![]() Rational and discussion of mission goals: The mass balance of Earth's great ice sheets and their contributions to sea level are key issues in climate variability and change. The requirements call for a 5-year operational mission with a goal of 7 years. ATLAS is designed to measure ice-sheet topography, sea ice freeboard as well as cloud and atmospheric properties and global vegetation. The ICESat-2 observatory contains a single instrument, an improved laser altimeter called ATLAS (Advanced Topographic Laser Altimeter System). ICESat-2 is a NASA follow-up mission to ICESat with the goal to continue measuring and monitoring the impacts of the changing environment. ICESat-2 (Ice, Cloud and land Elevation Satellite-2) Spacecraft Launch Mission Status Sensor Complement Ground Segment Preparatory Campaigns References It has 4 solar panels which produce an average of 1320 Watts to power the spacecraft, with four 22 N thrusters and eight 4.5 N thrusters to maintain the satellite’s orbit, determined through a high-precision GPS receiver and laser ranging. The spacecraft has an onboard recorder that stores 580 Gbits/day and is able to downlink data through X-band at a rate of 220 Mbit/s. It is powered by the LEOStar-3 spacecraft bus which also provides orbital control for ATLAS as well as propulsion, navigation, attitude control, thermal control, data storage and handling, and ground communication. The ICESat-2 spacecraft was built by Northrop Grumman. ICESat-2 is in a near-polar Low Earth Orbit (LEO) at an altitude of 496 km with an orbital inclination of 92° and repeat cycle of 91 days. The backscatter from clouds and aerosols from 14 km altitude to the surface is recorded in an atmospheric channel, which consists of 30m bins in a 14km long column with along track resolution of 280 m. ICESat-2 produces elevation measurements that enable the determination of global vegetation height to 3 m accuracy at 1 km spatial resolution in vegetated areas. For sea ice measurements, ATLAS can measure monthly surface elevation changes with an uncertainty of 0.03 m along 25 km. For land ice measurements, ATLAS can measure surface elevation changes as little as 0.25 m per year over areas of 100 km2, surface elevation changes with an accuracy of 0.4 m/year along 1 km track segments, and resolution of winter and summer ice-sheet elevation change to 0.1 m at 25 km x 25 km spatial scales. Performance SpecificationsĪTLAS has a swath width of 17 m, and is able to measure ice-sheet elevation changes to an accuracy of 4 mm per year. These atmospheric measurements are important in climate studies as they extend the data records begun by other Earth observation satellite lidars. ATLAS receives backscatter from thick clouds, aerosols and molecules in the atmosphere allowing it to measure atmospheric tenuous clouds and blowing snow to provide for atmospheric climate models. ICESat-2 will provide high quality topographic measurements that allow estimates of ice sheet volume change, key measurements in determining the rate of climate change on Earth. The overall objectives of ICESat-2 are to quantify the polar ice sheet mass balance to determine contributions to current and recent sea level changes and impacts on ocean circulation, determine the seasonal cycle and topographic character of ice sheet changes, estimate sea ice thickness to examine ice/ocean/atmosphere exchanges of energy, masss and moisture, and measure vegetation canopy height as a basis for estimating large-scale biomass and biomass change. ATLAS is designed to acquire high resolution measurements of Earth’s surface while also obtaining atmospheric backscatter from molecules, clouds, and aerosols. The Advanced Topographic Laser Altimeter System (ATLAS), for measuring elevation, is the only instrument onboard ICESat-2.
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