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Icesat-2 Brochure National Aeronautics and Space Administration MEASURING THE HEIGHT OF EARTH’S ICE FROM SPACE Ice, Cloud, and land Elevation Satellite-2 mission: icesat-2.gsfc.nasa.gov ICESat-2 Science Objectives The ICESat-2 mission is designed to accomplish four science objectives: 1. Quantify how much melting ice sheets in Greenland and Antarctica contribute to sea level changes. 2. Quantify how ice sheets and glaciers are gaining or losing mass at a regional level, to help researchers understand the mechanisms behind those changes. 3. Estimate the thickness of sea ice and monitor any changes. 4. Measure the height of vegetation in forests and other ecosystems worldwide. Table of Contents ICESat-2 at a Glance ................................................................................................ 4 ICESat-2: Measuring the Height of Ice from Space .................................................. 6 NASA’s View of Our Frozen Earth ........................................................................... 10 Instrument Overview: The Advanced Topographic Laser Altimeter System............ 14 Algorithm and Data Product Development ............................................................. 18 Spacecraft Design and Launch .............................................................................. 20 Ground System and Data Products ........................................................................ 22 Photo credit: Eric Rignot/NASA Photo credit: NASA’s new Earth-observing satellite will measure the height of our planet’s ice in unprecedented detail. Laser ICESat-2’s ATLAS laser instrument pulses 10,000 times a second, each pulse sending 300 trillion Telescope bright green laser photons to the The ATLAS receiver telescope ground. Scientists calculate height collects the handful of photons by using the time it takes individ- from each laser pulse that ual photons sent from the laser to return to the satellite. Every bounce off Earth’s surface and re- second, the instrument records turn to the satellite. data from 60,000 returning photons. Each photon’s flight time is measured with a preci- sion of 800 picoseconds. National Aeronautics and Space Administration Spacecraft The ICESat-2 spacecraft orbits Earth at 15,660 mph at an altitude of 310 miles. Every 91 days, it completes 1,387 unique orbits. The mission collects a terabyte of data daily. Land Ice Glaciers and ice sheets form as snowfall accumulates over centuries and millennia. As more land ice melts into the ocean, global sea level rises. ICESat-2 will measure the annual rise or fall of ice sheets to within a fraction of an inch. Sea Ice Sea ice forms when ocean water freezes, and in the Arctic Ocean forms a brightly Credit: Nathan Kurtz/Operation Credit: Icebridge/NASA reflective cap that helps regulate Earth’s temperature. The ICESat-2 mission will calculate the thickness of sea ice by measuring the freeboard—the difference between the top of sea ice and the ocean surface. Credit: Jeremy Harbeck/Operation Icebridge/NASA Jeremy Credit: ICESat-2 Measuring the Height of Ice from Space Earth’s ice is shrinking. Ice is being lost across the globe, especially in the polar regions. The continental ice sheets of Greenland and Antarctica are shedding ice to the oceans and raising sea level. Arctic sea ice is less than half its 1980s volume. Fundamentally changing the Arctic, this ice loss may also be affecting North American and global weather. NASA is launching the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) to measure changes in Earth’s ice and improve forecasts of the global impacts. With its fast-firing laser, the satellite will collect information enabling scientists to calculate—to within fractions of an inch—how much the vast ice sheets of Antarctica and Greenland rise or fall each year. ICESat-2 will take measurements across the globe and provide an incredibly precise height map of our planet in unprecedented detail. Its focus will be on Earth’s poles, including the Arctic region where temperatures are rising faster than at other latitudes. Credit: NASA Credit: Greenland Ice Height Change (m/yr) Gulf [Above] This image was created using data from the of original ICESat mission. Blue denotes decreases in ice Mexico height per year from 2003-2009 (when ICESat was in operation), while red denotes increases in ice height per year. More recently, between 2002 and 2016, NASA/Operation IceBridge Photo credit: about 280 gigatons of ice melted from Greenland [Above] The calving front of the Kangerlussuaq Glacier, on Greenland’s east coast. When each year, causing annual global sea level rise of 0.03 glacier ice calves and melts into the ocean, it contributes to sea level rise. Scientists inches (0.8 millimeters). Scientists are using height estimate global sea level could rise between 0.66 to 6.6 feet (0.2 to 2.0 meters) higher changes to calculate the mass loss of ice. by 2100, compared to