael Mouritz, PhD Student in Sustainability at Curtin University for help on the early structure of the text.

•Joseph Christiansen, Post-Doctoral Fellow in History, Murdoch University for editorial input on formatting, structure and advice on the dangers of plagiarism.

•James Malcolm for his editing and Mike Steber for his scrupulous editing and checking of facts.

We thank Richard’s wife Claire, his brother-in-law Bevan Sharp and James Lamerv, who kindly indulged us in proof reading. Richard’s son Matthew helped explain the mysteries of Word, particularly track changes, the art of formatting and much more.

With such a complex subject covering a vast array of science disciplines we were dependent on other authors and have tried to acknowledge where we have drawn on their writings.

At a time of rapid changes in space, information technology, science, climate change and species extinction, we acknowledge that such contemporary history is vulnerable to all sorts of political pressure and ideology.

Four hundred years ago Sir Walter Raleigh, writing under sentence of death, understood the dangers perfectly: Whosoever in writing a modern history shall follow the Truth too near the heels, he wrote, it may haply strike out his teeth.³

However, "… culture is simply the end-product of 3000 years of labour by our diverse ancestors. It is a heritage which we spurn at our peril and of which it would be a crime to deprive younger and future generations. Rather it is our task to preserve and renew it.⁴

CONTENTS

Dedication

Acknowledgements

Foreword by Professor Peter Newman

Foreword by Professor Alexandra Ludewig

Preface

Introduction

Chapter 1. Observing Earth from space - the beginnings

Chapter 2. Measuring the Earth to manage the future

Chapter 3. Commonwealth satellite remote sensing initiatives, 1970 - 1989

Chapter 4. The beginning of WA’s satellite remote sensing 1976 - 1983

Chapter 5. Establishing WA’s Satellite Remote Sensing Capability 1983 – 1993

Chapter 6. Recruiting the skills for an Earth Systems Science Centre

Chapter 7. Oceanographic, geological and agricultural research applications

Chapter 8. The Leeuwin Centre for Earth Sensing Technologies

Chapter 9. Products developed for environmental monitoring, 1993 – 2007

Chapter 10. Satellite remote sensing and climate change

Chapter 11. Awards won by SRSS, Landgate in The Leeuwin Centre

Chapter 12. Shutting the gate on the fourth dimension of changes over time

Chapter 13. Reflections on Landgate’s withdrawal from The Leeuwin Centre

Chapter 14. Sustainability challenges facing Western Australia

Chapter 15. Future possibilities for WA of satellite remote sensing applications

Afterword

References–Selected

Glossary

FOREWORD

Foreword by Professor Peter Newman

Peter Newman AO,

Professor of Sustainability,

Curtin University

I have been involved in WA community life since the 1970s, in particular how we can better manage our environment in cities and regions. In 1970 at the first Earth Day, I caught the bug to do this, when we celebrated for the first time, seeing the whole Earth as a living breathing, self-sustaining entity dependent only on the Sun.

I have been fortunate for the past 50 years to work at looking after our planet with a lot of good environmental scientists and engineers in WA who demonstrated global leadership. Many examples exist of adapting to climate change, with our dwindling water supplies, conserving forests and World Heritage sites, changing agricultural practices, creating renewable energy opportunities, building new railway lines and changing city planning to lower urban impacts.

But we could have done better. Especially in establishing more businesses and providing assistance to those parts of government, university sector and industry, that saw global opportunities. I remember the first wind turbines in Esperance were made in WA and with CSIRO assistance could have created a global industry. Instead, Denmark did it, now the whole world imports from them. This book is about a similar story. It sets out the rise and fall of a remarkable industry focussing on the new science and engineering of satellite remote sensing in WA. We were leaders, but we let it slip away.

The authors tell the story of how an intrepid group of scientists (from CSIRO and Curtin University) and surplus surveyors redeployed by the former Department of Lands and Surveys, explored this new way of viewing Australia and surrounding oceans. The authors reveal the importance of multi-agency collaboration and co-location of expertise in The Leeuwin Centre for Earth Sensing Technologies resulting in new discoveries about WA’s:

•Geology, helping exploration for new mineral deposits.

•Errors in existing maps – islands misplaced.

