http://www.wired.com/wiredscience/2012/03/envisat-anniversary/?pid=3266&viewall=true
- By Betsy Mason
- Email Author
- March 2, 2012 |
- 7:09 pm |
- Categories: Earth Science
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Ten years ago on March 1, the European Space Agency launched an 8-ton satellite called Envisat that would deliver back to Earth some of the most beautiful images of our planet taken from space.
Since then, Envisat has orbited Earth more than 50,000 times and has lived twice as long as planned.
The satellite has more than seven instruments on board that can use radar to see through clouds, capture ocean color and land cover, monitor the ozone layer and atmospheric pollutants, measure thermal-infrared radiation, and register surface topography.
To celebrate the satellite's 10th anniversary, we've selected a few of its most beautiful images for this gallery. Good luck deciding which one to use as wallpaper for your computer desktop.
Above:
Von Karmen Vortices
This false-color Envisat image, acquired on June 6, 2010, highlights a unique cloud formation south of the Canary Island archipelago, some 95 km from the northwest coast of Africa (right) in the Atlantic Ocean. Seven larger islands and a few smaller ones make up the Canaries; the larger islands are (left to right): El Hierro, La Palma, La Gomera, Tenerife, Gran Canaria, Fuerteventura and Lanzarote.
High-resolution version
Image and caption: ESA
Northwest Passage
Envisat ASAR image of the McClure Strait in the Canadian Arctic Archipelago, acquired on Aug. 31, 2007. The McClure Strait is the most direct route of the Northwest Passage and has been fully open since early August 2007.
High-resolution version
Image and caption: ESA
Algerian Sahara
Envisat radar image of the Tanezrouft Basin in the Algerian Sahara. Radar images reveal surface roughness – the rougher the surface, the brighter it appears. Hence, darker areas represent softer rock with a sandy or small-stoned surface. This image was created by combining three Envisat radar passes (March 23, 2009, June 1, 2009 and Sep. 14, 2009) over the same area. The colors result from changes in the surface between acquisitions.
High-resolution version
Image and caption: ESA
Galapagos Islands
This Envisat image features the Galapagos Islands, an archipelago situated some 1,000 km to the west of Ecuador in the Pacific Ocean. Galapagos’s largest island is Isabela (visible). The five volcanoes seen on the island are (from north to south): Wolf Volcano, Darwin Volcano, Alcedo Volcano, Sierra Negra Volcano and Cerro Azul Volcano. The bigger island to the right of Isabela is Santiago Island.
The image was obtained by combining three Advanced Synthetic Aperture Radar (ASAR) acquisitions (March 23, 2006, Aug. 14, 2008 and Jan. 1, 2009) taken over the same area. The colors in the image result from variations in the surface that occurred between acquisitions. Apart from mapping changes on the land surface, radar data can also be used to determine sea surface parameters like wind speed, wind direction and wave height. Different wave types and wind speeds are visible in the image as ripples on the water surface.
High-resolution version
Image and caption: ESA
Ganges Delta
This Envisat image highlights the Ganges Delta, the world’s largest delta, in the South Asia area of Bangladesh (visible) and India. The delta plain, about 350-km wide along the Bay of Bengal, is formed by the confluence of the rivers Ganges, Brahmaputra and Meghna.
As radar images represent surface backscatter rather than reflected light, there is no color in a standard radar image. This image was created by combining three Envisat Advanced Synthetic Aperture Radar acquisitions (Jan. 20, 2009, Feb. 24, 2009 and March 31, 2009) taken over the same area. The colors in the image result from variations in the surface that occurred between acquisitions.
High-resolution version
Image and caption: ESA
Himalayan Mountains
This Envisat image captures Asia’s diverse topography, altitude and climate with the snow-sprinkled Himalayan Mountains marking the barrier between the peaks of the Tibetan Plateau (top) in Central Asia and the plains of Nepal, Buthan and India in the Indian subcontinent. In this false-color image, lush or green vegetation appears bright red. This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on Feb. 20, 2009, working in Full Resolution mode to provide a spatial resolution of 300 m.
High-resolution version
Image and caption: ESA
Ireland
Resembling the brush strokes of French Impressionist Claude Monet, electric blue-colored plankton blooms swirl in the North Atlantic Ocean off Ireland in this Envisat image. Plankton, the most abundant type of life found in the ocean, are microscopic marine plants that drift on or near the surface of the sea.
While individually microscopic, the chlorophyll they use for photosynthesis collectively tints the surrounding ocean waters, providing a means of detecting these tiny organisms from space with dedicated "ocean color" sensors, like Envisat's Medium Resolution Imaging Spectrometer (MERIS), which acquired this image on May 23, 2010 at a resolution of 300 m.
High-resolution version
Image and caption: ESA
American West
The contrasting landscape of the western U.S. states of California (left) and Nevada (right) are highlighted in this Envisat image, acquired Feb. 9, 2011. The Sierra Nevada mountain range (snow-capped) runs along California’s eastern edge. Lake Tahoe (visible) is located in the Sierra Nevada on the California–Nevada border. Also visible in the image are the California cities of San Francisco (whitish area on the peninsula surrounding the San Francisco Bay, center left) and Los Angeles (sprawling grey area, bottom left).
