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Earth Matters

Explorer 1: The Beginning of American Space Science

January 24th, 2018 by Mike Carlowicz

This article was published by NASA’s Jet Propulsion Laboratory on January 23, 2018. NASA is beginning several months of commemoration of the beginning of the Space Age and the evolution of Earth science from space.

Sixty years ago next week, the hopes of Cold War America soared into the night sky as a rocket lofted skyward above Cape Canaveral, a soon-to-be-famous barrier island off the Florida coast.

The date was Jan. 31, 1958. NASA had yet to be formed, and the honor of this first flight belonged to the U.S. Army. The rocket’s sole payload was a javelin-shaped satellite built by the Jet Propulsion Laboratory in Pasadena, California. Explorer 1, as it would soon come to be called, was America’s first satellite.

“The launch of Explorer 1 marked the beginning of U.S. spaceflight, as well as the scientific exploration of space, which led to a series of bold missions that have opened humanity’s eyes to new wonders of the solar system,” said Michael Watkins, current director of JPL. “It was a watershed moment for the nation that also defined who we are at JPL.”

In the mid-1950s, both the United States and the Soviet Union were proceeding toward the capability to put a spacecraft in orbit. Yet great uncertainty hung over the pursuit. As the Cold War between the two countries deepened, it had not yet been determined whether the sovereignty of a nation’s borders extended upward into space. Accordingly, then-President Eisenhower sought to ensure that the first American satellites were not perceived to be military or national security assets.

In 1954, an international council of scientists called for artificial satellites to be orbited as part of a worldwide science program called the International Geophysical Year (IGY), set to take place from July 1957 to December 1958. Both the American and Soviet governments seized on the idea, announcing they would launch spacecraft as part of the effort. Soon, a competition began between the Army, Air Force and Navy to develop a U.S. satellite and launch vehicle capable of reaching orbit.

At that time, JPL, which was part of the California Institute of Technology in Pasadena, primarily performed defense work for the Army. (The “jet” in JPL’s name traces back to rocket motors used to provide “jet assisted” takeoff for Army planes during World War II.) In 1954, the laboratory’s engineers began working with the Army Ballistic Missile Agency in Alabama on a project called “Orbiter.” The Army team included Wernher von Braun (who would later design NASA’s Saturn V rocket) and his team of engineers. Their work centered around the Redstone Jupiter-C rocket, which was derived from the V-2 missile Germany had used against Britain during the war.

JPL’s role was to prepare the three upper stages for the launch vehicle, which included the satellite itself. These used solid rocket motors the laboratory had developed for the Army’s Sergeant guided missile. JPL would also be responsible for receiving and transmitting the orbiting spacecraft’s communications. In addition to JPL’s involvement in the Orbiter program, the laboratory’s then-director, William Pickering, chaired the science committee on satellite tracking for the U.S. launch effort overall.

The Navy’s entry, called Vanguard, had a competitive edge in that it was not derived from a ballistic missile program — its rocket was designed, from the ground up, for civilian scientific purposes. The Army’s Jupiter-C rocket had made its first successful suborbital flight in 1956, so Army commanders were confident they could be ready to launch a satellite fairly quickly. Nevertheless, the Navy’s program was chosen to launch a satellite for the IGY.

University of Iowa physicist James Van Allen, whose instrument proposal had been chosen for the Vanguard satellite, was concerned about development issues on the project. Thus, he made sure his scientific instrument payload — a cosmic ray detector — would fit either launch vehicle. Meanwhile, although their project was officially mothballed, JPL engineers used a pre-existing rocket casing to quietly build a flight-worthy satellite, just in case it might be needed.

The world changed on Oct. 4, 1957, when the Soviet Union launched a 23-inch (58-centimeter) metal sphere called Sputnik. With that singular event, the space age had begun. The launch resolved a key diplomatic uncertainty about the future of spaceflight, establishing the right to orbit above any territory on the globe. The Russians quickly followed up their first launch with a second Sputnik just a month later. Under pressure to mount a U.S. response, the Eisenhower administration decided a scheduled test flight of the Vanguard rocket, already being planned in support of the IGY, would fit the bill. But when the Vanguard rocket was, embarrassingly, destroyed during the launch attempt on Dec. 6, the administration turned to the Army’s program to save the country’s reputation as a technological leader.

