Crew Earth Observations (CEO) - 07.14.16

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
In Crew Earth Observations (CEO), crew members on the International Space Station (ISS) photograph the Earth using digital handheld cameras from their unique point of view located 200 miles above the surface. Photographs record how the planet is changing over time, from human-caused changes like urban growth and reservoir construction, to natural dynamic events such as hurricanes, floods and volcanic eruptions. A major emphasis of CEO is to monitor events needing immediate (disaster-level) response in support of the International Disaster Charter (IDC) (coordinated through the US Geological Survey). CEO imagery provides researchers on Earth with key data to understand the planet from the perspective of the ISS. Crew members have been photographing Earth from space since the early Mercury missions beginning in 1961. The images taken from the ISS ensure this record remains unbroken.
Science Results for Everyone
A picture may be worth a thousand words, but to science, images of Earth captured by ISS crew members through the Crew Earth Observation (CEO) program may be priceless. Available online (, these images have appeared in scientific papers on a variety of subjects, including Tahiti’s giant clams, urban vegetation, coral reefs, algal blooms, night-time remote sensing, and the break-up of Antarctic ice shelves. Scientists have also used CEO images for a global inventory of a new class of landform, megafans of river sediments in continental basins. Analysis of megafans may contribute to mineral exploration and has suggested the existence of past river systems on Mars.

The following content was provided by William L. Stefanov, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom: CEO

Principal Investigator(s)
William L. Stefanov, Ph.D., Johnson Space Center, Houston, TX, United States

Lisa A. Vanderbloemen, Ph.D., Jacobs Technology Inc., Houston, TX, United States
Murray J. Wilkinson, Ph.D., Texas State University, San Marcos, TX, United States
Amy M. Jagge, B.S., HX5, Houston, TX, United States
Michael H. Trenchard, M.S., Barrios Technology, Houston, TX, United States
Melissa D. Higgins, B.S., Jacobs Technology Inc., Houston, TX, United States

NASA Johnson Space Center, Houston, TX, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)

Research Benefits
Scientific Discovery, Earth Benefits

ISS Expedition Duration
November 2000 - December 2002; November 2002 - May 2003; April 2003 - March 2016; March 2016 - September 2017

Expeditions Assigned

Previous Missions
Crew Earth Observations have been ongoing since 1961 and more than 1,500,000 images have been taken during ISS operations.

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Experiment Description

Research Overview

  • The Crew Earth Observations (CEO) facility provides imagery planning, acquisition, quality control and delivery services for IDC activations of the CEO payload. Acquired imagery is provided to the US Geological Survey for access to the relevant end users.
  • The photographs from CEO document human impacts on Earth, such as city growth, agricultural expansion, reservoir construction, and other natural phenomena like volcanoes and hurricanes.
  • Through their photography of the Earth, ISS crew members build on the “time series” of imagery started with the first human spaceflights, ensuring that this continuous record of Earth remains unbroken.
  • Photographs taken from ISS account for almost one half of all Earth photographs from NASA human spaceflight missions.
  • The CEO facility receives numerous special requests from NASA Public Affairs Office,, the ISS Program Science Office, and NASA Headquarters for imagery, videos, and assistance identifying images and image features.

The ISS crew members use commercial and professional digital handheld cameras with a suite of lenses (from wide angle to a 1200 mm lens equivalent) to take Earth observation photographs that support research in a wide variety of Earth Science sub-disciplines. Scientists on the ground train the crew in basic areas of Earth system science and provide the crew a daily list of targets of the greatest scientific interest. Crew members take these photographs as time is available and during their leisure time. These digital photographs are downlinked, and both images and meta-data (especially lens used, moment the image was taken, and nadir point of the ISS) are assimilated into a public database. The images are used as educational and research tools, especially for disaster response and monitoring (see IDC above), as well as historical records of global environmental change, special geological and weather events, and the growth and change of human-made features, such as cities. Crew Earth Observations (CEO) are conducted from any available window on space station, but especially from the seven-window Cupola, from the windows in the Russian Zvezda service module and the nadir-viewing, optical-quality window in the U.S. Destiny laboratory module.

