pitting corrosion of stainless steel at the various surface treatment

Annual subscription: [A] 2 8 F Per copy: [A] 8.50 F A n y of the National Distributors listed at the end of this issue will accept subscriptions; rates in currencies other than the above will be supplied on application to the National Distributor in the country concerned. W h e n notifying change of address please enclose last wrapper or envelope. The articles appearing in I m p a c t express the views of their authors, and not necessarily those of Unesco.

Editor Jacques Richardson Editorial assistant: .Ariette Pignolo Illustrations : Jean-Louis Chauvin

•-••--•if- •

i

'-•;•&£%

This infra-red image obtained via Earth Resources Technology Satellite (EfíTSJ shows forested land in the Canadian province of Ontario, near the north-eastern shore of Lake Superior. Fumes containing sulphur dioxide, emitted by an iron sintering plant in the town of Wawa and driven by prevailing south-westerly winds, have killed or damaged forest (light-coloured, shapeless streak, bottom centre) over a 30-kilometre area. Lakes are black, clouds are white fluffs, and sites of fogging operations show up as rectangles in top half of ¡mage. Date: 6 August 7973. © Canadian Government.

A view of weather in the western hemisphere,as seen from A T S - 3 satellite. The white swirl A is hurricane B renda, as it appeared on 19 August 1973. At B, we see two different intertropical convergence zones, while the streak Joining the two points marked C was a frontal zone in the southern Pacific Ocean. The clouded region at D was a 'low' in the north Atlantic region. The north and south American continents are depicted in faint, superimposed outline form. © NASA. Inset: Stormy overcast cavers entire Japanese archipelago, early March 1974, as seen by contrast-intensified infra-red light from N O A A - 2 sate/lite. Portions of the U.S.S.R., the Korean peninsula and the People's Republic of China are visible on the reader's left. © Sho-cho (Meteorological Agency), Tokyo.

^ v ^ * w " E \ •-

tám':'*M

:£«K££?

ERTS picture of the Afar Triangle (Ethiopia), obtained by multispectral scanner; this is a singlechannel ¡mage in the near infra-red band. Bodies of water appear black. Lake Abe and smaller lakes at the end of the Awash River are in the centre of the frame adjacent to a large volcano. Geological fracture patterns in the volcanic rocks covering most of the area, and the different directions of their main trends, can be traced clearly. © NASA, provided by Hunting Surveys 8Consultants Ltd, Boreham Wood (United Kingdom).

Vol.

XXIV, N o . 3, July-September 1974

A new look at the earth's resources Jean-Philippe Mangin C o m m e n t 195 Kirill Ya. Kondratyev Observations from space in a global ecology programme 203 Hans George Classen Remote sensing via satellite: the Canadian experience 213 Howard

Brabyn

M a n and the biosphere 221 Konstantin I. Lukashev The problem of technical progress and mineral resources 225 Morris Tepper Observations from space and the future of meteorology 239 John

Plev in

Remote sensing of earth resources: a European point of view 2 4 7 Muammer Çetinçelik Is solar energy the fuel of the future? 261 Letters 2 6 7

An invitation to readers Reasoned letters which comment, pro or con, on any of the articles printed in Impact or which present the writer's view on any subject discussed in Impact are welcomed. They should be addressed to the Editor, Impact of Science o n Society, Unesco, 7 Place de Fontenoy, 75700 Paris (France). Requests for permission to reproduce articles published in Imoact should be addressed to the Editor. © Unesco 1974.

Technical prowess and the planetary setting

'We live in a time that is dominated by enormous technical power and extreme human need.... The gap between brute power and human need continues to grow, as the power fattens on the same faulty technology that intensifies the need. 'There is no apparent alternative between barbarism and the acceptance of the economic consequence of the ecological imperative. 'Nothing can survive on the planet unless it is a cooperative part of a larger, global life. Life itself learned that lesson on the primitive earth.' Barry C o m m o n e r 1

'For the first time in history, mankind has the technical possibility to escape the scourges that used to be considered inevitable. Global communication insures that the thrust of human aspirations becomes universal. Mankind insistently identifies justice with the betterment of the human condition. Thus economics, technology and the sweep of human values impose a recognition of our interdependence and of the necessity of our collaboration

It is technically within

our grasp to relate the resources of this planet to needs.'

man's

Henry Kissinger Secretary of State, United States of America, addressing the Sixth Special Session, General Assembly of the United Nations, 15 April 1974.

1. The Closing Circle: Nature. Man and Technology, N e w York, N . Y . , Knopf, 1971.

Comment

Professor Jean-Philippe Mangin is director of the Laboratory of Geology and Sedimentology at the University of Nice and has been concerned with how mankind assesses the natura/ resources available and chooses to use them wisely. His professional address is Faculté des Sciences, Université de Nice, Avenue de Va/rose, 06034 Nice Cedex (France). Put Jules Verne in p o w e r ! Nearly a year ago, at an international symposium dealing with the effects of modern science and technology o n h u m a n beings and their habitat, I accused politicians and technicians of lacking imagination. Whether w e consider energy resources, drinking water or foodstuffs, I s h o w e d , in a s u m m a r y table, what a variety of riches the planet earth could bestow on us if its potentialities were only properly explored and judiciously administered by scientists and engineers blessed with imagination and freedom. At that gathering I had a very able opponent w h o maintained that scientists had only t w o options: either to hire themselves out to governments or, working alone and in freedom, to pursue lines of research leading in most cases to results harmful to m a n . I then referred, as others had done before m e , to the leading role which could be played by scientists if they set their imaginations to work in the quest for standby solutions to be applied in the event of a crisis arising, for example, in the supply of drinking water, foodstuffs or energy. I s h o w e d that scientists had already proposed theoretical solutions to these problems, entailing world-wide changes of climate, the towing of icebergs to provide drinking water, nuclear fusion processes, and so o n . T h e only thing missing w a s the 'driving belt' or the political will needed in order to promote such research until it had developed standby devices ready for immediate application or for stocking. Yet such driving belts or political will did exist. In the conquest of space, for instance, they had been the

impact of Science on Society. Vol. XXIV, No. 3. 1974

195

means of mobilizing m o n e y and m a n p o w e r on a hitherto inconceivable scale. It w a s regrettable, and even criminal, systematically to neglect other ideas and other scientific inventions w h e n they offered w a y s of overcoming the grim shortages that could be caused by nature or the effects of commercial practices. Since then, the course of events has borne out those embittered remarks, very soon affording evidence of their prophetic significance. Soon enough, for instance, to prove that a natural disaster like the Sahel famine could not be avoided because no action had been taken, for want of a driving belt between scientists and politicians, to enable the necessary scientific remedy to be applied—namely the tapping of aquifers—which had already been located. S o o n enough, too, to prove that the sudden awakening of the possessors of an energy-producing commodity habitually used today had caught the countries dependent on that source of supply in a state of unpreparedness. In the latter case, the startled reaction observed in these countries serves as a warning: a tendency to overestimate resources potentially available m a y encourage a take-it-easy attitude and leave the poor grasshopper of La Fontaine's fable quite defenceless. M y words m a y have had a prophetic ring in 1 9 7 3 . But today they only help to swell the mass of widely published literature containing a thousand and one suggestions which all repeat the s a m e hackneyed tune: ' W e must face the problem with the w e a p o n s w e have.' These are meagre palliatives, seeking a purely technological solution, which is itself directly dictated by a political will (or by the lack of such). In any case, it is far too dependent on scientific solutions proper, which have hitherto been neglected. L e s s o n s to b e learnt f r o m the crisis I shall c o m e back later to the reasons for this neglect, but at this point in our reflections w e should, I think, see what lessons can be learnt from the artificially created crisis w e are facing today, and ponder the consequences to be expected if a cut-back in supplies or a shortage due to s o m e hidden cause suddenly obliged the consumer to g o without or to find an alternative product. This is not a mere academic exercise. Without calling u p memories of notorious wartime substitutes, w e have only to think, for instance, of the recent trouble with soya beans. A n engineered shortage m a d e the French Minister of Agriculture suddenly extol the virtues of natural grazing for cattle ! Agronomists had long ago developed

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grasses suitable for each type of soil and of herbivore, but it had seemed easier to buy meal from a source which might cease to send supplies, as w e s a w . Commercial practices no doubt c a m e into play in this case, but the warning signs of a shortage d u e to a world-wide change in agricultural policy are already to be seen in m a n y so-called advanced countries. Pollution control is all the rage just n o w , and this has had the good effect of highlighting concepts and facts, the importance of which is beginning to be appreciated by the general public. Here again w e see that the scientist k n o w s the solutions and has spelt them out, but that the politician hesitates or refuses to apply them, or applies them too drastically, for example, by imposing an absolute ban o n D D T (in the United States of America) or on non-biodegradable washing powder (in the Federal Republic of Germany). The lesson to be learned from the oil crisis which arose in the autumn of 1973 is clear from a host of articles published since then, and I could only add commonplaces. It is worth repeating, however, that the shock of the event has m a d e the rich countries aware of their vulnerability and of the need to revert to e c o n o m y measures (even fictitiously), whereas the hitherto 'poor' countries were suddenly revealed to others, and to themselves, as being in possession of an absolute (but temporary) power which m a y well draw them into a control spiral, this being the modern version of the intoxication of power. In m y view, the most important fact which emerges from this spectacular episode is the absence of a driving belt between scientists and the production circuit, between the highest level of creative imagination and its technological applications, as directed and stimulated by a political will. T h e threat of scarcity Since no such honest and lucid effort at communication exists, the businessman can quite easily deflect policies into production channels that offer a quick return. T h e electric car, for instance, has no chance of being marketed until intellectual and financial resources have been invested in its development by a political decision reflecting the will to by-pass the oil circuit and explore the possibility of applying the advanced techniques stemming from a discovery. Only w h e n the threat of scarcity has b e c o m e a short-term prospect can w e expect an upsurge of inventiveness, which produces a motley collection of h o m e - m a d e contraptions and brilliant ideas.