Unbeknownst to JPL, von Braun and his team had also been developing their own satellite, but after some consideration, the Army decided that JPL would still provide the spacecraft. The result of that fateful decision was that JPL’s focus shifted permanently — from rockets to what sits on top of them.

The Army team had its orders to be ready for launch within 90 days. Thanks to its advance preparation, 84 days later, its satellite stood on the launch pad at Cape Canaveral Air Force Station in Florida.

The spacecraft was launched at 10:48 p.m. EST on Friday, Jan. 31, 1958. An hour and a half later, a JPL tracking station in California picked up its signal transmitted from orbit. In keeping with the desire to portray the launch as the fulfillment of the U.S. commitment under the International Geophysical Year, the announcement of its success was made early the next morning at the National Academy of Sciences in Washington, with Pickering, Van Allen and von Braun on hand to answer questions from the media.

Following the launch, the spacecraft was given its official name, Explorer 1. (In the following decades, nearly a hundred spacecraft would be given the designation “Explorer.”) The satellite continued to transmit data for about four months, until its batteries were exhausted, and it ceased operating on May 23, 1958.

Later that year, when the National Aeronautics and Space Administration (NASA) was established by Congress, Pickering and Caltech worked to shift JPL away from its defense work to become part of the new agency. JPL remains a division of Caltech, which manages the laboratory for NASA.

The beginnings of U.S. space exploration were not without setbacks — of the first five Explorer satellites, two failed to reach orbit. But the three that made it gave the world the first scientific discovery in space — the Van Allen radiation belts. These doughnut-shaped regions of high-energy particles, held in place by Earth’s magnetic field, may have been important in making Earth habitable for life. Explorer 1, with Van Allen’s cosmic ray detector on board, was the first to detect this phenomenon, which is still being studied today.

In advocating for a civilian space agency before Congress after the launch of Explorer 1, Pickering drew on Van Allen’s discovery, stating, “Dr. Van Allen has given us some completely new information about the radiation present in outer space….This is a rather dramatic example of a quite simple scientific experiment which was our first step out into space.”

Explorer 1 re-entered Earth’s atmosphere and burned up on March 31, 1970, after more than 58,000 orbits.

For more information about Explorer 1 and the 60 years of U.S. space exploration that have followed it, visit:

https://explorer1.jpl.nasa.gov

On This Date: The Bingham Canyon Landslide

April 10th, 2017 by Adam Voiland

NASA/EO-1/ALI/Jesse Allen and Robert Simmon. More info about this image here.

Four years ago today, one of the largest non-volcanic landslides in U.S. history began high on the northern wall of Utah’s Bingham Canyon mine. During two main bursts of activity that day, several million cubic meters of rock and soil careened deep into the mine’s pit.

This was a case where science and the right preparation saved lives. The company that runs the mine had installed an interferometric radar system months before the slide, and it prevented miners from being blindsided. With the radar system in place, mine operators detected changes in the stability of the pit’s walls well before the landslide occurred. When the slope finally gave way, all the workers in the pit had already been evacuated. Not one person was injured.

The image above was acquired by the Advanced Land Imager (ALI) on the Earth Observing-1 satellite on May 2, 2013. For more detailed and recent images of the mine pit, see the montage below. Photos A, B, and C — from Rio Tinto Kennecott — show an overview of the pit, the source area, and slide debris in the immediate aftermath of the event. D is an aerial image from the state government of Utah that shows the mine nine months before the landslide. E is part of the ALI satellite image above. F is a second aerial image taken in February 2014. By then, much of the debris had been removed and a new access road had been built.

