(gentle music)
- [Narrator] Every day, the sun rises and the sun sets.
Seasons change, snows melt and flowers bloom.
Time marches on.
Some rivers run dry, while others crest their banks.
Some forests grow, while others burn.
Earth is a planet of constant change,
cities expand, coastlines shift, volcanoes erupt.
Tracking these changes, be they subtle or profound,
is critical to our understanding
of the health of our planet.
For nearly half a century,
the Landsat program has been at the forefront
of monitoring Earth's ever-changing surface,
providing an unparalleled record of our planet's land use,
vegetation cover, and natural resources.
From tracking deforestation in the Amazon
to monitoring water quality in the Chesapeake Bay,
Landsat data has become the foundation
for understanding Earth's ecosystems,
paving the way for many other remote sensing missions.
In recent years, a new player has emerged
in the world of Earth observation:
Europe's Sentinel-2A and 2B satellites.
Part of the European Space Agency's Copernicus program,
the Sentinel-2 satellites,
launched in 2015 and 2017 respectively,
circle the Earth and continuously collect data
from the planet's surface, much like Landsats 8 and 9.
The beauty of these two satellite systems is that,
while they are complementary,
they each have unique strengths.
While the Landsat program provides
the longest continuous record of Earth's land surfaces,
Sentinel-2 offers more frequent revisits
and additional spectral bands,
taking a complete picture of the planet every five days.
But what if we could bring these strengths together?
That's exactly what NASA's Harmonized Landsat
and Sentinel-2 project, or HLS, aims to do.
Imagine trying to put together a puzzle,
but the pieces come from two different puzzle sets,
the HLS project is like finding a way
to make those pieces fit together seamlessly
to create one unified picture.
HLS is a deliverable of the Satellite Needs Working Group,
an interagency effort of the US Government dedicated
to identifying and addressing Earth observation needs
across US civilian federal agencies.
With global production of HLS data being led
by NASA's Interagency Implementation
and Advanced Concepts Team, or IMPACT,
the HLS project takes the raw satellite data
from each mission and puts them through
a series of algorithms to make them compatible.
The algorithms remove atmospheric effects
such as haze and cloud cover,
adjust the imagery from each satellite to perfectly align,
account for varying sun angles
at different times of the day and year,
and fine-tune the spectral bands to calibrate
the colors between the satellites.
The end result is a harmonized Landsat
and Sentinel-2 data product ready for analysis
that provides a snapshot of the Earth's surface
every two to three days on average,
a powerful tool with the potential
to help farmers optimize their crop yields,
city planners more efficiently map urban growth,
and forestry managers more effectively monitor
the health of our forests, among many other uses.
Following the initial release of HLS in 2018,
it didn't take long for researchers to take advantage
of the high level of spatial
and temporal detail provided by the product.
A paper published in 2020 by a team led by researchers
from Boston University aimed to test the effectiveness
of using HLS data to track annual vegetation growth cycles,
also known as seasonal phenology, across North America.
Every year, plants across the continent sprout leaves
and flower in the spring, peak in the summer,
and come autumn, change color and fall
as the winter approaches.
Small variations in the timing
of this annual change, however, can have ripple effects,
impacting how plants absorb carbon dioxide
or how nutrients cycle throughout the ecosystem.
Some insects and birds, for example,
time their life cycles and migration patterns
based on when plants emerge in the spring.
In the past, satellite imagery has been a key tool
for tracking seasonal phenology,
but the coarse temporal resolution of the data has limited
the detail and accuracy of the analysis.
But researchers believed the detail afforded
by harmonized Landsat and Sentinel-2 data
could be the answer to these challenges.
They developed a sophisticated multisource
land surface phenology algorithm
and fed it HLS data from 2016 to 2018.
The results were impressive,
applying the algorithm across North America,
the researchers were able to track vegetation phenology
at a level of detail through time
and consistency never before possible.
They could map out the greening and browning
of vegetation in incredible detail,
observing differences not just on a continental scale,
but even within single fields and forests.
And they were even able to observe
how elevation in Tennessee's Smoky Mountains affected
the timing of leaves emergence in the spring.
Researchers believe that, going forward,
their algorithm could have a wide range
of potential applications, from precision farming,
helping farmers increase crop yields,
to monitoring our ecosystems,
allowing conservationists to make informed decisions
about the timing of controlled burns.
Every year, thousands gather in the spring
to witness the cherry blossoms bloom
in Washington DC's Tidal Basin
or, in the fall, to take in the vibrant Vermont foliage,
seasonal changes everyone can look forward to.
But other seasons, such as the Atlantic Ocean's
hurricane season, fail to generate such enthusiasm.
Every summer, the warm waters
off the coast of Western Africa create
the perfect breeding ground for spawning hurricanes,
storms that travel west across the Atlantic,
with some developing the potential to wreak havoc
along the eastern coasts of North and South America.
States like Florida are no stranger
to these devastating hurricanes,
with coastal communities contending
with violently high winds
and damaging storm surges on an annual basis.
Quickly locating and assessing the extent of damage
in the aftermath of a hurricane can be critical
in aiding search and rescue operations on the ground,
especially if you're getting help from high above in orbit.
In September 2022, Florida fell directly
in the path of Hurricane Ian,
a category 5 hurricane with wind speeds topping out
at 160 miles per hour,
causing damages estimated at over $100 billion.
In the aftermath, environmental researchers
at the University of Connecticut sprang into action,
leveraging HLS data to create a near real-time map
of the damage caused by Hurricane Ian.
Building on previous work
the team had done with Landsat data,
the researchers developed an algorithm
that could sift through the massive HLS dataset
and detect even subtle changes in the satellite imagery,
allowing them to map out the areas
that were likely damaged by the storm.
As soon as the research team had access to the first,
clear satellite images following the storm,
they were able to put their system to work.
The open-source disturbance map was released
to the public just days after the storm,
highlighting areas where damage
was likely to be most severe,
allowing rescue teams to prioritize their efforts.
By harnessing the power of harmonized Landsat
and Sentinel-2 data,
these researchers were able to provide yet another example
of how advanced remote sensing techniques
and open-source data sharing can have a real,
tangible impact in emergency situations.
Whether it's giving us insight to the seasonal changes
of our planet or helping us respond to natural disasters,
the Harmonized Landsat and Sentinel-2 project
is a potential game-changer
in the world of Earth observation.
By combining the strengths of two
of the most advanced satellite systems,
HLS data is providing us with an unprecedented view
of our ever-changing planet.
But the future of HLS isn't just about more data,
it's also about making that data
more accessible and actionable.
HLS data scientists are working on developing new tools
and platforms that will allow users to easily visualize,
analyze, and share harmonized Landsat and Sentinel-2 data.
With projects like HLS lighting the way,
the future of international cooperation
for Earth observation is bright.
New missions with enhanced spatial
and temporal resolution throughout
the electromagnetic spectrum will offer fusion capabilities
to provide unprecedented information about our Earth system.
As the project continues to grow and evolve,
it will undoubtedly play a crucial role
in our efforts to better understand
and protect this incredible planet we call home.