One of the wonderful things about working for the Earth Observatory is that we often get first crack at examining imagery from satellites new and old. It’s been especially exciting to look at data from Landsat 8, a joint U.S. Geological Survey and NASA mission launched in February 2013.
But with new things comes new challenges. We’ve had some odd problems with the very intense memory demands of Landsat 8 imagery, for example. And when I saw the image below, I thought for sure I had stumbled on a processing error.
This is a natural-color, pan-sharpened image of the Elbe River near Wittenberg, Germany, obtained by Landsat 8 on May 6, 2013. I had obtained this to compare to a new acquisition from June 7, 2013, which showed major flooding in the Elbe.
Oh dear. Look at that ripple pattern along the river banks. Superficially, it looks a lot like a software processing error. New code I wrote: my error, right? In fact, at first glance, it looked a lot like Landsat data of a decade or so ago when the source files were being distributed with nearest-neighbor resampling–a technique used in remapping and resizing data which limits interactions between adjacent measures, something often useful in science measurements, but which causes jagged-looking edges. Since this was not the first time my code had done something unexpected, it was the obvious first place to look for the cause. The software failed me! Again!
However, a quick glance through the data files showed that, whatever was going on, it was coming from the source data: the same rippling showed up in all the bands. Ha! Someone else’s software had failed!
Because Landsat 8 is so new, it is easy to assume maybe I was not the only one having occasional processing problems with old software on new data. There was one more check I should have done before contacting customer service at USGS, but…
…I didn’t think of it. If you see something odd in imagery, it is always good to check reality. In this case, a quick zoomed-in view in Google Earth (as shown here) would have informed me that the jagged edges along the banks of the river in the imagery are real jagged edges along the banks of the river.
In hindsight, there were other clues. Notice that the jagged features are present in some places and not others. And notice that the rippled pattern along the banks bends and curves with the flow of the river. A processing artifact might only show up on very strongly contrasting features (the boundary between land and water here, for example), but would most likely be aligned consistently through the image. It wouldn’t appear and disappear like it does here, and it would probably be more regular. It would probably distort in the same direction every time it happened.
In the end, it turns out that all the new systems were working just fine and there really is a very oddly shaped series of features along the banks of the Elbe River near Wittenberg, presumably to stablize the banks of the river and control sediment flow.
But there’s not much they can do in the face of severe flooding.
Today’s guest post is from Kate Ramsayer of the NASA Earth Science News Team. Kate wrote the caption for today’s Image of the Day about El Paso and the mountains of data collected by Landsat over four decades.
When the first Landsat satellite — originally called the Earth Resources Technology Satellite (ERTS) — launched in 1972, it was no small feat to visualize the data it sent back and to conduct research with it.
“When ERTS was first launched, there was one cathode ray tube in the country that could take in the digital data and display an image,” said Jeff Masek, Landsat project scientist at NASA Goddard.
In the early years, satellite observations of the light reflected off of Earth were transmitted to receiving stations and mailed to processing centers. Computers translated the image data into photographic prints or transparencies that could be placed on light tables for interpretation. Alternatively, computers translated the numbers in each pixel into alpha-numeric symbols that were printed on large reams of paper. Analysts, often graduate students, could then color-in the symbols with crayon or magic markers. Standing on ladders over the colored-in data, they’d try to visualize the landscape represented by the maps.
“Things were pretty primitive in those days,” Masek said. “People say, ‘Why didn’t they produce a global land cover map in those first few years?’ They were lucky to be able to look at one image for a Ph.D. dissertation.”
Read more about the history of Landsat in “Landsat Looks and Sees.”
Here is the first published image from ERTS…nee, Landsat 1.
The following is a guest post from Erin Jones (pictured above), the scientific outreach lead for the Global Modeling and Assimilation Office at Goddard Space Flight Center. As a graduate student at Purdue University, she used to chase tornadoes.
June 2, 2013, started as most Sundays do. My alarm went off; I got out of bed; I came downstairs, and I turned on my computer. I logged on to facebook. A quick look at my news feed told me that this Sunday would not be the same as most Sundays:
Getting lots of rumors that veteran chasers were killed by the El Reno tornado. I really hope this is not real.
