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Landslides Can Cause More Landslides

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One might think that if there was already a landslide in a particular location that there’d be nothing left to make another landslide in the future. Regrettably that is not always the case. Indeed, in some geologic settings evidence of a preexisting landslide plays a role in the mapping of future landslide hazards. The deadliest individual landslides in the U.S. recently were in places where there had previously been a landslide. In the small beach community of La Conchita, CA, just south of Santa Barbara along Highway 101, a landslide occurred in 1995 followed by a debris flow in 2005, killing 10 people and damaging 36 homes. In Oso, WA situated next to the North Fork of the Stillaguamish River about 50 miles SW of Seattle, a 2006 landslide was reactivated in 2014 as a debris-avalanche flow that killed 43 people and damaged private property and local highways. A few months later a large rock avalanche near the remote town of Collbran, Colorado occurred from the location of a preexisting rockslide, resulting in the deaths of 3 people. These are just a few examples of many repeat landslides that have been observed.

(Map of Puget Sound Washington, showing the location of the field site in Mukilteo. The gray hillshade inset shows a digital elevation map with the location of the two hillslope monitoring sites, labelled LS and VH.)

USGS landslide scientists Ben Mirus, Joel Smith, and Rex Baum have been studying the coastal bluffs of Puget Sound, WA near Mukilteo where landslides often interrupt railway service. They instrumented two contrasting hillslopes: a steep but stable slope with dense vegetation, and another nearby slope that had experienced a recent landslide. They installed various sensors at 5 locations down the two slopes and waited for rain. They monitored the slopes and collected data for one year and then analyzed what they had. They were curious whether their data might show why landslides were happening in the same place they had before, instead of on nearby slopes that appeared to be just as likely, if not more likely, to slide.

(Topography and aerial imagery of the two slopes LS and VH with locations of the monitoring instrumentation. The top slope, LS, is the one with a previous landslide, and the bottom slope, VH, is the one without a landslide.)

From their measurements, they were able to tell that there were a couple of reasons why the no-landslide location remained stable compared to the preexisting landslide location that remained unstable. Not only did the non-landslide slope have roots from vegetation that stabilized the soil, but also the vegetated slope drained better after rainstorms, shedding the water that would otherwise make the slope more unstable and landslide-prone. The preexisting landslide slope, on the other hand, with less vegetation and roots, had more unstable soil made even more so by the moisture that stayed in the soil after a rainfall, rather than draining away. Repeated rainfalls added more and more moisture to the slope, increasing the instability and potential for a landslide during the wet season.

So despite intuition that a landslide might mitigate further landslides, the disruption by a landslide can actually create a situation that makes the slope even more unstable and prone to further landsliding.

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Modeling Landslide Threats in Near Realtime

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For the first time, scientists can look at landslide threats anywhere around the world in near real-time, thanks to satellite data and a new model developed by NASA. The model (Landslide Hazard Assessment for Situational Awareness (LHASA)), developed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, estimates potential landslide activity triggered by rainfall. Rainfall is the most widespread trigger of landslides around the world. If conditions beneath Earth’s surface are already unstable, heavy rains act as the last straw that causes mud, rocks or debris or all combined – to move rapidly down mountains and hillsides.

(A new model has been developed to look at how potential landslide activity is changing around the world. A global Landslide Hazard Assessment model for Situational Awareness (LHASA) has been developed to provide an indication of where and when landslides may be likely around the world every 30 minutes. Credits: NASA’s Goddard Space Flight Center/ Joy Ng)

The model is designed to increase our understanding of where and when landslide hazards are present and improve estimates of long-term patterns. “Landslides can cause widespread destruction and fatalities, but we really don’t have a complete sense of where and when landslides may be happening to inform disaster response and mitigation,” said Dalia Kirschbaum, a landslide expert at Goddard and co-author of the study. “This model helps pinpoint the time, location and severity of potential landslide hazards in near real-time all over the globe. Nothing has been done like this before.”

The model estimates potential landslide activity by first identifying areas with heavy, persistent and recent precipitation. Rainfall estimates are provided by a multi-satellite product developed by NASA using the NASA and Japan Aerospace Exploration Agency’s Global Precipitation Measurement (GPM) mission, which provides precipitation estimates around the world every 30 minutes. The model considers when GPM data exceeds a critical rainfall threshold looking back at the last seven days.