Comment

197

But w h o will k n o w h o w to sort them out? W h o is capable of discerning what scientists will find applicable, and what will merely serve commercial purposes? W h o will be or is already qualified to trust the ideas of scientists, unless it is the scientists themselves? Here I must agree with that opponent of mine. At present, a discoverer or an inventor (I a m not thinking of adapters of inventions, w h o s e aim is a commercial one) can only 'sell' his product to a government or keep his discovery to himself and perhaps expatiate on it with his colleagues at puerile gatherings laughed at by the c o m m o n m a n w h o does not sense the wind of change. Apart from the great periods of enlightenment or patronage w h e n m e n like Archimedes or D a Vinci were able to turn their concepts into realities, the ideas of a Pascal, a Sadi Carnot, a Kelvin or a Marconi had to wait m a n y long years before anyone took any interest in them. C o m m o n p l a c e though it is, this is an infuriating thought. With the techniques and resources at their disposal, most nations are equipped to give practical effect to what m a y seem to be the most far-fetched ideas such as : altering the course of marine currents to produce more food; modifying the circuit of ice flows so as to tap their resources; circulating surface water through deep-lying rock strata to bring it up again w a r m and charged with potential energy; converting garbage into economically productive materials; using atomic explosives for major earthworks or open-cast mining or to break through barriers around insalubrious areas which have to be drained. W h o ventures to undertake such projects even at a time w h e n probes are ranging far beyond our o w n globe to explore Venus and Mercury? Is it merely a question of prudence? Is it because these plans of scientists fail to inspire confidence? W h y , w h e n the m e a n s are the s a m e , does a project for the conquest of space get accepted while others aimed at conquering our planet earth are turned down? Here w e are touching on a crucial point. M a n y of the apparently futuristic projects proposed by the 'scientific planners' are admittedly fraught with the seeds of destruction. If w e m a n a g e to thaw out the Asian shores of the Arctic Ocean, the whole of Central Europe will perhaps be frozen as a result. But any scientific project involves scientific control tests. Before m e n were sent into space, had not the essential degree of reliability been achieved ? In order to carry an idea through to its practical application it is necessary to use either n e w technical m e a n s or well-established methods, but in any case it cannot be done without a government decision.

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and this can only be operative on the s a m e geographical scale as the project. T h e present scheme of things on our planet, which is artificially divided between producers and avid consumers of energy, points to the following choices: w e can revert to a tribal or national form of patriarchal self-sufficiency, which is possible anywhere on earth provided w e g o back to a more or less distant stage in history, the size of the population being likewise adjusted (this is something like w h a t the advocates of zero-growth want) ; or w e can pair producers off with consumers, facing all the attendant hazards of divorce or matrimonial triangles since n o union can last in such a setting ; or w e can set up a system for the administration of our planet, which has been the dream of all sciencefiction writers from H . G . Wells to the present day. It is interesting to note that/for these futurists, the masters of the world are always m e n of science—doctors or professors. This reflects their feeling that it makes sense to entrust the administration of natural wealth to those w h o k n o w where it lies or even h o w to create it and use it to the best advantage; to those w h o are the first to exercise their powers of imagination; to the poet of our planet w h o can look beyond the horizon of day-to-day living, being free of social or political ambitions. In short, to the m a n of science.

W h o will make the decision? At this point in m y argument I should specify that if the natural resources of the planet are to be administered, it is to a naturalist that w e must turn in the first place, though he might be assisted by specialists in other branches of science, w h o m a k e nothing of calculating and converting the gross natural product. Farther d o w n the line will c o m e the technicians and adapters. But, finally, w h o will m a k e decisions? In simplified terms, the present-day m a n of science can be said to be in s o m e danger of losing caste because, working on his o w n or in a team, he is becoming increasingly e n grossed in the ever-lengthening experimentation stage of his work, which is necessary to prove his theory. Creation flags because m e n of science, having b e c o m e routine working scientists, gradually slip into the role of interpreter or seeker of 'spin-off'. True creativity is getting rarer. It must be revived. Hence m y opening call: 'Put Jules Verne in p o w e r ! ' Even though that novelist w a s not the originator of the discoveries p o p u larized by him, for m e he is a symbol: he produced freely and

Comment- 199

vigorously, unfettered by constraints. In fact, it is not enough to ask of a Jules Verne that he should invent; he would have to supervise the follow-up to his ideas. That would not be the end of the problem, alas ! T h e n e w idea would still have to be put into circulation. Commercial and political considerations would inevitably deflect the invention from its natural course to suit ulterior motives or lucrative or strategic aims. In current parlance, the economist is always described as distinguished and the scientist as disinterested, this being a true example of tautology, in m a n y a case. Yet it is usual to find that the chain of progress starts with the designer and continues with the manufacturer and then the tradesman, to end with the consumer. T h e politician influences the choice of the manufacturer (or is influenced by it, as in the case of the car-oil-plastics triad). Under a sound system of administration of our planet, e n d o w e d only with its natural resources in finite quantities but potentially lending themselves to reversible transformations, the sequence should, in m y view, be as follows: scientist, technician, m a n u facturer, and so o n . W e k n o w , however, that u p to n o w the scientist has seldom or never had his say, or else it has been from beyond the grave ! It is a rare thing indeed for a politician to follow in the footsteps of a scientist or offer him a contract for an idea, except perhaps in the matter of armaments, a field in which naturalists are not altogether at h o m e . Can the m o v e m e n t be reversed and then reset in motion ? In other words, and this is an old Platonic idea, can the responsibility for the administration of terrestrial resources be vested in an Areopagus of scientists, leaving them free to give the politicians whatever advice they consider necessary even if it were to clash with w h a t seemed to be economically expedient at the time? It would be a pity if this idea were regarded as Utopian, for the present pattern of m a n a g e ment of our resources leads, as w e k n o w , to division, or in any case to negligence, and eventually to inequality of opportunity. M u s t w e await s o m e post-war period w h e n m a n kind has been numerically reduced to Neolithic proportions? T o administer the planet earth, w e must get to k n o w it. In this matter of stock-taking, great progress has recently been m a d e and the following pages supply interesting facts about remote sensing by satellite of our natural assets and their utilization (e.g. solar energy). It will b e possible to g o further and, in time, w e shall even control the weather. But, I must repeat, the step forward that w e k n o w w e have m a d e by becoming aware that our planet is a unique and irreplace-

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able c o m m o n heritage, should be followed u p by the still more decisive step of entrusting this heritage, from the stocktaking to the m a n a g e m e n t stage, to those really qualified for the job, with the intention of heeding their advice. This is a task which should be tackled by politicians in our time. O u r international organizations could well serve as meeting places for the architects of a structure giving effect to such a decision. J . - P . Mangin

Comment

201

Observations from space in a global ecology programme Kirill Y a . Kondratyev

In order to resolve problems arising from the possibility of ecological crisis, we need more and better information about our environment. The condition of nature on a planetary scale can be monitored efficiently only with the aid of satellites. The contributions, too, of human coherent scheme

observers In earth orbit are no less vital to a

of 'space ecology' than the automated

acquisition of data, by

fast computer, concerning resources and hazards on land and In the sea.

In recent years study of the environment and its changes, combining various disciplines, has emerged on the public scene as 'ecology'—a term borrowed from biology. Ecology is the science of the interaction between animate nature and its total milieu. The ever-increasingly gigantic scale of m a n ' s industrial activity, concomitant with the continuing scientific and technical revolution, n o w brings to the fore problems of global ecology. This is because technical progress, on the one hand, does not always m e a n less dependence on environmental conditions; successful operation in modern aviation, for instance, requires extremely detailed meteorological data on atmospheric conditions. O n the other hand, contemporary development of manufacturing, transport and large-scale hydrotechnical facilities, as well as the growth of cities and the other consequences of industrialization, have brought about essential changes in our environment which are sometimes planet-wide in character. The.pollution of air and water is a typical example of our globe's changing ecological condition. The rapidly growing population of the world, the considerable decrease (and sometimes exhaustion) of natural resources in s o m e countries, and the deteriorating quality of air and

Impact

of Science on Society, Vol. XXIV, N o . 3 , 1 9 7 4

the seas resulting from m a n ' s technology have brought forth prognoses of ecological catastrophe for mankind, the first serious signs of which would appear before the end of the century. The Limits to Growth, The Closing Circle, such are the meaningful titles of s o m e well-known publications on the subject. T h e basic conclusion of these investigations is that only the prevention of further growth of population>and the stabilization of industrial production can save us from calamities as grave as an extreme shortage of food or critical pollution of our natural surroundings. A useful aspect of these prognostications is the opportunity they provide to elaborate mathematical models of the development of h u m a n society in its interaction with the environment. Attention should be paid, however, to the conclusions concerning environmental pollution because these should serve as a warning that combined action will be necessary to avoid future levels of dangerous contamination. Nevertheless, there is evidence of methodological vice in the theoretical discussions of s o m e futurologists: they sound neoMalthusian [1]. 1 1. Figures in brackets correspond to the references at the end of this article.

203

•

Lack of necessary data

A w e a k point in m a n y of the hypotheses dealing with ecological crisis is the lack of data on the current status of our environment; this makes prediction of future change unconvincing. Monitoring of the present condition of the environment on a planetary scale and evaluation of global natural resources can be done efficiently only with the help of satellites. W e have experienced, in recent years, a turning point in space research: w e have c o m e to accept the dominant role of space technology in the study of the terrestrial environment and its resources. This reorientation has been determined to s o m e extent by the general preoccupation I have already alluded to, that of regional' ecological change affected by growing industrial activity. But continuing development of aerial and marine navigation—activities which extend all over the globe—has accentuated further the need for more, and more reliable, information on the processes at work in the atmosphere and the world ocean. That is w h y the need to study these systems and their phenomena, occurring over vast expanses of land and sea, has m a d e investigation of the dynamics involved (seen from the surface or from aircraft aloft) insufficient. Here again, analysis and assessment of technical data require the application of remote sensing methods to detect and measure from satellites various environmental and resource parameters. Compared with other methods of studying the environment, the important advantages of remote sensing from space include: (a) the possibility of global coverage; (b) the high speed of data collection and processing; and (c) the possibility of rapid, repetitive procurement of data. A n important feature exclusively that of remote sensing from space is the possibility of obtaining not only n e w information on the statics of phenomena not available by other means (data, for example, on the macrostructure of cloud formations or on tectonic structures of the planet), but also its acquisition in perspective. The latter includes the collection of sufficient data on the dynamics of phenomena, especially those which develop quickly and sometimes catastrophically (floods, typhoons, even earthquakes). •