The montage was originally published in March 2017 by the Journal of Geophysical Research as part of a study authored by Jeffrey Moore of Lawrence Livermore National Laboratory. The University of Utah wrote about the research in a recent blog post:

On April 10, at 9:30 p.m. and again at 11:05 p.m., the slope gave way and thundered down into the pit, filling in part of what had been the largest man-made excavation in the world. Later analysis estimated that the landslide was at the time the largest non-volcanic slide in recorded North American history. Now, University of Utah geoscientists have revisited the slide with a combined analysis of aerial photos, computer modeling, and seismic data to pick apart the details. The total volume of rock that fell during the slide was 52 million cubic meters, they report, enough to cover Central Park with 50 feet of rock and dirt. The slide occurred in two main phases, but researchers used infrasound recordings and seismic data to discover 11 additional landslides that occurred between the two main events. Modeling and further seismic analysis revealed the average speeds at which the hillsides fell: 81 miles per hour for the first main slide and 92 mph for the second, with peak speeds well over 150 mph.

The interferometric radar system is not the only safety technology in place at Bingham Canyon. Drones, GPS, and trained experts keep a vigilant eye out for signs of landslides at this mine. Technology and tactics like this  mean landslides cause very few injuries and deaths in the United States even though significant landslide potential exists in many parts of the country. As we recently reported, many other parts of the world (notably Africa and South America) are not nearly so fortunate.

Remembering Tohoku Earthquake

March 11th, 2016 by Adam Voiland

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On this day five years ago, the largest earthquake in modern Japanese history shook the mainland region of Tohoku. The tsunami that followed was devastating. Nearly 16,000 people were killed, and more than 127,000 buildings completely collapsed. The wave triggered power outages, explosions, and reactor meltdowns at a nuclear plant in Fukushima.

What is perhaps most tragic about the quake is that early-warning systems initially underestimated the magnitude of the event. If these systems had gotten it right, word may have spread more rapidly along Japan’s coast that a massive wave was fast approaching.

Five years later, seismology remains as one of the most unsettling fields of Earth science. As the New Yorker put it: “For seismologists, the Tohoku earthquake was a humbling reminder that our geophysical records offer only a peephole view of Earth’s behavior over time, and that our most advanced models for geological phenomena are cartoonish oversimplifications of nature.”

To learn more about the earthquake, see this gallery of NASA Earth Observatory images. Among the images included is the wave height map at the top of the page, and the closeup view of damage in the town of Rikuzentakata seen below.
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Best of the Archives: Dunes of the Great Bahama Bank

January 16th, 2014 by Adam Voiland

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Thirteen years ago, a satellite acquired this beautiful image (above) of light and sand playing off a portion of the ocean floor in the Bahamas. The caption that accompanied the image didn’t include many details, only noting that the image was acquired by the Enhanced Thematic Mapper Plus (ETM+) sensor on Landsat 7 and that, “tides and ocean currents in the Bahamas sculpted the sand and seaweed beds into these multicolored, fluted patterns in much the same way that winds sculpted the vast sand dunes in the Sahara Desert.”

An image as beautiful as this seemed like it deserved a bit more explanation, so I  grabbed a recent (January 9, 2014) scene of the same area captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. That image (below) shows a much broader view of the area. You can still see some details of the intricate network of dunes, but the MODIS image offers a much better sense of the regional geology.  For instance, you can easily see that the section of dunes shown in the first image (the white box in the lower image) is part of a much larger limestone platform called the Great Bahama Bank. Limestone is a sedimentary rock formed by the skeletal fragments of sea creatures, including corals and foraminifera, and this particular limestone platform has been accumulating since at least the Cretaceous Period. 

You can also see a sharp division between the shallow (turquoise) waters of the Great Bahama Bank and the much deeper (dark blue) parts of the ocean. The submarine canyon that separates Andros Island from Great Exuma Island is nearly cut off entirely from the ocean by the Great Bahama Bank, but not quite.  A connection to deep waters to the north gives the trench the shape of a tongue, earning the feature the name “Tongue of the Ocean.” At its lowest point, the floor of the Tongue of the Ocean is about 14,060 feet (4,285 meters) lower than Great Bahama Bank. The shallowest (lightest) parts of the the feature, in contrast, are just a few feet deep.

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From the Archives: Making Ice Cubes

November 19th, 2013 by Mike Carlowicz

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Last week, a city-state sized chunk of ice broke off of Pine Island Glacier (PIG), sending iceberg B-31 into a bay off West Antarctica. Though the formation of the 700 square-kilometer iceberg could be a purely natural event — the result of a floating ice tongue growing too long and losing its balance on the sea — some scientists suspect that changes in Pine Island Glacier are due to changing conditions below.