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Space Applications
The imagery captured by crew members during long-duration missions provides insight for future manned planetary surveys within our solar system as well as documenting other cosmic events such as planet transits across the Sun and meteor showers. In addition, photographing the Earth has been shown to improve crew members' mental well-being during long-duration missions on the ISS. Crew members enjoy taking Earth photos and spend much of their free time shooting from the ISS windows or Cupola.

Earth Applications
Using off-the-shelf digital cameras with powerful lenses, crew members take pictures of Earth, documenting locations specially requested by scientists and educators on the ground. A global view of Earth from space can place human-caused or naturally caused events in greater context, and record the ways in which these events impact the planet. The long history of crew photography also provides a unique record of how surface features have changed over time. High-resolution images of cities and natural features such as coral reefs, river deltas and icebergs can help scientists understand urban growth,impacts of changing land use, and global ocean and weather events. Continuous ISS flybys enable various viewing and lighting angles for the same locations.

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Operational Requirements and Protocols

Crew members spend approximately ten minutes a day, five days a week, recording their Earth observations. Some crew members have found Earth observations very enjoyable, and have dedicated extra time to photographing the beautiful and extraordinary views from the windows of ISS.
A list of regions and specific sites to be photographed is uplinked to the ISS daily, except during docked operations; crew members also select regions to photograph. Currently, all CEO images are captured with an electronic still camera and downlinked daily. Requested imagery is cataloged by the CEO group operations team and made accessible via the Gateway to Astronaut Photography of Earth. Imagery is curated by the Earth Science and Remote Sensing Unit at NASA JSC whose servers handle 20-40 million search requests per month, one of the highest totals of any NASA website.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

ISS provides a unique opportunity to capture a variety of sites on Earth by providing repeated overflight passes of the Earth with different lighting and viewing angles. Through CEO, ISS crewmembers share their view of the Earth with the public and take pictures of some of the most dramatic examples of change on the Earth's surface. These sites have included major deltas in south and east Asia, coral reefs, cities, alpine glaciers, volcanoes, large megafans (major fan-shaped river deposits), and features on Earth, such as impact craters, that are analogs to structures on other planets. Astronauts also record dynamic events: in 2004 and 2005, station astronauts took key photographs of the four Florida hurricanes, the December 2004 tsunami, and Hurricanes Katrina and Wilma. Other notable images capture volcanic eruptions on Mt. Etna (Sicily) and Cleveland volcano (Alaska), dust storms, smog, forest fires in the western U.S., and the Kolka glacier collapse in Russia.

From Expedition 1 through December 2007, ISS crewmembers took more than 300,000 images of Earth, almost half of the total number of images taken from orbit by astronauts since the first Mercury missions. Scientists and the public around the world have access to CEO images captured by astronauts on ISS through the Gateway to Astronaut Photography of Earth Web site ( Between 400,000 and 1,000,000 digital photographs of Earth taken from the CEO collection are downloaded by the public each month. The Web site also features an Image of the Weekand searchable access to all the photographs. Scientific analyses using CEO data have been published in scientific journals in a wide variety of disciplines. A few highlights of these publications are summarized here.

Spatial resolution is a measure of the smallest object that can be resolved by the sensor, or the size of the area on the ground represented by each pixel determined by geometric properties of the altitude of the spacecraft, lens magnification, size of the original image, and look angle. To achieve maximum potential spatial resolution, a camera system must capture information at sufficient speed to eliminate the effects of relative ground motion. Using handheld motion compensation, ISS crewmembers have achieved a spatial resolution of less than 6 meters in photographs of Earth from ISS. The ISS provides great potential as a remote-sensing platform capable of providing high-resolution imagery of the Earths surface (Robinson and Evans 2002).

CEO images captured from ISS of Pacific Ocean atolls (islands consisting of a circular coral reef surrounding a lagoon) allowed for an assessment of spatial resolution on estimates of landscape parameters of the atolls. Data gathered indicated that landscape parameter estimates were fairly accurate regardless of spatial resolution changes from 5 to 30 meters. This study of ISS imagery showed that spatial resolution, as well as spectral resolution, is of equal importance when studying these formations (Andréfouët et al. 2003). The most detailed images of Fangatau Atoll, taken from ISS, were used to measure the biomass of the giant clam fishery at Fangatau Atoll with accuracy similar to that obtained from aerial photography (Andréfouët et al. 2005). Astronaut photographs of reefs in the Indian Ocean have been used as base maps for dive surveys of reef resources in the region (Quod et al. 2002).