Evolution of space ecology

Thus has broadened considerably our k n o w -

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Kirill Y a . Kondratyev

ledge of earthly surroundings. T h e evolution of a n e w scientific direction—space-borne sensing of our environment, or space ecology— will m a k e it possible to garner more and more reliable information on m a n y of the peculiarities of the planet's structure and resources as well as to monitor on an ever-larger scale the course of both natural and anthropogenic processes. Thus far in the current decade, programm e d , systematic theoretical and experimental investigations in the field of remote sensing have been carried out by various countries. This has been done by both the conventional methods of surface, balloon and aircraft observation, and space technology: meteorological satellites, manned spacecraft and orbital stations, and automatic interplanetary stations. The results obtained are valuable to numerous earth sciences, including geology and g e o morphology, geography, climatology and atmospheric physics, pedology and oceanology, as well as to biology, agriculture and forestry. The collection methods used are meant, basically (a) to obtain images of the earth on different scales ranging from global to local, and in various regions of the electromagnetic spectrum and (b) to use, as well, the results of measurement of spectral absorptivity and reflectivity and those of infra-red thermal emission of natural formations. A n additional important source of information is the visual observations m a d e by astronauts. """ Soviet scientists are contributing greatly to the development of both methods of remote sensing from space and to space ecology itself. Programmes already completed s h o w the outstandingly high efficiency of the solution of scientific and applied problems of space ecology by the use of m a n n e d spacecraft; these m a k e it possible to combine visual, photographic, spectrophotometric and other methods of remote sensing [2]. Let us consider the interconnected problems of environment and resources by taking t w o examples, one relating to food and the other to fresh-water resources. •

F o o d f r o m the sea

In order to increase food supplies, it is necessary that by the year 2000 w e catch twice (but probably four times) as m u c h fish as w e d o today. It is evident that this goal can b e reached only if w e raise the efficiency of catching fish and, concurrently, ensure the contin-

ued reproduction of food fish. Very i m p o r tant, too, is our forecasting of the migratory characteristics of fish shoals and of environmental conditions likely to influence greatly the harvesting of fish from the sea. These include: (a) location, extent, and m e a n displacement of fishing regions; (b) density of fish in these regions; (c) depths at which shoals are situated; (d) 'free path length' between shoals; (e) composition, by species, of shoals; (f) sizes of individuals within shoals and their living habits; (g) state of oceanic surface; (h) wind, cloudiness, ice and other weather conditions; (i) factors harmful to fish life, such as pollution of the sea. Lacking these forecasting data, the ratio of search time to actual catch time is about 10:1. The construction of fish-catch models makes it possible to determine the most important of these parameters. Thus, according to one model, the key parameters are those of data on the ocean's surface temperature, its vertical temperature profile, and salinity. B y comparing different models, it is then possible to consider the following parameters as the most significant: vertical profile and temperature variation beneath the ocean's surface; salinity; chlorophyll content; evolution of conditions of cloudiness; chemical composition of sea water; wind conditions near the surface. S o m e of these parameters can be determined by remote-sensing methods. Others, such as chemical composition, require direct measurement. Optimal solution of the entire problem, therefore, needs the combined application of indirect (satellite) and direct (buoy) methods of measurement as well as the use of satellites to accumulate and transmit information collected from buoys. Regarding the problem of fresh-water resources, w e k n o w that this is a most urgent problem because about 97 per cent of the world's aqueous resources are the salty water of the oceans. Of the remaining 3 per cent of fresh water, 9 5 per cent is 'preserved' in the ice of the polar caps and glaciers. Rapid increase in the d e m a n d for fresh water and the fact that its supply is so limited have underlined the obligation to push forward with detailed investigations in continental hydrology. After all, it is precipitation over land which is our main source of sweet water at present. A specific problem is the careful study of watershed areas, establishing the following parameters: amount of precipitation; duration of precipitation; moisture of soil; variations in water level, and speed of

flow of water courses. T o determine all these characteristics, the situation is the s a m e as with commercial fishery: the problem can be solved efficiently only if methods combining direct measurement and satellites are used. •

Value of m a n n e d spacecraft

There is no doubt that automatic satellites offer the most convenient means to investigate the environment and terrestrial resources on a global scale. A n example of this kind is to be found in the 'Meteor' meteorological system (see Fig. 1). There is a great variety of sensing problems, however, which can be resolved more efficaciously with manned spacecraft w h o s e crews have been trained to conduct well-defined scientific programmes. T h e need for long-period cycles of continuing, complex observation suggests that m a n n e d orbital stations offer the best means to investigate the environment and the resource potential [3]. O n e of the main advantages of the m a n n e d orbital station ( M O S ) is the eventuality to perform, on board, a logical analysis of the situation and m a k e decisions as to the choice of objects to investigate under the most favourable conditions; another is the possibility of choosing the instruments available at M O S which can provide the most complete data- concerning the phenomenon being studied. A n d the presence of a flight engineer almost precludes possible failures in the instrumentation, ensuring its efficient and durable operation. Replacement crews for M O S m a k e feasible the direct transfer to earth stations of experimental records (such as photographic material) for analysis and, if necessary, subsequent correction of the experimental programme. The experience, in both the U . S . S . R . and the United States, of the flight programmes of m a n n e d spacecraft and M O S has confirmed completely the soundness of the arguments in favour of using M O S for scientific investigations. The pioneering space flight of Yuriy A . Gagarin w a s important, not only from the points of view of validating the spacecraft's flight and confirming m a n ' s ability to withstand a stay in space, but also because of the first observations of earth m a d e visually from a spacecraft. Let m e repeat, here, that the observations m a d e by the eye of an astronaut are a most valuable source of information [4], Continuing achievements in rocket and spaceflight technology have m a d e it possible to

Observations from space in a global ecology programme 2 0 5

Aviation

+ Coordination centre

Transformation meteorological information

HydrometeoroProcessing of radiation r^A^oo

Agriculture

* /

Ice conditions

Fig. 1. The 'Meteor' meteorological system.

increase gradually the duration of flights and the volume of research programmes. T h e construction of the first scientific M O S (Salyut) and the experience of Skylab were the natural results of the progressive implementation of launching m a n n e d spacecraft; they opened wide the perspective of using M O S for scientific experiments. Most substantial in volume, and most varied in terms of the possibilities for interpretation, are the images of the earth's surface as seen from space, including pictures of the surface in various wave-length regions ranging from the visible to the microwave. The development of space meteorology has provided convincing examples of the efficiency of surveys m a d e from space. 1

daily service as a space weather patrol. T h e television and infra-red instruments installed aboard these satellites yield, day and night, images of the globe's surface and cloud cover which help our study of the distribution of the latter. Geostationary satellites in equatorial orbit at an altitude of 37,000 kilometres m a k e it possible to follow continuously the dynamics of cloud cover in tropical and subtropical zones; the time of one revolution of these satellites round the earth is 2 4 hours, as if they ' h a n g ' over a fixed point at the equator. In short, the use of meteorological information received from satellites has m a d e it possible for the weather service to forecast the weather more reliably and more in advance than previously [5].

•

A complete set of scientific instruments aboard a meteorological satellite includes radiometers for measuring the amount of solar

Reliable, fast w e a t h e r reports

Satellites of the Soviet 'Meteor' meteorological space system and of the United States are in

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Kirill Y . Kondratyev

1 . See article by Dr Tepper, beginning o n p . 2 3 3 .

radiation reflected from earth and the earth's o w n thermal emission into space. Data from the radiometers m a k e it possible to study the regularity of the distribution by our planet of its heat income and outgo, i.e. to characterize its energetics, or heat budget. These recent investigations have introduced basic corrections to data concerning energetics which had been accumulated earlier. Solar radiation measurements from highaltitude balloons (begun at Leningrad University in 1 9 6 1 ) , for instance, have led to the conclusion that the earlier value of the constant describing the amount of solar energy which reaches the outer atmospheric boundary in the case of the m e a n distance between sun and earth (2 c a l / c m ' . m i n ) had been considerably overestimated. It appears n o w that the maximal solar constant's value does not exceed 1.94 c a l / c m 2 . m i n , a result which recently has been confirmed by data in quite a number of investigations m a d e by scientists from the United States. It seems that this constant value can dip to 2 . 0 - 2 . 5 per cent below its maximal value, depending on solar activity. This difference m a y appear, at first glance, to be insignificant. The fact that there is this difference is of fundamental value: theoretical calculations indicate that variation in the sola constant by 1 per cent should be followed by variation, in the corresponding direction, of the m e a n atmospheric temperature by approximately 1 degree. T o estimate properly the basic significance of this, it is not out of place to mention here that the m u c h discussed phenom e n o n of the warming of the climate (especially in the Arctic and Antarctica) during the first half of the present century expressed itself as a rise in temperature of several tenths of a degree. The variations discovered in the solar constant are so marked that further confirmation of recent data is necessary. •

O c e a n s a b s o r b m u c h of solar rays

Another interesting fact is that satellite data indicate noticeably overestimated values of the earth's albedo (its reflectivity), obtained earlier from calculations m a d e mainly at low altitudes. This m e a n s , in effect, that in calculating the income and outgo of heat w e underestimated substantially the quantity of solar radiation absorbed by the earth. Detailed analysis thus far s h o w s that 'surplus' radiation is absorbed chiefly by the oceans. Highly

accurate measurements of the planet's revenue and expense in terms of heat are currently of great interest in regard to the impact of m a n ' s industrial activity on the earth's energy balance [6]. The use of numerical methods to forecast the weather with the help of computers—prediction of the values of atmospheric pressure, wind speed and direction, atmospheric preci. pitation and other parameters by precise hydrodynamical and thermodynamical equations describing these atmospheric processes— is connected with the need for data on the initial values of these s a m e parameters, but not necessarily taken together. From this has recently emerged the problem of developing methods to obtain quantitative meteorological information. This is most urgent, from the point of view of onward development of satellite meteorology, and is characteristic of the stage at which the evolution of satellite meteorology stands today: meeting the practical requirement to supply the initial informational needs demanded by numerical methods of forecasting the weather. By measuring from satellites the earth's emissions at various wave-lengths, the socalled outgoing radiation, it is possible to obtain information concerning, for example, vertical temperature profiles and humidity of the air. Information of this kind c o m e s most readily from the measurements of infra-red thermal emission. A multicomponent gaseous m e d i u m , the infra-red emission of the atmosphere depends in a very complicated w a y on wave-length. In those wave-length regions where the atmosphere is almost transparent (known as the transparency w i n d o w s ) , it is largely the emission from the earth's surface which reaches a satellite; this is what makes possible the determination of temperatures at the earth's surface. W h e r e the atmosphere absorbs radiation most intensively, the outer layers of the atmospheric thickness involved contribute considerably to the outgoing radiation; the radiation's value characterizes the temperature of these layers. Thus, by measuring the outgoing radiation of differing wave-lengths, it is possible to 'stratify' the atmosphere in order to determine its vertical temperature profile. T h e practical solution of this kind of atmospheric thermal sounding from satellites, however, is no easy matter: the problem itself belongs to the class of so-called non-correct problems, problems which have no single solution. T h e difficulty