the first decade of this century. Global land-ocean temperature index for Greenland ice mass change since 2002: Greenland ice loss 2002-2018: Antarctic ice mass change since 2002: Antarctic ice loss 2002-2018: 2017 relative to the 1951-1980 average: -286 gigatons/year 4,576 gigatons -127 gigatons/year 2,032 gigatons +0.9°C 6 ICESat-2 is poised to capture changes in the planet’s ice in unprecedented detail, shedding light on rising sea levels and shifting ocean currents. Credit: NASA Credit: Hundreds of billions of tons of land of ice sheets will help researchers narrow reflects the Sun’s heat back into space. ice melt into the oceans annually, that range of possibilities to forecast sea When white ice melts away, leaving dark raising sea levels worldwide. In recent level rise with greater certainty, allowing waters, the ocean soaks up that heat. years, meltwater from the ice sheets on communities to be better prepared. This alters wind and ocean circulation Greenland and Antarctica alone has raised patterns that span the globe, affecting Floating sea ice doesn’t change sea level global sea level by more than a millimeter Earth’s weather and climate. when it melts, just like melting ice cubes a year, and the rate is increasing. Based don’t overflow a glass of water. But sea Shrinking sea ice cover also disrupts on computer simulations and satellite ice loss has a different suite of global traditional ways of life for native Arctic data, global sea level could be anywhere consequences. The bright Arctic ice cap from 0.66 to 6.6 feet (0.2 to 2.0 meters) higher by 2100 than in the first decade of this century. ICESat-2 data documenting the ongoing height change [Right] In this image, created using data from the original ICESat mission, blue denotes decreases in ice height per year from 2003-2009 (when ICESat was in operation), while red denotes increases in ice height per year. While some areas gained ice from 2003-2009, data from 2002 to 2016 show that overall the ice from the continent is melting, sending approximately 125 gigatons of ice into the ocean and raising sea level about 0.01 inches (0.35 mm) per year. Antarctica Ice Height Change (m/yr) Credit: NASA Credit: Arctic sea ice minimum Antarctic ice mass change since 2002: Antarctic ice loss 2002-2018: Arctic sea ice loss since 1980: Sea level rate of change 1993-2018: relative to the 1981-2010 average: -127 gigatons/year 2,032 gigatons ~40% 3.2 millimeters/year -13.2 %/decade 7 [Left] Earth’s 2017 surface temperatures were the second warmest since modern mea- surements began in 1880, with 2016 taking the record. This map shows global tempera- ture anomalies averaged from 2013 through 2017 in degrees Fahrenheit. Red shades show how much warmer a given area was compared to an averaged base period from 1951 to 1980. Warming is concentrated over the Arctic and some land areas (darkest shades of red). Generally, warming is greater over land than over the ocean because water is slower to ab- sorb and release heat. Credit: NASA Credit: communities, and changes habitats for In the blink of an eye—half a second— to travel from the spacecraft to Earth wildlife such as polar bears and whales. ICESat-2’s laser altimeter will fire 5,000 and back—and does so with a precision While scientists routinely measure sea times, sending trillions of photons to better than a billionth of a second. In ice coverage from satellite images, the ground in six beams of green light. the course of three months, ATLAS will they lack region-wide sea ice height The instrument, called the Advanced cover the globe with 1,387 individual measurements that would allow them Topographic Laser Altimeter System orbits, collecting billions of measurements to derive thickness and volume—height (ATLAS), measures height by timing to create a three-dimensional portrait of measurements that ICESat-2 will provide. how long it takes individual photons our planet. [Right] In 2017, Arctic sea ice reached its lowest extent for that year on September 13, according to NASA and the National Snow and Ice Data Center (NSIDC). Since satellites began continually monitoring sea ice in 1978, researchers have observed a steep decline in the average extent of Arctic sea ice for every month of the year. With ICESat-2 data, scientists will be able to track the thickness of the sea ice in addition to the extent. Credit: NASA Credit: Arctic sea ice extent has consistently shrunk below Between 2003 and 2009, Arctic sea ice declined in thickness by more than the 1980–2010 average since 2011. 23.6 inches (60 centimeters). 8 As the satellite orbits, it will also connect the mission science to societal measure the height of the ocean and needs. ICESat-2 measurements of res- land. Researchers investigating vegetation, ervoir heights could help local govern- clouds, and more will be able to use the ments plan for flooding or drought, for satellite’s terabytes of data to study the example.
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