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A Brief History of Remote Sensing Applications, with Emphasis on L`andsat Staniey A. Moraine By 1997, at least six civilian land remote sensing satellite systems were being operated by the United States, France, India, Japan, Canada, Russia, and the European Space Agency. On command, all of them make measurements of the land surface, transmitting spectral data to a global network of strategically located ground receiving stations. Data from these earth-observing satellites are used to map, monitor, and manage the earth's natural and cultural resources. Perhaps the first person who believed that not only machines but humans, too, could venture into space was Jules Verne, a French provincial lawyer with no scientific or technical training (Mark, 1984~. Verne made the extraordinary prediction that a rocket would be launched from Florida by means of chemical propulsion, and that the crew would include three people (and a dog). First they would only circle the moon and return to earth, as did Apollo 8. This would be followed by a trip to the moon' s surface, the return to earth ending with a "splash down" in the Pacific Ocean and recovery by a warship. Perhaps Verne's most remarkable prediction was that Americans would make this first journey. What he did not predict was that astronauts would be awed by the blue marble, or that their photographs would so sensitize the world that subsequent human scientific interest would shift toward space as a means for studying the earth. The United States was not only the first to land on the moon, but beyond Verne's vision, it also developed the first remote sensing satellites, whose profound importance to today's concept of a global village cannot be overstated. Most histories of remote sensing identify Gaspard Felix Tournachon as the first person to photograph "remotely," using balloons above Paris in 1859. Bal- loons were also used for aerial reconnaissance during the American Civil War. 28

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STANLEY A. MORAIN 29 By 1909, aerial photographs were being taken from airplanes for a wide range of uses, including warfare, land-use inventory, and publicity. Aerial photography remains an important application of remote sensing, with a sophisticated range of cameras being used to collect information on geology, land use, agricultural conditions, forestry, water pollution, natural disasters, urban planning, wildlife management, and environmental impact assessments (Lillesand and Kiefer, 1987~. Evelyn Pruitt of the Office of Naval Research originally coined the term "remote sensing." GROWTH OF THE REMOTE SENSING COMMUNITY The Environmental Research Institute of Michigan (ERIM) is credited with organizing the first technical conference on remote sensing in the United States, perhaps in the world. Its First Symposium on Remote Sensing of Environment, sponsored by the Navy's Office of Naval Research (ONR), had 15 presenters and 71 participants (Environmental Research Institute of Michigan, 1962~. In the audience was Dr. William Fischer of the U.S. Geological Survey (USGS), an early advocate of an earth-observing system. The field was so new that Dana Parker's inaugural address focused on fundamentals of the electromagnetic spec- trum. In October 1962, the second symposium was held, drawing 162 partici- pants to hear 35 technical papers (Environmental Research Institute of Michigan, 1963~. It was sponsored by the Geography Branch of ONR, the Air Force Cambridge Research Laboratory, and the Army Research Office. At the third symposium in October 1964,280 participants heard 54 technical papers (Environmental Research Institute of Michigan, 1965~. By this time, all of the principal government, academic, and private-sector motivators for an orbiting resource satellite system were represented. Among the papers in the proceedings was one by Dr. Robert Alexander from ONR. He gave the first announcement for what evolved into Landsat-l. His abstract read: The National Aeronautics and Space Administration is sponsoring a study of the geographic potential of observations and experiments which might be car- ried out from the remote vantage of earth-orbiting spacecraft. The investigation will involve both the value of the science of geography and the expected practi- cal applications of an earth-viewing-orbiting laboratory and other possible geo- graphic satellite systems. Early emphasis will be on problems of systematizing and managing the flow of geographic information which would result from such a program. (p. 453) The eighth symposium (Environmental Research Institute of Michigan, 1972), held 8 years after Alexander's announcement and only a few weeks after the first Landsat-1 images had been released, included 14 presentations describ- ing the utility and quality of the Landsat data. By that time, the broader field of remote sensing had attracted over 700 participants who selected from a program of 116 papers on topics including theoretical and applied engineering, natural and

