This
Planet Earth: The Vision and Majesty of NASA's Remote
Sensing Legacy
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Sight
yields insight. New observations afford new ideas, and new
ideas allow for new levels of understanding. With its strong
commitment to developing powerful remote sensing technologies,
NASA has led the way in opening stunning vistas for exploration
about our home.
Take
the Landsat program, now late into its third decade. The ability
to see the Earth’s surface in terms that can be visually classified—"thematically
mapped," to use the jargon-- have profoundly changed
millions of people’s lives and helped shape the future of
scientific research about our home planet. Landsat 7 is the
latest in a string of highly successful spacecraft. Based
on the program’s impressive and consistent successes, researchers
have developed daring new ideas for continuing its work into
the twenty-first century.
The powerful Earth observing flagship called Terra is beginning
to pay remarkable dividends to researchers around the world.
With five advanced instruments designed to study the Earth
as a collection of interrelated systems, the future of remote
sensing is already into its dawn.
Last
year an experimental satellite called EO-1 also arrived on
orbit. It’s designed to test next generation Landsat-type
technologies, as well as try out several entirely new notions
in spacecraft design. As you’ll see in the following collection
of images, the efforts of those involved in these programs
can show us the Earth as most of us have never seen it before.
GREAT
ZOOMS FROM SPACE: AMERICAN CITIES
No
doubt about it: these are new. Using data from different spacecraft
and some powerful computer technology, visualizers at the
Goddard Space Flight Center present you with the following
collection of American cities in a way you’ve never seen them
before. Starting with our camera high above the Earth, we
rush in towards the surface at what would be an impossible
speed for any known vehicle. Passing though layers of atmosphere,
the colors of our destinations shimmer with their own unique
characteristics, and suddenly we find ourselves floating in
virtual space just above the ground.
Enjoy
the ride!
Featured
Cities Include:
Image 2
Washington,
DC To
zoom into DC, click here.
To
zoom out of DC, click here.
To
pan the DC area, click here.
Image 3
Atlanta,
GA
To
zoom into Atlanta, click here.
To
zoom out of Atlanta, click here.
Image 4
Los
Angeles, CA
To zoom into LA, click here.
To
zoom out of LA, click here.
Image 5
San
Francisco, CA
To
zoom into SF, click here.
To
zoom out of SF, click here.
To
pan SF, click here.
Image 6
Orlando,
FL
To
zoom into Orlando, click here.
To
zoom out of Orlando, click here.
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ZOOMS
FROM SPACE: HOW DID THEY DO THAT?
Image 7 Animation
There’s
no Earth observing telescope parked in orbit. There are no
geosynchronous elevators on which a camera can be mounted.
The images that went into each of the remarkable city zooms
come from data collected by a group of Earth imaging satellites.
And while not all of the zoom sequences use precisely the
same series of data sets, most do. Plus, those that include
data from alternative sources employ techniques similar to
the general case described here.
Farthest
away we see the Earth as a globe. This comes from data stitched
together using information from MODIS, an instrument on Terra.
This first picture has a resolution of 8000 meters. As our
virtual camera begins its long fall to ground, we pass through
a different kind of MODIS information; data in the second
layer resolves details as small as 250 meters across. Our
measure of detail has just improved dramatically.
Next
we find our apparent speed increasing as the surface of the
Earth envelops our sense of horizon. The data supporting this
perspective comes from the land imaging workhorse of NASA’s
fleet: Landsat 7. These images resolve features 15 meters
across.
Finally,
as we rush in to the limits of Landsat 7’s data capabilities,
we move to our final slice of visual information. Taken by
a remarkable commercial satellite called Ikonos, features
as small as one meter across come into view. Individual cars,
trees, and baseball diamonds appear like ghostly apparitions
on the ground. In virtual space we’ve traveled far more than
a thousand miles…but in real terms, nothing besides electrons,
photons, and an elite group of computer and spacecraft personnel
have moved to make these images possible.
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Landsat's
Legacy
THE DESERT BLOOMING: URBAN GROWTH IN LAS VEGAS
Image
8 Image
9
When
a city grows, far more than buildings and roads change. Atmospheric
conditions, vegetation, available fresh water, and many other
features of the natural world change in response to increased
urbanization. A careful record of that change is imperative
for accurate scientific assessment of a city’s evolutionary
path.
