Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


New NASA Laser Technology Reveals How Ice Measures Up

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

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.

NASA's Multiple Altimeter Beam Experimental Lidar flew over Southwest Greenland's glaciers and sea ice to test a new method of measuring the height of Earth from space.
Image Credit: NASA/Tim Williams

MABEL, short for "Multiple Altimeter Beam Experimental Lidar," serves as an ICESat-2 simulator.
Image Credit: NASA/Kelly Brunt

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.

This kind of photon-counting technology is novel for satellites; from 2003 to 2009, ICESat-1’s instrument looked at the intensity of a returned laser signal, which included many photons. So getting individual photon data from MABEL helps scientists prepare for the vast amounts of elevation data they'll get from ICESat-2.

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

ICESat-2 is tasked with measuring elevation across Earth's entire surface, including vegetation and oceans, but with a focus on change in the frozen areas of the planet, where scientists have observed dramatic impacts from climate change. There, two types of ice – ice sheets and sea ice – reflect light photons in different patterns. Ice sheets and glaciers are found on land, like Greenland and Antarctica, and are formed as frozen snow and rain accumulates. Sea ice, on the other hand, is frozen seawater, found floating in the Arctic Ocean and offshore of Antarctica.

MABEL's 2012 Greenland campaign was designed to observe a range of interesting icy features, said Bill Cook, MABEL's lead scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. With the photon counts from different surfaces, other scientists could start analyzing the data to determine which methods of analyzing the data allow them to best measure the elevation of Earth's surface.

"We wanted to get a wide variety of target types, so that the science team would have a lot of data to develop algorithms," Cook said. "This was our first real dedicated science mission."

The flights over the ocean near Greenland, for example, allowed researchers to demonstrate that they can measure the height difference between open water and sea ice, which is key to determining the ice thickness. MABEL can detect enough of the laser light photons that bounce off Earth surface and return to the instrument, and programs can then make necessary elevation calculations, Cook said.

"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."

In an article recently published in the Journal of Atmospheric and Oceanic Technology, Kwok and his colleagues showed how to calculate elevation from MABEL data, and do so over different types of ice – from open water, to thin, glassy ice, to the 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." And the density of photons detection could also tell researchers what type of ice the instrument was flying over.

The contours of the icy surface are also important when monitoring ice sheets and glaciers covering land. The original ICESat-1 mission employed a single laser, which made it more difficult to measure whether the ice sheet had gained or lost elevation. With a single beam, when the instrument flew over a spot a second time, researchers couldn't tell if the snowpack had melted or if the laser was slightly off and pointed down a hill. Because of this, scientists needed 10 passes over an area to determine whether the ice sheet was changing, said Kelly Brunt, a research scientist at NASA Goddard.

"ICESat-1 was fantastic, but it was a single beam instrument," Brunt said. "We're more interested in repeating tracks to monitor change – that's hard to do."

ICESat-2 addresses this problem by splitting the laser into six beams. These are arranged in three pairs, and the beams within a pair are spaced 295 feet (90 meters), or just less than a football field apart. By comparing the height of one site to the height of its neighbor, scientists can determine the terrain's general slope.

Brunt and her colleagues used MABEL data from the 2012 Greenland campaign to try to detect slopes as shallow as 4 percent incline; their results will be published in the May 2014 issue of the journal Geoscience and Remote Sensing Letters. They counted only a portion of the photons, in order to simulate the weaker laser beams that ICESat-2 will carry. With computer programs to determine the slope, the researchers verified it against results from earlier missions.

"The precision is great," Brunt said. "We're very confident that with ICESat-2's beam pair, we can see slope."

And there are still more things for MABEL to measure. The instrument team is planning a 2014 summer campaign to fly over glaciers and ice sheets in warmer weather. "We want to see what the effects of the melt is," Cook said. "How do glaciers look if they're warmer, rather than colder?"

Kate Ramsayer
NASA's Goddard Space Flight Center, Greenbelt, Md.

Kate Ramsayer | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>