Peer-Reviewed Articles
831 The Landsat Program: Its Origins, Evolution, and Impacts
Donald T. Lauer, Stanley A. Morain, and Vincent V. Salomonson
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Landsat 1 began an era of space-based resource data collection
that changed the way science, industry, governments,
and the general public view the Earth. For the last 25 years,
the Landsat program - despite being hampered by institutional
problems and budget uncertainties - has successfully
provided a continuous supply of synoptic, repetitive, multispectral
data of the Earth 's land areas. These data have profoundly
affected programs for mapping resources, monitoring
environmental changes, and assessing global habitability,
The societal applications this program generated are so compelling
that international systems have prolifemted to cany
on the tasks initiated with Landsat data.
839 Three Decades of Landsat Instruments
Aram M. Mika
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This paper traces the development history of the multispectral
sensors for the Landsat series of satellites, from the first
Multispectral Scanner aboard Landsat 1 to the latest variant
of the Enhanced Thematic Mapper for Landsat 7. For each
sensor, we begin with an overview of the design objectives
and program context in which the instrument specifications
were established. This is followed by a design description
that outlines the operation of each sensor and highlights key
technology features. The discussion for each of these instruments
is concluded by a performance summary and operational
history.
853 Radiometric Calibration of Landsat
K. Thome, B. Markham, J. Barker, P. Slater, and S. Bigger
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The radiometric calibration of the sensors on the Landsat series
of satellites is o contributing factor to the success of the
Landsat data set. The calibration of these sensors has relied
on the preflight laboratory work as well as on inflight techniques
using on-board calibrators and vicarious techniques.
Descriptions of these methods and systems ore presented.
Results of the on-board calibrators and reflectance-based,
ground reference calibrations of Landsat 5 Thematic Mapper
are presented that indicate the absolute radiometric calibration
of bands I to 4 should have an uncertainty of less than
5.0 percent. Bands 5 and 7' have slightly higher uncertainties,
but should be less than 10 percent. The results also show
that the on-board calibrators are of higher precision than the
vicarious calibration but that the vicarious calibration results
should have higher accuracy.
859 The Evolution of Landsat Data Analysis
David Landgrebe
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In this paper a description is presented of how the multispectral
data analysis technology, which has come to be synonymous
with Landsat, was begun and how it developed and
spread through the broader research and user community.
The paper is concluded with brief remarks about key factors
which moderated the development and what the future may
hold for its further development. To describe a 25-year-long
octiwV1atys varied and complex as the evolution of the Landsat
related data analysis is a daunting task. Many significant
events must be omitted and others only briefly mentioned.
Example activities have been chosen which occurred early
and led to perhaps the largest impact in the development of
the technology.
869 The Availability of Landsat Data: Past, Present, and Future
William C. Draeger, Thomas M. Holm, Donald T. Lauer, and R.J. Thompson
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It has long been recognized that the success of the Landsat
program would depend on an effective distribution of its
data to a wide variety of users, worldwide, in a timely manner.
Since 1972, nearly $250 million worth of data haw been
distributed by a network of ground stations around the
world. The policies of the U.S. Government affecting the distribution,
availability, and pricing of Landsat data have been
controversial, and have been strongly affected by the attempts
to commercialize the program. At the present time,
data are being distributed in the U.S. by either government
or commercial entities, depending on the date of acquisition
of the data in question and whether or not the customer is
affiliated with the Federal Government. Although the future
distribution of Landsat data is currently under discussion, it
seems likely that data distribution initially will be the responsibility
of NOAA. In any case, the long-term archive and
distribution of all Landsat data will be the responsibility of
the Department of In Interior's U.S. Geological Survey.
877 The Landsat Legacy: Remote Sensing Policy and the Development of Commercial
Remote Sensing
Ray A. Williamson
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This paper summarizes the policy history of Landsat and examines
its place in the development of land remote sensing
for science, practical applications related to land use, end
the marketplace. In particular, it identifies key steps in treating
the foundations for a commercial market in remotely
sensed land date and information products. This paper further
analyzes the interplay between government policy and
technology development for remote sensing. It concludes that
one of the primary forces behind the developing market for
Earth observation data is the creation of information technologies.
including powerful personal computers, geographic information
system (GIS) software, CD-ROM, and the Internet.
These end other technologies are creating the infrastructure
necessary to incorporate remotely sensed data into the
broader information marketplace.
887 Landsat and Earth Systems Science: Development of Terrestrial Monitoring
Samuel N. Goward and Darrel L. Williams
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One of the major catalysts leading to the development of the
global-scale Earth Systems Science concept, the International
Geosphere-Biosphere Program, and the U.S. Global Change
Research Program were the unique views of Earth provided
by Landsat sensors over the past 25 years. This paper addresses
Landsat's contributions in the Earth Systems Science
arena.
Early successes in observing the Earth 's cloud patterns from space led to the use of this new spaceborne perspective to observe surface terrestrial features. Deployment of Landsat demonstrated that significant information about the Earth 's land areas could be acquired from such an observatory, Numerous studies indicated that assessments of agricultural production, forest resources, human population surveys. and environmental conditions could be derived from Landsat data. Thus. on unanticipated outcome of the Landsat program was the evolution of unique new insights concerning terrestrial biospheric patterns and dynamics. The electronic, high precision spectral radiometry, combined with Landsat's repetitive coverage, revealed that a critical new environmental measurement, the spectral vegetation index, could be acquired with these sensors. These measurements are also of critical importance in understanding the hydrology, land surface climatology, and biodiversity characteristics of the Earth.
Recognition of the value of this vegetation index in regional and global-scale studies of the Earth's environment served as a strong stimulus to the development of the Earth Systems Science research agenda, one of the major foci of NASA's mission to Planet Earth, Earth Observing System. Since the innovation of the Landsat Thematic Mapper instrument in the early 1980s, significant progress has been achieved in assessing human impacts within the Earth systems. Significant further inputs to Earth Systems Science from Landsat are expected when Landsat 7 is launched in 1998. Refinements in radiometric response and calibration, inclusion of a 15-m panchromatic band, improvement of the spatial resolution of the thermal band to 60 m, and an aggressive acquisition strategy will all contribute to Landsat's new role as a major component of NASA's Mission to Planet Earth, Earth Observing System. Development of technologies for more refined, as well as lower cost, sensors and platforms is now underway to continue the Landsat science mission. These technology advances are expected to further enhance the capability to monitor the Earth's land areas.
901 Technologies for Future Landsat Missions
Stephen G. Ungar
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Advanced technologies am available that may potentially
lower the cost and improve the quality of future Landsat systems.
The NASA New Millennium Program (NMP) Earth Orbiter
Mission (EO-1), serving as a technology pathfinder, is
implementing several sensor and spacecraft technologies to
further define the possibilities for Landsat 8 and beyond. The
technologies involved include high spectral resolution grating
and wedge imaging spectrometers; advanced multispectral
chip assemblies; Pulsed Plasma Thruster (PPT), included as
a reaction wheel replacement for improved spacecraft attitude control; X-band phase array ground transmission antenna and high speed fiber optics data bus (FODB] for
enhanced data transmission; a carbon-carbon radiator panel
for power/heat dissipation; and a light-weight flexible solar
array employing highly efficient photosensitive materials. In
aggregate, these technologies and others nor only offer considerable
enhancements, but also the real possibility of implementing and operating future Landsat systems at
substantially less cost