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Table 1. Possibilities of interpreting multispectral images 1

Spectral region ( ^ m ) Characteristic souaht Colour I.R. 0.51-0.89

Green-light blue 0.47--0.61

Red I.R. 0.68-0.89

Yellow-green 0.59-0.715

3 1 2 1 1

4 4 2 1 1

4 2 3 2 2

3 4 2 1 1

1 1 1 3 4 4 1 4

2 3 2 3 4 4 2 4

2 2 2 4 4 4 2 4

3 3 2 3 4 4 1 4

Vegetation type Vegetation phase Pastures Sand Barren rocks Rivers and clean water basins Dried river-beds Lake Town Buildings Mine Highways and raiilways Road surface composition

1. Numerical designations: 1 = interpretation is always possible; 2 - interpretation is usually possible; 3 = interpretation is sometimes possible ; 4 = interpretation is impossible.

can b e overcome, using m e t h o d s of regularizar o n of the solution of non-correct problems already w o r k e d out by Soviet mathematicians; the efforts of both Soviet and American scientists have m a d e it possible to surmount practically these mathematical difficulties b y making use of different kinds of m e t h o d s of regularization. T h e problem of high accuracy measurement of outgoing radiation, also, has been resolved successfully [7]. •

C l o u d s a s technical barriers

T h e need to take account of the influence of cloudiness presents a complication from the point of view of measuring the outgoing infra-red radiation (in order to determine the vertical temperature profile). Since dense clouds are non-transparent to infra-red radiation, sounding of the atmospheric subcloud layer is impossible.in the presence of overcast; it is preferable, in those conditions, to m a k e use of measurements of outgoing microwaves

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Kirill Y a . Kondratyev

(in the centimetre wave-length region of the spectrum). Studies d o n e using microwave measurement data, obtained for the first time by the C o s m o s - 2 4 3 satellite, revealed the possibility of solving problems such as the determination of the a m o u n t s of water vapour and liquid water in the atmosphere, the state of the sea's surface, the presence of ice, a n d so forth. O n e important phase of this kind of problem-solving w a s the joint SovietAmerican expedition in the Bering S e a held in February and M a r c h of last year. T h e development of satellite meteorology has paved the w a y to a broadened use of remote sensing m e t h o d s from space for extensive investigations in space ecology. Similar to the situation w h i c h prevailed during the first stage in the use of meteorological satellites, the very beginning of the developm e n t of space ecology is characterized by the utilization of data produced by aerial surveys m a d e from space. It is important, in this respect, that multispectral surveying m e t h o d s —

taking pictures of the earth using radiation from several spectral regions—be done beforehand. Table 1 s h o w s s o m e of the possibilities of interpreting multispectral images. I should emphasize that the examples given are merely by w a y of illustration; the real possibilities for interpretation are m u c h more extensive [8]. A s a rule, the interpretation of images is qualitative. It is obvious that the development of quantitative methods of interpretation is possible only on the basis of employing quantitative information; in this case, the data m a y be the brightness fields in various spectral regions. The most promising means of obtaining multispectral images, therefore, should be considered those which are associated with utilization of multichannel telephotometers or radiometers. These yield not only a 'picture' but also the brightness field in absolute values. The next stage in the development of space ecology, n o doubt, will be connected with the wide use of methods of multispectral surveying and spectrophotometry. This has been pointed to clearly by the fulfilment of the scientific programmes of the Soyuz manned spacecraft, the three Skylab missions and the earth resources technology satellite ( E R T S ) . •

D u s t particles a n d the w e a t h e r

A substantial component of the programme of atmospheric sounding from space is the determination of the vertical profile of dust' particles, or aerosol, concentrated there. Aerosol studies are interesting for m a n y reasons, especially in meteorology. It has been long k n o w n , for example, that atmospheric pollution subsequent to volcanic activity results in a considerable diminution of the income of solar radiation as well as a noticeable change in the thermal régime of the atmosphere. A n d industrial pollution is n o less important. Therefore systematic aerosol soundings from space were conducted aboard Soviet manned spacecraft. These investigations began with photography of the horizon at twilight, by cosmonauts Nikolayeva-Tereshkova and Feoktistov. Spectra of the twilight aureole were obtained for the first time by cosmonauts Volynov and Khrunov aboard Soyuz-5. Interpretation of these data provided important n e w information on atmospheric optics and the spatial distribution of aerosols. A n urgent aspect of the scheme of remote sensing from space is a broad group of prob-

lems related to studying characteristics of the earth's surface, including surface layers of both land and sea. The main objective here is to investigate natural formations from the base of their reflection spectra as registered in space [9]. The first example of a 'complete approach' to the solution of a problem of this kind w a s a combined sub-orbital experiment accomplished during the combined flights of Soyuz-6, Soyuz-7 and Soyuz-8. Photographs and spectra of various natural formations were derived from this experiment, as well as optical measurements m a d e on the ground and from t w o aircraft laboratories flying at different altitudes [10]. Analysis of the results demonstrated that a complete set of optical data makes it possible to differentiate very accurately b e tween natural structures. In this connexion, resolving the problem of selecting an optimal set of data proved to be of primary importance, making it possible to characterize with reliability the natural formations being studied. W e learned that it is not necessary to register completely the reflection spectra of these structures, yet it is quite sufficient to k n o w the values of spectral brightness coefficients for several wave-lengths. The accomplishment for the first time of these integrated suborbital geophysical experiments has furnished us with a good example of h o w to plan and execute synchronous programmes of research over a given test site. Here again, it is problems of this kind which in the near future will b e c o m e the most significant phase in the development of space ecology and in the elaboration of reliable methods of interpreting data acquired b y remote sensing in space. Complete data are essential, at the s a m e time, to determine what is called the atmospheric transfer function: knowledge of this is indispensable in order to eliminate the atmosphere's influence in registering from space the spectra of natural formations at ground level. •

Sensing the nature of soil a n d sea

Considerable attention has been paid recently to the development of methods for remote sensing of soil characteristics, especially moisture and temperature. Attempts to use data forthcoming from microwave emission measurements have proved successful in this respect, and are being continued. Interpretation of the results of polarization measure-

Observations from space in a global ecology programme 2 0 9

merits of radiation reflected from the ground, at about 0.5 (im, can also be considered as quite promising. This is possible because polarized, reflected sunlight is greatly intensified as the soil's moisture increases; with saturating moisture, reflected light becomes fully polarized at what is called the Brewster angle. It is important that the variations in polarization depend only slightly on the incident angle of the sun's rays. A n d since polarizing conditions are specific for the light reflected by various kinds of ground, a sufficiently reliable solution of the problem is possible only if there has been a preliminary identification of soil type. The need for increased production of food has drawn our attention more and more to the biological resources in the world ocean. Since biological production in the seas is determined by photosynthesis, the need arises to develop methods to monitor the spatial distribution and the dynamics of photosynthetic activity. These methods will have to be of the remote kind because direct measurements can be m a d e only on a very limited scale. Since the key indicator of the ocean's biological productivity is chlorophyll, measurements of the chlorophyll content of sea-water and its variations will describe the intensity of photosynthetic processes and other conditions obtaining in the production of 'biomass'. T h e rate of photosynthesis, and consequently that of biomass production, depend on the presence of nutrient components such as nitrogen and phosphorus. Pollutants have great influence on photosynthesis. Thus the presence of mercury, for instance, with a concentration of 1 . 1 0 - ' (1 part per 1,000 million) reduces the speed of photosynthetic activity by 5 0 per cent. A concentration of D D T of 1 . 10~ 8 (1 part per 100 million) also suppresses substantially the processes of photosynthesis. T h e measurement of chlorophyll can thus make, it possible to evaluate both the content of the biomass (specifically, phytoplankton) and accompanying factors (concentration of nutrients, degree of pollution). Since data exist to support a correlation between chlorophyll content and the ocean's surface temperature, simultaneous remote measurements of both these parameters would b e very interesting. These measurements have another importance: d e -

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scription of the upwelling of deep, cold-water layers at the boundaries between zones of sea currents and waters of different origin (e.g. where major rivers or glaciers join the sea). The atmospheric transparency w i n d o w in the visible [spectrum (referred to earlier) is the only one that can be used in the development of a remote method of chlorophyll measurement because this is the unique w a v e length region at which radiation penetrates deeply, as m u c h as 1 5 0 metres, into ocean water. Preliminary investigations have s h o w n that b y measuring the difference, or ratio, in reflected radiation intensity between a wave-length of 4 4 3 microns (443 millionths of a millimetre, the maximal absorption) and 525 microns (the region being compared), it is possible to obtain a characteristic which is highly sensitive to chlorophyll content. •

T h e future: vast a m o u n t s of data

I have presented only scattered illustrations of results obtained, with the aid of space vehicles, in the study of the earth's environment and resources. I have omitted problems related to geology, geobotany, and geomorphology, for example. S u m m i n g up the research done so far in space ecology, w e can conclude that the most promising w a y of obtaining the information w e require is by combining methods to acquire multispectral images (especially by using multichannel scanning radiometers) and the use of spectroscopy in the broad wave-length region, from ultra-violet to microwaves. Furthermore, the applications of laser-radar, or lidar (light detection and ranging), open wide the prospects for the future [11]. Let m e repeat that, because the methods of remote sensing from space are ambiguous, adequate schemes for the interpretation of measurement data can be worked out only on the basis of the combined analysis of information derived via space vehicles, laboratories aboard aircraft and surface observations of selected sites. T h e search for the most efficient techniques of processing these data continues. In the future, space ecologists will require the processing of such a huge amount of information that this will be possible only with the fastest computers.

•

Dr Kirill Ya. Kondratyev

A specialist in atmospheric physics and space ecology. Professor Kondratyev is a former rector of Leningrad University where he now heads the Atmospheric Physics Department. Concurrently, the author is chief of the Radiation Studies Department, Main Geophysical Observatory of the U.S.SJÎ. Address: Kafedra Fiziki Atmosfer, Leningradskiy Universitet, Leningrad 199164 (Union of Soviet Socialist Republics).