Extracting clear water depths from a variety of sources allows the examination and mapping of shallow water from global to local scales. Scientists from the National Oceanic and Atmospheric Administration (NOAA) used four sources of data to map shallow water bathymetry near U.S. coral reef areas. These included the sea-viewing wide field-of-view sensor (SeaWiFS) on board the OrbView 2 Satellite (SeaWiFS, allows global mapping within 1-kilometer pixels), the IKONOS satellite (global mapping within 4 meters), the Landsat Satellite (global mapping within 30 meter pixels), and handheld photography by the ISS crew (CEO local mapping within 6 meters). A new technique was applied to the blue and green bands from astronaut photography, allowing construction of a bathymetry map for Pearl and Hermes reef with accuracies similar to that obtained from IKONOS (Stumpf et al. 2003).

High-resolution astronaut photography collected from station has provided useful data for urban analysis, especially vegetation measurements. The accuracy of the data obtained from the astronaut photographs was similar to the data obtained by satellite remote sensors. The high-resolution astronaut photography obtained by the CEO investigation gives insights into vegetation density in urban areas (Stefanov and Robinson 2003). Imagery of cities at night captured during ISS Expedition 6 by Astronaut Don Pettit and subsequent astronauts aboard the ISS have provided researchers preliminary data for potential applications modeling urban landuse and population density. ISS photographs of cities at night are unique because they provide greater spatial resolution than any other source of city light data. Night time images of cities taken by ISS crew members have been used to support the concept of a new satellite sensor for night-time lighting called Nightsat (Elvidge et al. 2007 a; 2007b; Lulla 2003).

Imagery taken by astronauts has been collected and used to identify and build a global inventory of a new class of landform called megafans. These are large cones of sediments deposited by rivers that empty into large continental basins. Megafans are more easily identified using the wide, oblique views provided by astronaut photography. The results have been applied to interpreting features on both Earth and Mars. Wilkinson et al. (2005) mapped megafans in South America from imagery collected by Space Shuttle and ISS crews to understand how aquatic organisms might diversify in different river systems in South America. By identification of megafan systems and their processes that involve switching stream courses, habitat fragmentation and new habitat combinations can be hypothesized that, over time, may enable new speciation in aquatic systems. Another application of megafan landform analysis discusses how these features might provide a new perspective on mineral exploration (Wilkinson 2004). This analysis resulted in a patent (Wilkinson 2006). Finally, mapping megafans on Earth have provided a framework for interpreting similar landforms on Mars, supporting the existence of fluvial systems on Mars (Wilkinson et al. 2008).

CEO observations of large tabular icebergs in the South Atlantic Ocean stimulated new research with relevance to global warming and the break-up of Antarctic ice shelves (Scambos et al. 2005). Large chunks of ice calve off the Ronne Ice Shelf in Antarctica, and drift northward towards South Georgia Island in the South Atlantic Ocean. Polar scientists track these icebergs; as they drift into warmer waters, they melt and break-up. These icebergs can be used as a proxy for understanding how the ice shelves respond to global warming. Imagery collected by ISS astronauts in 2004 showed, for the first time, meltwater on one of the ice bergs. This indicated a different ice profile on the icebergs than previously modeled -- one with ramparts along the edge that pond the meltwater inboard. These observations allowed scientists to create new models for the forces experienced by these icebergs to help explain how they break up. This work has continued under CEO support of the International Polar Year (CEO-IPY).

In a different application that ties two ISS experiments together, Robinson et al. (2006) describe the benefits of photographing the Earth to the mental well-being of astronauts on long duration missions on the ISS. For more information about this study, see the Interactions results.

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Results Publications

    Elvidge CD, Cinzano P, Pettit DR, Arvesen J, Sutton PC, Small C, Nemani R, Longcore T, Rich C, Safran J, Weeks J, Ebener S.  The Nightsat mission concept. International Journal of Remote Sensing. 2007 June 20; 28(12): 2645-2670. DOI: 10.1080/01431160600981525.

