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(gentle music)

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- [Narrator] Every day, the
sun rises and the sun sets.

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Seasons change, snows
melt and flowers bloom.

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Time marches on.

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Some rivers run dry, while
others crest their banks.

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Some forests grow, while others burn.

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Earth is a planet of constant change,

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cities expand, coastlines
shift, volcanoes erupt.

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Tracking these changes, be
they subtle or profound,

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is critical to our understanding

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of the health of our planet.

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For nearly half a century,

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the Landsat program has
been at the forefront

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of monitoring Earth's
ever-changing surface,

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providing an unparalleled
record of our planet's land use,

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vegetation cover, and natural resources.

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From tracking deforestation in the Amazon

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to monitoring water quality
in the Chesapeake Bay,

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Landsat data has become the foundation

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for understanding Earth's ecosystems,

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paving the way for many other
remote sensing missions.

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In recent years, a new player has emerged

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in the world of Earth observation:

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Europe's Sentinel-2A and 2B satellites.

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Part of the European Space
Agency's Copernicus program,

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the Sentinel-2 satellites,

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launched in 2015 and 2017 respectively,

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circle the Earth and
continuously collect data

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from the planet's surface,
much like Landsats 8 and 9.

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The beauty of these two
satellite systems is that,

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while they are complementary,

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they each have unique strengths.

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While the Landsat program provides

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the longest continuous record
of Earth's land surfaces,

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Sentinel-2 offers more frequent revisits

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and additional spectral bands,

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taking a complete picture of
the planet every five days.

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But what if we could bring
these strengths together?

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That's exactly what
NASA's Harmonized Landsat

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and Sentinel-2 project,
or HLS, aims to do.

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Imagine trying to put together a puzzle,

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but the pieces come from
two different puzzle sets,

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the HLS project is like finding a way

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to make those pieces
fit together seamlessly

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to create one unified picture.

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HLS is a deliverable of the
Satellite Needs Working Group,

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an interagency effort of
the US Government dedicated

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to identifying and addressing
Earth observation needs

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across US civilian federal agencies.

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With global production
of HLS data being led

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by NASA's Interagency Implementation

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and Advanced Concepts Team, or IMPACT,

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the HLS project takes
the raw satellite data

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from each mission and puts them through

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a series of algorithms
to make them compatible.

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The algorithms remove atmospheric effects

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such as haze and cloud cover,

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adjust the imagery from each
satellite to perfectly align,

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account for varying sun angles

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at different times of the day and year,

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and fine-tune the spectral
bands to calibrate

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the colors between the satellites.

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The end result is a harmonized Landsat

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and Sentinel-2 data
product ready for analysis

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that provides a snapshot
of the Earth's surface

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every two to three days on average,

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a powerful tool with the potential

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to help farmers optimize
their crop yields,

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city planners more
efficiently map urban growth,

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and forestry managers
more effectively monitor

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the health of our forests,
among many other uses.

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Following the initial
release of HLS in 2018,

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it didn't take long for
researchers to take advantage

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of the high level of spatial

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and temporal detail
provided by the product.

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A paper published in 2020
by a team led by researchers

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from Boston University aimed
to test the effectiveness

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of using HLS data to track
annual vegetation growth cycles,

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also known as seasonal
phenology, across North America.

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Every year, plants across
the continent sprout leaves

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and flower in the spring,
peak in the summer,

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and come autumn, change color and fall

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as the winter approaches.

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Small variations in the timing

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of this annual change, however,
can have ripple effects,

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impacting how plants absorb carbon dioxide

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or how nutrients cycle
throughout the ecosystem.

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Some insects and birds, for example,

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time their life cycles
and migration patterns

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based on when plants emerge in the spring.

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In the past, satellite
imagery has been a key tool

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for tracking seasonal phenology,

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but the coarse temporal
resolution of the data has limited

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the detail and accuracy of the analysis.

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But researchers believed
the detail afforded

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by harmonized Landsat and Sentinel-2 data

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could be the answer to these challenges.