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30 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS cultural resource monitoring, state and local government applications, and even environmental and public health issues. The National Aeronautics and Space Administration (NASA) became an official sponsor of ERIM symposia in 1971. In 1973, NASA's administrator inaugurated the agency's decade-long program of University Research Grants to stimulate cooperative research at the local level. In some cases it supported construction of laboratory facilities and supplied the equipment needed to train the 1970s generation of Ph.D. remote sensing specialists. By the mid- to late 1970s, many of these young professionals were employed on collaborative fed- eral government research projects for proof-of-concept applications embracing the whole range of natural and cultural resources. The Large Area Crop Inven- tory Experiment (LACIE) and its spin-off AgriSTARS are examples of these projects. The Application System Verification Tests (ASVTs) are another. While these were not the only application development programs under way, they were symptomatic of a massive spontaneous adaptation to fundamentally new ways of studying the earth. Within little more than a decade of ERIM's first symposium, the core remote sensing community had increased its numbers by several orders of magnitude. This community brought about major changes in organizational structures, became the basis for a new international research agenda, and germinated the first seeds of thought on global habitability. STIMULI FOR AN ORBITING RESOURCES SATELLITE In 1946, the United States Army Air Corps requested that the RAND Corpo- ration consider how objects might be inserted into orbit (Mark, 1988~. The study resulted in a report titled Preliminary Design of an Experimental World-Circling Spaceship (Burrows, 1986~. The proposed midget moon, or "satellite," would provide "an observation aircraft [sic] which cannot be brought down by an enemy who has not mastered similar techniques." After many aborted liftoffs and sys- tem failures, the military successfully launched its first earth-observing satellite in August 1960. It was called Discoverer and was expected to be an unclassified system to support biomedical research and earth observations (Tsipis, 1987; Whelan, 1985~. A few months after launch, however, a presidential directive classified the Discoverer program and plunged it into deep secrecy. Only re- cently have images collected by its successor, the Corona program, been declas- sified for public use (McDonald, 1995~. In parallel with the early military/intelligence programs in space, the scien- tific and industrial communities in the United States were awakening to the potential of space for providing a new world perspective. In 1951,6 years before Sputnik 1, Arthur C. Clarke, a science fiction writer and prophet of technology, proposed that a satellite could be inserted into orbit over the north and south poles while the earth revolved beneath it, allowing humans to view the planet in its entirety (Fink, 1980~. In April 1960, NASA and the Department of Defense

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STANLEY A. MORAIN 31 (DOD) launched the Television and Infrared Observational Satellite (TIROS-1) into such an orbit, inaugurating the first experimental weather satellite (U.S. Department of Commerce and National Aeronautics and Space Administration, 1987~. This system generated the first television-like pictures of the entire globe in a systematic and repetitive manner. The ongoing series of TIROS satellites became operational in 1966 as the TIROS Operational Satellites (TOS), renamed the National Oceanic and Atmospheric Administration (NOAA) Polar Orbiting Environmental Satellites (POES) in 1970 (Morain and Budge, 1996~. Although the early weather satellites could not provide details on land processes or use, they were invaluable in understanding the weather and thus providing warn- ings of weather-related natural disasters, as well as information on rainfall of rel- evance to agriculture and water management (Lillesand and Kiefer, 1987~. The series of NOAA weather satellites carrying the Advanced Very High Resolution Radiometer (AVHRR) from 1978 on was important not only to me- teorological research and prediction, but also to studies of vegetation and land use. Over the last two decades, AVHRR data have been used to construct vegeta- tion indices for monitoring crop failures, urban climate, locust outbreaks, range conditions, deforestation, and desertification (Ehrlich et al., 1994; Gallo et al., 1993; Townshend and Tucker, 1984; Tucker et al., 1991~. The NOAA satellites have been important in the development of famine warning systems, such as those described by Hutchinson in this volume. These satellites are of much coarser resolution than the Landsat series discussed below (one AVHRR image can cover as many as 100 Landsat images), but the lack of detail is somewhat compensated by the broad coverage, lower costs, and more frequent (twice daily) flyovers. Roller and Colwell (1986) argue that the AVHRR images can be used very efficiently to stratify land use and topography for more detailed studies with Landsat and other higher-resolution satellites. At an even coarser scale, the Geostationary Earth-Orbiting Satellite (GOES) provides the continuous hemi- spheric coverage of cloud cover and other aspects of the atmospheric circulation shown on evening weather forecasts as a visual confirmation of approaching weather, particularly extreme events such as hurricanes. Other satellites, launched predominantly for ocean research applications, such as Nimbus, SeaSat, and SeaWifs, have provided information of relevance in coastal zone studies and fisheries management (Consortium for International Earth Science Information Network, 1997~. The photographs taken from manned space expeditions such as Gemini and Apollo were used in several land inventory applications. In 1973, Skylab took more than 35,000 images that have become classics in many resource manage- ment and earth science texts. In recent years the Space Shuttle has taken numer- ous images of sites of human interest, many at the request of researchers con- cerned with deforestation, urbanization, pollution, and water resource management. The United States pioneered land remote sensing from space and has been

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32 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS the unquestioned leader in the development and application of this unique tech- nology. Americans take pride in having developed the Landsat program, as well as other, more recent civilian programs. The evolution of Landsat, however, has been neither linear nor predictable. The remainder of this chapter provides an overview of its conception, genesis, and growth; its accomplishments and current status; and its uncertain future. At this point, Landsat still dominates remote sensing applications in the United States. FORCES MOTIVATING THE DEVELOPMENT OF REMOTE SENSING At first, civilian space remote sensing consisted of experimental missions to develop proofs of concept for any applications that had a sound scientific basis- and some, perhaps, that did not. All of the missions conducted in the 1960s and 1970s, including those that acquired hand-held Gemini, Apollo, Skylab, and Apollo-Soyuz photography and the early Landsats, were approved and funded as experiments to advance space science. The forces that stimulated and motivated today's Landsat program were numerous and complex. Five of the most compel- ling were (1) the need for better information about the earth's features, (2) na- tional security, (3) commercial opportunities, (4) international cooperation, and (5) international law. Need for Better Information Society requires better information about the geographic distribution of the earth's resources, and satellites help in obtaining this information. Earth now supports more than 5 billion people, and human populations are growing at 1.5 percent per year, or 3 people per second. By 2000, the world's population will exceed 6 billion. Nobody knows how many people the earth can sustain; some guess 8 billion, while others say nearly double that number (McRae, 1990; Ashford and Noble, 1996~. Regardless of how many people can be squeezed onto the planet, however, there are limits to the renewable and nonrenewable re- sources needed to support them. Efficient management of renewable resources and judicious use of nonrenewable resources, as well as improved conservation and protection of fragile and endangered environments, depend on timely infor- mation about, and accurate analysis of, those resources. In the late 1960s, there was a convergence of thought that the best means for acquiring the needed data was earth-orbiting satellites that could provide continuous and nearly synoptic coverage of terrestrial resources. This would be the case in particular for under- standing and measuring earth system processes at regional, continental, or global scales. Human numbers and human impacts on resources thus became an early and globally compelling argument for studying the earth from space.

