April 22nd, 2013 by Robert Simmon
May 2nd, 2012 by Robert Simmon
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September 28th, 2011 by Robert Simmon
During every minute of the day, every day, a volcano is erupting somewhere on Earth. Actually, it’s more like a dozen. Or two. Satellites capture much of this activity, and we try to highlight as many eruptions as possible, but for one reason or another (like clouds) some of them fall through the cracks. Here are a handful from the past few weeks:
Natural-color satellite image of Mount Etna, Italy; acquired on September 18, 2011, by the Advanced Land Imager (ALI). Credit: NASA Earth Observatory/EO-1 Science Team.
Natural-color satellite image of Bezymianny Volcano, Russia; acquired on September 20, 2011 by the Advanced Land Imager (ALI). Credit: NASA Earth Observatory/EO-1 Science Team.
False-color satellite image of Kizimen Volcano, Russia; acquired on September 21, 2011, by the Advanced Spaceborne Thermal Reflection and Emission Radiometer (ASTER). Credit: NASA Earth Observatory and the NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.
Natural-color satellite image of Ambrym Volcano, Vanuatu; acquired on September 23, 2011, by the Advanced Land Imager (ALI). Credit: NASA Earth Observatory/EO-1 Science Team.
September 19th, 2011 by Robert Simmon
Once upon a time Landsat images were expensive (Landsat 7 data was $600 per scene, and the earlier satellites were even pricier) and difficult to find. Now the data—which dates to 1972—is free, and reasonably easy (or at least not painfully difficult) to browse and download from the Global Visualization Viewer, or even the Google Earth Engine (which still has some rough edges).
There are some amazing things buried in the archive, like this natural-color image of an eruption at Rabaul. According to the Global Volcanism Program the activity at the time was “continuous, forceful emissions of thick, light-to-dark gray ash clouds.”
Poke around, and let me know what you find.
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September 16th, 2011 by Robert Simmon
September 14th, 2011 by Robert Simmon
Sometimes I’ll find a surprise in a satellite image. In this case, kilometer-tall letters that spell out “LUECKE” near Austin, TX (Near the Bastrop Fire):
Although this could have just been a curiosity for passing pilots and astronauts, it turns out that Johnson Space Center scientists used the letters to estimate the maximum resolution of cameras aboard the Space Shuttle.
We also made an empirical estimate of spatial resolution for lower contrast vegetation boundaries. By clearing forest so that a pattern would be visible to landing aircraft, a landowner outside Austin, Texas (see also aerial photo in Lisheron 2000), created a target that is also useful for evaluating spatial resolution of astronaut photographs. The forest was selectively cleared in order to spell the landowner’s name ‘LUECKE’ with the remaining trees (figure 10). According to local surveyors who planned the clearing, the plan was to create letters that were 3100 ´ 1700 ft (944.9 ´ 518.2 m). Photographed at a high altitude relative to most Shuttle missions (543 km) with a 250-mm lens, Formula 3 predicts that each pixel would represent an area 28.6 ´ 36.0 m on the ground (table 5). When original film was digitised at 2400 ppi (10.6 mm/pixel), letters correspond to 29.4 ´ 18.8 pixels for a comparable pixel size of 27 – 32 m.
It’s reminiscent of the map of Italy I saw on a hillside near Castellucio, in the Apennines, or even the Nazca Lines. What other examples of landscaping visible from space are out there?
May 13th, 2011 by Robert Simmon
While poking around looking for imagery of the 1973 flooding on the Mississippi, I discovered some fascinating, very high resolution aerial photography. Images of Morgan City—a community near the mouth of the Atchafalaya River that was damaged by flooding in 1973, and will likely be hit by rising water in the next few weeks. Both are false color, but the May image is either a poor scan or the originals have degraded. These photographs, and thousands like them, are available from Earth Explorer, the online USGS archive of satellite data and aerial photography. John Mcphee’s essay “Atchafalaya” from his book The Control of Nature beautifully describes Morgan City and the 1973 flood.
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February 28th, 2011 by Robert Simmon
Russia’s Kamchatka Peninsula is perhaps the most volcanically active spot on the planet. Last week’s Global Volcanism Program weekly report (for February 16–22, 2011) listed three Kamchatkan volcanoes currently in eruption—Karymsky, Kizimen, and Shiveluch—and two others—Bezymianny and Klyuchevskaya—were mentioned earlier in February. In one overpass a NASA satellite captured four of these volcanoes in one narrow overpass, only 60 kilometers wide and 300 kilometers long. All of them exhibit plumes. I zoomed in on the most spectacular—Kizimen and Shiveluch—for our Natural Hazards section, but I’d like to share Klyuchevskaya (below) and the entire image—all 9,822 by 20,729 pixels of it (13 MB JPEG).
NASA Earth Observatory image by Robert Simmon, using data from the NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.
October 1st, 2010 by Robert Simmon
North and South America, August 9, 2010.
By Mark Robinson, LROC Team.
As LRO orbits the Moon every two hours sending down a stream of science data, it is easy to forget how close the Moon is to the Earth. The average distance between the two heavenly bodies is just 384,399 km (238,854 miles). Check your airline frequent flyer totals, perhaps you have already flown the distance to the Moon and back on a single airline!
LROC’s most recent Earth calibration sequence captured a magnificent view of the Americas with only minimal cloud cover. Contrast the current image with the NAC view taken last June, which revealed much of central Asia.
The Moon is a spectacular sight in the nighttime sky. Now imagine the Earth from the Moon, four times larger, a delicate blue, and it does not rise nor set. To astronauts, the Earth is a constant companion, at least on the nearside. Of course, on the farside you can never see the Earth.
The overarching goal of the LRO mission is to obtain the data needed to enable engineers and scientists to design the hardware and instruments to pick up lunar exploration where it was paused in December of 1972, after Apollo 17. LRO has now collected these data, so we are ready to move along the path of returning to the Moon! Will designs for lunar habitats include Earth windows? Certainly a human factor to consider! Are there any adverse psychological effects for future lunar explorers on the farside with no Earth overhead? What do you think? For now, we are happy to occasionally snap an image of the Earth as the NAC collects routine calibration data.
View the full-size image (4400 by 440 pixels) on the LROC gallery.
September 29th, 2010 by Robert Simmon
An astronaut took this photograph of dust obscuring the Taklamakan Desert, with the Tien Shan mountains in the distance, on September 5, 2010.
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