Studying vegetation canopy with ICESAT-2
This visualization depicts how ICESat-2 data is being used to study vegetation canopy. The visualization begins with a view of 6 beams passing over forested mountains, before zooming in on a single beam and introducing the data classification scheme. Data points are classified as ground (light brown), vegetation (green), vegetation canopy (tan), or unclassified (grey). A transparent scale using meters for distance and altitude is overlaid momentarily before the camera moves on and explores the rest of the beam data. Altitude is exaggerated 5x.
Although the primary mission goal of ICESat-2 is to monitor changes in the cryosphere, ICESat-2 also collects elevation data over the Earth’s land surfaces providing geodetic measurements to support a wide range of terrestrial applications. In the temperate and tropical regions, ranging measurements from ICESat-2 are used to produce estimates of terrain and canopy heights of the worlds’ forests. The density and vertical distribution of the returned photons from within the canopy can be utilized to infer information regarding forest biomass, canopy volume, habitat mapping, biodiversity, and parameterization of land-climate models. The ICESat-2 satellite is in a polar orbit (92 degrees) and is the only space based laser altimeter capable of collecting ranging measurements over all land surfaces.
The instrument onboard ICESat-2 is the Advanced Topographic Laser Altimeter System (ATLAS) and ATLAS is sensitive to detect single photons reflected from the surface. ATLAS uses a 532 nm laser that fires at a rate of 10 kHz (or every 70 cm on the Earth’s surface) which facilitates high spatial resolution in the along-track direction. A diffractive optical element splits the ATLAS laser into 6 beams; 3 beam pairs approximately 3 km apart. Each beam pair is comprised of a strong beam and weak beam. Because ATLAS is sensitive at the photon level, solar background noise can present a challenge in the analysis or photon counting data. ICESat-2 is a profiling lidar and a result of the beam configuration is high resolution in the along-track direction; however gaps exist between beams. In the mid-latitudes, ICESat-2 operates in vegetation mode which consists of off-nadir pointing the satellite to a different ground track each 91-day repeat cycle. Thus, rather than repeating an orbit every 91 days, ICESat-2 will point to a different location on the Earth to improve the spatial sampling. Over a period of two years, this series of off-pointing maneuvers has reduced the distance between tracks at the equator from 29 km to approximately 2 km. As the mission continues through time with more off-pointing maneuvers, the distance between ground tracks will continue to decrease.
Please give credit for this item to:
NASA's Scientific Visualization Studio
Datasets used in this visualization
ICESat-2ID: 1112Collected with Advanced Topographic Laser Altimeter System (ATLAS) 04/15/2019
Note: While we identify the data sets used in these visualizations, we do not store any further details, nor the data sets themselves on our site.