    Andrefouet S, Gilbert A, Yan L, Remoissenet G, Payri C, Chancerelle Y.  The remarkable population size of the endangered clam Tridacna maxima assessed in Fangatau Atoll using in situ remote sensing data. ICES Journal of Marine Science. 2005 July 12; 62(6): 1037-1048. DOI: 10.1016/j.icesjms.2005.04.006.

    Wilkinson MJ, Marshall LG, Lundberg JG.  River behavior on megafans and potential influences on diversification and distribution of aquatic organisms. Journal of South American Earth Sciences. 2006; 21: 151-172.

    Cembella AD, Ibarra DA, Diogene J, Dahl E.  Harmful Algal Blooms and their Assessment in Fjords and Coastal Embayments. Oceanography. 2005; 18(2): 160-173.

    Kotarba AZ, Aleksandrowicz S.  Impervious surface detection with nighttime photography from the International Space Station. Remote Sensing of Environment. 2016 April; 176: 295-307. DOI: 10.1016/j.rse.2016.02.009.

    Quod J, Bigot L, Blanchot J, Chabanet P, Durville P, Nicet J, Wendling B.  Research and monitoring of the coral reefs of the French islands of the Indian Ocean. Assessment activities in 2002. Mission carried out in Glorieuses. Reunion: IFRECOR (l'Initiative Francaise pour les Recifs Corallines). 2002; 2. [French]

    Kohlmann B, Wilkinson MJ.  The Tarcoles Line: biogeographic effect of the Talamanca Range in lower Central America. Giornale Italiano do Entomologia. 2007; 12: 1-30. [Italian]

    Stefanov WL, Robinson JA, Spraggins SA.  Vegetation Measurements From Digital Astronaut Photography. International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2003; 24: 185-189.

    Lulla K.  2003 Nighttime Urban Imagery from International Space Station:Potential Applications for Urban Analyses and Modeling. Photogrammetric Engineering and Remote Sensing. 2003; 69: 941-942.

    Andrefouet S, Robinson JA, Hu C, Feldman GC, Salvat B, Payri C, Muller-Karger FE.  Influence of the spatial resolution of SeaWiFS, Landsat 7, SPOT and International Space Station data on landscape parameters of Pacific Ocean atolls. Canadian Journal of Remote Sensing. 2003; 29(2): 210-218.

    Stumpf RP, Holderied K, Robinson JA, Feldman GC, Kuring N.  Mapping water depths in clear water from space. Proceedings of the 13th Biennial Coastal Zone Conference, Baltimore, MD; 2003

    Wilkinson MJ, Allen CC, Oehler DZ, Salvotore MR.  A New Fluvial Analog for the Ridge-Forming Unit, Northern Sinus Meridiani/Southwest Arabia Terra Mars. 39th Lunar and Planetary Science Conference, Houston, Texas; 2008 1392-1393.

    Gebelein J, Eppler DB.  How Earth remote sensing from the International Space Station complements current satellite-based sensors. International Journal of Remote Sensing. 2006; 27(13): 2613-2629. DOI: 10.1080/01431160600552250.

    Robinson JA, Amsbury DL, Liddle DA, Evans CA.  Astronaut-acquired orbital photographs as digital data for remote sensing: spatial resolution. International Journal of Remote Sensing. 2002; 23(20): 4403-4438. DOI: 10.1080/01431160110107798.

    Jehl A, Farges T, Blanc E.  Color pictures of sprites from non-dedicated observation on board the International Space Station. Journal of Geophysical Research: Space Physics. 2013 January; 118(1): 454-461. DOI: 10.1029/2012JA018144.

    Kyba CC, Garz S, Kuechly H, de Miguel AS, Zamorano J, Fischer J, Holker F.  High-Resolution Imagery of Earth at Night: New Sources, Opportunities and Challenges. Remote Sensing. 2015; 7(1): 1-23. DOI: 10.3390/rs70100001.

    Elvidge CD, Safran J, Sutton PC, Cinzano P, Pettit DR, Arvesen J, Small C.  Potential for Global Mapping of Development via Nightsat Mission. GeoJournal. 2007; 69(1-2): 45-53. DOI: 10.1007/s10708-007-9104-x.