•Indian Ocean currents from the north (Leeuwin) and south (Cape) and their influence on the climate, fisheries and marine ecosystems of WA.

•Massive late season bushfires sweeping across northern tropical savannas and inland areas that was traced to the decline of traditional indigenous early season burning.

•Agricultural deforestation and impacts on salinisation, degradation of surface and coastal waters, declining rainfall, and loss of biodiversity.

•Seasonal and spatial response of vegetation to rainfall in relation to crop yields, plague locusts and periodic overgrazing of pastoral leases during droughts.

•Impact of major cyclones and storms on broad scale flooding, wind, and water erosion.

•Urban development, changing vegetation cover and impacts on ambient temperatures.

This amazing work was contributing to local, national and global environmental science and management, but has now largely been lost. How did this happen?

Could it be revamped and given new impetus to help create multiple benefits in WA? This book will help us get some perspective on these questions as the authors were deeply involved in The Leeuwin Centre and believe their story needs to be told. I do too.

Foreword by Professor Alexandra Ludewig

Alexandra Ludewig,

Head of the School of Humanities

The University of Western Australia

Scientists, not unlike historians, interrogate data. Historians use evidence from the past – oral, written and pictorial – to ask fundamental questions that inform the present and enable more informed views on the future of humanity. Through understanding more about the past, we illuminate the present and create visions of the time to come. The interrogation of historical data also informs us with the benefit of hindsight about missed opportunities and turns not taken, slip-ups and oversights. Historians use this process of creating meaning to advance discoveries and debate.

Richard Smith and Henry Houghton work at the intersection of science and history by telling their story of repeated trials and errors, extinctions and emergences. Both worked in many countries and institutional settings to understand that the problems created by past decision-makers can only be tackled in a multi-disciplinary and cross-institutional approach. Their analysis of the history and future of satellite remote sensing in Western Australia complements the gaze of so many Aboriginal peoples of the land. Their analysis of data from eyes in the sky complements eyes to the sky and a respect for the resources at hand. Moving forward, opportunities may arise from the Square Kilometre Array in the Murchison as much as from collaboration with Western Australia’s traditional owners and custodians.

A popular saying in the profession of historians for a long time has been: ‘The eyewitness is the enemy of every historian.’ In earlier times, contradictory, unreliable or subjective accounts might have been dismissed by the profession. Nowadays most of us have learnt to live and deal with ambiguity. Richard Smith and Henry Houghton write from the perspective of eyewitnesses and from that of embedded scholars, participating researchers and two individuals who want to leave a legacy and are acutely aware of their responsibility. Positions of power and privilege, in spite of setbacks and funding constraints have not made them grumpy old men but public intellectuals on a mission. I get the feeling they are not done yet, not by a mile or square kilometre.

PREFACE

Earth observing satellites have been continually scanning the Earth for over 50 years, building massive archives of data on human impacts on the Earth. For example, this image of Western Australia (WA) was captured in just 6.2 minutes, around 10.30 am on 24 August 2004, by the MODerate resolution Imaging Spectroradiometer (MODIS), on the NASA Terra satellite.

The satellite, in a sun-synchronous orbit, 713 km above the earth, was travelling at 27,000 km/hour, completing an orbit every 99 minutes while scanning a 2,300 km-wide swath of Earth below. MODIS was measuring reflected and emitted irradiance¹ in 36 spectral bands and broadcasting the data at 10 megabits per second, to the ‘SeaSpace’ tracking antenna at Murdoch University. Via the internet, the data was transmitted for automatic analysis and archiving at Satellite Remote Sensing Services (SRSS) in The Leeuwin Centre for Earth Sensing Technologies, Floreat WA, from where the antenna was controlled.

This almost cloud-free satellite image was retrieved from the SRSS archive of ‘quick looks’ by Sarfraz Khokhar, who enhanced just 3 of the 36 spectral bands, masking cloud over the oceans and emphasising the topography, by combining the image with digital elevation data from the Shuttle Radar Topography Mission (SRTM).²

Crucially, these 36 spectral bands contain information that can improve our understanding of environmental processes on land, in oceans, and in the lower atmosphere. MODIS extends the heritage data from earlier sensors, such as NOAA’s Advanced Very High-Resolution Radiometer (AVHRR), a data series critical for monitoring short- and long-term trends in environment and climate, while providing input for Earth system models and long-term weather forecasts. The image was presented as a retirement gift to SRSS Manager, Richard Smith and became an inspiration for this book.

