NASA has discovered a novel way to measure the melt and growth of ice using a new laser technology.
Known as the Multiple Beam Experimental Lidar, or MABEL, the device, along with NASA's ICESat-2 satellite's ATLAS instrument, are photon counters. This means they measure the amount of time it takes for individual light photons to bounce off the Earth and return, which they then use to measure the planet's elevation down to the difference of the width of a pencil.
"Using the individual photons to measure surface elevation is a really new thing," Ron Kwok, a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif, said in a statement. "It's never been done from orbiting satellites, and it hasn't really been done much with airborne instruments, either."
In order to confirm the validity of the technology, researchers carried out a test run over Greenland in April 2012.
"We wanted to get a wide variety of target types, so that the science team would have a lot of data to develop algorithms," MABEL's lead scientist at NASA's Goddard Space Flight Center Bill Cook said. "This was our first real dedicated science mission."
The Greenland mission gave scientists a chance to prove the method is capable of measuring the height difference between open water and sea ice. Knowing this is crucial for determining ice thickness, the scientists explained.
"Part of what we're doing with MABEL is to demonstrate ICESat-2's instrument is going to have the right sensitivity to do the measurements," Cook said. "You can do this photon counting if you have enough photons."
Published in the Journal of Atmospheric and Oceanic Technology, the study showed that researchers were able to use MABEL data to calculate the elevation of a variety of surfaces, including open water, glassy ice and snow-covered ice.
"We were pretty happy with the precision," Kwok said. "The flat areas are flat to centimeter level, and the rough areas are rough."
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