    Robinson JA, Evans CA.  Space Station Allows Remote Sensing of Earth to within Six Meters. Eos, Transactions American Geophysical Union. 2002; 83: 185-188.

    Scambos T, Sergienko O, Sargent A, MacAyeal D, Fastook J.  ICESat profiles of tabular iceberg margins and iceberg breakups at low altitudes. Geophysical Research Letters. 2005; 32: L23S09. DOI: 10.1029/2005GL023802.

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Ground Based Results Publications

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ISS Patents

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Related Publications

    Spalding MD, Ravilious C, Green EP.  Reef Mapping. Ewing, NJ: World Atlas of Coral Reefs; 2001.

    Stern RJ, Beyth M, Bodechtel J, Wetzel H.  Potential of the International Space Station for imaging Earth: Lessons from MOMS-2P aboard Mir. Geology. 2002; 30: 851-854.

    Kratzenberg-Annies V.  Space: A Journey of Discovery. New York City, NY: Space: A Journey of Discovery; 2005.

    Scott KP, Runco S, Eppler DB.  Pressurized Earth observations capabilities on board the International Space Station. 53rd International Astronautical Congress, The World Space Congress, Houston, TX; 2002 IAC-02-B.2.03.

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Related Websites
Astronauts View of the Home Planet
Earth Observatory News
The Gateway to Astronaut Photography
Earth Observatory Collections
Latest NASA News Releases

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NASA Image: ISS036E32853 - Taken with a short lens (50 mm), this west-looking image from the International Space Station covers much of the forested central Idaho- the dark areas are all wooded mountains. Within this mountainous region, several fires can be seen producing extensive smoke plumes. Some of the fires in the image were named Little Queens, Leggit, and Gold Pan shortly after the image was taken. The fires were mostly set by lightning and burned over 53,000 acres. This image shows the common pattern of westerly winds transporting smoke in an easterly direction.

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NASA Image ISS044E18893 - Astronauts took this detailed image of small island cays in the tropical waters of the Bahamas, with prominent tidal channels cutting between them. The string of cays (14.4km, 8.9mi long) shown in the image extends west from Great Exuma Island (outside the image right). Great Exuma is known for being remote from the bigger islands of the Bahamas, with privately owned cays as celebrity get-aways, and real pirates such as Captain Kidd in its history. The water surrounding the cays is so shallow it appears aqua. This is the most recognizable points on the planet for astronauts.

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image NASA Image: ISS044E89407 - Astronauts aboard the International Space Station looked near the sun's reflection point to shoot this high-contrast grid pattern of fish farms on the coast of China's northeast province of Liaoning. The fish farm basins have been built out from the darktoned, wooded coast to a distance of nearly 6 km (4 mi) (image top left). Fish farms have been constructed at many points along the Province's coastline, but this group, facing the Yellow Sea, is the largest (ranking sixth in China for aquaculture production).
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NASA Image: ISS044E885 - This detailed astronaut photograph shows strikingly regular shoreline patterns at Roebuck Bay on the coast of the desert country of Western Australia. The indents along the shoreline (image center and left) are points where small straight stream patterns reach the bay. Even smaller tributaries give a feathered appearance to this shoreline. By contrast, more typical meandering channel patterns of coastal wetlands appear top right. Almost no human-built patterns can be seen even though the town of Broome lies just outside the image top right.

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NASA Image: ISS042E33842 - This image shows the complex pattern of city lights in the metropolitan region of Cairo—the largest city in the Middle East and Africa's second largest city after Lagos (Nigeria). The brightly lit areas show greater Cairo with a population of about 20.5 million, fully a fifth of Egypt's population. Lights of the newer extensions of the city show a distinctly yellower color, probably related to sodium-vapor streetlight lamps.

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NASA Image: ISS042E101371 - This astronaut photograph illustrates a snowy view of two volcanoes in Russia's Far East. The image is centered on the Bolshaya Ipelka volcano that measures 40 km (25 miles) wide at its base—considered by geologists to be the largest volcanic structure in southern Kamchatka. But this older volcano is inactive with deep valleys along its flanks that were excavated by glaciers flowing radially out from the summit zone during the ice ages of the last two million years. The summit is severely eroded and originally had a much higher elevation. By contrast, the much smaller Opala stratovolcano is still active and therefore shows the classic cone shape.