It is a sad paradox that Khokhar’s work in this area ended prematurely in 2017, when it was decided that such brilliant technical skill was no longer a commercial priority. This image is a lasting legacy of Sarfraz Khokhar’s service to satellite remote sensing in WA.

INTRODUCTION

The authors, Henry Houghton a surveyor and later Richard Smith, an agricultural scientist and economist then earth system scientist, happened by fate and chance between 1976 and 2006 to be the first two managers to introduce the radical new technology of Earth Observations from Space (EOS), using satellite remote sensing (SRS) into the Western Australian (WA) Government. The early history told by Ron Hutchinson in his book Managing a Million Square Miles: A History of Western Australia’s Department of Lands and Surveys,⁵ did not recognise that WA’s renewable resources were poorly mapped and not well managed. Satellite observations by covering the fourth dimension of time, would reveal the totality of human impacts on the environment, providing a method of repeat measurement for sustainable management into the future.

Our eyes enable us to comprehend the world around us; replicated on satellites, these ‘Eyes in the Sky’ provide unparalleled data about the changing face of the Earth. A new branch of science develops (Earth Systems Science); of the inter-relationship between all parts of our planetary system. A science essential for sustainability ‘… development that meets the needs of the present, without compromising the ability of future generations to meet their own needs’.⁶

WA is a third of the Australian continent, with an ancient landscape, flat, deeply weathered, infertile, within which nature has evolved an amazing and unique biodiversity. WA has the sparsest population (0.01 people per hectare) of any Australian state, with 90% huddled in the south-west corner. Since 1829, the processes of urbanisation, agriculture, pastoralism, mining and gas extraction have resulted in WA having the second highest GDP per capita ($100,000), but the highest biodiversity extinction rate and per capita rate of greenhouse gas (GHG) emissions expressed in units of CO2 equivalents (CO2-e).

Into the future, sustainable management of WA will depend on the success of using technologies such as SRS for, ‘to measure is to manage’ the 2.646 million km², particularly the 92% of WA which remains Crown Land, held in trust for present and future generations. Therefore, the authors’ focus is on applications of SRS to renewable resources. Earth’s natural environment is the largest component of the ecosphere and the major sink for the principal greenhouse gas of carbon dioxide.⁷ The crisis of climate change calls for action now, to avert the predicted catastrophe, if global atmospheric CO2 exceeds 450 ppm. With CO2 increasing at 2.7 ppm per year from the present 411 ppm, this threshold will be reached by 2035.⁸

The importance of scientific research and development, management and conflict between The Market vs Mother Nature from the ever-expanding demand on a finite Earth, are considered in this book. From the lessons learnt over 45 years of the ongoing developments of satellite and airborne remote sensing, the authors speculate on the future potential of this technology within the WA Government. The laws of nature are the working hypotheses of science, which constantly need empirical evidence to advance understanding. To realise the potential of the technology, the authors conclude by arguing for a centre of scientific expertise - a Western Australian Centre for Application of Earth Observations (WACAEO), to service all government agencies and industry, issuing SRS contracts where applicable to private sector companies. The objective of the centre would be to address the challenges of climate change and conservation of biodiversity on which the future welfare of humankind depends.

Department names

The WA Government’s Departments had various names during the period within which SRS developed:

•1891 to 1986 Department of Lands and Surveys

•1986 to 2003 Department of Land Administration

•2003 to 2006 Department of Land Information

•2007 ……… Landgate

Outline of the chapters on the past and possible future of SRS within WA Government

Chapter 1 briefly introduces the science of multi-spectral satellite or airborne remote sensing and the early challenge of geo-locating each pixel in an image for integration with other geographic data, to produce image maps for visual interpretation and management decisions.

Chapter 2 explains the principles of ‘Measuring the Earth to Manage the Future’, to realise the possibilities offered by the emergence of Earth Observing Satellites (EOS) using remote sensing technology in the late 20th century, vital for the social, environmental and economic sustainable management of Western Australia in the 21st century.