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STANLEY A. MORAIN 33 National Security The U.S. government maintains national security, a mission that includes using data from civilian satellites to protect and defend the nation against aggres- sors. It is no secret that defense/intelligence satellites are assets for maintaining national security. It is not as widely known, however, that the defense/intelli- gence community has always used data from civilian satellite systems in carrying out its security mission (National Space Council, 1989~. While there were, and still are, many security limitations imposed on the first generation of earth- observing systems, there was nevertheless a defensible argument that such a system should be developed. It was recognized that timely information about the global distribution of critical natural resources and the factors that affect global environmental conditions is integral to national security and would be gleaned in part from civilian systems. Indeed, the decision to build and launch Landsat-7 was driven partly by requirements of the defense/intelligence community (Office of the President, 1992~. Commercial Opportunities The U.S. government encourages private-sector investment in the nation's space program, including civilian earth-observing satellites. Remote sensing technology was developed by aerospace industries under contract to federal gov- ernment agencies to satisfy both government and public needs. Commercializa- tion of this know-how is fundamental to American ideals and has been a stimulus for continued industry investment. By the early 1970s, several industries, in- cluding communications satellites and booster launch services, had already proven the commercial value of the space environment. The prospects for similar finan- cial gain from data on the earth's resources seemed self-evident, but a successful experimental system would be a necessary first step. The assumption that data on the earth's resources would have commercial value beyond their benefit for the public good was thus a powerful argument for developing the Landsat program. Full commercialization of both the space and ground segments may yet prove to be intractable, but there is clearly a viable and profitable role for industry in building space platforms, sensor systems, and ground processing facilities, as well as providing value-added data processing services. The commercial value of space- based remote sensing products and services is a hypothesis that will finally be tested with several privately owned satellites scheduled for launch in 1998. International Cooperation The U.S. government seeks international cooperation on civilian earth- observing satellites in order to better understand, manage, share, and protect the earth's resources. The United States is committed to using space for peaceful and

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34 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS defense purposes only. To this end, Americans want to share benefits from space technology with other nations, but they also want to protect their commercial interests. Earth observations from space have never been the sole domain of the United States, and several nations now participate in this activity with competing spacecraft and sensor systems. The argument for promoting cooperation among nations was originally driven by opportunities for America to promote its foreign policy objectives, but have evolved to include elimination of unnecessary redun- dancies among different national programs and the savings that might be realized from joint programs through cost sharing (Office of the President, 1996~. While these objectives were not publicly articulated in the early 1970s, they were a driving political force in the Landsat planning process. International Law Societies are governed by laws, rules, and regulations to maintain organiza- tion and order not only on earth, but also in space. Societies establish laws by which they govern against chaos and anarchy. Space law is relatively new to jurisprudence, but it is a central force because it sets the rules by which all nations, not just the space-faring ones, have a voice in how to participate in space technology. Legal aspects of civilian space-based remote sensing are compli- cated and sometimes controversial, especially regarding the issues of national sovereignty, rights of privacy, and, most recently, commercial gain. The United States has always argued strongly for an open-skies and nondiscriminatory data distribution policy for civilian space data, believing the greatest good for the greatest number will come from free and open exchanges of data and information (Stowe, 1976; Office of the President, 1988~. When the United States implemented the Landsat program, it made an extraordinary effort to ensure that every nation had access to these data, even to the extent that foreign ground receiving stations were installed. THE EVOLUTION OF LANDSAT The Landsat Concept The concept of a dedicated, unmanned land-observing satellite emerged in the mid-1960s from the complex milieu of synergisms and conflicting interests described above. It arose primarily in ONR and USGS under the latter's late director Dr. William T. Pecora (Waldrop,1982~. In fact, scientists within USGS, working in cooperation with Dr. Archibald Park and others in the U.S. Depart- ment of Agriculture (USDA), originally proposed to the (then) Bureau of Budget (now Office of Management and Budget) that an Earth Resources Observation Satellite (EROS) be built, launched, and operated. The Under Secretary of the Interior announced the objectives of EROS in a memorandum dated July 12,

