NASA’s Ice, Cloud and land Elevation Satellite (ICESat) has resumed measurements of the Earth’s polar ice sheets, clouds, mountains and forests with the second of its three lasers. Crisscrossing the globe at nearly 17,000 miles per hour, this new space mission is providing data with unprecedented accuracy on the critical third dimension of the Earth, its vertical characteristics. The first set of laser measurements is revealing features of the polar ice sheets with details and is detecting dust storms, cloud heights, tree heights and smoke from forest fires in new and exciting ways, said Jay Zwally, ICESat Project Scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md. The principal mission of ICESat is to measure the surface elevation of the large ice sheets covering Antarctica and Greenland. Measurements of elevation-change over time will show whether the ice sheets are melting or growing as the Earth’s climate undergoes natural and human-induced changes. The Geoscience Laser Altimeter System (GLAS) instrument on ICESat sends short pulses of green and infrared light though the sky 40 times a second, all over the globe, and collects the reflected laser light in a one-meter telescope. The elevation of the Earth’s surface and the heights of clouds and aerosols in the atmosphere are calculated from both precise measurements of the travel time of the laser pulses, and ancillary measurements of the satellite’s orbit and instrument orientation.
ICESat is also making unique measurements of cloud heights and global distribution. ICESat detects distributions of aerosols from sources such as dust storms and forest fires. And because its laser pulses continuously, ICESat also measures the Earth’s topography with high accuracy.