Education News & Blogs – NASA Jet Propulsion Laboratory

Find out how the upcoming NISAR mission, an Earth satellite designed to capture detailed views of our planet's changing surface, will provide new insights into everything from natural disasters to climate change. Plus, connect it all to STEM learning.

The next addition to NASA’s fleet of Earth Science orbiters is launching in 2024 and will represent a monumental leap forward in how we monitor our changing planet. The NISAR mission is a collaboration between NASA and the Indian Space Research Organisation that’s designed to monitor and study tiny movements of Earth’s surface from events like natural disasters and climate change.

Read on to find out how NISAR is pushing the boundaries of Earth science from space. Plus, learn how you can bring science and engineering from the mission to your students.

How NISAR Works

NISAR is among the most advanced radar systems on an Earth science mission to date due to its supersized antenna reflector, use of synthetic aperture radar, and ability to observe Earth in two different radar frequencies simultaneously.

Hear mission experts describe how the NISAR satellite will track our changing Earth in fine detail. Credit: NASA/JPL-Caltech

Extending above the spacecraft like a giant catcher's mitt, NISAR’s antenna reflector is 39 feet (12 meters) wide – the largest ever launched as part of a NASA Earth-observing mission. This antenna creates an observational window, or swath, of the surface beneath the spacecraft that is 150 miles (242 kilometers) wide. The swath size is determined by the radar wavelength and antenna size, which is important because there is a direct relationship between antenna size and the resolution of images and data that can be captured by NISAR.

The NISAR spacecraft flies over Earth's glowing blue horizon. A long boom extending above the spacecraft holds up a cylindrical structure with the antenna reflector stretched across its center.

NISAR's antenna reflector extends above the spacecraft like a catcher's mitt and is engineered to help the mission get an unprecedented view of Earth's surface. Credit: NASA/JPL-Caltech | + Expand image

We typically want the best resolution possible, but we’re limited by the size of the antenna we can build and deploy in space. Conventionally, the resolution on a satellite is a function of the wavelength it uses and the size of the antenna. The larger the wavelength, the bigger the antenna needs to be to get quality images. At typical radar wavelengths, with a 12 meter diameter reflector, the best achievable resolution would be as coarse as 10s of kilometers, which is not very useful for observing features on Earth at the human scale.

An angle extends down from a rectangle labeled radar antenna. A series of stacked ellipses representing radar pulses is at the widest part of the angle along a path labeled radar swath.

This diagram shows how synthetic aperature radar works by sending multiple radar pulses to an area on the ground from an antenna passing overhead. Credit: NASA | + Expand image

This is why NISAR utilizes an approach called synthetic aperture radar, or SAR, to synthetically magnify the resolution achievable from the antenna. With SAR, the spacecraft sends multiple signals, or pulses, to an area as it flies overhead. Each signal gets reflected back to the spacecraft, which is meticulously designed to “catch” the reflected signals thanks to its position and velocity. Each signal in the sequence is then focused into a single high-resolution image, creating an effect as if the spacecraft is using a much larger antenna.

Radar uses radio wavelengths, which are longer than those of visible light, allowing us to see through clouds and sometimes even tree coverage to the ground below, depending on the frequency of the radio waves. We’re also able to interpret a lot of information about the surface from the way the signal returns back to the orbiter. This is because NISAR will measure the amount of scatter, or dispersion, of the signal as compared to when it was originally transmitted.

For example, a rigid, sharp angled building will bounce the signal back to the receiver differently than a leafy tree. Different radio frequencies are better used for different surfaces because they are influenced by the type of surface being analyzed. To this end, NISAR is the first mission to use two different radar frequencies simultaneously. The L-Band can be used to monitor heavier vegetation and landscapes while the S-Band is better tuned for lighter vegetation and crop growth. The two wavelengths in general extend the range of sensitivity of the measurement to smaller and larger changes.

This combination of tools and features will allow NISAR to construct global maps of changes in the position of any given pixel at a scale of just centimeters as well as subtle changes in reflectivity due to land cover changes on all land and ice surfaces twice every 12 days. The resolution combined with repetition will allow scientists to monitor the changes taking place on our planet in a matter of days more comprehensively than ever before.

Specks of brightly covered squares dot an overhead image of Jefferson Parish, Louisiana. A key indicates how the colors correspond with the vertical velocity in mm/yr.

This satellite image of New Orleans is overlaid with synthetic aperature radar data from the UAVSAR instrument to show the rate at which the land was sinking in a section of New Orleans from June 2009 to July 2012. Credit: NASA/JPL-Caltech, Esri | › Learn more

What the NISAR Mission Will Show Us

Because of the massive amount of data produced by NISAR, we’ll be able to closely monitor the impacts of environmental events including earthquakes, landslides, and ice-sheet collapses. Data from NISAR could even be used to assess the risk of natural hazards.