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STANLEY A. MORAIN 35 1967, and addressed to the Department of the Interior's assistant secretaries and bureau heads (Luce, 1967~. These objectives were to (1) construct and fly an earth-observing system by the end of 1969, and follow this with improved and modified systems as required by the operational needs of resources programs; (2) provide unclassified remotely sensed data to facilitate the assessment of land and water resources of the United States and other nations; and (3) design specific systems on the basis of users' data requirements, distribute such data to users, and make operational use of the data in resource studies and planning. The overall goal of the proposed EROS program was to acquire satellite remotely sensed data in the simplest possible way, deliver these data to users in an uncomplicated form, and ensure the data's easy use (Pecora, 1972~. Since development of space technology was the responsibility of NASA, the Department of the Interior's proposal was rejected. NASA Administrator James Webb met with President Johnson to discuss Interior's announcement, and Webb succeeded in retaining control of what was to become an "experimental" program (Covert, 1989~. In cooperation with the Department of the Interior, USDA, and other agencies, NASA designed an earth-observing satellite, obtained funding for the project, and successfully launched the first Earth Resource Technology Satel- lite (EATS-1) in July 1972. Although unsuccessful with its own satellite system, the Department of the Interior continued with an EROS program under the direction of USGS. The EROS mission was to archive and distribute remotely sensed data, and to support remote sensing research and applications development within Interior.2 To carry out the EROS responsibilities, USGS built the EROS Data Center (EDC) in 1972. After the launch of Landsat-l, Goddard Space Flight Center (GSFC) hosted three symposia in quick succession (National Aeronautics and Space Administra- tion, 1973a, b). These symposia were designed especially for their Landsat- sponsored investigators to report "user identified significant results." The appli- cation categories were agriculture/forestry, environment, geology, land use/land cover, water, and marine. Each of the proceedings approached 2000 pages of text and graphics, mainly detailing early application concepts and models. The Landsat program had such a powerful impact in so many arenas that it was declared operational in late 1979 after a prolonged debate among participating government agencies (U.S. Department of Commerce, 1980~. In the decades to follow, however, Landsat-1 replacement satellites were the subject of severe political uncertainty. The program witnessed a change of guard among its staunchest supporters, and the satellites were casually labeled a "tech- nology in search of an application." Kuhn's (1962) prescription for scientific revolutions foreshadowed these developments by predicting a period of scientific uncertainty, if not outright denial, by whole sectors of the science and technology community. In the waning years of the twentieth century, complexity science views such developments as inherent to self-adaptation in complex systems (Waldrop, 1992~. Once a critical mass of support had been attained, the indi

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36 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS vidual actions of sensor developers, data suppliers, data analysts, and end-users ensured the continuity of the technology, even if its development seemed chaotic, and even if the direction of that development was unclear. After a quarter- century of successful data gathering, the fate of the Landsat program remains uncertain, but the technology derived from the program continues to permeate user communities and become more complex as the applications it has spawned mature. Even as the first Landsat was being prepared for launch, conflicts in agency roles had begun to appear. NASA's charter was to engage in space research and technology development. That charter did not include earth resource data han- dling, processing, archiving, or distribution to a large and diverse scientific com- munity, or to an even larger group of public and private users. Consequently, NASA reached agreement with several resource management agencies to transfer responsibility for the program' s ground segment, while NASA retained responsi- bility for the space segment. The Landsat System ERTS-1 was launched from Vandenberg Air Force Base in California. A Nimbus-type platform was modified to carry the sensor package and the data relay equipment. ERTS-2 was launched on January 22, 1975. It was renamed Landsat-2 by NASA, which also renamed ERTS-1 as Landsat-l. Three addi- tional Landsats were launched in 1978, 1982, and 1984 (Landsat-3, -4, and -5, respectively). As documented by USGS (1979) and by USGS and NOAA (1984), each successive satellite system had improved sensor and communications capa- bilities (see Table 2-1~. TABLE 2-1 Background Information and Status of Landsat Satellites Satellite Launched Decommissioned Sensors Landsat-1 July 23, 1972 January 6, 1978 MSS and RBV Landsat-2 January 22, 1975 February 25, 1982 MSS and RBV Landsat-3 March 5, 1978 March 31, 1983 MSS and RBV Landsat-4 July 16, 1982 a TM and MSS Landsat-5 March 1, 1984 b TM and MSS Landsat-6 October 5, 1993 c ETM Landsat-7 May 1998 d ETM+ aIn standby mode bOperational CNever achieved orbit dAnticipated launch