REFERENCES 1. F E D O R O V . E. Vzaimodeistviye obshchestva i prirod [Interaction between society and nature]. Leningrad, Gidrometeoizdat, 1972. 2 . K O N D R A T Y E V , K. (ed.). Issledovaniya prirodnoy sred s pilotiruyemkh orbrtalnikh stantsiy [Investigations of the environment from manned orbital stations]. Leningrad, Gidrometeoizdat, 1972. 3. V I N O G R A D O V , B . : K O N D R A T Y E V , K. Kosmicheskiye metod zem/evedeniya [Space methods of terrestrial studies]. Leningrad, Gidrometeoizdat, 1971. P E T R O V , B. Orbitalnye stantsii I izucheniye zemli iz kosmosa [Orbital stations and study of the earth from space]. Vestnik AN SSSR. no. 10, 1970. 4. B U Z N I K O V , A . et al. Atmosferniye yavleniya po nab/yudeniyam s pilotiruyemykh kosmicheskikh korablei [Atmospheric phenomena from observations from manned spacecraft]. Leningrad, Gidrometeoizdat, 1972. 5. B U G A Y E V , V . Novoye prognozirovanii pogod [Recent achievements in weather forecasting], Leningrad, Gidrometeoizdat, 1972.

6 6. K O N D R A T Y E V , K. Radiation processes in the atmosphere. Geneva, World Meteorological Organization, 1972 (Monograph no. 309.) 7 7 . K O N D R A T Y E V , K.: TIMOFEYEV, Y u . Termicheskoye zondipovaniye atmosfery so sputnikov [Thermal sounding of the atmosphere from satellites]. Leningrad, Gidrometeoizdat, 1970. 8 . Proceedings of the eighth International Symposium on Remote Sensing of the Environment. Vols. I-II. A n n Arbor, University of Michigan, 1973. 9. K O N D R A T Y E V , K. Spectrophotometry of environment from space. Naturwissenschaften, vol. 5 8 , no. 1 1 . 1 9 7 1 . 10 10. K O N D R A T Y E V , K. et al. Nekotoriye rezultaty spektrofotometrirovaniya prirodnikh obrazovaniy s pilotiruyemogo kosmicheskogo korablya 'Soyuz-9' [Some results of the spectrophotometry of natural formations from the 'Soyuz-9' manned spacecraft]. Kosmicheskiye issledovaniya, vol. X , no. 2 , 1 9 7 2 . 11. 11 Z U Y E V , V . Lazer pokoryayet nebo [The laser conquers the sky]. Novosibirsk, ZapadnoSibirskoye Knizhnoye Izdatelstvo, 1972.

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Remote sensing via satellite the Canadian experience Hans George Classen

Remote

sensing, meaning

here the scanning of the earth's surface from aircraft

or satellites, is a new technology particularly applicable to a country such as Canada;

there, a vast territory rich in natural resources shelters a sparse and

scattered population. The launching of the Earth Resources Technology Sate/lite by the National Aeronautics and Space Administration of the United States has provided Canadian scientists and specialized planners with a valuable new to survey the land and water endowments natural and man-made

of their enormous

method

land as well as the

processes affecting these.

Remote sensing has been defined by a Canadian expert in that field as 'the airborne and orbital practices of surveying the ultra-violet, visible, infra-red and microwave radiations emitted and reflected from the surface of the earth'. Radiation of these kinds is emitted or reflected in various intensities by every kind of surface, natural or m a n - m a d e , animate or inanimate: water, soil, rocks, vegetation, animals, buildings and so o n . Remote sensing, by this definition, has little or no depth penetration. It should be distinguished from such well-established aerial surveys as those of terrestrial magnetism and other geophysical phenomena. Although these are also a form of remote sensing, strictly speaking, they are omitted from consideration in this article because they are essentially low-altitude aerial techniques and cannot be employed in high-altitude aircraft and spacecraft. Aerial photography also c o m e s under the heading of remote sensing, but the latter obtains additional information with advanced techniques which m a k e use of portions of the electromagnetic spectrum above and below the visible range, as well as the visible spectrum itself.

Canada is a country that seems predestined for a flourishing remote-sensing industry. It is one- of the f e w countries o n this globe— Australia, Brazil and the Soviet Union are others—with a vast, often roadless territory, a population concentrated chiefly in a relatively small part of the country, and an e c o n o m y that depends to a large extent on the efficient use of natural resources scattered over enormous distances. •

Surveys f r o m aircraft

Therefore it is not suprising that Canadian map-makers, forestry officials, prospectors, road-builders, water-resources planners and others took early advantage of the bird's-eye view offered by the combination of aircraft and camera. T h e topographic mapping of all of Canada, including the Arctic Islands, at a scale of 1 : 2 5 0 , 0 0 0 could not have been accomplished without the extensive use of air photographs; this project w a s completed in 1968. T h e National Air Photo Library (a division of the Surveys and Mapping Branch in the Department of Energy, Mines and Resources) has for m a n y years accumulated a stock of all aerial photos taken by or o n

Impact of Scienc» on Society, Vol. XXIV, No. 3, 1974

213

Orbital altitude

Theoretical analysis

Laboratory experiments

Fig. I. Development of remote-sensing techniques. The elements include field experiments ('ground truth') to establish the spectral signatures of features that can be sensed from various distances, at decreasing scales and increasing coverage per image as the sensing platform rises higher from the earth's surface.

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Hans George Classen

behalf of the federal government, and its services have been used extensively b y government and private agencies. W h e n remote-sensing imagery became available, it w a s natural that the s a m e National Air Photo Library should be entrusted with its distribution. Canada's first experiments in this n e w technology were also carried out from aircraft (see Fig. 1). A necessary part of the experiments w a s 'ground-truthing', i.e. learning to interpret what w a s seen o n the image b y making observations on the ground. In addition to colour photography, wide use w a s being m a d e of colour infra-red photography. Although the eye is sensitive only to light in the visible part of the spectrum—from red at one end to violet at the other, or the colours of the rainbow—photographic film can be m a d e sensitive to 'light' in regions outside the visible region: infra-red and ultra-violet. The near infra-red band of the spectrum is particularly sensitive to light reflected from material containing chlorophyll, an ingredient of all healthy plants, and can therefore be used to survey and assess the health of all types of vegetation, from minute algae to great forests.

The opportunity for such a project arose in the early 1970s w h e n the United States National Aeronautics and Space Administration offered Canada a share in the imagery expected to be provided by a so-called Earth Resources Technology Satellite (ERTS), which w a s scheduled to be placed in orbit in early spring 1972. After consultation between N A S A and our o w n department, an agreement w a s drawn up and signed on 14 M a y 1971 ; this stipulated that the joint programme of remote sensing with E R T S would last four years and would be experimental, with the exchange of technical data but n o exchange of funds. The Canadian Department of Energy, Mines and Resources ( E M R ) would receive data direct from the satellite at a ground station situated in Canada, and would handle and analyse such data in Canada. 'It is further understood that E R T S data acquired by E M R and N A S A will be m a d e available as soon as practicable to the international community', i.e. the accord specified that no secrecy and no copyright were attached to the imagery. It would be m a d e available to any person or agency, anywhere in the world.

Other techniques involve the use of line scanners, which produce images one line at a time, somewhat like a television tube; radar, which is unaffected by darkness or cloud cover; thermal infra-red sensors which register variations in heat emission (for example, differences in temperature between polluting effluents and clean river water) ; and devices employing laser beams, which have been used experimentally to detect oil spills.

Canada has greatly appreciated this offer of cost-free collaboration. It must be realized that the cost of the launch vehicle alone w a s $4.2 million—two-thirds the cost of Canada's entire annual budget for remote sensing—while the complete E R T S programme in the United States, which m a d e provision for t w o satellites (ERTS-1 and E R T S - 2 ) , w a s put at $ 1 7 4 million. Negotiating and concluding the agreement w a s one thing. Providing the technical facilities for implementing it w a s another. Before describing the receiving and processing facilities that had to be constructed in Canada, it m a y be best to describe briefly the design of E R T S . Built for N A S A under contract by the General Electric C o m p a n y , the satellite weighs 891 kilograms; the sensors alone weigh 2 2 0 kilograms. There are t w o sensor systems. O n e is of the return b e a m vidicon cameras, designed to take snapshot-type pictures of the earth and to relay this imagery to ground stations by m e a n s of television-type electronic signals. The other system is called the multispectral scanner ( M S S ) ; this w a s designed to scan the ground continuously, line by line, in four spectral bands. Because of a minor technical defect, the return beam vidicon cameras had to be switched off soon after launching, and only

•

A d v e n t of satellites

A scientific-technological community that had been so eager in earlier years to take advantage of the aeroplane as a platform for sensors w a s hardly likely to overlook the even more exciting possibilities offered by orbiting platforms, i.e. satellites. Canada has not developed rockets capable of placing satellites into orbit, nor did it seem economically practical to proceed to the development of special sensor-equipped satellites. Instead, Canadian scientists active in the field sought to take advantage of the space technology being developed in the United States, in a manner that would be consistent with Canada's desire for an independent dataacquisition and interpretation capability.