Chapter 3 addresses the importance and role of the Commonwealth of Australia and the mining industry in securing access to data from USA and European satellites through international agreements, and developing the infrastructure for data reception, archiving and distribution. Early scientific research into SRS by CSIRO and universities proved essential for upskilling scientists in WA Government agencies.

Chapter 4 the WA Department of Lands and Surveys (DLS), with its scientific and mapping expertise, assumed the lead role in developing applications of SRS and providing bureau services for the private sector and WA Government agencies under the leadership of Henry Houghton.

Chapter 5 describes the development of two important collaborations; the WA Satellite Technology and Applications Consortium (WASTAC) giving access to real-time meteorological satellite data, and the WA Remote Sensing Industry Development and Education Centre (WARSIDEC) for access to EOS expertise and infrastructure in WA. WARSIDEC became The Leeuwin Centre for Earth Sensing Technologies.

Chapter 6 describes the recruitment of Dr Richard Smith, a research scientist from CSIRO to lead development of applications of SRS for renewable resource management in the WA Government.

Chapter 7 covers some of the early oceanographic, geological and agricultural research that led to operational applications for fisheries management, mineral exploration and precision agriculture.

Chapter 8 the achievements of co-location in The Leeuwin Centre, resulting from the transition of producing once-off image maps to near real-time monitoring of ocean and land processes: made possible by access to low-cost meteorological satellite data from WASTAC’s receiving stations in Perth and other stations around Australia.

Chapter 9 documents the wide range of products developed in The Leeuwin Centre, their internet delivery, applications and future possibilities.

Chapter 10 describes the impact of an emerging Commonwealth climate policy on SRS developments in The Leeuwin Centre for northern Australia, to reduce greenhouse gas emissions from savanna wildfires and to earn carbon credit offsets, under the Kyoto Protocol from reduction in emissions from deforestation and land degradation in Indonesia.

Chapter 11 lists the achievements awarded to Landgate’s Satellite Remote Sensing Services (SRSS) in The Leeuwin Centre, illustrating the wide recognition received from clients and stakeholders.

Chapter 12 records how Landgate, in the pursuit of profit, shuts the gate on many SRS developments, withdrawing SRSS from The Leeuwin Centre and terminating WASTAC, to instead, focus on the protection of private property covering barely 1% of WA’s total land area.

Chapter 13 reflections by the authors on the lessons learnt from 45 years of introducing SRS technology into the WA Government; the enduring impact of previous government legislation on land release and environmental degradation, revealing the conflict between economy and ecology (The Market vs Mother Nature).

Chapter 14 describes the ongoing international developments of satellite remote sensing sensors and systems for deriving and delivering application ready information, knowledge and wisdom from SRS and possibilities for sustainable development.

Chapter 15 is on future applications of SRS to achieve sustainability, including net zero carbon emissions and recommendations for a WA Centre for Applications of Earth Observations to service the needs of government agencies, as well as the private sector.

CHAPTER ONE

Observing Earth from space - the beginnings

… it will enlighten the human race and help us all to comprehend that we are an important part of a much bigger universe than we can normally see from the front porch

On the meaning of the Moon landing - Neil Armstrong.⁹

When mankind orbited the Moon in 1968, the Earth was seen for the first time in human history as a living planet, in the vastness of space, wholly dependent on the Sun. Observations from space subsequently followed, with the launching of satellites with multi-spectral sensors into orbit around the Earth, with the remotely sensed data being broadcast back to ground. Methods were developed to process the data and extract the information, to improve knowledge of the Earth for exploration, environmental monitoring, and management. By Western Australia’s sesquicentenary in 1979, it had become apparent this technological and scientific revolution of observing Earth from space promised ‘the most powerful and effective technique of regional analyses’ yet known.¹⁰