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STANLEY A. MORAIN Landsats-1, -2, and -3 37 The first three Landsats operated in near-polar orbits from altitudes of 920 km. They circled the earth every 103 minutes, completing 14 orbits a day and producing a continuous swath of imagery 185 km wide. To provide nearly complete coverage of the earth's surface, 18 days and 251 overlapping orbits were required. The amount of swath sidelap varied from 14 percent at the equator to nearly 85 percent at latitude 81 north or south. These satellites carried two sensors: a Return Beam Vidicon (RBV) and a MultiSpectral Scanner (MSS). The REV sensor was a television camera designed for cartographic applications, while the MSS was designed for spectral analysis of terrestrial features. The MSS sensor scanned the earth's surface from west to east as the satellite moved in its descending (north-to-south) orbit over the sunlit side of the earth. Six detec- tors for each spectral band provided six scan lines on each active scan. The combination of scanning geometry, satellite orbit, and earth rotation produced the global coverage originally suggested by Arthur C. Clarke for viewing the earth' s entire land surface. The spatial resolution of the MSS was approximately 80 m with spectral coverage in four bands from visible green to near-infrared (JR) wavelengths (see Table 2-2~. Only the MSS sensor on Landsat-3 had a fifth band, in the thermal-IA. ERTS-1 delivered high-quality data for almost 4 years beyond its designed life expectancy of 1 year and was finally shut down on January 6, 1978. Landsats-2 and -3 were decommissioned in February 1982 and March 1983, respectively. TABLE 2-2 Radiometric Range of Bands and Resolution for the MSS Sensor Band Wavelength Resolution Landsats-1,-2,-3 Landsats-4,-5 (micrometers) (meters) 4 1 0.5-0.6 79182a 5 2 0.6-0.7 79/82 6 3 0.7-0.8 79/82 7 4 0.8-1.1 79/82 8b 10.4-12.6 237 aThe nominal altitude was changed from 920 km for Landsats-1 to -3 to 705 km for Landsats-4 and -5, which resulted in a resolution of approximately 79 and 82 m, respectively. bLandsat-3 only. SOURCE: U.S. Geological Survey and National Oceanic and Atmospheric Administration, 1984.

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38 Landsats-4 and -5 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS Landsats-4 and -5 carried both the MSS and a more advanced sensor called the Thematic Mapper (TM).3 Their orbits were somewhat lower than those of their predecessors at 705 km and provided a 16-day, 233-orbit repeat cycle with image sidelap that varied from 7 percent at the equator to nearly 84 percent at latitude 81 north or south. The MSS sensors aboard Landsats-4 and -5 were identical to earlier ones. Both sensors detected reflected radiation in the visible and near -IR bands, but the TM sensor provided seven spectral channels of data as compared with only four channels collected by MSS. The wavelength range for the TM sensor spanned the blue through mid-IR bands (see Table 2-3~. The 16 detectors for the visible and mid-IR bands in the TM sensor provided 16 scan lines on each active scan. The TM sensor had a spatial resolution of 30 m for the visible, near-IA, and mid-IR bands and a spatial resolution of 120 meters for the thermal-IA band. As with all earlier Landsats, sensors on these satellites imaged a 185-km swath. Today, Landsat-4 has lost all capability to communicate TM data and is in standby mode. Landsat-5 has lost its Tracking and Data Relay Satellite System (TDRSS) capability, but continues to provide data via direct downlink to the United States and the international ground stations. TABLE 2-3 Radiometric Range of Bands and Resolution for the TM Sensor Band,Wavelength Resolution Landsats-4,-5(micrometers) (meters) 10.45-0.52 30 20.52-0.60 30 30.63-0.69 30 40.76-0.90 30 51.55- 1.75 30 610.40-12.50 120 72.08-2.35 30 SOURCE: U.S. Geological Survey and National Oceanic and Atmospheric Administration, 1984. Landsat-6 Landsat-6 was launched on October 5,1993, but failed to achieve orbit. It was similar to Landsats-4 and -5 in terms of spacecraft design and planned orbital con- figuration. The MSS and TM sensors were replaced by an improved TM sensor called the Enhanced Thematic Mapper (ETM), from which no data were received. ASSESSING THE IMPACT Beyond the personalities and visions that led to Landsat-l, the program's

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40 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS etated/unvegetated areas, forested/unforested lands, urban/nonurban areas, and agricultural/nonagricultural lands. Each of these categories served as the founda- tion for formulating upward-spiraling interpretations of human economic uses of the land, for assessing environmental health, and for addressing what would later be called earth system science (U.S. National Aeronautics and Space Administra- tion, 1988~. It was, moreover, recognized that, by virtue of its 18-day orbital repeat cycle, Landsat-1 would offer scientists their first unrestricted opportunity to observe synoptic changes in surface covers that would be impossible to obtain using aerial platforms. The temporal dimension of remote sensing had always been appreciated, but seldom employed usefully outside DOD because high-quality time-series data were essentially nonexistent. With Landsat-l, the time dimen- sion not only was a key design parameter, but also was immediately recognized by the scientific community as an essential ingredient in spectral analyses. By holding solar azimuth relatively constant with an equatorial crossing of approxi- mately 9:30 a.m., the orbital design offered an opportunity to calibrate spectral readings radiometrically across latitudes and longitudes and throughout the an- nual greening and yellowing cycles of vegetation. Attention shifted sharply away from building spectral libraries to monitoring temporal changes and patterns. Time was also the enabling parameter for promoting a deeper understanding of physical models in several land analysis applications (Reeves, 1975; Colwell, 1983~. In surface hydrology, for example, measurements from data collection platforms were merged experimentally with Landsat-1 data to monitor spatial and temporal changes in the water levels of Lake Okeechobee in order to opti- mize swamp ecology and balance Miami's urban water needs. Run-off predic- tion models were augmented by monitoring the geographic extent and depth of river basin snow levels, and temporal dynamics of major floods such as those that occurred along the Mississippi River and Cooper's Creek (Australia) in 1973 were examined in the context of disaster assessment. Other time-sensitive applications were also advanced. In agriculture, MSS imagery was used to improve an existing production estimation model for wheat in western Kansas, thus proving the concept that satellite-acquired data could provide accurate and timely crop predictions (Morain and Williams, 1975~. For- est clear-cuts in Oregon and Washington were monitored, and in Washington, remote observations were actually used to assess lessee compliance. Rangeland studies included spectral responses through time for the assessment of biomass production and general range condition. Landsat MSS and TM data have also become important in global and local studies of biodiversity and biogeography, and have become key to the emerging framework of "landscape ecology," whereby remote sensing is used to identify vegetation gaps and patterns in the landscape that influence habitats and ecosys- tem functioning and dynamics. These early modeling efforts evolved into satellite applications that address