… just received the news of the possible passing of Tim, Carl and Paul. We are in total shock… God rest their souls if this is true.
Hopes that messages about Tim Samaras are not true… Bad news if this is true…
I put my hand to my chest.
The rumors were true. Tim Samaras, his son Paul, and his chase partner Carl Young were gone. They had been killed while chasing a storm on May 31 near El Reno, Oklahoma, when a large tornado hit their car and reduced it to scrap metal.
I was in shock.
The sad truth of the matter is that many in the community have thought for years that it was only a matter of time before a storm chaser was killed. Since the practice of storm chasing began over 50 years ago, not a single chaser had died in pursuit of a storm. Over the past several years, however, increased media coverage and TV shows like Storm Chasers have glamorized chasing and spurred the growth of an entire industry built around following storms.
The number of chasers has exploded, and it has made chasing for science more difficult and dangerous. I’ve seen it. I’ve felt what it’s like to be on a storm, just hoping that the circulation getting ready to pass over your head stays aloft because you’re stuck in chaser-induced gridlock and there’s no way you’d be able to escape if a tornado forms. I’ve known that fear. It’s like we have been on borrowed time.
As much as I dreaded the day when I would hear that a tornado had killed a storm chaser, I thought I was prepared for it. But nothing could have prepared me for what I heard on Sunday morning. Tim Samaras—a pillar of the chase community—was dead. He was a well-respected, veteran chaser. He wasn’t out for the thrill, and he wasn’t out to get the best picture or to take some extreme video. He was a serious scientist. And he was gone.
These questions have been at the forefront of the minds of many of my friends and colleagues over the past few days. As people begin to piece together accounts of what happened…as they process and analyze the data that were collected during the storm, a clearer picture is beginning to emerge. The tornado that hit near El Reno was more than 2.5 miles wide, making it the widest tornado ever recorded. It had a multiple vortex structure with wind speeds of up to 296 miles per hour. Toward the end of its life, it became occluded and turned northeast, deviating from its forecast path.
Tim Samaras and his crew had always chased safely. They knew what they were doing but it didn’t matter. Had they been caught off guard? Had they ended up stuck in traffic? Were they driving on unpaved roads that were difficult to navigate in storm conditions? Was the tornadic circulation so large that it was impossible for them to get to safety? We still don’t know.
Many of my friends were out there that day. By chance or circumstance, they all stationed themselves out of harm’s way. Three of them–Paul Robinson, Eddie Smith, and Jon Lutz–were several kilometers away from the tornado, collecting mobile Doppler radar data on the storm when it hit Tim Samaras. I asked them if they had any thoughts or stories they’d like to share about what happened.
“I’m not sure what to contribute,” Eddie said. “At the same time Paul, Jon, and I were high-fiving each other over our great positioning and the phenomenal data set we were recording, we were watching, in real-time, this thing kill our friends. How do you reconcile that?”
Jon reflected that “that thing could have killed any of us, depending on which way it turned.”
And Paul told me how he was struck by a sense of eerie irony when they ended up in Moore, Oklahoma, after fleeing the storm, where they then witnessed an EF-0 tornado disturb the same landscape that an EF-5 tornado had devastated just two weeks before.
We still don’t have a great understanding of how tornadoes form, and we still don’t know much about what the wind fields are like near the ground. Tim Samaras spent his career trying to answer these questions so that the losses due to tornadic storms might be minimized. When Tim left this world, his work was not done. It would be a disgrace to his memory if we were to stop trying to collect scientific data on severe storms and to retard the progress on tornado research that he so diligently strove for.
Earth Observatory reader Warren Bonesteel sent us this shot of mammatus clouds over Duncan, Oklahoma, on May 20, 2013. They were taken at about 7:00 p.m. CST, a few minutes after a large supercell storm passed. The same storm system spawned a violent tornado that devastated the nearby city of Moore. While most clouds form in rising air and have flat bottoms, mammatus clouds have pouch-like protrusions caused by sinking air that hang on their undersides.
Mammatus clouds can only form if the sinking air is cooler than the air around it. The sinking air must also have high water or ice content. Though they are often associated with thunderstorms, the clouds are harmless and usually form in pockets of turbulent air after the worst of a storm has passed. They are not an indicator that a tornado is about to hit. You can learn more about mammatus clouds from Astronomy Picture of the Day, Earth Science Picture of the Day, AccuWeather, CBC News, EarthSky, and UCAR.