Satellites begin orbiting Earth

The first step in this technology was solving the problem of launching satellites and maintaining them in orbit around the Earth.¹¹ This was first achieved by the Soviet Union who (in 1957) launched Sputnik, the first satellite to orbit the Earth and broadcast a radio signal. This challenged the USA and on 25 May 1961, President John F. Kennedy went one step further, declaring to Congress ‘that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth’.¹² The National Aeronautical and Space Agency, NASA, had been created in 1958 for the purpose of space exploration and thereafter the USA spent 0.5% of GDP each year supporting NASA’s moon effort, mobilising an estimated 500,000 workers and 20,000 companies in the race to fulfil Kennedy’s promise.¹³ The results in computing, semiconductors, aeronautics, telecommunications, material sciences and other areas of science and technology were profound. Among the major outcomes was the development of repeat earth observations from space using remote sensing technologies. Other orbiting satellite systems were developed for communications and global positioning, these would be essential for applications of satellite remote sensing for environmental monitoring and management. While these developments had important military applications, NASA’s mandate was to develop peaceful applications of space science.

In December 1968, the crew of Apollo 8 became the first humans to leave Earth orbit and head for the moon. They were the first in history to look back at their home planet and see their entire world in one glimpse (Figure 1). The photograph of the fragile Earth against the backdrop of the moon in the vastness of space, became known as the ‘blue marble’. It had an everlasting impact. It stimulated human consciousness, contributing to the modern environmental movement, with the first Earth Day being celebrated on April 22, 1970 to inspire, challenge and motivate human energy towards solving environmental issues.¹⁴, ¹⁵

The world was awakened to concerns of chemical pesticide pollution by Rachel Carson’s Silent Spring and resource limitations from Paul Ehrlich’s The Population Bomb and the Club of Rome’s Limits to Growth.¹⁶, ¹⁷, ¹⁸ This growing awareness provided an important impetus for the birth of Earth Systems Science, with the ability to make global measurements from satellite of the atmosphere, land and oceans and associated bio-physical processes. Such seminal works fostered a new awareness of the need to care for the Earth and would shape environmental applications of SRS in the Western Australian Government. Data from satellite remote sensing would prove essential for establishing the initial conditions for climate models, to forecast the impact of global warming from rising carbon emissions and for making daily weather forecasts.¹⁹

Figure 1 - The Earth from Apollo 8 within the vastness of space with moon in the foreground Source: NASA

Observing Earth from satellites – ‘Eyes in the Sky’

The first successful earth observing satellites were for weather forecasting.²⁰ Named Polar-orbiting Operational Environmental Satellites (POES), they were in low earth orbit between 700 to 800 km above the earth (Figure 2). POES became a constellation of polar orbiting weather satellites to improve the accuracy and detail of weather analysis and forecasting at a spatial resolution of 1 km. The first of the POES constellation was the Television Infrared Observation Satellite (TIROS) launched on April 1, 1960. POES instruments not only monitored clouds and atmospheric conditions, but also when clouds were not present, land and ocean surfaces were being observed (Figure 3). As multispectral sensors were incorporated on POES they became an invaluable, low-cost source of information for real-time monitoring of WA’s renewable resources of land and oceans.

The first satellite, in low earth orbit with a higher spatial resolution, designed specifically to observe land, was launched in 1972, as the Earth Resources Technology Satellite (ERTS-1), later renamed Landsat-1. This marked the world’s first and longest-running satellite imaging program for observing the land surface.²¹ The majority of remote sensing satellites such as Landsat and POES are in near-polar, sun-synchronous orbits, passing near the north and south poles, crossing the equator at the same time each day, with their sensors imaging the surface below as they pass overhead (Figure 3). They simultaneously broadcast data to ground, where a tracking antenna anywhere in the world can download the stream of multi-spectral data. Some remote sensing satellites such as Landsat have an overpass in mid-morning, when shadows give texture to the image, that helps visual interpretation. Night orbits of POES, with their thermal sensors provide invaluable data on sea surface temperatures and the location of bushfires in remote areas. Day-time orbits reveal sea surface temperature, water bodies, burn scars from bushfires and the photosynthetic greenness of vegetation cover.

Global Positioning Satellites (GPS) in medium earth orbit (at a height of around 20,000 km above the earth) are used for navigation where signals are received by on-ground satellite navigation (SatNav) systems and in space by polar orbiting satellites. GPS satellites are important for survey, navigation and registering Earth observations from remote sensing satellites to a standard map base. A handful of satellites are in elliptical orbits, which brings them closer into the Earth for the very high spatial resolution needed for military surveillance.

