Sunday, July 6, 2014

Insights about Earth: Landsat Photos from NASA Part 1

NASA’s website for the Landsat program quotes the baseball player Yogi Berra, saying “You can see a lot by just looking”. If you’ve never heard of the Landsat program before, that quote pretty much sums it up. There have been eight Landsats since 1972, and their purpose from the beginning was to take photographs of the earth. And by photographing the same place over 40 years, these photos give amazing insights into things like soil erosion, the effects of natural disasters, and the migration of penguin colonies.
 Alaska’s Columbia Glacier: The Columbia Glacier descends from an ice field 3,050 meters (10,000 feet) above sea level, down the flanks of the Chugach Mountains, and into a narrow inlet that leads into Prince William Sound in southeastern Alaska. It is one of the most rapidly changing glaciers in the world. This false-color image, captured by the Thematic Mapper (TM) instrument on Landsat 5, show the glacier and the surrounding landscape in 2011. Snow and ice appears bright cyan, vegetation is green, clouds are white or light orange, and the open ocean is dark blue. Exposed bedrock is brown, while rocky debris on the glacier’s surface is gray.

Yukon Delta: Countless lakes, sloughs, and ponds are scattered throughout this scene of the Yukon Delta in southwest Alaska. One of the largest river deltas in the world, and protected as part of the Yukon Delta National Wildlife Refuge, the river’s sinuous waterways seem like blood vessels branching out to enclose an organ.
Pretty much everyone knows the ‘blue marble‘ image. Taken by the crew of Apollo 17 in 1972, it’s a picture of the earth, framed against the vast emptiness of space. The image is common now, but no one knew what the earth looked like from space until the late 1960′s, when people actually went up there. And though we went up to explore space, there was no denying the sudden appeal of the earth below. For the first time we could really see the earth in all its glory, and NASA and the Department of the Interior decided to see more. So the Landsat program was born.
When Landsat 1 was being designed, a new type of imaging system was installed, which could detect light wavelengths outside the visible spectrum, like infrared. This was helpful in showing things like water saturation in soil. So instead of trying to tell the difference between slightly different shades of green, as you would in a ‘true color’ photograph, the imaging system could use other wavelengths and display saturated areas in pink and dry areas in yellow. The different way of looking meant greater understanding, and some amazing looking images.
 Lake Eyre: The scary face in this image is actually inundated patches of shallow Lake Eyre (pronounced “air”) in the desert country of northern South Australia. An ephemeral feature of this flat, parched landscape, Lake Eyre is Australia’s largest lake when it’s full. However in the last 150 years, it has filled completely only three times.
 Meandering Mississippi: Small, blocky shapes of towns, fields, and pastures surround the graceful swirls and whorls of the Mississippi River. Countless oxbow lakes and cutoffs accompany the meandering river south of Memphis, Tennessee, on the border between Arkansas and Mississippi, USA. The “mighty Mississippi” is the largest river system in North America.
Possibly even more amazing however, are the images that are ‘true color’. Red clouds, anyone?