Did you have other dramatic shots of this storm system that you would like to share? Please send them to email@example.com. I’ll add the best of what we receive to this post.
The photo below was taken on Sunday May 19, 2013, by Darren Purcell. It was taken in advance of the storm that hit Norman, Oklahoma.
On May 22, 2013, GOES-East, a key weather satellite that observes the eastern part of the United States stopped working normally. After initial efforts to revive the satellite failed, National Oceanic and Atmospheric Administration (NOAA) engineers have put the satellite in storage mode for troubleshooting.
Losing one of the two geostationary weather satellites that National Weather Service meteorologists rely upon could have serious consequences at any time, but that is especially true with the 2013 hurricane season just around the corner. Fortunately, NOAA had planned ahead. The agency always keeps a “spare” satellite in orbit, ready to spring into action when problems arise. On May 23, the spare satellite—GOES 14—was active and had started to acquire images.
When GOES-East experienced a similar technical problem in September 2012, we published the image above showing the field of view of all three weather satellites. GOES-15, which has served as GOES-West since December 2011, is on the left and orbits at 135 degrees west longitude; GOES-14, the spare, is in the middle and resides at 105 degrees west. GOES-13, the malfunctioning satellite that has served as GOES-East since April 2010, is on the right and sits at 75 degrees west. The top row of images shows visible images acquired by the three satellites on September 15, 2012. The lower row shows the field of view of each satellite.
Each month, Earth Observatory offers up a puzzling satellite image here on Earth Matters. The sixteenth puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, and why the scene is interesting. For instance, what do you think the horizontal line is on the upper part of the image? The tan areas below? The blue-black blotches on the right?
How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 300 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.
The prize. We can’t offer prize money for being the first to respond or for digging up the most interesting kernels of information. But, we can promise you credit and glory (well, maybe just credit). Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. In the credits, we’ll acknowledge the person who was first to correctly ID the image. We’ll also recognize people who offer the most interesting tidbits of information. Please include your preferred name or alias with your comment. If you work for an institution that you want us to recognize, please mention that as well.
Recent winners. If you’ve won the puzzler in the last few months, please sit on your hands for at least a few days to give others a chance to play.
“Who’d have thought that five months away from the planet would make you feel closer to people,” mused Canadian astronaut Chris Hadfield a few days before his return trip back to Earth. Along with two crew members, the commander of International Space Station Expedition 35 landed safely in Kazakhstan on May 13, 2013, via a Russian Soyuz space capsule.
What a tour it has been. After 2,336 orbits, 62 million miles traveled, Hadfield returns as a rock star of sorts. His recording of a cover of David Bowie’s “Space Oddity” quickly went viral this week (6 million+ views and counting). But it’s not just his skill with a guitar that has attracted attention. More than anything else, it has been Hadfield’s mastery of the camera—and Twitter—that has catapulted him to fame.
Hadfield isn’t the first astronaut to tweet from space. Mike Massimino did that in 2009. But the abundance and quality of Hadfield’s tweets has set a new standard. He spent several hours per day taking photographs from the Cupola, and with the help of his son Evan (back on Earth) posted the best of them to his feed.
The photos they shared didn’t seem to be raw. One of the Hadfields must have been tweaking the brightness and contrast of the images to make them pop. When paired with snappy, heartfelt captions, the photos proved irresistible. Hadfield’s online followers skyrocketed from about 20,000 when he went into space to more than 900,000 when he returned. Many of his images were retweeted thousands of times.
To celebrate the safe return of Expedition 35, I’ve posted fifteen of my favorites below. Thank you, Commander Hadfield, for the remarkable tour. And welcome home.