Remote sensing via satellite: the Canadian experience

215

the M S S system continued to function. Since the two systems were largely redundant (designed to perform almost identical tasks), little information has been lost. The sensors would scan a swath 185 kilometres wide, from an altitude of approximately 915 kilometres. The satellite would be launched into what the experts termed a sun-synchronous, near-polar orbit. This meant that it would orbit roughly from north to south, each orbit shifting westward in relation to the earth in synchronism with the sun so that the satellite always crosses the same latitude at the same local time. In this manner the entire globe could be covered every eighteen days. •

C a n a d a ' s role in E R T S

In order to receive E R T S imagery of Canadian territory, Canada had to build and equip a ground receiving station. A s luck would have it, there w a s a moth-balled radar research station with a 27-metre parabolic dish at Prince Albert, Saskatchewan, not too far from the geographical centre of the country. This w a s converted at a cost of §1,127,000, with the installation of a tracking system and another for receiving and tape-recording the satellite's electronic signals. The station is not used to control the operation of the satellite itself, all such control being carried out by NASA. At the same time, a ground data handling centre, together with administration, interpretation and modest research facilities w a s being established in Ottawa, the Canadian capital. There the taped imagery would be corrected with the aid of a complex computer system, transformed into photographs, and m a d e available for distribution. A certain amount of experimentation and research in image interpretation and application would also be carried out. The entire effort w a s m a d e the responsibility of a newly created branch of the Department of Energy, Mines and Resources; it w a s given the n a m e of the Canada Centre for Remote Sensing. Since the department also administers federal activities in the fields of geology, geophysics, and surveying and mapping, remote sensing w a s thus a fitting complement to its older activities. At the same time it w a s realized that the objectives and applications of remote sensing far transcended the interests of federal programmes in the earth sciences. Great care w a s

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Hans George Classen

taken from the start to solicit the views and enlist the expertise of the m a n y government, university, and private agencies in Canada that have either participated in the development of remote-sensing technology or stand to benefit from the interpretation and application of this n e w technique. At present, the Canada Centre for Remote Sensing is advised, on the federal level, by an inter-agency committee on remote sensing and, at the broader national level, by the Canadian Advisory Committee on Remote Sensing. The latter draws its membership from provincial remote-sensing agencies and from specialized institutions and private companies. M u c h of the work in establishing and operating remote-sensing facilities has been let on contract, and there is provision for outside consultants and for temporary postings with the centre. It bears emphasizing that the Canada Centre for Remote Sensing w a s created to manage not only Canada's E R T S programme but also the country's activities in airborne sensing. Since this article is devoted essentially to the application of space technology, however, the airborne effort will not be described in further detail. •

E R T S launched t w o years a g o

Because of technical difficulties, the launching of the satellite w a s postponed to July 1 9 7 2 ; this gave Canadian contractors more time to complete and test the installations at Prince Albert and Ottawa. The satellite w a s launched on 2 3 July by a Delta-89 rocket from N A S A ' s Western Test Range in California. A few days later its sensors were switched o n over Canada, and the first imagery began to c o m e in. A s soon as the initial recording tape w a s ready it w a s rushed to Ottawa, where scientists and technicians worked around the clock to transfer the imagery, which covered a track through Labrador and eastern Quebec, to photographic reproductions. The International Congress of Photogrammetry w a s then in session in Ottawa, and the first E R T S image of Canada w a s exhibited there, arousing considerable interest. The ¡mage, in colour, showed a portion of central Labrador, 1 8 5 by 185 kilometres, with the numerous lakes and hilly topography of the region standing out in excellent contrast. There ensued a period of several months which were a time of troubles. Expectations had been extremely high, partly because of the

pre-launch persuasiveness of the specialists w h o would process and distribute the imagery and w h o , quite naturally, were anxious to build widespread public support for E R T S in Canada. Various delays were experienced in the processing and distribution of imagery/ which produced disappointments a m o n g the m a n y research scientists w h o had placed early orders for E R T S imagery and w h o had actually drawn up research programmes dependent on it. M a n y people involved in remote sensing tended to overlook the fact that E R T S w a s , as the Canada-United States agreement clearly spelt out, experimental, with all that the word implies. Gradually, however, the technical and organizational difficulties were overcome, and the Canadian E R T S project is n o w functioning well. A year and a half after the launching of the satellite, a preliminary assessment can be m a d e of its usefulness to Canada in terms of resource studies and evaluation. •

A first appraisal

S o m e of the outstanding advantages of an orbiting sensor platform over an airborne unit were obvious even before E R T S w a s launched. To begin with, E R T S covers all of Canada (with the exception of the northern tip of Ellesmere Island) every eighteen days. T h e amount of flying that would be required for such a coverage staggers the imagination and is far beyond the bounds of feasibility. T h e frequent coverage by satellite n o w makes it possible to observe seasonal and other relatively rapid changes in the environment, such as the extent of s n o w cover, crop growth and harvesting, freeze-up and break-up on lakes and rivers, the expansion and contraction of the sea-ice cover in the Arctic, the spread of urbanization, land-use patterns, cutting of forests, and forest fires. Another important E R T S advantage is the synoptic viewing of large areas, each image normally covering 34,225 square kilometres which are seen at the same instant under the same light conditions. This is not possible with airborne sensing. The disadvantages of E R T S imagery are its relatively low resolution—the smallest features distinguishable on it vary in size from 5 0 to 300 metres, depending on various conditions— and the inflexibility of the eighteen-day cycle which precludes response to emergencies, such as coverage of sudden floods, or oppor-

tunities, such as rare sunny days in those parts of Canada that are usually overcast. E R T S has to take weather as it comes and a large proportion of the imagery is unusable because of cloud cover. Given these factors, it is not surprising that s o m e of the most impressive and promising applications of E R T S information relate to that Canadian region which is most difficult to cover by other information gathering systems, , the Arctic. It also happens that there is a considerable degree of overlap between E R T S orbits in the Arctic, so that m a n y points are covered more frequently than in the south, sometimes on ten consecutive days. A so-called quick-look facility attached to the receiving equipment at Prince Albert makes it possible to obtain uncorrected black-andwhite photographs of E R T S imagery within twenty minutes of a satellite's passing. The distribution of this imagery has been placed in the hands of a private contractor, w h o during the s u m m e r of 1974 is undertaking to transmit imagery of the Arctic Ocean to ships plying those ice-infested waters. Transmission can be accomplished via a communication satellite or by other, conventional means. If our efforts will finally prove to have been successful, it will enable ship's captains to 'see' what ice conditions are like hundreds of kilometres from their position. It would be as if the ships had been equipped with a crowsnest 9 1 5 kilometres high. In terms of economics, the operation of ships carrying out geophysical surveys is extremely expensive, and every day lost because of ice barriers can m e a n a loss of $100,000. Losses of this kind could be minimized if captains k n e w where such obstacles could be penetrated or circumvented. •

N e w technology brings economies

other

The experiment, which w a s started last s u m mer, has been observed with great interest by the Ice Forecasting Central of the Department of the Environment, which provides a service to ships plying the waters of the Arctic. Ice forecasts have been based hitherto on aerial reconnaissance, each sortie lasting about fifty flying hours at a cost of about $1,000 per hour. After analyzing E R T S imagery of Arctic ice conditions, it w a s recommended that these flights be discontinued during April, the period of least cloud cover, and that E R T S imagery be used instead—at a total cost per month of

Remote sensing via satellite: the Canadian experience

217

$1,500. The financial saving w a s modestly described as 'considerable'. Occasional use would be m a d e of E R T S imagery during the succeeding months, however, allowing aircraft to concentrate on the areas where ships were actually navigating. Another interesting use of quick-look imagery is the inventory of burned-out forest areas in the northern parts of the western provinces. Forest fires, often started by lightning, take a heavy toll of Canadian forests each year, especially in inaccessible areas where firefighting is difficult and sometimes impracticable. N o w E R T S will m a k e it possible to obtain at least a reasonably accurate assessment of the d a m a g e wrought by these natural disasters, again at a considerable saving in flying time. Dr Lawrence Morley, the Director of the Canada Centre for Remote Sensing, has estimated that the cost of an E R T S receiving station possessing only a quick-look facility, without the equipment needed to correct and process further the imagery, would be a relatively modest $600,000, with operating costs amounting to about $200,000 per year. H e notes that several developing nations could join in financing and operating a regional facility of this nature. Thus far, the only nation outside the United States and Canada with its o w n E R T S receiving station is Brazil, which has been extremely active in adopting remotesensing techniques. Dr Archie McQuillan, a research scientist with the centre's Program Analysis Unit, has been conducting a cost-benefit study of remotesensing applications. H e states flatly that E R T S is pre-eminently a mapping tool. ' A n y type of small-scale m a p ' , he emphasizes, 'stands to benefit from n e w information provided by E R T S imagery.' In cartographic applications, the elimination of distortions from imagery is essential. This is done by comparing selected points on individual images with points on m a p s and 'pulling' the image gently in various directions, like a rubber sheet, until the points agree. •

Accurate data for m a p revision

In the southern, densely populated'part of Canada additional cartographic information gained from E R T S imagery is usually what map-makers call 'culture', i.e. m a n - m a d e structures or alterations of the environment In the north, it is usually geomorphological infor-

218

Hans George Classen

mation, or information related to the north's climatic régime, such as permafrost. For example, a road following a river valley had been mapped from aerial photographs, a standard mapping procedure. W h e n the m a p w a s compared with E R T S imagery, it w a s found that the position of the road w a s s o m e times in error. This w a s due to the fact that the large-scale aerial photographs had not always s h o w n road and river on the same photo, so that the distances between them had been miscalculated. T h e smaller-scale E R T S image did s h o w road and river, and correction w a s m a d e . Ground verification showed that E R T S had in all cases been correct, or more nearly correct than the aerial photos. 'It seems evident at this time', said one specialist, 'that E R T S imagery can provide revision information of accuracy suitable for 1 : 250,000 m a p ping' (when 1 centimetre on the m a p equals 2.5 kilometres on the ground). E R T S imagery has been useful in the Arctic also, where engineers are attempting to define a suitable route for a projected natural-gas pipeline from the Queen Elizabeth Archipelago to Canada's industrialized heartland. There are m a n y terrain features that cannot be ascertained from conventional m a p s . E R T S imagery s h o w s the land during the four seasons, and s n o w o n the ground often enhances the relief, showing the locations of choppy terrain. It s h o w s areas burned over by forest fire, which changes the thermal régime of the ground and thus the terrain's stability and erosion factors. E R T S imagery is useful, too, to delineate the migration routes of animals, an environmental factor which pipeline planners are required to take into account: the financial stakes are high, and every inch counts. Construction costs of a gas pipeline in the Arctic will be enormous— as m u c h as $1 million per mile on land, and perhaps five times as m u c h on the sea bottom. In the latter case, the pipe will probably be laid from the surface ice, through trenches, during the winter w h e n the ice forms solid bridges from island to island. Obviously patterns of freeze-up and break-up, along with the extent of shore ice, must be k n o w n before any venture of the kind is attempted. Here again, repeated E R T S imagery is the best source of information. A n interesting experiment involving E R T S imagery, along with airborne photography and ground-truthing, is the so-called Spring Wheat Project. It consists of parallel studies in Canada and the United States aimed at the computer-

¡zed identification of wheat acreage in selected test sites. Dr A . M a c k , from Canada's Department of Agriculture, w h o has considerable experience in the application of remote sensing to crop and soil classification, explains that the project (to be continued through a number of growing seasons) is based on the selection of about ten test locations, each measuring 3.2 by 16 kilometres (2 by 10 miles). Ground observers check on the type and condition of the crop, field by field, every eighteen days coincident with E R T S orbits. O n c e during the height of the growing season the sites are overflown with airborne sensors. Thus a threew a y system of data acquisition is being maintained. Both E R T S and airborne varieties of imagery are enlarged to a scale of 1 : 50,000. Identification of crop type is accomplished through the measurement of ¡mage density in four spectral bands. Four bands are needed because two different crops, at s o m e stage of their maturation, could produce exactly the s a m e density in one or t w o bands; it is unlikely that they will have the s a m e density in all four bands. •

States, under the terms of the E R T S agreement. Both countries thus benefit from the other's observations, interpretations and conclusions. It will be apparent from the foregoing that, while space technology has added an exciting n e w dimension to remote sensing, it does not, and cannot, replace older, more established methods of monitoring the environment. N o remote-sensing project can d o without what specialists call ground-truthing, the laborious and painstaking collection of data from test sites on the ground, so that extrapolations can be m a d e on the larger views produced by airborne or orbital sensors. Again, orbital platforms generally require the larger-scale and usually more precise imagery produced from airborne platforms, also for purposes of correlation and extrapolation. This applies not only to E R T S but also to the recent Skylab project, in which various types of observations, including photographic coverage of selected ground sites, are m a d e from a manned satellite. Several Canadian agencies are participating in Skylab subprojects concerned with the use of satellite photography for mapping purposes. This is being co-ordinated with airborne coverage of the same areas.