High-resolution version
Image and caption: ESA
Kamchatka Peninsula
This image, acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on Nov. 12, 2009, captures the rugged and remote Kamchatka Peninsula on Russia's East Coast. The 1,250-km long peninsula lies between the Pacific Ocean to the east and the Sea of Okhotsk to the west.
High-resolution version
Image and caption: ESA
Hurricane Katrina
Hurricane Katrina as seen by Envisat's MERIS in Reduced Resolution mode, off southern Florida on Aug. 25, 2005, when it was still Category One on the Saffir-Simpson scale measuring hurricane intensity. The storm caused great damage after landfall, mostly due to heavy rainfall.
High-resolution version
Image and caption: ESA
Great Barrier Reef
This Envisat image features one of the natural wonders of the world – the Great Barrier Reef in the Coral Sea off the east coast of Queensland, Australia. Australian researchers have discovered that Envisat's Medium Resolution Imaging Spectrometer (MERIS) sensor can detect coral bleaching down to 10 m deep. This means Envisat could potentially map coral bleaching on a global scale. MERIS acquired this image on May 18, 2008, working in Full Resolution mode to yield a spatial resolution of 300 m.
High-resolution version
Image and caption: ESA
Yukon Delta
This Envisat image features Alaska’s Yukon Delta, where the Yukon River fans out into a labyrinth of distributaries before emptying into the Bering Sea. The Yukon, North America’s fifth-longest river system, flows some 3,190 km across central Alaska in the US before emptying into Norton Sound (top left).
This image was created by combining three of Envisat's Advanced Synthetic Aperture Radar (ASAR) acquisitions (Nov. 19, 2009, April 8, 2010 and May 13, 2010) over the same area. The colors represent changes in the surface between acquisitions.
High-resolution version
Image and caption: ESA
Etna Erupting
This Envisat MERIS image, acquired on Jan. 11, 2011, shows the plume of smoke billowing into the atmosphere from Mount Etna, Sicily, Italy. Activity gradually increased the following day, peaking in the evening.
High-resolution version
Image and caption: ESA
Strait of Gibraltar
This Envisat radar image shows internal waves in the Strait of Gibraltar, between the southern coast of Spain (top) and the northern coast of Morocco. From space, internal waves can be detected very efficiently using Synthetic Aperture Radar (SAR) instruments that are sensitive to changes in the small-scale surface roughness on the ocean surface. Internal waves in this image show up as a semi-circular rippled pattern east of the strait’s entrance in the Mediterranean Sea. Additional sets of internal waves generated in the Atlantic Ocean are visible as dark pink lines on the western side of the strait. This image was created by combining three Envisat SAR acquisitions (Aug. 12, 2010, Oct. 1, 2009 and Aug. 27, 2009) over the same area. The colors result from changes in the surface between acquisitions.
High-resolution version
Image and caption: ESA
Hawaiian Islands
This Envisat radar image features six of Hawaii’s eight major volcanic islands. Visible from right to left are the Big Island of Hawaii, Kahoolawe, Maui, Lanai, Molokai and Oahu. In addition to two other major islands, there are also 124 islets. This image was created by combining three Envisat ASAR acquisitions (March 27, 2006, April 16, 2007 and Jan. 21, 2008) taken over the same area. The colors in the image result from variations in the surface that occurred between acquisitions.
High-resolution version
Image and caption: ESA
Magnetic North Pole
Sea ice around the North Magnetic Pole, a wandering point on the Earth’s surface, is featured in this Envisat radar image, acquired on Dec. 8, 2008. Just as Earth has two geographic poles, the North Pole and the South Pole, it also has a North and South Magnetic Pole. Although the geographic and magnetic poles are near each other, they are not located in the same places. Currently, the North Magnetic Pole is located in the Canadian Arctic at approximately 82.7 north and 114.24 west.
High-resolution version
Image and caption: ESA
Indus River
This Envisat image shows western India and southern Pakistan, with the Indus River snaking through Pakistan’s Sindh province before emptying into the Arabian Sea. The red area in the lower-central portion of the image covers a seasonal salt marsh over Pakistan’s border with western India.
This image is a compilation of three passes by Envisat’s radar on May 15, July 14 and Sep. 12, 2011. Each is assigned a color (red, green and blue) and combined to produce this representation. The colors reveal changes in the surface between Envisat’s passes.
High-resolution version
Image and caption: ESA
Phytoplankton Bloom
In this Envisat image, acquired on Dec. 2, 2011, a phytoplankton bloom swirls a figure-of-8 in the South Atlantic Ocean about 600 km east of the Falkland Islands. Different types and quantities of phytoplankton exhibit different colors, such as the blues and greens in this image.
Earth-observing satellites like Envisat can monitor these algal blooms. Once a bloom begins, an ocean color sensor can make an initial identification of its chlorophyll pigment, and therefore its species and toxicity.
High-resolution version
Image and caption: ESA
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