Scientists can use NISAR to monitor tiny movements in Earth’s surface in areas prone to volcanic eruptions or landslides. These measurements are constructed using what’s called an interferogram, which looks at how the maps generated for each pass of the spacecraft have changed over time. For example, we could see immediate changes to the topography after an earthquake with an interferogram made from images NISAR collected shortly before and soon after the event.

On the left, a satellite takes a radar image of an area of Earth's surface during its first pass. On the right, during pass two, the satellite takes a radar image of the same area of the surface, which has now been displaced by an earthquake.

Using interferometry, as shown in this diagram, NISAR can capture changes or deformation in land surfaces, such as after an earthquake. | + Expand image

By tracking and recording these events and other movements on the surface leading up to natural disasters, it may be possible to identify warning signs that can improve detection and disaster response.

Two thin rectangular satellite images labeled Nov 13, 2009 and Nov 18, 2010 are followed by an equal sign and a third image of the same area with a neon colors overlaid and a heat-map scale showing movement in cm.

The first two images in this series were captured by the UAVSAR instrument during two separate passes over California's San Andreas Fault about a year apart. The two images were then combined to create the third image, which an interferogram that shows how the surface changed between the two passes of the instrument. Credit: NASA/JPL-Caltech | + Expand image

And NISAR isn’t just limited to studying the solid Earth. As missions prior have done, it will also be able to generate maps of polar ice sheets over time and detect changes in permafrost based on the regional movement of the soil below. These measurements will give climate scientists a clear picture of how much the ice is moving and deforming due to climate change and where it is thawing as the ground warms.

Additionally, NISAR can track land usage, deforestation, sea levels, and crustal deformation, informing scientists about the impacts of environmental and climate change on Earth.

Follow Along With NISAR

NISAR is scheduled to launch in 2024 from the Satish Dhawan Space Centre in Sriharikota, India, and will enter a polar orbit 460 miles (747 kilometers) above Earth. For the first 90 days after launch, the spacecraft will undergo checks and commissioning before beginning scientific observations for a primary mission designed to last three years.

Science from the mission will be downlinked to both NASA and ISRO ground stations below with data and the tools to process it freely available for download and use to all professional and citizen scientists.

Visit NASA’s NISAR mission page for the latest updates about the mission.

Teach Earth Science With NISAR

With the launch of NISAR, we will be better able to monitor and mitigate natural disasters and understand the effects of climate change. Bring the fleet of NASA Earth Science missions to your classroom with the following lessons and activities:

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Teachable Moments in Climate Change

Explore this collection of Teachable Moments articles to get a primer on the latest NASA Earth science missions, plus find related education resources you can deploy right away!

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ABOUT THE AUTHOR

Brandon Rodriguez, Educator Professional Development Specialist, NASA-JPL Education Office

Brandon Rodriguez is the educator professional development specialist at NASA’s Jet Propulsion Laboratory. Outside of promoting STEM education, he enjoys reading philosophy, travel and speaking to your dog like it's a person.

Explore how and why the SWOT mission will take stock of Earth's water budget, what it could mean for assessing climate change, and how to bring it all to students.

Update: Dec. 15, 2022 – NASA, the French space agency, and SpaceX are now targeting 3:46 a.m. PST (6:46 a.m. EST) on Friday, Dec.16, for the launch of the Surface Water and Ocean Topography (SWOT) satellite. Visit NASA's SWOT launch blog for the latest updates.

NASA is launching an Earth-orbiting mission that will map the planet’s surface water resources better than ever before. Scheduled to launch on Dec. 16 from Vandenberg Space Force Base in California, the Surface Water and Ocean Topography, or SWOT mission is the latest international collaboration designed to monitor and report on our home planet. By providing us with a highly detailed 3D view of rivers, lakes, and oceans, SWOT promises to improve our understanding of Earth’s water cycle and the role oceans play in climate change, as well as help us better respond to drought and flooding.

Read on to find out why we're hoping to learn more about Earth's surface water, get to know the science behind SWOT's unique design, and follow along with STEM teaching and learning resources.

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Why It's Important

Observing Earth from space provides scientists with a global view that is important for understanding the whole climate system. In the case of SWOT, we will be able to monitor Earth’s surface water with unprecedented detail and accuracy. SWOT will provide scientists with measurements of water volume change and movement that will inform our understanding of fresh water availability, flood hazards, and the mechanisms of climate change.

