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♪♪Music♪♪ 

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Nathan Kurtz: For me, I've only done airborne field work, which is very
different than being on a ship.

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And we're just very isolated, like the ship is really your whole world and all those people
on the ship are your whole world.

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And then just outside the ship is just a very hostile landscape. It's cold. There's polar bears.

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There's water that can open up underneath your feet.

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*Ship horn*

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And so, it was a very interesting experience to

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to be on the ship which was very safe and warm, and felt good. 

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But then we'd go out and do our fieldwork, and we'd set things up.

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And we'd be out on the ice, we could feel like this is a very wild environment.

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As we were transiting through the ice, we were searching for a suitable 
icefloe.

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Something that would be thick enough that could support us

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working on safely, and also survive through the year.

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While searching for that floe, we had different satellite tools that we're using. 

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That would identify the shape of the floes. We could see how big the floes were.

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But what we didn't know was how thick they were.

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We went to some of these floes and we found, no. These were really thin.

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We can't actually use this floe.

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We looked at some ICESat-2 tracks in hopes that some of the floes that we had identified 

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we could see how thick they were.

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It didn't work out this time, but for a future expedition

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I think we've identified ways that we could utilize ICESat-2, or something like ICESat-2.

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♪ Upbeat Music ♪

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Text: GLOBE Observer Presents

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♪ Upbeat Music ♪

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Text: Why Observe?: Tree Height

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Narrator: While there wasn't enough ICESat-2 data for MOSAiC, or the Multidisciplinary
drifting Observatory for the Study of the Arctic Climate to use.

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Dr. Nathan Kurtz and the team were able to locate an area with the right amount 
of sea ice thickness

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by using different methods.

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Likewise, scientists often use various methods to measure other aspectst of our planet. 

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Like forests.

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So, why take measurements of the same thing, using different methods?

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And how does measuring sea ice thickness relate to tree height?

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Let's take closer look at the Ice, Cloud, and land Elevation Satellite, or ICESat-2.

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Its main purpose is to measure ice thickness using its sole instrument, ATLAS.

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But, it also measures tree heights as it orbits Earth.

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This is doen with photon-counting lasers and algorithms developed to differentiate
what environments they are measuring.

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An algorithm is a step by step procedure for solving a problem

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usually a mathematical one, in a limited number of steps.

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Claudia Carabajal was the Deputy Lead for the Flight Science Receiver Algorithms.

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One of the many subsystems of the ATLAS instrument.

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Claudia Carabajal: The algorithms that process the data on the ground for ICESat-2 
are tailored 

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directly to address that characteristics of the surface.

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So they're tailored to sea ice and vegetation.

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The coherence of those photons when reaching the surfaces changes.

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So the algorithms need to be specifically tailored to the surface type.

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Of course the comparisons against all the data sets help you.

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And sometimes you need the help of an additional data set. As you're processing.

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Nathan Kurtz: When I was on MOSAiC, we took specific measurements 
that are useful, and will be used.

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By combining mutliple measurements together, we're able to 

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quantify and see whether ICESat-2 is making its measurements
accurately and how it's needed to be done.

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Claudia Carabajal: One of the ways that you can actually figure out if ICESat-2 
is actually measuring

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the right thing is to compare it with observations that are being collected by other means.

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For example, airborne campagins, other satellite data, 

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and see what the surface looks like.

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You can look at how things are changing in different seasons.

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Narrator: Whether it's sea ice thickness or tree height, comparing data 
collected by different missions

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and field campagins allows scientists to better understand how the instrument works.

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Dr. Laura Duncanson uses LIDAR data to create 3D maps of forests.

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And Dr. Nancy Glenn is currently looking at various ways in which tree height data collected

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by ICESat-2 and GLOBE Observers can be utilized.

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For both, tree height data adds to our understanding of Earth's systems.

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Laura Duncanson: Of course we can't go out into the woods all over the planet

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and measure every dingle tree on the ground.

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So, for ICESat-2 these estimates of tree height,

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we don't know exactly how precise they are, or how good they are in all of the different
forests around the globe.

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There's a lot of variability in forests.

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Narrator: Just like how taking field observations and airborne data collected 
of sea ice thickness 

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can act as supplementary data to ICESat-2.

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Tree height measurements collected in the field can also be used to do the same.

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This supplementary data can help scientists account for variability between different 

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environments when looking at measurements collected by satellites.