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NASA Image: ISS040E112662 - There are many natural and built features highlighted in this detailed photograph. The street pattern of Mexico's tourist mecca, Cancun, contrasts with the waterways of the marinas that open into the bay and the lagoons. Brilliant blue water over coral reefs contrasts with the dark waters of inland lagoons. The reefs are the second largest reef system on earth, and draw tourists from al over the world. The wide, well developed beach on the gulf coast (image upper right) is the result of vigorous wave energy; it's white sand making it easily visible from space. But the wave energy is reduced along Cancun's protected shoreline (image center) and the beaches are thin or non-existent. Fair-weather cumulus clouds are scattered across the image top left.

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NASA Image ISS037E15305 - Part of the astronaut experience is seeing the planet transform from day to night, in ways that earth-bound people usually never see. A crew member aboard the International Space Station took this image of the northern Mediterranean Sea, centered on the island of Elba, with city lights of the Italian towns of Piombino and Punta Ala image right. Shooting towards the reflection of the moon on the sea surface, moon glint reveals the highly complex patterns on the sea surface—in the night equivalent of sun glint. The strongest reflection is near the center of the moon's disc, which brightens the sea surface around the island of Elba. But in the complex patterns seen from space, the dark areas of the sea surface even make the islands like Elba, Montecristo (lower left) and Pianosa (left) more difficult to see.

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NASA Image: ISS044E44347 - The image shows not only roads and buildings in great detail, but also evidence of flooding of Southeast Asia's largest river, the Mekong. The Mekong River serves as a trans-boundary river between Thailand and Laos as it meanders and spills a reddish brown channel of floodwater from a heavy monsoon rainfall. ISS crews have been specially tasked to document floods photographically—photos such as this represent the best kind of imagery that NASA tries to gather to assist relief authorities on the ground.

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NASA Image: ISS040E124198 - Puget Sound is partly reflecting the sun in this detailed image. Patterns of boat wakes are prominent in this reflection zone. The difference between the boat wakes relates to the speed of the boat and the particular patterns (of several) that happen to be captured in the specific light reflection angles at the time the image is taken. The land areas show parts of Seattle. The darkest areas with rectangular grids are suburbs richly covered with trees. The broadly gray zones of the central city are brighter where structures are lower, as in the harbor zone (Harbor Island), and darker where the shadows of high-rise buildings downtown cast black shadows. Interstate Highway 5 bisects downtown.