Reliability of crop 'signatures' •

Since density and two-dimensional spatial patterns—individual fields of crops—are easily susceptible to computer analysis and printout, the next step is the development of c o m puter programmes embodying the interpretation techniques developed in such correlation studies. Dr M a c k has pointed out that, because of various factors, E R T S imagery is not well suited to producing a nation-wide assessment of wheat acreage. Topography, soil type, climate, groundwater régime, and other regional peculiarities m a y affect spectral signatures of crops. Country-wide evaluations are therefore best left to the questionnaire approach of Statistics Canada, the federal office for the collection and distribution of statistical information. Statistics Canada has done less well with regional data, however, and it is here that remote sensing m a y be able to fill a gap. A n exchange of information on the methodology and results of the Spring W h e a t Project takes place between Canada and the United

International collaboration

T o recapitulate, then, a complete remote-sensing programme integrates at least three levels of observations—satellite, airborne and ground —along with the necessary staff and facilities for the processing and interpretation of imagery. O n e of the most significant features of remote sensing, and one to which I have already alluded, is that it tends to foster collaboration and the exchange of information a m o n g nations concerned about their resource base. Beyond that, remote sensing also c o m pels nations to take a broader, international view of. m a n y environmental problems. F e w other m e a n s of observation s h o w with such clarity that pollution of air and water, and the m o v e m e n t of sea ice, d o not stop at national boundaries. This applies, too, to other factors affecting the global environment. Remote sensing thus has the capacity of acting as a cohesive and integrative force in a world too often afflicted by national jealousies and selfinterest.

Remote sensing via satellite: the Canadian experience 2 1 9

•

Hans George Classen

Born in the U.S.S.R. of German ancestry, the author translates scientific texts from Russian and German into English, and is an information specialist in the Department of Energy, Mines and Resources, 588 Booth Street, Ottawa K1A 0E4 (Canada).

T O DELVE M O R E DEEPLY CANADIAN D E P A R T M E N T OF ENERGY, MINES A N D R E S O U R C E S . Resource satellites and remote airborne sensing in Canada (proceedings of the First Canadian Symposium on Remote Sensing). Ottawa, February 1972. 2 vols. . Resource satellites and remote airborne sensing in Canada (proceedings of the Second Canadian Symposium on Remote Sensing). Guelph, Ont., April-May 1974. (In press.) KAMINSKI, H . Neuartige hichauflösende Satellitenbilder zur Erderkundung. Umschau in Wissenschaft und Technik, vol. 74, no. 6, 15 March 1974. T H E C E N T E R F O R R E M O T E SENSING I N F O R M A T I O N A N D ANALYSIS, E N V I R O N M E N T A L R E S E A R C H INSTITUTE O F M I C H I G A N (WILLOW R U N L A B O R A T O R I E S ) . Symposium on Remote Sensing of Environment, 15-19 April 1974. (Proceedings in press.)

220

Hans George Classen

Man and the biosphere Howard Brabyn 1

A concrete scheme, at the international level, to enable both man and his environment to adapt themselves one to the other is described here.

If Alexander Pope were alive today, he would probably agree that 'the proper study of m a n kind is m a n and the biosphere in which he lives', though he would doubtless have found a more elegant w a y of putting the second half of this dictum. There are n o w seven times as m a n y people in the world as there were in Pope's time and this ever-increasing population is exerting growing pressure on the environment. The vital problem is to prevent this pressure from causing irreversible d a m a g e to the environment and destroying irreplaceable resources o n which mankind depends. In other words, the. time has c o m e for m a n either to m a k e rational use of the natural resources of the biosphere or to perish. This, in a nutshell, is the purpose of Unesco's M a n and the Biosphere ( M A B ) programme, the general objective of which is: ... to develop within the natural and social sciences a basis for the rational use and conservation of the resources of the biosphere and for the improvement of the relationship between m a n and the environment; to predict the consequences of today's actions on tomorrow's world and thereby to increase man's ability to manage efficiently the natural resources of the biosphere.

M a n and the Biosphere: the n a m e itself evokes the complex w e b of interacting elements contained in the thin layer of soil, water and air surrounding our planet to which life is confined. The total extent of these interactions and interrelationships has only recently begun to be understood and w a s largely ignored by the traditional, specialized approach to scientific research.

Impact of Science on Society. Vol. XXIV, N o . 3 , 1974

In the M A B programme the emphasis is on an integrated, global, interdisciplinary a p proach. Indeed, so boldly, almost arrogantly, far-reaching are the scheme's objectives that one is tempted to ask whether Unesco thinks that it is capable of looking at the entire world and then putting it to rights. Such a question would be misconceived for t w o important reasons. First, M A B is an international programme in which, at present, more than' sixty countries are involved. Unesco's role is to stimulate and co-ordinate research and provide organizational support to teams of experts from the natural and social sciences from all over the world. Secondly, it is a mistake to think that M A B believes that it can examine the whole world, still less put it to rights. The M A B programme consists of a number of closely defined projects which nevertheless are of global or regional impact. They are concerned with the e x a m ination of ecological units, or ecosystems, within which the objectives are as follows: T o identify and assess the changes in the biosphere resulting from m a n ' s activities and the effects of these changes on m a n . To study and compare the structure, functioning and dynamics of natural, modified and managed ecosystems. To study and compare the dynamic interrelationships between 'natural' ecosystems and socio-economic processes and especially the

1. Author Brabyn is editor of Unesco's journal Nature and Resources.

221

Metres Parabiospheric zone .10,500 Bacteria, spores exist higher. _9,000 Aeolian zone

Bird life.

Atmosphere

_7,500 Tprrpçtrial animale

f

6,000 Green plants Troposphere Cultivation

f 1 |

., . Alpine zone

_4,500 .3,000

95 per cent of all life ^ / " / S

Desert, forest, grassland

-1,500

,'

Sea level

^—7'

"

"" (Life exists to 60 metres below surface) —1,500 3,000

Dysphotic zone

Hydrosphere

Lithosphère

_

4,500 6,000 7,500 9,000

-10.500

Fig. 1. The biosphere. impact of changes in h u m a n populations, settlement patterns and technology on the future viability of these systems. T o establish scientific criteria to serve as a basis for rational management of natural resources. T o establish standard methods for acquiring and processing environmental data. T o promote the development of simulation and other techniques of prediction as tools for environmental management. T o promote environmental education in its broadest sense and encourage the idea of m a n ' s responsibility for and personal fulfilment in partnership with nature. •

Multifaceted

innovation

The present M A B programme consists of thir-

222

Howard Brabyn

teen projects, but these, by their very nature are inevitably overlapping and interlinked. Projects arbitrarily designated 1 - 7 cover the main ecological systems and physiographical units: tropical forests; temperate and Mediterranean forests; grazing lands (savannah, grassland, etc.) ; arid and semi-arid zones; lakes, marshes, rivers, deltas, estuaries and coastal zones ; mountain and tundra lands and island ecosystems. M a n - m a d e as opposed to natural ecosystems and m a n ' s use or abuse of energy are covered in Project 1 1 , the utilization of energy in urban areas. Projects 8 , 9, 1 0 and 1 2 cover four major fields of h u m a n activity or interaction with the biosphere: conservation of natural areas, effects of pesticides and fertilizers, major engineering works, genetic and d e m o graphic changes. Project 1 3 , the perception of environmental quality, views the global pro-

blem with the aim of providing criteria for the value judgements which the programme necessarily entails. H o w can such a programme retain its international character and not break d o w n into a series of isolated projects? Obviously certain projects or combinations of projects will be of greater interest to s o m e countries than to others. There is, mercifully, still a great diversity in the world, not only in terms of geographical or climatic conditions, but also in standards of value. A s another poet put it : Still the world is wondrous large—seven seas from marge to marge— A n d it holds a vast of various kinds of m a n : A n d the wildest dreams of K e w are the facts of Khatmandhu A n d the sins of Clapham chaste at Martaban.

The resolution of this paradox highlights the t w o greatest innovative virtues of the M A B programme. First, the research carried out under the programme is designed to provide 'core' material of international value. The problems of Northern Australia, for example, m a y seem hardly comparable with those of the Sahel, yet 'core' material from M A B Proj-

ect 3 , on savannah, could be of use to them both. The second innovative feature of the M A B programme is that at every stage scientists are being asked to make broad social judgements about the work they are doing. N o longer can they put on the blinkers of specialization and ignore the biosphere around them. Each project or proposed piece of research work must be examined in the light of its global effect. Ivory towers have given w a y to c o m munal dwellings in which the interactions b e tween disciplines are the rule rather than the exception. The ultimate h u m a n goal implied by the concept of rational use of the biosphere is a high standard of living coupled with retention of the maximal variety of natural and m a n m a d e environments, the protection of animal and plant species, and the safeguarding of the world's genetic stock. Before such a goal can be achieved a vast amount of research will have to be undertaken to overcome our present ecological ignorance and provide the basic tools for future planning. With M A B w e are making a beginning.

The adjustment of m a n to his ecosphere

223

The problem of technical progress and mineral resources Konstantin I. Lukashev

Of all the natural materials used In man's productive activity, mineral resources are the most

important; they become

advance.