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STANLEY A. MORAIN 41 today's social and environmental issues (e.g., food security, deforestation im- pacts, desertification trends, resource sustainability, and news gathering). Yet none of them led directly to these more profound applications. They all required iterations that included many false starts. Early applications, therefore, were important as pioneering efforts and for what they taught the scientific community about future satellite requirements and collateral inputs for problem solving. All of the Landsat- 1 results relied on collateral, ground-based data (today's relational database or geographic information system [GIS] technology) and suffered from gaps in temporal data that would have made them more robust. Further, the spectral data were often too coarse. If satellite earth observations were to deliver on their early promise, more spectral channels with narrower bandwidths would have to be acquired from a larger number of platforms providing more frequent observations. It was believed that if this could be achieved, the data and imagery would have commercial as well as public value. Pri vatiz ation/C ommerci al iz all on As the nation's civilian space research and development agency, NASA successfully executed its role by launching Landsat-l. The handoff of responsi- bility for data dissemination from NASA to USGS/EDC had already been com- pleted by the time Landsat-1 was launched. The plan was for EDC to serve as the supplier of Landsat products, while NASA would continue to develop future sensors and platforms. Differing agency responsibilities and management agen- das, however, plagued the Landsat program from its inception. To resolve these issues, the Carter Administration undertook an extensive review of both the military and civilian space policies. By 1979, new policies had been formulated by which the civilian program was to be made operational, administered by NOAA, and eventually privatized. At about this same time, Congress merged land-, ocean-, and weather-sensing systems under the administration of NOAA. A crisis ensued (National Research Council, 1985~. Among the major play- ers in this crisis were an ever-growing community of Landsat data users, includ- ing the news-gathering media, which wanted inexpensive, publicly accessible data; an increasingly vociferous industrial sector that was concerned about pend- ing international competition and believed privatization would preserve America's niche in commercial earth observations; and a federal establishment disinclined to privatize all land, ocean, and weather satellite data systems. In its effort to reduce the size of government, the first Reagan Administration moved quickly to privatize the Landsat program. What resulted was the Land Remote-Sensing Commercialization Act of 1984 (P.L. 98-965~. NOAA solic- ited bids to manage the existing Landsats and civilian meteorological satellites and, aided by large government subsidies, to build and operate future systems. Bids were received from aerospace companies, an insurance company in New York, a small geoscience firm in Michigan, and a farmer in North Dakota (U.S.

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42 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS Department of Commerce, 1984~. In 1985, a contract was signed with EOSAT Corporation (now Space Imaging/EOSAT Corporation), and the transfer was complete (U.S. Department of Commerce, 1985~. A history of the national debate leading up to and following privatization is provided by Morain and Thome (1990~. It is interesting that the most compelling arguments made to Congress for Landsat privatization focused on data and pro- gram continuity not spectral analyses and fine-resolution time-sequential data. Although data continuity has never been defined, and program continuity re- mains a political question, Congress continues to legislate most aspects of America's space remote sensing activities. Following another series of program reviews, the National Space Council released its National Space Policy Directive #5, which established new goals and implementation guidelines for the Landsat program (Office of the President, 1992~. The directive called for a joint DOD/NASA effort to build, launch, and operate Landsat-7. In October 1992, the Land Remote Sensing Policy Act (P.L. 102-55) was signed into law. It reversed the 1984 decision to commercialize the Landsat system and recognized the scientific, national security, economic, and social utility of land remote sensing from space (Scheffner, 1994~. It mandated that DOD and NASA (1) establish a management plan, (2) develop and imple- ment an advisory process, (3) procure Landsat-7, (4) negotiate with EOSAT for a new data policy regarding existing systems, (5) assume program responsibility from the Department of Commerce, (6) conduct a technology demonstration program, and (7) assess options for a successor system. Scarcely a year had passed before the Landsat program was evaluated for a third time, principally because of severe budget constraints surrounding the High Resolution Multispectral Stereo Imager instrument proposed by DOD for Landsat-7. The National Science and Technology Council (NSTC) recommended that Landsat-7 be developed only with an improved TM instrument and that a new management structure be established so DOD could withdraw from the program. The result was Presidential Decision Directive/NSTC-3, dated May 5, 1994, which reconfirmed the administration's support for the program, but gave NASA, NOAA, and USGS joint management responsibility (Office of the Presi- dent, 1994~. These three agencies negotiated with EOSAT for new Landsat-4 and -5 product prices for the U.S. government and its affiliated users, and are proceeding to develop Landsat-7. Meanwhile a tired but operable Landsat-5 (into its fourteenth year) remains aloft, transmitting consistent and reliable im- ages of the earth to the U.S. ground station and its foreign counterparts. It has been argued that government policies designed to transfer the Landsat program from the public to the private sector were seriously flawed. These policies did not result in market growth, were more costly to the federal govern- ment than would have been the case if the system had been federally operated, did not significantly reduce operating costs, and significantly inhibited applications of the data (Lauer, 1990~. Costs of imagery increased from about $200 for an