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As mentioned, tree height measurements can be taken in different ways.

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One method is to use trigonometry to estimate the height of a tree.

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This is the method that students and citizen scientists use.

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By measuring the distance to the tree

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along with angles a and b, using a handheld clinometer. Or the one built into a smartphone.

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Observers can calculate the height.

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Laura Duncanson: Having people go into the woods and actually measure tree height

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to compare to the satellite estimates of tree height, gives us a sense of how reliable those 
tree height estimates are

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and maybe some ecosystems that they're particularly good at doing tree height, or 
particularly challenged doing tree height.

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Narrator: Now we know that by taking measurements of the same thing using different methods
can help scientists.

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Taking tree height measurements adds a whole new data set for satellites 
and instruments such as ICESat-2 and GEDI to compare with.

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These measurements also provide content that only an observer on the 
ground can provide.

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Like recent changes including drought, fire, invasive species and more.

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Now that leaves the question.

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Why do scientists study trees?

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Laura Duncanson: So, for decades now we've had really good maps of where
there are forests and where there aren't forests.

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But we've never before known how tall those trees in those forests are.

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And this is a really critical piece of information because it tells us not only of course 
how tall the forests are

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but how much above ground woody carbon they store.

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Forests represent one of the biggest carbon stocks on the Earth's surface.

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And if we cut down and burn forests, we essentially are pushing more carbon 
into the atmosphere.

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And if we allow those forests to regrow, we are sucking that carbon out of the atmosphere.

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But we don't know right now how much carbon is where in Earth's forests 

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because we've never had that third dimensional measurement of Earth's forests

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which is so tightly linked to its carbon content.

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Narrator: Using tree height not only helps scientists track how much carbon is getting
released into the air

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but can also be used in other ways.

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Nancy Glenn: Tree height is really important for us. As it is we're interested in knowing 
how tree height is affected

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by increased CO2 or increased temperatures, or decreased temperatures.

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And that gives us an indicator for making future predictions about trees in the future.

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We're interested in is that trees and the differences in tree heights

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provides some level of what we call structural diversity.

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And structural diversity can be really really important for the health of an ecosystem.

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As well as provide habitat for a variety of different types of animals.

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So we're using NASA resources, NASA airborne data as well as satellite-based data like ICESat.

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Narrator: Many Earth observing satellites such as Landsat can only see a top down view
of Earth.

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*camera shutter**camera shutter**camera shutter*

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Narrator: This information comes in the form of two-dimensional images

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made up of pixels between the size of 30 meters squared to 500 meters squared. 

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But now with GEDI on board the International Space Station and the launch 
of the ICESat-2 satellie in 2018,

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scientists are able to see height added to this top down view of Earth.

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By taking and submitting tree height observations, citizen scientists and students can help

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scientists and researchers. 

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Not just by providing measurements from different ecosystems, 
but by providing a different type of data.

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What seems like such a small piece to contribute, can help scientists across the world.

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Laura Duncanson: The GLOBE Observer tree observation essentially let people all over
the world

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measure tree heights and give us that information where we can't 
go into every single forest ourselves as a small group of scientists.

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Nancy Glenn: From a scientist's perspective, but also as somebody who participates
in citizen science.

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It's a great intersection.

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The more data the better.

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But also, the connection, right? Is this connection between scientists and the community. And

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scientists understanding what's important to our communities.

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And being able to engage and learn from one another.

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Claudia Carabajal: There is a large part of collaboration

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between the instrument scientists and everybody working on every aspect
of the ATLAS instrument.

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And the mission scientist and his deputy and everyone else, and all the universities.

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Citizen science is really important to get the community involved.

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It motivates everybody to be more informed about the science.

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And also perhaps motivate a crowd new scientists.

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Nancy Glenn: All of this is important because one, it's the pursuit of 

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answering questions about our natural environment.

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Our natural environment is changing very rapidly.

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Nathan Kurtz: A tree height measurement that's taken by citizen scientists
could be useful for us.

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Nancy Glenn: It's really important for us to monitor what is here now.

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So we can document that, but also use that in models to predict what might be 
here in the future.

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Narrator: To learn more about GLOBE Observer

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check out the website at 

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observer dot globe dot gov

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And download the app to start taking your own observations today.

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Explore Earth

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NASA

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♪Music♪