Las
Vegas is one of the fastest growing cities in the United States.
Even more remarkable is the fact that this desert city is
essentially located in a part of the world that doesn’t at
first seem to be ideally situated for more than a million
permanent residents. Limited water supplies, blazing temperatures,
and rocky, challenging land suggest the needs for clever solutions
to daily life for this vibrant town known for its more human
inspired sights and sounds.
Over
a period of 27 years, a series of Landsat satellites has taken
pictures of Las Vegas from space. Seen in sequence, the series
vividly displays powerful forces of urban growth there. Spreading
out from the center of town, we see how construction and its
effects has changed the nature of the surrounding area, replacing
natural features in many parts, and simply altering characteristics
in others.
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DISAPPEARING
WATER: THE ARAL SEA OVER TIME
 Image
10 Animation
A
time series is a powerful illustrative tool. Where in the
case of Las Vegas we see the direct effects of people on the
land, in the case of the Aral Sea, separating the countries
of Kazakhstan and Uzbekistan, we see indirect, but no less
dramatic effects on a different part of the world.
The
Aral Sea is actually not a sea at all. It is an immense lake,
a body of fresh water, although that particular description
of its contents might now be more a figure of speech than
practical fact.
In
the last thirty years, more than sixty percent of the lake
has disappeared. As you’ll see in the visualization, the change
over time is dramatic.
In
the 1970s, farmers and state offices opened significant diversions
from the rivers supplying water to the lake, sending millions
of gallons to irrigate cotton fields and rice paddies. So
voluminous were these irrigation sluices that concentrations
of salts and minerals began to rise in the shrinking body
of water. That change in chemistry has led to staggering alterations
in the lake’s ecology, causing precipitous drops in the Aral’s
fish population.
A
secondary effect of this reduction in the Aral Sea’s overall
size is the rapid exposure of the lake bed. Powerful winds
that blow across this part of Asia routinely pick up and deposit
tens of thousands of tons of now exposed soil every year.
This has not only contributed to significant reduction in
breathable air quality for nearby residents, but also appreciably
affected crop yields due to those heavily salt laden particles
falling on arable land.
In
the following sequence of images, we see a series of Landsat
scenes taken several years apart. As the years pass, we see
the profound reduction in overall area covered by the Aral,
and a commensurate increase in land area as the floor of the
sea now lies exposed.
For
the movie, click here.
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LAKE
CHAD DISAPPEARING
 Image
11 Animation
Planetary
change is neither simple nor easily explained by an individual
cause. Where the Aral Sea’s demise is largely the product
of years of direct mismanagement and human hubris, reasons
for change in another vast body of fresh water are less easily
identified. But as we’ll see in this sequence, the ability
to monitor that change over time offers researchers insights
that might otherwise not have been possible from ground based
observations.
When
it thrived, Lake Chad was one of those ironic points of planetary
formation in that it seemed to defy the vast ocean of sand
directly to its north. Located on the edge of the Sahara and
bordering four countries—Chad, Cameroon, Nigeria, and Niger--
the immense area of this land locked lake has nearly disappeared
in recent years. Persistent drought has caused the lake to
drop from its former sixth place position in the list of world’s
largest lakes; it is now one tenth its former size.
The
basin of the lake is not naturally deep, so the surface area
of the lake tended to spread out, keeping the total depth
to little more 23 feet (7 meters). In recent years, rainfall
patterns have begun to change, and tributaries to Lake Chad
have not been refilling the basin as rapidly as they used
to. The lush, productive flora and fauna fed by the wetlands
of the shallow lake have suffered as a result. This has led
to significant changes for various communities of people that
live in the vicinity of the Lake. While for some the now exposed
lake bed has enabled new land to be cultivated, much of the
available fresh water that might have been used for irrigation
is no longer dependable. As rainfall rates appear to be declining
year after year, people living nearby develop even greater
dependence on the lake, draining it even faster.
The
Landsat images showing the dramatic decrease in Lake Chad’s
size can not only help quantify the changes there, but can
help researchers evaluate the root causes for such large transformation
events on Earth, from climate change to human use of natural
resources.