Scientists and engineers provide an overview of the SWOT mission. Credit: NASA/JPL-Caltech | Watch on YouTube

Water Flow

Scientists use a variety of methods to track Earth’s water. These include stream and lake gauges and even measurements from space such as sea surface altimetry and gravitational measurements of aquifer volumes. Monitoring of river flow and lake volume is important because it can tell us how much freshwater is readily available and at what locations. River flow monitoring can also help us make inferences about the downstream environmental impact. But monitoring Earth’s surface water in great detail with enough frequency to track water movement has proven challenging. Until now, most monitoring of river flow and lake levels has relied on water-flow and water-level gauges placed across Earth, which requires that they be accessible and maintained. Not all streams and lakes have gauges and previous space-based altimetry and gravitational measurements, though useful for large bodies of water, have not been able to adequately track the constant movement of water through smaller rivers or lakes.

Here's why understanding Earth’s "water budget" is an important part of understanding our planet and planning for future water needs.

SWOT will be able to capture these measurements across the globe in 3D every 21 days. The mission will monitor how much water is flowing through hundreds of thousands of rivers wider than 330 feet (100 meters) and keep a close watch on the levels of more than a million lakes larger than 15 acres (6 hectares). Data from the mission will be used to create detailed maps of rivers, lakes, and reservoirs that will enable accurate monitoring to provide a view of freshwater resources that is not reliant on physical access. Meanwhile, SWOT’s volumetric measurements of rivers, lakes, and reservoirs will help hydrologists better track drought and flooding impacts in near-real-time.

Coastal Sea Level Rise

SWOT will measure our oceans with unprecedented accuracy, revealing details of ocean features as small as 9 miles (15 kilometers) across. SWOT will also monitor sea levels and tides. Though we have excellent global sea level data, we do not have detailed sea level measurements near coastlines. Coastal sea levels vary across the globe as a result of ocean currents, weather patterns, land changes, and other factors. Sea levels are rising faster than ever, and higher sea levels also mean that hurricane storm surges will reach farther inland than ever before, causing substantially more damage than the same category of hurricanes in the past. SWOT will be able to monitor coastal sea level variations and fill gaps in the observations we currently have from other sources.

What is sea level rise and what does it mean for our planet? | › View Transcript

Ocean Heat Sinks

Further contributing to our understanding of the role Earth’s oceans play in climate change, SWOT will explore how the ocean absorbs atmospheric heat and carbon, moderating global temperatures and climate change. Scientists understand ocean circulation on a large scale and know that ocean currents are driven by temperature and salinity differences. However, scientists do not currently have a good understanding of fine-scale ocean currents, where most of the ocean's motion-related energy is stored and lost. Circulation at these fine scales is thought to be responsible for transporting half of the heat and carbon from the upper ocean to deeper layers. Such downward ocean currents have helped to mitigate the decades-long rise in global air temperatures by absorbing and storing heat and carbon away from the atmosphere. Knowing more about this process is critical for understanding the mechanisms of global climate change.

JPL scientist Josh Willis uses a water balloon to show how Earth's oceans are absorbing most of the heat being trapped on our warming world. | › Related lesson

These fine-scale ocean currents also transport nutrients to marine life and circulate pollutants such as crude oil and debris. Understanding nutrient transport helps oceanographers assess ocean health and the productivity of fisheries. And tracking pollutants aids in natural hazard assessment, prediction, and response.

How It Works

A joint effort between NASA and the French space agency – with contributions from the Canadian and UK space agencies – SWOT will continue NASA’s decades-long record of monitoring sea surface height across the globe. But this mission will add a level of detail never before achieved.

SWOT will measure more than 90% of Earth’s surface water, scanning the planet between 78°N latitude and 78°S latitude within 1 centimeter of accuracy and retracing the same path every 21 days. Achieving this level of accuracy from a spacecraft height of 554 miles (891 kilometers) requires that the boom using radar to measure water elevation remain stable within 2 microns – or about 3% of the thickness of a human hair.

This visualization shows ocean surface currents around the world during the period from June 2005 through December 2007. With its new, high resolution wide-swath measurements, SWOT will be able to observe eddies and current features at greater resolution than previously possible. Credit: NASA Scientific Visualization Studio | Watch on YouTube

Prior to SWOT, spacecraft have used conventional nadir, or straight-down, altimetry to measure sea surface height. Conventional nadir altimetry sends a series of radar or laser pulses down to the surface and measures the time it takes for each signal to return to the spacecraft, thus revealing distances to surface features. To acquire more detailed information on surface water, SWOT will use an innovative instrument called the Ka-band Radar Interferometer, or KaRIn, to measure water height with exceptional accuracy. Ka-band is a portion of the microwave part of the electromagnetic spectrum. SWOT uses microwaves because they can penetrate clouds to return data about water surfaces.

A radar signal is sent straight down from the SWOT spacecraft as it flies over Earth. Beams are shown bouncing back to receivers on either side of the spacecraft. The section of Earth measured by the spacecraft is shown as two side-by-side tracks colored in as a heatmap. The camera zooms out to show these tracks criscrossing the planet and eventually covering a majority of the surface.