To some this may look like a sunset. But it’s a new dawn. pic.twitter.com/iVgyUihqEN
Australia. Jackson Pollock would have been even further inspired by seeing the Outback from orbit. pic.twitter.com/UHtp6lqp
The Richat Structure. A giant gazing eye upon the Earth. pic.twitter.com/Uqv9JSh17b
When I look at thunderstorms from above, I see faces. What do you see in the clouds? pic.twitter.com/IxSu5XUqGQ
I have no idea what this Brazilian outcrop looks like on the ground, but from orbit, it’s a brain. pic.twitter.com/QPRcdRGkov
Same land, different politics. The US – Mexican border, seen from space. pic.twitter.com/rsEnFX0enN
Spaceships glowing blue in the dawn as we leave Florida headed across the Atlantic. pic.twitter.com/GzEoCg2bb5
Crazed patchwork of farms in Central Asia, a monochromatic 3D hallucination in the snow. pic.twitter.com/PaKYxOn7fg
Morning jet traffic over San Francisco. pic.twitter.com/xgtLVjDD6G
Our Sun is immensely, unfathomably powerful. pic.twitter.com/j10CCpP6ya
Dubai, the Palm Island like a trilobite in the night. pic.twitter.com/RxBHEnSzst
Shadow play of cloud and mountain at sunset. pic.twitter.com/PRggJS7ZOe
The Moon ushering in the dawn over the Southeastern United States. pic.twitter.com/i3ETfHP79m
Not all of NASA’s rovers are headed to Mars. A new Earth science rover nicknamed GROVER started roaming Greenland’s ice sheet this week. The autonomous, solar-operated robot carries a ground-penetrating radar that will be used to examine how snow is accumulating on the Greenland ice pack. Its findings could help scientists understand how the massive ice sheet gains and loses ice.
The GROVER team, led by Goddard Space Flight Center glaciologist Lora Koenig, arrived in Summit Camp, the highest spot in Greenland, on May 6, 2013. After loading and testing the rover’s radar and fixing a minor communications glitch, tests began on the ice on May 8, in spite of winds that blew up to 23 miles (37 kilometers) per hour and temperatures that were as low as -22 degrees Fahrenheit (-30 degrees Celsius).
The tank-like GROVER prototype stands six feet (two meters) tall, including its solar panels. It weighs about 800 pounds and traverses the ice on two repurposed snowmobile tracks. The robot is powered entirely by solar energy, so it can operate in pristine polar environments without adding to air pollution. The panels are mounted in an inverted V, allowing them to collect energy from the sun and sunlight reflected off the ice sheet.
Thanks to everybody who offered answers to our five puzzlers last week. Congratulations to Christina Stiefel for solving Puzzler #5, Alan Wessman for solving Puzzler #3, and Angie Connelly for solving Puzzler #2! Honorable mention to Marcus Scherer for nearly solving Puzzler #1.
- Puzzler #1 showed undisturbed rainforest canopy in Brazil in part of Pará centered near 0° 58′ 37.1994″ S, 56° 42′ 39.5994″ W.
- Puzzler #2 showed two unnamed glacial lakes in Tibet’s Ngari Prefecture centered near 30° 20′ 31.63″ N, 84° 35′ 26.74″ E.
- Puzzler #3 showed a gorge formed by the Katherine River in Australia’s Northern Territory near the entrance of Nitmiluk National Park; it was centered near 4° 18′ 55.929″ S, 132° 25′ 31.1622″ E.
- Puzzler #4 showed salt pans in the floodplain of the Zambezi River centered near 15° 23′ 28.0638″ S, 23° 21′ 7.5528″ E in Zambia’s Western Province.
- Puzzler #5 showed Thetford Forest in southeastern Britain.
Each month, Earth Observatory offers up a puzzling satellite image here on Earth Matters. In celebration of Earth Month 2013, we’re upping the ante. We are going to release a new puzzler image every day this week. The fifth image is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, and why the scene is interesting. We’ll post the answer to all five puzzlers at 6 p.m. EST on Friday, April 26.
How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.
The prize. We can’t offer prizes, but we can promise you credit and glory (well, maybe just credit). Later this week when we post annotated and captioned versions of the puzzler images as our Image of the Day, we will acknowledge the people who were first to correctly ID the images. We’ll also recognize people who offer the most interesting tidbits of information. Please include your preferred name or alias with your comment. If you work for an institution that you want us to recognize, please mention that as well.
Recent winners. If you’ve won the puzzler in the last few months, look at this week as a new challenge — can you get all five image locations?