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MOZAMBIQUE
FLOODING
Animation
Image
12 Image
13
Following
weeks of heavy rains in late Winter 2000, massive flooding
inundated wide tracts of eastern and southern Africa, displacing
more than 200,000 people. Torrential rains fell over wide
areas. Vastly overflowing rivers sent much of that water rushing
towards Mozambique, which has been one of the hardest hit
countries.
The catastrophe provoked international efforts to aid victims
from the rushing waters, but extreme devastation nonetheless
befell dozens of towns and villages. In addition to heavy
rains, Cyclone Leon-Eline pounded the region on February 23rd,
blanketing a wide area already saturated with sheets of rain.
This
side by side Landsat sequence shows the comparative size of
rivers in Mozambique before and during the floods. Notice
how the high waters have all but covered the lowlands, far
exceeding the boundaries of the normal river system.
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MOZAMBIQUE
FLOODING COMPARED TO SIZE OF WASHINGTON DC
 Image
14 Animation
This
sequence shows the scale of the tragic floods that washed
through Mozambique in 2000. As the visualization begins, we
see the relative size of Washington, DC, shown in red, superimposed
over the flood area. In this case, remote Earth imagery becomes
useful as a tool for communication, allowing accurate and
clear description of the scale of a particular natural event.
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MT.
ST. HELENS OVER TIME
Animation
Image
15 (upper left) Image 16 (upper
right)
Image 17 (bottom left)
The
explosion of Mt. St. Helens volcano in Washington State on
May 18, 1980 sets the scene for one of Landsat's most important
capabilities. As a means for archiving surface features, researchers
can study how the Earth changes over time. In this sequence,
pictures of the mountain taken in 1973, 1983, and 2000 show
how the eruption changed the surrounding area. Notice how
the north face of the mountain dramatically changed following
the blast. The crater's mouth elongated, and significant ash
deposits altered the down slope terrain.
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THE
BIG BREAK—ANTARCTIC GLACIER CRACKS
Image 18 Animation
When
NASA glaciologist Bob Bindschadler saw the picture, he knew
he had found something important.
Taken
by the Landsat 7 spacecraft, the image in question showed
a thin, 25 kilometer (15 mile) crack in what’s called the
Pine Island Glacier in Antarctica. What surprised him and
the scientists he immediately contacted was the fact that
images taken just ten months before showed no sign of such
a fissure. A major break was forming in the Antarctic ice,
and he and his colleagues had caught it in the act.
Further
study would show that the tear in Antarctica’s icy cloak had
happened in a period of little more than five weeks. Although
the speed of the crack seems to have slowed as it picks its
way across the ice, Bindschadler says he believes there will
be a huge new iceberg falling into the south seas within the
next year and a half or so, assuming the crack continues to
grow.
The
Landsat 7 spacecraft actually passes over the southernmost
continent 16 times a day as it orbits the Earth. During the
southern summer months, the instrument takes an average of
300 images per week. This regular acquisition of surface information
is what enabled researchers like Bindschadler to keep track
of relatively sudden changes to the surface of the Earth.
In
fact, by employing a clever strategy of image acquisition
and processing, researchers hope to reveal important details
about Antarctica following this year’s data collection. Previously
the spacecraft took images of the surface as it flew towards
the pole. But this year marked a change. For the first time,
images were taken as the spacecraft moved past the pole—heading
away, in other words. What this does in practical terms is
offer a different angle on already catalogued features. The
change in viewing angle helped expose detail that could not
be seen from the other direction.
But
there’s more. By combining the two angles, experts will not
only be able to see things in the ice they’ve never seen before,
but will also be able to infer detail about the land and ice
hidden below the surface. This is because surface features
on wide stretches of ice tend to reflect the contour, shape,
and texture of more durable material underneath. By getting
a refined picture of the ice on top, new pictures of the hidden
ground underneath suddenly become possible like never before.
