Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NASA's Landsat Satellite Looks for a Cloud-Free View

23.05.2013
For decades, Landsat satellites have documented the desiccation of the Aral Sea in Central Asia.

Once one of the largest seas in the world, it shrunk to a tenth of its original volume after Russia diverted its feeder rivers in the 1960s. Scientists studying the Aral Sea's changing ecology and retreating shoreline have looked to Landsat -- and a new feature of the Landsat Data Continuity Mission will help ensure they get a clear, cloud-free view.


Clouds are hard to spot in this natural-color image of the Aral Sea in Central Asia, taken March 24, 2013.
Credit: NASA Goddard/Landsat/Michael Taylor

One of two new spectral bands identifies high-altitude, wispy cirrus clouds that are not apparent in the images from any of the other spectral bands. The March 24, 2013, natural color image of the Aral Sea, for example, appears to be from a relatively clear day. But when viewed in the cirrus-detecting band, bright white clouds appear.

"Cirrus clouds are popping out," said Pat Scaramuzza, a senior scientist with the U.S. Geological Survey in Sioux Falls, S.D. "Cirrus clouds can be so thin, they won't be visible in a typical image. But the cirrus band will see it, and it will tell users: There's a thin cloud layer and it can affect your results."

Landsat picks up different wavelengths of light reflected off Earth's surface, and clouds can obscure the view. Because of this, scientists will often disregard images or pixels gathered on cloudy days. That's easy to do when big, puffy cumulus clouds appear like popcorn strewn across a landscape -- but harder when the thin, almost transparent cirrus clouds move in.

To identify cirrus-covered areas, LDCM's Operational Land Imager instrument has detectors for a specific wavelength of light -- 1.38 microns -- that bounces off of ice crystals of the high altitude clouds, but is absorbed by the water vapor in the air closer to the ground.

"Cirrus clouds are composed of ice crystals. So, at this wavelength they are reflecting sunlight, very high up in the atmosphere," said Lawrence Ong, a research scientist with NASA's Goddard Space Flight Center in Greenbelt, Md. "Below that, the energy is being absorbed by the water vapor in the air."

The cirrus band's key job will be to alert scientists and other Landsat users to the presence of cirrus clouds, so they know the data in the pixels under the high-altitude clouds could be slightly askew. Scientists could instead use images taken on a cloud-free day, or correct data from the other spectral bands to account for any cirrus clouds detected in the new band.

"The science people are still looking to how they can best use this, since it's a new band," Ong said. "It's like roads, you build them and people will find a better use for them."

LDCM, the newest spacecraft in the Landsat family, was launched on Feb. 11, 2013. When the on-orbit calibration and checkout phase of LDCM is over, scheduled for late May 2013, the satellite will be renamed Landsat 8 and handed over for operation by the U.S. Geological Survey.

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

Kate Ramsayer | EurekAlert!
Further information:
http://www.nasa.gov
http://www.nasa.gov/mission_pages/landsat/news/cloud-free-aral.html

More articles from Earth Sciences:

nachricht Multi-year submarine-canyon study challenges textbook theories about turbidity currents
12.12.2017 | Monterey Bay Aquarium Research Institute

nachricht How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas
11.12.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

A whole-body approach to understanding chemosensory cells

13.12.2017 | Health and Medicine

Water without windows: Capturing water vapor inside an electron microscope

13.12.2017 | Physics and Astronomy

Cellular Self-Digestion Process Triggers Autoimmune Disease

13.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>