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  Image: Geographic Location Photo #: STS117-E-6998 Date: Jun. 2007
Geographic Region: CLOUDS

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  Polar Mesospheric Clouds

In the summertime in the far northern or southern latitudes, high in the Earth's atmosphere at the edge of space, thin, silvery clouds sometimes become visible just after sunset. These high clouds, occurring at altitudes of about 80 kilometers (50 miles), are called polar mesospheric clouds (PMCs). They are also called noctilucent ("night-shining") clouds. In recent years, polar mesospheric clouds seem to be occurring more frequently and at lower latitudes than they have in the past, and studies are underway to determine whether their occurrence is related to global climate change.

In June 2007, the Space Shuttle crew visiting the International Space Station (ISS) observed spectacular polar mesospheric clouds over north-central Asia (top). This image was taken looking north while the Shuttle and ISS were docking and flying over the border between western China, Mongolia, and Kazakhstan. The red-to-dark region at the bottom of the image is the dense part of the Earth's atmosphere. Because this image was taken with a long lens (180mm), the entire profile of the Earth's limb (the edge of the atmosphere) was not captured.

Astronauts frequently observe polar mesospheric clouds over Canada, northern Europe, and Asia during June, July and August. While polar mesospheric clouds also occur over high latitudes in the Southern Hemisphere summer, astronaut observations of southern clouds are less frequent. Studies of polar mesospheric clouds are part of the research activities for the International Polar Year (IPY); to support IPY research, ISS astronauts will be looking for and documenting polar mesospheric clouds in both hemispheres. NASA's AIM (short for "Aeronomy of Ice in the Mesosphere") mission is also studying polar mesospheric clouds.
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Images: All Available Images Low-Resolution 123k
Mission: STS117  
Roll - Frame: E - 6998
Geographical Name: CLOUDS  
Center Lat x Lon: N x E
Film Exposure:   N=Normal exposure, U=Under exposed, O=Over exposed, F=out of Focus
Percentage of Cloud Cover-CLDP: 0
Camera: E4
Camera Tilt: HO   LO=Low Oblique, HO=High Oblique, NV=Near Vertical
Camera Focal Length: 180  
Nadir to Photo Center Direction:   The direction from the nadir to the center point, N=North, S=South, E=East, W=West
Stereo?:   Y=Yes there is an adjacent picture of the same area, N=No there isn't
Orbit Number: 30  
Date: 20070610   YYYYMMDD
Time: 191140   GMT HHMMSS
Nadir Lat: 41.5N  
Latitude of suborbital point of spacecraft
Nadir Lon: 86.0E  
Longitude of suborbital point of spacecraft
Sun Azimuth: 14   Clockwise angle in degrees from north to the sun measured at the nadir point
Space Craft Altitude: 181   nautical miles
Sun Elevation: -24   Angle in degrees between the horizon and the sun, measured at the nadir point
Land Views:  
Water Views: ICE  
Atmosphere Views: NOCTILUCENT CLOUDS  
Man Made Views:  
City Views:  
Photo is not associated with any sequences

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