The problem of their consumption

even more

but in the pattern of consumption—one

vital as science and

technology

lies not only in the rise of total use

in which rare metals and other elements

figure increasingly. Here are examined the estimate of known

and potential reserves

of the major raw materials; future sources thereof; the geological and technological problems associated with these; the manufacture of artificial minerals; and international co-operation in this sphere.

Present world extraction and consumption of m a n y kinds of mineral resources, such as coal, petroleum, salts and building stone, runs into thousands of millions of tonnes. In the last seventy years, the consumption of s o m e metals and chemical elements, e.g. aluminium, m a g n e sium, copper, chromium, manganese, tungsten, molybdenum, nickel and vanadium (see Fig. 1 ), has increased by t w o or three figure factors [1, 2 ] . 1 Other minerals (such as uranium, titanium, beryllium, zirconium, germanium, niobium, tantalum, boron and lithium) are n o w also used in industry, while the rareearth elements are essential for several industrial processes [3, 4 ] . It is of the utmost importance that industry's increasing quantitative and qualitative demands should be satisfied, if present-day scientific and technical progress is to be maintained. According to our estimates, mankind will need more mineral resources in the next halfcentury than in the whole of its previous history. This applies to all types of minerals but particularly to fuels and to rare metals and elements. In m a n y of the modern alloys and materials used in industry and science, m a n y different constituents are added to the basic metals.

Impact of Science on Society. Vol. XXIV, N o . 3, 1 9 7 4

including large quantities of rare elements. M a n y of these have to be of a particularly high degree of purity. But this is not the only distinctive feature of the modern problem of mineral resources. M a n y kinds of minerals, occurring in large deposits containing a wealth of different c o m ponents, are being rapidly exhausted. In s o m e cases, these have already been exhausted; this is especially true of iron ores, manganese, chromium, nickel, copper, lead, zinc, gold, silver and platinum. Fewer and fewer deposits of metallic and non-metallic minerals are being discovered near the surface and at depths of t w o or three kilometres. Prospectors are concentrating more and more on deeper levels of the earth's crust. This calls for n e w drilling techniques, n e w methods of studying such deposits and calculating their extent, and n e w ways of interpreting data on ores. M o r e prospection for deposits of rare minerals is being carried out, requiring more detailed k n o w ledge of the laws governing their formation and distribution in rocks and ores, and n e w 1. Figures in brackets correspond to the references at the end of this article.

225

Coal (million tonnes)

1800

Oil (million tonnes) 1,800,

Natural gas (thousand million cubic metres) 1,000

Iron ore (million tonnes) 56IX,

w.

4S0. 400. 320. 240. 160.

80-

^#VVV° Manganese ores (million tonnes) 10,

^s*vvv

Chromite (million tonnes) 10-,

Nickel (thousand tonnes) 450-,

9. 8. 7. 6. 5. 4. 3. 2.

•

•fi

1 •

.##vvv

Vanadium (thousand tonnes) 25-,

15.

J

1.

.cP - O -tP _cP -\0 Tungsten (thousand tonnes) 25-.

H

•$> tP «P «P -\0

* * #° ^ 4? Molybdenum (thousand tonnes) 75-,

# ^ ^ ^> ^ Copper

Zinc (thousand tonnes) 5.0 4.5. 4.0. 35.

P

3.0.

25. 20.

1510.

as.

^VWV° Lead (thousand tonnes)

50,

A W # Bauxite (million tonnes) 50,

.tfjSPjfl&lSP

#vvvv° Phosphates (million tonnes) 60L I ' 36.

1 (majority < 5) 2 to 3 0 2 0 to 5 0 5 0 to 200 2 0 0 to 2,000

Scattering processes produce m a n y of the atmospheric effects w e see and normally take for granted. For example, Rayleigh scattering which increases at the shorter wavelengths causes the sky to appear blue and, because the longer wavelengths are scattered less, the sun to appear red at sunrise and sunset. A good example of non-selective scattering is clouds which appear white because the water vapour particles have diameters that are large w h e n compared to the wavelength of visible light. Other influences such as turbulence, refraction and atmospheric emission tend to be less important, but in s o m e instances corrections m a y be necessary. A n important point to remember is that if real use is to be m a d e of remote-sensing methods,. the physical interactions between the incident electromagnetic energy and the environment must be understood and (where necessary) corrections m a d e for any interfering influences. This is the case for most applications of interest to Europe; mathematical models of environmental situations need to be established before monitoring by remote-sensing methods can become effective. The need for a mathematical and physical understanding is fundamental to the acceptance of these methods to perform the complex tasks w e envisage today. Simpler tasks, such as cartographic mapping, which rely on an understanding of the spatial rather than spectral distributions are less critical; in m a n y cases they are already at an operational level.

•

Borrowing f r o m the military

Remote sensing has evolved primarily from military reconnaissance systems, as I have said. Typical examples are the infra-red scanners used for night observations and camouflage detection, and side-looking airborne radar ( S L A R ) for high resolution, all-weather, day and night imaging. In addition to these military developments, sensing methods have been borrowed and adapted from radio astronomy, planetary and lunar reconnaissance, classical aerial photography, and geophysical surveying. The military airborne reconnaissance methods mentioned above are n o w being extended to outer space; the spy satellite is with us whether w e like it or not. Our immediate tasks are to use these methods in an optimal w a y for civil applications in environmental monitoring, and in the management and inventory of the earth's resources. If w e look at the types of sensors that are currently being used operationally or are under investigation as a part of an experimental programme, they can be conveniently classed as either passive or active sensors. Passive sensors obtain their input from either reflected solar energy or thermally emitted radiation. A n example of a passive sensor used to obtain high resolution image data at m a n y different spectral bands between the ultra-violet and thermal infra-red wavelengths (typically 0.3 to 1 4 microns) is s h o w n schematically in Figure 5. O n the other hand, active sensors such as laser and radar systems generate their o w n sources of incident energy. Rather than provide a lengthy description of these different sensor types, I have listed in Table 2 those sensors that are the most important or the most promising, together with brief details ' on their operating wavelengths and typical . applications in earth resources surveys [6,7,8]. The platforms on which sensors are mounted are often a subject of controversy, particularly with regard to the choice of airborne or satellite systems. In m y opinion, such conflict is usually meaningless; the optimal platform depends very m u c h on the application intended. Local surveys, like those of estuarine systems, are best performed using aircraft platforms; but if the survey is required at a continental or even on a global scale (as is the case in s o m e environmental or océanographie applications and where repetitive measurements are necessary) satellite methods are clearly to b e preferred. . -. .. .

Remote sensing of earth resources: a European point of view

251

Table 2 . Characteristics of main remote-sensing distribution

Sensor

Cameras (metric and multispectral)

Passive/ active

Spectral Examples of Remarks bands typical applications1

Passive

Visible Cartography (0) and Basic land-use solar-IR maps (0)

IBasic sensors used in aerial photography. M a n y space photographs available from manned satellites, particularly Apollo 9 and Skylab

Line scanning Passive instruments (single and multi-channel)i

U V to Agriculture (inclu- ! thermal ding land use. IR crop and forest surveys) (E) Hydrological surveys (E) Surface temperature (0)

Radiometers

Thermal IR

Geothermal surveys Non-imaging sensor providing accurate (0) measure of surface temperature Thermal pollution (0) Surface temperature (0)

Microwave

All weather non-imaging sensor (imaSoil moisture ging is possible using scanning surveys (E) antenna)3 Sea ice (E) Near shore salinity (E)

Passive

thermal-IR band. U p to 2 4 channels for airborne systems. Satellite multispectral high resolution (50-80 m e tres) sensors flown on ERTS-1 and Skylab*

Scatterometer

Active

Microwave

Surface roughness Research instrument aimed at increasing (land and sea) (E) our understanding of material properties at millimetre and centimetre wavelengths. Flown on Skylab; results should be available shortly

Side-looking radar

Active

Microwave

General reconnais- High resolution all-weather system, currently limited to aircraft operation. sance (e.g. R A D A M or Radar- Normally single frequency, but multifrequency, multi-polarization systems Amazon needed for future* programme) (0) All weather surveys (0)

Laser

Active

Visible to IR

Precision altimetry Future applications will require laser (0) scatterometer and imaging systems

1 . 0 = Operational ; E = Experimenta!. 2 . See A . H igham, et al.. Multispectral Scanning Systems and their Potential Application to Earth Resource Surveys, Paris,

ESRO, 1972. 3. See E. Ohlsson, Summary Report on a Study of Passive Microwave audiometry and its Potential Applications to Earth Resources Surveys. Paris, E S R O , 1972. 4 . See K. Grant, ef »/., Side Looking Radar Systems and their Potential Applications to Earth Resource Surveys. Paris,

ESRO. 1973.

252

John Plevin

Tape recorder

Prism

Predetermined pattern of uniform coverage by scanning or raster line

Ground resolution patch

Fig. 5. Schematic diagram of an airborne multispectral scanner. (Note : a dichroic grating refracts light of one colour, reflects that of others.) Source: International W o r k s h o p . . . , op. cit.

The range of platforms that are being planned extends from balloons to m a n n e d spacecraft. Although there ¡s a certain amount of overlap between types of platforms, there is n o compelling argument supporting the view that one platform can be completely substituted by others. T h e final choice will depend on m a n y factors, including the size and character of the area to be surveyed, requirements for repetition, ground resolution, the sensors to be carried, operational or experimental aspects and costs. The main platforms n o w being used are listed in Table 3 which summarizes their chief advantages and limitations. A n important point to emphasize is that m a n y programmes, particularly the experimental programmes, often require simultaneous use of several platform types in what is called multi-level sampling. For a thorough understanding of the physical

processes involved in a measurement method, extensive ground, airborne and, if necessary, satellite data are required (as s h o w n on page 2 1 4 of this issue) before the final, simpler operational methods can be established. •

Current European activities

The use of remote-sensing methods in Europe is at present primarily an experimental activity conducted almost entirely by universities or government research institutes. Recent surveys of ¡European activities [9, 10] identified approximately 1 7 0 experimental programmes in remote sensing within the ten E S R O M e m b e r States (see box). This total w a s divided almost equally between universities and government research and development institutions.

Remote sensing of earth resources: a European point of view

253

Table 3 . Different types of platforms

Remote-sensing platform

Typical operating altitude (km)

Area sensed (km '/frame)

Balloons (stratospheric)

20-40

500-1,000

Aircraft M e d i u m and low altitude High altitude

< 10

>10