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STANLEY A. MORAIN 43 MSS scene in 1972 to more than $4,500 for a TM scene in 1997, a rate much greater than inflation and prohibitive to many users. Nevertheless, the program continued to provide a flow of high-quality, well-calibrated, synoptic imagery of the earth. Whether or not Landsat privatization was premature given existing and an- ticipated markets, it can be argued that a global groundswell of government and academic users, particularly within developing nations in Africa, Latin America, and Asia, stimulated a proliferation of international Landsat look-alike satellites. After 1986, these systems augmented Landsat data around the world, further verifying proof-of-concept applications and elevating overall space-based capa- bilities to a new plane. The proposed series of NASA's Earth Observing System (EOS) satellites is designed to provide information on a wider range of variables and at a more detailed resolution than that provided by Landsat, and a number of other nations have launched satellites to provide information of relevance to land-use and other applications. For example, the French Systeme pour ['Observation de la Terre (SPOT) satellite has a higher resolution (10 m) than that of the latest Landsat satellites and has been used in a variety of applications, including observation of the Chernobyl accident and agricultural monitoring (Sadowski and Covington, 1987~. The primary constraint on widespread use of SPOT data is the cost, especially for studies over large areas. India has launched two satellites with sensor systems similar to the Landsat TM, which are being used for natural resources management. Japan and Europe have launched Earth Resources Satel- lites, which use synthetic aperture radar to provide information on the physical and electrical conditions of terrain. These radar satellites are beginning to pro- vide information of relevance to studies of fire, deforestation, crop monitoring, and urbanization (Consortium for International Earth Science Information Net- work, 1997; Office of Technology Assessment, 1993~. The Legacy Landsat-7 Landsat-7 is scheduled for launch in mid-1998. Its payload will be an En- hanced Thematic Mapper (Plus) instrument designated the ETM+. The ETM+ has the same basic design as the TM sensors on Landsats-4 and -5, but includes some conservative advances (Obenschain et al., 1996~. It will provide 60-m (as opposed to 120-m) spatial resolution for the thermal band and a full-aperture calibration panel that will result in improved absolute radiometric calibration (5 percent or better). The geodetic accuracy of systematically corrected ETM+ data should be comparable to that characterizing Landsat-4 and -5 TM data, with a specific uncertainty of 250 m (1 sigma) or better. Other features have been added to the Landsat-7 program to facilitate use of the data, particularly by private

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44 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS industry. For example, Landsat-7 will directly downlink ETM+ data to domestic and international ground receiving stations at 150 megabits per second using three steerable X-band antennae. Although transmissions to international ground stations will continue, the system is being designed so that the United States can capture and refresh a global archive to be located at EDC. To make it possible for ETM+ to capture data over regions beyond the range of EDC's receiving antenna, Landsat-7 will use a 378 gigabits per second solid-state recorder capable of storing approximately 40 minutes or 100 scenes of ETM+ data. A second North American receiving station is being added near Fairbanks, Alaska, so that 250 scenes of data per day can be collected. Thus, the recorder will downlink re- corded data when the satellite is within range of either EDC or the Alaskan station, and EDC will receive and archive 250 ETM+ scenes per day. These features will provide the capability for global coverage of continental surfaces on a seasonal basis. On the other hand, Landsat-7 does not include some useful technologies, such as the ability to "point," and its 15 x 15-m spatial resolution may be rapidly overtaken by the 1 x 1-m resolution of the Space Imaging EOSAT system in 1998. Beyond Landsat-7 The 1992 Land Remote Sensing Policy Act called for developing cost- effective advanced-technology alternatives for maintaining data continuity be- yond Landsat-7 (Scheffner, 1994~. To address this requirement, NASA plans to launch EO-1 as part of its New Millennium Program (Ungar,1997~. This mission will be devoted to testing new technologies for use beyond Landsat-7. Some concepts for an advanced sensor are described by Salomonson et al. (1995) and Williams et al. (1996~. In essence, advanced Landsat concepts use solid-state, push-broom, multispectral linear arrays, and hyperspectral area arrays that em- ploy grating and wedge filter technologies. Exactly how an advanced Landsat observing capability will be implemented is still under study. One option is to fly the advanced-technology Landsat sensor on one of the NASA EOS satellites, such as the AM-2 mission. This option would reduce launch costs. Other possibilities include flying the sensor on a separate, smaller and less expensive advanced-technology spacecraft. A third possibility is for the advanced-technology capabilities and Landsat continuity requirements to be incorporated in a capability provided by a commercial entity. In any case, it is clear that the earth science and applications community needs the Landsat TM quality and type of data to be provided and continuity to be ensured so that the integrity of the databases inaugurated by Landsat-1 can be preserved. It appears clear that advanced technology can be used to meet these requirements and possibly provide highly desirable enhancements. Table 2-4 is a chronology of Landsat and similar international satellite sys