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They developed a sophisticated multisource

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land surface phenology algorithm

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and fed it HLS data from 2016 to 2018.

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The results were impressive,

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applying the algorithm
across North America,

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the researchers were able to
track vegetation phenology

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at a level of detail through time

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and consistency never before possible.

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They could map out the
greening and browning

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of vegetation in incredible detail,

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observing differences not
just on a continental scale,

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but even within single fields and forests.

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And they were even able to observe

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how elevation in Tennessee's
Smoky Mountains affected

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the timing of leaves
emergence in the spring.

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Researchers believe that, going forward,

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their algorithm could have a wide range

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of potential applications,
from precision farming,

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helping farmers increase crop yields,

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to monitoring our ecosystems,

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allowing conservationists
to make informed decisions

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about the timing of controlled burns.

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Every year, thousands gather in the spring

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to witness the cherry blossoms bloom

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in Washington DC's Tidal Basin

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or, in the fall, to take in
the vibrant Vermont foliage,

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seasonal changes everyone
can look forward to.

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But other seasons, such
as the Atlantic Ocean's

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hurricane season, fail to
generate such enthusiasm.

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Every summer, the warm waters

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off the coast of Western Africa create

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the perfect breeding ground
for spawning hurricanes,

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storms that travel west
across the Atlantic,

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with some developing the
potential to wreak havoc

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along the eastern coasts
of North and South America.

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States like Florida are no stranger

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to these devastating hurricanes,

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with coastal communities contending

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with violently high winds

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and damaging storm surges
on an annual basis.

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Quickly locating and
assessing the extent of damage

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in the aftermath of a
hurricane can be critical

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in aiding search and rescue
operations on the ground,

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especially if you're getting
help from high above in orbit.

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In September 2022, Florida fell directly

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in the path of Hurricane Ian,

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a category 5 hurricane with
wind speeds topping out

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at 160 miles per hour,

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causing damages estimated
at over $100 billion.

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In the aftermath,
environmental researchers

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at the University of
Connecticut sprang into action,

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leveraging HLS data to
create a near real-time map

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of the damage caused by Hurricane Ian.

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Building on previous work

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the team had done with Landsat data,

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the researchers developed an algorithm

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that could sift through
the massive HLS dataset

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and detect even subtle changes
in the satellite imagery,

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allowing them to map out the areas

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that were likely damaged by the storm.

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As soon as the research team
had access to the first,

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clear satellite images
following the storm,

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they were able to put
their system to work.

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The open-source disturbance
map was released

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to the public just days after the storm,

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highlighting areas where damage

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was likely to be most severe,

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allowing rescue teams to
prioritize their efforts.

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By harnessing the power
of harmonized Landsat

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and Sentinel-2 data,

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these researchers were able
to provide yet another example

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of how advanced remote sensing techniques

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and open-source data
sharing can have a real,

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tangible impact in emergency situations.

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Whether it's giving us insight
to the seasonal changes

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of our planet or helping us
respond to natural disasters,

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the Harmonized Landsat
and Sentinel-2 project

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is a potential game-changer

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in the world of Earth observation.

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By combining the strengths of two

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of the most advanced satellite systems,

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HLS data is providing us
with an unprecedented view

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of our ever-changing planet.

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But the future of HLS
isn't just about more data,

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it's also about making that data

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more accessible and actionable.

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HLS data scientists are
working on developing new tools

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and platforms that will allow
users to easily visualize,

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analyze, and share harmonized
Landsat and Sentinel-2 data.

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With projects like HLS lighting the way,

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the future of international cooperation

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for Earth observation is bright.

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New missions with enhanced spatial

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and temporal resolution throughout

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the electromagnetic spectrum
will offer fusion capabilities

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to provide unprecedented
information about our Earth system.

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As the project continues
to grow and evolve,

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it will undoubtedly play a crucial role

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in our efforts to better understand

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and protect this incredible
planet we call home.