|
|
Solar Eclipse over Africa
| Title |
Solar Eclipse over Africa |
| Description |
Eastern Africa was cloaked in darkness when the Moderate Resolution Imaging Spectroradiometer (MODIS [ http://modis.gsfc.nasa.gov ]) on NASA's Aqua [ http://aqua.nasa.gov/ ] satellite caught this image on October 3, 2005. The inky blackness that covers much of Ethiopia, Kenya, Uganda, and parts of Sudan and the Democratic Republic of the Congo in this image was caused when the Moon crossed in front of the Sun in an annular solar eclipse. During such an eclipse, the Sun is visible as a fiery circle around the black disk of the moon. In the dimness beneath the Moon's shadow, very little light remained for MODIS to capture this image. Under normal conditions [ http://rapidfire.sci.gsfc.nasa.gov/subsets/?NAfrica_3_07/2005276 ], the land in the lower half of the image is a lush green, with patches of tan where the land is bare. Here, the tan areas have a red tint in the low light, while the green is completely black. Red dots show where fires were burning in vegetated areas. In the top half of the image, the orange of the Sahara desert is shown in darker tones than normal [ http://rapidfire.sci.gsfc.nasa.gov/subsets/?NAfrica_2_07/2005276 ]. Only in the upper right corner of the image, where full daylight has returned, does the desert look normal. Gradations of darkness within the shadowed area can be seen in the clouds. Bright white clouds reflect light well, so they are easily visible, even in the shadow. Since some light reached the Earth, the clouds remain bright along the outer edges of the shadowed region. As the eclipse progressed, the moon's shadow traveled southeast across the globe. When this image was taken, the deepest shadow lay over Kenya in the lower right corner of the image. Here the clouds are darker, an indication that there was less light to reflect back to the satellite. If this had been a total solar eclipse, the shadow cast by the moon would have been complete. The difference between a total solar eclipse and an annular eclipse is caused by the Moon's orbit around the Earth. The Moon's orbit is not circular, it is elliptical, like a squashed circle with the Earth at its center. This means that the Moon is not always the same distance from the Earth. When it is close to the Earth, the Moon appears larger than when it is far away. During a total solar eclipse, the Moon is closer to the Earth and so is able to block out the Sun entirely. An annular eclipse occurs when the Moon is farther from the Earth, and so the Moon's disk is not large enough to cover the Sun. The large image provided above has a resolution of 500 meters per pixel. It is available in additional resolutions from the MODIS Rapid Response Team. Tiny blue flecks in the large image are defects in the data. NASA image courtesy the MODIS Rapid Response Team [ http://rapidfire.sci.gsfc.nasa.gov ] at NASA GSFC. |
|
Floods in Chad
| Title |
Floods in Chad |
| Description |
Ghana, [ http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14528 ] Senegal, [ http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14526 ] Mali, [ http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14534 ] Uganda, [ http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14536 ] and Sudan [ http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14499 ] are available on the Earth Observatory. Daily images [ http://rapidfire.sci.gsfc.nasa.gov/subsets/ ] of Africa's Sahel region, where the floods were concentrated, are available from the MODIS Rapid Response System. NASA images courtesy the MODIS Rapid Response Team [ http://rapidfire.sci.gsfc.nasa.gov ] at NASA GSFC., The Sahel grassland is a rain-dependent ecosystem. With no mountain snowpacks to provide water during the dry season or daily infusions of water from moist air masses, the fortunes of the great African grasslands depend entirely on seasonal rain. The contrast between the dry season and the rainy season is illustrated by this pair of images, both captured by the Moderate Resolution Imaging Spectroradiometer (MODIS [ http://modis.gsfc.nasa.gov ]) on NASA's Terra [ http://terra.nasa.gov/ ] satellite. MODIS took the top image on September 18, 2007, after several weeks of unusually heavy rain had fallen over the Sahel. At the time, as many as 17 countries were flooded, from Senegal, bordering on the Atlantic Ocean in the west, to Kenya on the continent's east coast. The lower image was taken on July 4, 4007, a short time before the rains started in earnest. The images show Lake Firtri and the Batha River in southern Chad, a short distance east of Lake Chad. In the combination of infrared and visible light used to create these images, water is typically black, though in this case, it is bright blue. Sediment in the water scatters light, creating the blue color. In July, the only visible water is in Lake Fitri. Traces of green vegetation in the wetlands around the lake and along the Batha River are the only indication that water might be present elsewhere in the scene. Beyond these green areas, the landscape around the lake is mostly the rosy tan of barren land. The cluster of waves in the land to the north of Lake Fitri is likely a dune field along the southernmost edge of the Sahara Desert. Clouds, turquoise blue in this false-color image, gather on the southern edge of the scene. By September 18, water had changed southern Chad completely. The region went from dry to flooded. Lake Fitri had nearly doubled in size as the wetlands filled with water. The Batha River ran high, its channel clearly defined by a bold blue line of water. The land is vibrant green, covered with the grasses that sprang up in response to the rains. The rains and resulting floods cut off or severely hampered access to refugee camps along Chad's southeastern border with the Darfur region of Sudan, making the delivery of supplies difficult, said the United Nations Office for the Coordination of Humanitarian Affairs in a report [ http://www.reliefweb.int/rw/rwb.nsf/db900sid/LRON-778HGZ?OpenDocument&rc=1&emid=FL-2007-000151-TCD ] issued on September 20. The rains were expected to continue through early October. Chad was just one of many African countries that were flooded in September 2007. As many as 17 countries and more than a million people were affected by flooding across Africa, reported BBC News on September 17. Images of flood areas in Nigeria, [ http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14532 ] |
|
Nalubaale Dam, Uganda: Image
…
nasa, nasaimageofthedaygalle
…
Dam KML file for use with ea
…
nalubaale_etm_2001331
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2001-11-27 |
| creator |
NASA -- NASA image by Robert Simmon, based on landsat.gsfc.nasa.gov/ Landsat-7 data provided by the UMD glcf.umiacs.umd.edu/index.shtml Global Land Cover Facility. |
| identifier |
nalubaale_etm_2001331 |
|
Floods in Chad: Image of the
…
nasa, nasaimageofthedaygalle
…
* eoimages.gsfc.nasa.gov/ima
…
Chad_TMO_2007261
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2007-09-18 |
| creator |
NASA -- NASA images courtesy the rapidfire.sci.gsfc.nasa.gov MODIS Rapid Response Team at NASA GSFC. |
| identifier |
Chad_TMO_2007261 |
|
Solar Eclipse over Africa: I
…
nasa, nasaimageofthedaygalle
…
Eastern Africa was cloaked i
…
EastAfrica_AMO_2005276
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2005-10-03 |
| creator |
NASA -- NASA images courtesy the rapidfire.sci.gsfc.nasa.gov MODIS Rapid Response Team at NASA GSFC. |
| identifier |
EastAfrica_AMO_2005276 |
|
Drought in Eastern Africa: I
…
nasa, nasaimageofthedaygalle
…
In eastern Africa, most area
…
africandvia_spt_200602_palet
…
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of Jennifer Small, NASA ltpwww.gsfc.nasa.gov/gimms/htdocs/ GIMMS Group at Goddard Space Flight Center. |
| identifier |
africandvia_spt_200602_palette |
|
Drought in Eastern Africa: I
…
nasa, nasaimageofthedaygalle
…
In eastern Africa, most area
…
africandvia_spt_200602_palet
…
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of Jennifer Small, NASA ltpwww.gsfc.nasa.gov/gimms/htdocs/ GIMMS Group at Goddard Space Flight Center. |
| identifier |
africandvia_spt_200602_palette |
|
Drought in Eastern Africa: I
…
nasa, nasaimageofthedaygalle
…
In eastern Africa, most area
…
