Photon-counting technique to help track melt or growth of Earth's frozen regions

New results from NASA's MABEL campaign demonstrated that a photon-counting technique can allow researchers to track the melt or growth of frozen regions on Earth.

When a high-altitude aircraft flew over the icy Arctic Ocean and the snow-covered terrain of Greenland in April 2012, it was the first polar test of a new laser-based technology to measure the height of Earth from space.

Aboard that aircraft flew the Multiple Altimeter Beam Experimental Lidar, or MABEL, which is an airborne test bed instrument for NASA's ICESat-2 satellite mission slated to launch in 2017.

Both MABEL and ICESat-2's ATLAS instrument are photon counters - they send out pulses of green laser light and time how long it takes individual light photons to bounce off Earth's surface and return.

That time, along with ATLAS' exact position from an onboard GPS, will be plugged into computer programs to tell researchers the elevation of Earth's surface - measuring change to as little as the width of a pencil.

Ron Kwok, a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, said that using the individual photons to measure surface elevation is a really new thing, asserting that it's never been done from orbiting satellites, and it hasn't really been done much with airborne instruments, either.

The results are set to be published in journal Geoscience.