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STANLEY A. MORAIN TABLE 2-4 Chronology of Landsat and Landsat-like Launches, 1972-2007 45 Year Platform (Nationality) Sensor 1972 Landsat-1 (United States) MSS; RBV 1975 Landsat-2 (United States) MSS; RBV 1978 Landsat-3 (United States) MSS; RBV 1982 Landsat-4 (United States) MSS; TM 1984 Landsat-5 (United States) MSS; TM 1986 SPOT-1 (France) HRV 1988 RESURS-01 (Russia) MSU-SK 1988 IRS- 1A (India) LISS- 1 1990 SPOT-2 (France) HRV 1991 IRS-1B (India) LISS-2 1992 JERS-1 (Japan) OPS 1993 Landsat-6 (United States) ETM 1993 SPOT-3 (France) HRV 1993 IRS-PI (India) LISS-2; MEOSS 1994 IRS-P2 (India) LISS-2; MOS 1994 RESURS-02 (Russia) MSU-E 1995 IRS-1C (India) LISS-3 1996 ADEOS (Japan) AVNIR 1996 PRIRODA (Germany/Russia) MOMS 1997 IRS-ID (India) LISS-3 1998 CBERS (China/Brazil) LCCD 1998 SPOT-4 (France) HRVIR 1998 Landsat-7 (United States) ETM+ 1998 EOS AM-1 (United States/Japan) ASTER 1998 IRS-P5 (India) LISS-4 1999 Resource 21 (United States) Resource 21 2000 IRS-2A (India) LISS-4 2002 ALOS (Japan) AVNIR-2 2002 SPOT-5A (France) HRG 2004 IRS-2B (India) LISS-4 2004 SPOT-5B (France) HRG 2004 ALOS-A1 (Japan) AVNIR-3 2007 ALOS-A2 (Japan) AVNIR-4 NOTE: The acronyms in this table are the terms by which the platforms and sensors listed are commonly known; for the full names, see Morain and Budge (1996). SOURCE: From Morain and Budge (1996) and Stoney et al. (1996). tems. It lists only so-called earth resources satellites having sensors operating in the visible and near infrared spectrum, and channels roughly equivalent to those of the Landsat MSS or TM sensors. In the past 25 years there have been nearly 20 launches and 4 distinct international systems (a fifth will become operational with the launch of the China/Brazil Earth Resources Satellite). Data from these satellites are used daily by international donor agencies, government agencies at all levels, oil and mineral exploration companies, environmental consultants,

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46 A BRIEF HISTORY OF REMOTE SENSING APPLICATIONS value-added commercial firms, academia, and the general public. The first-order land-cover categories predictable in 1972 have expanded to include rather so- phisticated higher-order applications. Continuity has been achieved in more than one sense (Morain and Budge, 1995~. Use of time as a discriminant has envel- oped the user community in ways that were not foreseen, and will be integral to future applications in ways that are not yet perceived. Spectral analytical proce- dures have evolved around the time dimension and will also be stimulated by future hyperspectral data collectors. It can truly be said that even if the Landsat program heads toward extinction, its progeny will continue to support the tech- nology it has created. CONCLUSIONS The earliest visionaries, such as Jules Verne, Arthur C. Clarke, Robert Alexander, William Fisher, Archibald Park, and William Pecora, predicted great things to come as humans took their first steps into space. Of all the ventures to date, the U.S. Landsat program ranks among the most successful. Interestingly, most of the problems that have plagued this national program have not been technical, but administrative and political. Despite the difficulties related to national security issues, agency roles, delays in data delivery, funding uncertain- ties, and a shaky attempt to privatize a federal program, the accomplishments of the Landsat program have been extraordinary. For the 25 years from 1972 to 1997, synoptic, high-quality data have been routinely acquired, processed into an ever-improving array of digital and photographic products, and used to better measure and monitor earth resources. The Landsat series has provided new insights into geologic, agricultural, and land-use surveys, and opened new paths in the exploration of new resources. Understanding of the earth, its terrestrial ecosystems, and its land processes has been advanced remarkably through the Landsat program. Of equal importance, this program has stimulated new ap- proaches to data analysis and academic research, and provided opportunities for the private sector to develop spacecraft, sensors, and data analysis systems and provide value-added services. It has also fostered strong international participa- tion and a whole new generation of Landsat-like systems around the world. The political, scientific, and commercial currents over the next 25 years of earth- observing systems will be no easier to chart than were those of the first 25, but the systems that result are certain to advance human understanding and use of the planet's resources. NOTES 1 A related, longer version of this paper appeared in Photogrammetric Engineering and Remote Sensing (Lauer et al., 1997). 2 The "S" in EROS was subsequently changed to stand for "System" rather than "Satellite." 3 Routine collection of MSS data was terminated in late 1992.

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