africandvia_spt_200602_palet
…
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of Jennifer Small, NASA ltpwww.gsfc.nasa.gov/gimms/htdocs/ GIMMS Group at Goddard Space Flight Center. |
| identifier |
africandvia_spt_200602_palette |
|
Drought in Eastern Africa: I
…
nasa, nasaimageofthedaygalle
…
In eastern Africa, most area
…
africandvia_spt_200602_palet
…
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of Jennifer Small, NASA ltpwww.gsfc.nasa.gov/gimms/htdocs/ GIMMS Group at Goddard Space Flight Center. |
| identifier |
africandvia_spt_200602_palette |
|
Mt. Elgon, Africa, Shaded Re
…
PIA04958
Sol (our sun)
C-Band Interferometric Radar
…
| Title |
Mt. Elgon, Africa, Shaded Relief and Colored Height |
| Original Caption Released with Image |
Location: 1 degree north latitude, 35 degrees east longitude Orientation: North toward the top, Mercator projection Size: 223 by 223 kilometers (138 by 138 miles) Image Data: shaded and colored SRTM elevation model Date Acquired: February 2000, The striking contrast of geologic structures in Africa is shown in this shaded relief image of Mt. Elgon on the left and a section of the Great Rift Valley on the right. Mt. Elgon is a solitary extinct volcano straddling the border between Uganda and Kenya, and at 4,321 meters (14,178 feet) tall is the eighth highest mountain in Africa. It is positioned on the Pre-Cambriam bedrock of the Trans Nzoia Plateau, and is similar to other such volcanoes in East Africa in that it is associated with the formation of the Rift Valley. However one thing that sets Mt. Elgon apart is its age. Although there is no verifiable evidence of its earliest volcanic activity, Mt. Elgon is estimated to be at least 24 million years old, making it the oldest extinct volcano in East Africa. This presents a striking comparison to Mt. Kilimanjaro, the highest mountain in Africa at 5,895 meters (19,341 feet), which is just over one million years old. Judging by the diameter of its base, it is a common belief among geological experts that Mt. Elgon was once the highest mountains in Africa, however erosion has played a significant role in reducing the height to its present value. Juxtaposed with this impressive mountain is a section of the Great Rift Valley, a geological fault system that extends for about 4,830 kilometers (2,995 miles) from Syria to central Mozambique. Erosion has concealed some sections, but in some sections like that shown here, there are sheer cliffs several thousand feet high. The present configuration of the valley, which dates from the mid-Pleistocene epoch, results from a rifting process associated with thermal currents in the Earth's mantle. Two visualization methods were combined to produce the image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northwest-southeast direction, so that northwest slopes appear bright and southeast slopes appear dark. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations. Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Geospatial-Intelligence Agency (NGA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D.C. |
|
STS-57 Earth observation of
…
| Title |
STS-57 Earth observation of Lake Victoria, Africa |
| Description |
STS-57 Earth observation taken aboard Endeavour, Orbiter Vehicle (OV) 105, is of Africa's Lake Victoria, which sits in the middle of the East African Rift Valley System.Lake Victoria is a major resource in eastern Africa, especially to the countries bordering the lake -- Uganda, Kenya and Tanzania. Typical summer indicators in equatorial Africa -- puffy clouds over land mass and clear skies over the lakes -- are in the view. Lake Albert in the western section of the Rift Valley and Lake Turkana in the eastern section can be seen to the west and east of Lake Victoria, respectively. Most of the other features on the right are obscured by clouds. NASA scientists studying the STS-57 Earth photography point out that the wide perspective of this scene gives a sense of the three-dimensional profile of the whole rift system. The scientists cite the way in which the component valleys of the rift system ramp up to Lake Victoria on either side. |
| Date Taken |
1993-07-01 |
|
|