The rest of the earth observing satellites in space are in geostationary earth-synchronous orbit, at an altitude of almost 36,000 km, appearing to hang motionless in the sky above the Earth. The fact that they remain over the same geographic area means they provide the perfect platform for telecommunications and near-continuous observations for weather forecasting in equatorial and mid-latitude regions (Figure 2).²²

Figure 2 - Orbits of Polar and Geostationary satellites. Source: www.quora.com

Figure 3 - Diagram of a polar orbiting satellite scanning the Earth, generating multiple spectral digital image data. Source: NASA

In time, POES, with temporal resolution of daily coverage and spatial resolution of 1 km, would be of major value for the WA Government. At 1 km spatial resolution, POES provides global coverage of the Earth day and night, broadcasting data free to ground for reception by low-cost tracking receivers. To receive these POES data to provide daily coverage for environmental monitoring, the WA Government entered into a collaboration with CSIRO, Bureau of Meteorology (BoM) and two local universities (Chapter 5). There is always a trade-off between spatial and temporal resolution. For example, satellites with higher spatial resolution, such as Landsat, scan the earth in much narrower swaths, transmit at much higher data rates and cover the same area less frequently, at intervals of about 16 days. These data being more costly and transmitting at higher data rates, could only be received by the Commonwealth receiver at Alice Springs.

Passive and Active satellite remote sensing

Observation of the Earth from satellite began with spectroscopic measurements of reflected and emitted electromagnetic radiation from solar radiation (Figure 5).²³ Spectroscopy is widely used in physical and analytical chemistry to identify atoms and molecules by their unique spectra. Spectroscopy is used in astronomy, looking at planets in space and at earth from space. Therefore, early research scientists into applications of satellite remote sensing were trained in spectroscopy.

Figure 4 - Diagram of the principles of Earth Observations from Space (EOS) using spectral radiometry. Source: CRISP University of Singapore

Passive remote sensing uses energy from the sun to measure reflected and/or emitted thermal radiation from the Earth. Active sensors create their own source of radiation as radio waves (RADAR) or as laser light (LIDAR). Passive sensors first became operational because of their low cost and ease of analysis of the data. Later, when passive sensors proved unsuitable or too limited, RADAR and LIDAR sensors were developed for specialist purposes, though their data were more expensive and difficult to process. Passive sensors in the microwave region of the electromagnetic spectrum would later be used for measuring soil water content and flooding at large spatial scales.

The pixel size determines the amount of energy available for measurement by a sensor on a passive remote sensing satellite. Therefore, the greater the energy being measured by a sensor the higher the spatial resolution of the imagery. More frequent coverage requires a larger swath using a greater pixel size to generate sufficient energy for detection by the sensor.

Satellite Remote Sensing (SRS) becomes an ‘eye’ in the sky

A feature of SRS is the ability to ‘see’ beyond the frequencies of light the naked human eye can perceive, encompassing the longer wavelengths of near and far infrared and thermal infrared (Figure 5). These satellite observations are repeatedly collected over vast areas, far beyond human physical and visual capability.

Figure 5 - Spectral reflectance curve for vegetation, soil and water from bands of the Landsat TM sensor. Source: gisgeography. com/spectral-signature/ (Accessed 14 Oct 2019)

However, the satellite information is in different physical units (reflectance or emittance) which have to be calibrated against ground-based observations. Hence application of SRS represents a major scientific challenge to the conventional surface monitoring techniques of government agencies. Some agencies were not prepared to collaborate, or able to make the investment needed to use SRS to improve their legacy monitoring systems. Satellite imagery is also in digital radiometric units in many spectral bands unlike conventional single-band panchromatic aerial photography. Scientists with new skills in computing, specialist image analysis software and hard copy image creation are needed to extract useful information from the vast streams of spectral data being transmitted from space.

SRS radiometers capture image data at a range of frequencies or wavelengths across the electromagnetic spectrum (Table 1). The wavelengths are separated by filters or sensors that are sensitive to particular wavelengths. Multispectral images acquired by SRS radiometers are more complex than panchromatic