SWOT will track Earth's surface water in incredible detail using an innovative instrument called the Ka-band Radar Interferometer, or KaRIn. Image credit: NASA/JPL-Caltech | + Expand image

The KaRIn instrument uses the principles of synthetic aperture radar combined with interferometry to measure sea surface height. A radar signal is emitted from the end of the 10-meter-wide boom on the spacecraft. The reflected signal is then received by antennas on both ends of the boom, capturing data from two 30-mile (50-kilometer) wide swaths on either side of the spacecraft. The received signals will be slightly out of sync, or phase, from one another because they will travel different distances to return to the receivers on either end of the boom. Knowing the phase difference, the distance between the antennas, and the radar wavelength allows us to calculate the distance to the surface.

The first of three images shows two paths of different lengths extending diagonally from a point on Earth’s surface to receivers on either side of the SWOT spacecraft. A second image shows the paths as light waves that are slightly out of phase. The third image shows a line drawn directly from the rightmost receiver to the path leading to the leftmost receiver, such that the intersected paths from Earth are equal in length. The upper triangle formed by this intersection has a short leg, highlighted in yellow, that represents the remaining length of the leftmost path. The yellow short leg represents the range difference between the two paths from Earth.

Radar signals bounced off the water’s surface will be received by antennas on both ends of SWOT's 10-meter-wide boom. The received signals will be slightly out of phase because they will travel different distances as they return to the receivers. Scientists use this phase difference and the radar wavelength to calculate the distance to the surface. Image credit: NASA/JPL-Caltech | + Expand image

The observations acquired by the two antennas can be combined into what is known as an interferogram. An interferogram is a pattern of wave interference that can reveal more detail beyond the 1-centimeter resolution captured by the radar. To explain how it works, we'll recall a couple of concepts from high school physics. When out-of-phase waves from the two antennas are combined, constructive and destructive interference patterns result in some wave crests being higher and some wave troughs being lower than those of the original waves. The patterns that result from the combination of the waves reveal more detail with resolution better than the 1-centimeter wavelength of the original Ka-band radar waves because the interference occurs over a portion of a wavelength. An interferogram can be coupled with elevation data to reveal a 3D representation of the water’s surface.

A diagram illustrating the swaths of data that SWOT will collect, including labels for the following: 10 m baseline between SWOT's receivers; a distance of 891 km between the surface and Interferometer Antenna 1; Interferometer Left Swath resulting in ocean topography with an H-Pol swath of 10-60 km; Interferometer Right Swath resulting in surface water topography with a V-Pol of 10-60 km; a straight-down Nadir Altimeter path directly below the spacecraft in the gap between the swaths; a cross-track resolution from 70m to 10m.

The KaRIn instrument illuminates two parallel tracks of approximately 50 kilometres on either side of a nadir track from a traditional altimeter. The signals are received by two antennas 10 metres apart and are then processed to yield interferometry measurements. Image credit: NASA/JPL-Caltech | + Expand image

This highly accurate 3D view of Earth’s surface water is what makes SWOT so unique and will enable scientists to more closely monitor the dynamics of the water cycle. In addition to observing ocean currents and eddies that will inform our understanding of the ocean’s role in climate change, SWOT's use of interferometry will allow scientists to track volumetric changes in lakes and quantify river flooding, tasks that cannot yet be done on a wide scale in any other way.

A colorful swath of yellows, oranges, magentas, purples is overlaid horizontally on a satellite image of desert landscape with thin yellow and red lines cutting diagonally across the image. On the center-left of the image, the colors fan out like a rainbow sprinkler. On the left side of the swath are a cluster of yellow dots.

This interferogram was captured by the air-based UAVSAR instrument of the magnitude 7.2 Baja California earthquake of April 4, 2010. The interferogram is overlaid atop a Google Earth image of the region. Image credit: NASA/JPL/USGS/Google | › Learn more

Follow Along

SWOT is scheduled to launch no earlier than Dec. 16, 2022, on a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California. Tune in to watch the launch on NASA TV.

After launch, the spacecraft will spend 6-months in a calibration and validation phase, during which it will make a full orbit of Earth every day at an altitude of 553 miles (857 kilometers). Upon completion of this phase, SWOT will increase its altitude to 554 miles (891 kilometers) and assume a 21-day repeat orbit for the remainder of its mission.

Visit the mission website to follow along as data are returned and explore the latest news, images, and updates as SWOT provides a new view on one of our planet's most important resources.

Teach It

The SWOT mission is the perfect opportunity to engage students in studying Earth’s water budget and water cycle. Explore these lessons and resources to get students excited about the STEM involved in studying Earth’s water and climate change from space.

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