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Shenzhen,
China 1988-1996: Explosive Urban Growth Changes the
Shape of a Continent
True
Color Sequence
Image 19 Animation
The
People’s Republic of China is one of the fastest growing economies
in the world. Additionally, much of the Chinese political
and cultural landscape is in a state of transition, and economic
development is remarkably strong, particularly in southern
industrial cities. As seen by Landsat, Shenzhen, China practically
transforms from a regional urban center to a metropolitan
powerhouse in the space of roughly ten years. Notice along
the southern peninsula as the actual outline of the land changes,
with huge structures emerging in the waters off-shore.
Landsat
5 collected the data. You can see how roads, bridges, and
massive construction projects transform the landscape. New
structures appear off the southern coast, and highways grow
less distinct against the background as significant building
spreads along the sides of the roads. Also notice how the
massive growth alters lakes and mountains in the area, adding
sediment and changing borders.
Image 20
Changes
in Vegetation—False Color Sequence
As
construction goes up, something has to go down. In these images,
the same scenes are presented in a way that highlights vegetation
concentration. Red indicates density of plant life, and as
becomes immediately apparent, vegetation all but disappears
across the region over the last ten years. By using data like
this, researchers can better understand the causes of environmental
changes they find in cities like Shenzhen, and better monitor
a region’s overall health.
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LOSING
FORESTS IN BOLIVIA
Animation
Image
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Image 22
This
scene starts in space, high above South America. As we zoom
in closer, we see the national outlines of Bolivia come into
view on the map.
By
focusing on one particular region, we’re able to see effects
of deforestation in the equatorial forest. The sequence that
follows shows two images of the Santa Cruz region of Bolivia.
The first was taken in 1984. Landsat 7 took the second in
2000. In just a few short years, we see how intense agricultural
development has transformed the forest.
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COLORADO
MOSAIC
Image 23
Using
the data collected by the versatile Enhanced Thematic Mapper
Plus instrument onboard the Landsat 7 satellite, we can take
a tour of Colorado in a way that was impossible just a few
years ago.
This
virtual fly-over of Colorado is the product of dozens of Landsat
scenes digitally stitched together into a single, unified
mosaic. We see the state as an unbroken whole, but only after
it’s been cut into manageable sections, beamed to Earth, stored,
retrieved from the Landsat database, assembled, and digitally
reprocessed.
For
the fly-over movie, click here. Note: this
is 55 MB in size.
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TREES
FALLING: MAPPING DEFORESTATION IN RONDONIA, BRAZIL
Image 24 Animation
Throughout
much of the 1980s, deforestation in Brazil eliminated more than
15,000 square kilometers (5800 square miles) per year. That
pace has only increased through the 90s and into the 21st
century.
Brazil
is also home to more than a quarter of Earth’s tropical forests.
Considering that the band of lush green that circles the globe
through many equatorial nations is fundamental to the overall
health of the whole planet’s environment, careful monitoring
of forest health in the tropics is essential. Tropical forests
act as major carbon "sinks", places where ambient
carbon dioxide in the atmosphere can be absorbed by growing
things and sequestered for years. Definitive evidence shows
that excess carbon dioxide can contribute to the greenhouse
effect and speed global warming. Similarly, tropical forests
also act as a primary producer of oxygen. In the respiration
process that absorbs gaseous carbon dioxide, trees and other
plants give off oxygen. It is for these and a host of other
reasons why scientists and policy makers need to monitor and
forestall wholesale deforestation.
This
sequence shows how profligate clear cutting can influence
that trust. Data gathered over time by several in the Landsat
series of spacecraft shows enormous tracts of forest disappearing
in Rondonia, Brazil. This territory underwent an enormous
rise in population towards the end of the twentieth century,
buoyed by cheap land offered by the national government for
agricultural use. As you see the visualization progress, it’s
useful to note how the human phenomenon of deforestation generally
works, especially in the dense tropical forests of Brazil.
Systematic cutting of a road opens new territory to potential
deforestation by penetrating into new areas. Clearing of vegetation
along the sides of those roads tends to fan out to create
a pattern akin to a fish skeleton. As new paths appear in
the woods, new areas become vulnerable. The spaces between
the "skeletal bones" fall to defoliation, and another
inch of the Earth’s biological rudder is no longer reliably
steering the planet into the future.
To
continue to the second page of images and animations, click
here.
To
skip to the third page of images and animations, click here.
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