Five years ago this week, another block of ice broke off of the Antarctic Peninsula (radar image above from November 26, 2008). The seaward edge of Wilkins Ice Shelf spent much of 2008 breaking loose from the continent. Unlike PIG, Wilkins shattered and splintered into much smaller bits. And in that case, few doubted that global warming — or at least warming of the Antarctic Peninsula — played a major role.

NASA satellites are still tracking the last week’s PIG offspring. Check out these images from:

Best of the Archives: India During Diwali

November 6th, 2013 by Adam Voiland

Hindus are celebrating Diwali this week. That means cities and towns around the world—but particularly in South Asia—are ablaze with lamps, candles, and firecrackers. It’s also become a tradition (of sorts) to share a colorful image via social media that was supposedly taken by a satellite during Diwali. If that image turns up on your feed, be skeptical.

As we pointed out last year, that image is a composite created and colored back in 2003 by NOAA scientists to illustrate population growth over time. In reality, India during Diwali looks something more like the image you see at the bottom of this page. The fact is that any extra light produced during Diwali would be so subtle that it would be extremely difficult to detect from space.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite collected the data that was used to make the image below on November 12, 2012.  Read more about the fake Diwali image from Earthsky or USA Today. 

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Best of the Archives: Oh, Sandy

October 30th, 2013 by Mike Carlowicz

One year ago today, citizens of New Jersey, New York, Connecticut, and much of the northeastern United States woke up to flooded avenues and homes, wind-ravaged neighborhoods, blackouts, and ripped up trees, coastlines, and lives. In the dark, early hours of October 30, 2012, the VIIRS instrument on the Suomi NPP satellite caught this glimpse of the monster storm named Sandy, a hurricane that collided with two other weather fronts and merged into one of the most destructive storms in recorded American history.

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Our gallery of Sandy images conveys an abstract, distant sense of the event. In satellite images, the eye is drawn to the awesome and beautiful cloud forms; to the potent, organized march across the skies; to  the incredible scale of the storm. But the shoreline of my New Jersey childhood was nearly wiped clean, and a satellite can’t really show that. It’s not until you get down to the street level  such as the aerial photo below  that the human cost comes into better focus.

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The odds said Sandy shouldn’t happen; it was too late in the season, and too far north for a hurricane. But the odds of such storms seem to be changing as the world grows warmer and the weather grows a bit less predictable. Read our feature story on how storms may become less frequent but more destructive.

The Intergovernmental Panel on Climate Change has some good insights on anticipating and preparing for a future where extreme storms like Sandy could become more likely and more devastating. It should be required reading if you live near the coast.

Best of the Archives: Mud Trails from Fishing Trawlers

October 24th, 2013 by Adam Voiland

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Fourteen years ago, the Enhanced Thematic Mapper Plus on Landsat 7 acquired these images of mud trails off the coast of Louisiana. They were caused by bottom trawling in the Gulf of Mexico, a fishing technique that involves dragging large nets across the sea floor.

Bottom trawling is an efficient way to scoop up shrimp and squid, but that’s not all that ends up in the nets. As our earlier caption explained: “In addition to harvesting intended species, many trawls indiscriminately capture non-target species, like sea turtles, which are discarded. Trawling crushes or destroys the seafloor habitat that feeds and shelters marine life; the nets literally scrape the mud off the ocean bottom. As the mud resettles, it can smother surviving bottom-dwelling creatures.”

Some things have changed and some things have stayed the same since this image was acquired in 1999. In 2006, the National Oceanic and Atmospheric Administration prohibited bottom trawling off of most of the Pacific Coast of the United States. Other countriesincluding Norway, Canada, Australia, and New Zealandhave also taken steps to discourage the practice. Yet in many parts of the world, including the U.S. Gulf Coast, the practice persists. You can read more about bottom trawling in the Gulf of Mexico from Sky Truth, the Gulf of Mexico Fishery Management Council, and Science Daily.

Bottom trawling isn’t the only type of fishing visible from space. Read our new feature about the city of light that appears off the coast of southern Argentina.