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image NASA Image ISS043E101832 - This image provides a view of muddy floodwaters and distributary channels in the northern sector of the Tsiribihina River delta on Madagascar's west coast. Delta distributaries have two morphologies, large and relatively straight, and the small, highly contorted channels between. Brown sediment from recent heavy rains reaches the sea where it is swept slowly north by local ocean currents (image lower left), with clearer blue water visible lower right. Over thousands of years sediment supplied by the river is shaped by waves along the shoreline into beach ridges—which appear as numerous parallel lines (image lower center and image right). Each line represents a prior coastline on this geologically fast-changing coast, with the oldest coastline lying further inland.
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image NASA Image ISS043E93251 - This oblique image was taken from the International Space Station as astronauts flew over the Himalaya range in China near the Indian border. The view shows one of the main ranges of the Himalaya Mountains across the bottom of the image, where peaks cast strong evening shadows against the snow. The peaks reach great altitudes (5200 m, 17,000 feet), with those just outside the lower margin reaching high enough (6500 m, 21,325 feet) to host glaciers. Rivers have eroded rock from these high mountains and deposited the sediment as broad alluvial fan surfaces (across the middle of the image). The snow cover shows these strikingly smooth surfaces. A trelliswork of gullies cuts into these surfaces casting sinuous shadows. The largest river in the view has cut a 500 m-deep (1650 foot) canyon through the fans (image left). Although the rivers in the view drain northward from the Himalayas, they ultimately flow back south through the mountain ranges as the Sutlej River (outside the image)—in one of the largest canyons in the world—before entering the lowlands of Pakistan and finally reaching the Arabian Sea.
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image NASA Image ISS044E868 - Coastlines are usually the best indicators for astronauts in telling them quickly which part of the world they are looking at from the windows of the International Space Station. Here coastal lagoons with numerous rounded islands are typical of the Indian Ocean coastline of Western Australia. These shapes contrast with the angular, white ponds of the salt extraction industry. Muddy red-brown inland water (image right and lower left) from recent rains is prevented by low causeways from mixing with darker (clearer) water nearer the coast.
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image NASA Image ISS038E35416 - This sector of the Green River canyon in eastern Utah is known as Bowknot Bend because of the way the river doubles back on itself. The loop carries river rafters 14.5 kilometers (9 miles) before bringing them back to nearly the same point they started from— though on the other side of a low, narrow saddle (image center). In this photograph, the Green River appears dark because it lies in deep shadow, 300 meters (1,000 feet) below the surrounding landscape. The yellow-tinged cliffs that face the rising sun give a sense of the steep canyon walls. The straight white line across the scene is the contrail from a jet liner that passed over Bowknot Bend. Note that north is to the bottom of the image. The reason for the tight bends in the Green River is the same as it is for the Mississippi: river courses often wind over time when they flow across a bed of relatively soft sediment in a floodplain. Geologists assume that the Green River, before its present canyon phase, once snaked across a wide valley on a bed of its own sediment and made a series of striking meander bends. Vertical uplift of the entire landscape—by deep-seated tectonic forces related to the growth of the Rocky Mountains—caused the Green River to erode downwards into the hard rocks under the valley. In the process, the present vertical-sided canyon was formed, preserving the tight loops reminiscent of an earlier time.
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NASA Image ISS036E35665 - Guadalupe Island (image left) is a volcanic edifice 35 km long that lies 240 km off the coast of Mexico’s Baja California peninsula. Winds on the August day this astronaut photograph was taken were blowing from the north (left), and gave rise to a series of eddies in the atmosphere which appear as circles and swirls in the clouds downwind of the island. Known technically as a Von Karman vortex street, obstacles of any kind can set up such vortices, from islands to craters to chimneys. The size of each swirl can be judged from the length of the island. Under ideal conditions clouds make the swirls visible.

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NASA Image ISS043E101953 - Astronauts aboard the International Space Station used a high magnification lens to capture the detail of the Aswan High Dam region of the River Nile in southern Egypt, a vast engineering project built between 1960 and 1970 (the Aswan Low Dam, outside the image lower right, was completed in 1902). The highly indented shoreline of 550 kmlong (340 mi) Lake Nasser is a familiar sight to space-farers. Aswan International Airport lies due west near the settlement that hosts Aswan University. Completed in 1970, the Aswan High Dam is one of the largest earthen embankment dams in the world—12,565 feet (3830 m) long and nearly 3281 feet (1000 m) wide—and holds back 132 cubic km (31.7 cubic mi) of water in Lake Nasser. Hydropower generated at the dam wall provides 2.1 gigawatts, fully half of Egypt’s needs when the dam was first completed (about 15% by 1998, with population growth), giving numerous villages access to electricity for the first time. The dam has virtually eliminated the danger of floods downstream in the Nile valley.

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NASA Image ISS029E6020 - Astronauts on the International Space Station (ISS) used a digital camera to capture several hundred photographs of the aurora australis, or “southern lights,” while passing over the Indian Ocean on September 17, 2011. Solar panels and other sections of the ISS fill some of the upper right side of the photograph. Auroras are a spectacular sign that our planet is electrically and magnetically connected to the Sun. These light shows are provoked by energy from the Sun and fueled by electrically charged particles trapped in Earth’s magnetic field, or magnetosphere.

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NASA Image ISS028E6687 - Regions where fresh water flowing in rivers and salt water from the seas and oceans mix are called estuaries, and they are among the most biologically productive ecosystems on Earth. This astronaut photograph, taken from the International Space Station, highlights two estuaries located along the northwestern coastline of the island of Madagascar. The Mozambique Channel (image top) separates Madagascar from the southeastern coast of Africa. Bombetoka Bay (image upper left) is fed by the Betsiboka River and is a frequent subject of astronaut photography due to its striking red floodplain sediments.

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