Landslide changes

(This animation shows the potential landslide activity by month averaged over the last 15 years as evaluated by NASA’s Landslide Hazard Assessment model for Situational Awareness model. Here, you can see landslide trends across the world. Credits: NASA’s Goddard Space Flight Center / Scientific Visualization Studio)

In places where precipitation is unusually high, the model then uses a susceptibility map to determine if the area is prone to landslides. This global susceptibility map is developed using five features that play an important role in landslide activity: if roads have been built nearby if trees have been removed or burned, if a major tectonic fault is nearby, if the local bedrock is weak and if the hillsides are steep. If the susceptibility map shows the area with heavy rainfall is vulnerable, the model produces a “nowcast” identifying the area as having a high or moderate likelihood of landslide activity. The model produces new nowcasts every 30 minutes.

“The model has been able to help us understand immediate potential landslide hazards in a matter of minutes,” said Thomas Stanley, a landslide expert with the Universities Space Research Association at Goddard and co-author of the study. “It also can be used to retroactively look at how potential landslide activity varies on the global scale seasonally, annually or even on decadal scales in a way that hasn’t been possible before.”

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GPM Mission

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May the Forest Be With You: GEDI Moves Toward Launch to Space Station

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A first-of-its-kind laser instrument designed to map the world’s forests in 3-D is moving toward an earlier launch to the International Space Station than previously expected. The Global Ecosystem Dynamics Investigation – or GEDI, pronounced like “Jedi,” of Star Wars fame – the instrument is undergoing final integration and testing this spring and summer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The instrument is expected to launch aboard SpaceX’s 16th commercial resupply services mission, targeted for late 2018. GEDI is being led by the University of Maryland, College Park; the instrument is being built at NASA Goddard.

“Scientists have been planning for decades to get comprehensive information about the structure of forests from space to deepen our understanding of how this structure impacts carbon resources and biodiversity across large regions and even globally, as well as a host of other science issues,” said Ralph Dubayah, GEDI principal investigator and a professor of geographical sciences at the University of Maryland. “This is why seeing the instrument built and racing toward launch is so exciting.” From its perch on the exterior of the orbiting laboratory, GEDI will be the first space-borne laser instrument to measure the structure of Earth’s tropical and temperate forests in high resolution and three dimensions. These measurements will help fill in critical gaps in scientists’ understanding of how much carbon is stored in the world’s forests, the potential for ecosystems to absorb rising concentrations of carbon dioxide in Earth’s atmosphere, and the impact of forest changes on biodiversity.

GEDI will accomplish its science goals through an ingenious use of light. The instrument is a lidar, which stands for light detection and ranging. It captures information by sending out laser pulses and then precisely measuring the light that is reflected back.

(From its perch on the exterior of the orbiting laboratory, GEDI will be the first space-borne laser instrument to measure the structure of Earth’s tropical and temperate forests in high resolution and three dimensions. Credits: NASA’s Goddard Space Flight Center)

GEDI’s three lasers will produce eight ground tracks – two of the lasers will generate two ground tracks each, and the third will generate four. As the space station and GEDI orbit Earth, laser pulses will reflect off clouds, trees and the planet’s surface. While the instrument will gather height information about everything in its path, it is specifically designed to measure forests. The amount and intensity of the light that bounces back to GEDI’s telescope will reveal details about the height and density of trees and vegetation, and even the structure of leaves and branches within a forest’s canopy.

NASA has flown multiple Earth-observing lidars in space, notably the ICESat (Ice, Cloud and land Elevation Satellite) and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) missions. But GEDI will be the first to provide high-resolution laser ranging of Earth’s forests.

“GEDI originally was scheduled to launch aboard a resupply mission in mid-2019, but the team at Goddard who is building and testing GEDI was always on track to deliver a finished instrument by the fall of this year,” said Project Manager Jim Pontius, making the move to an earlier resupply mission feasible. The team is now preparing to put GEDI through a battery of pre-launch tests to ensure it is ready to withstand the rigours of launch and operating in space.

NASA selected the proposal for GEDI in 2014 through the Earth Venture Instrument program, which is run by NASA’s Earth System Science Pathfinder (ESSP) office. ESSP oversees a portfolio of projects ranging from satellites, instruments on the space station, and suborbital field campaigns on Earth that are designed to be lower-cost and more focused in scope than larger, free-flying satellite missions.

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The Saga of Indian Remote Sensing Satellite System

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IRS-1A, the first of the series of indigenous state-of-art operating remote sensing satellites, was successfully launched into a polar sun-synchronous orbit on March 17, 1988, from the Soviet Cosmodrome at Baikonur.

The successful launch of IRS-1A was one of the proudest moments for the entire country, which depicted the maturity of the satellite to address the various requirements for managing natural resources of the nation. Its LISS-I had a spatial resolution of 72.5 meters with a swath of 148 km on the ground.  LISS-II had two separate imaging sensors, LISS-II A and LISS-II B, with the spatial resolution of 36.25 meters each and mounted on the spacecraft in such a way to provide a composite swath of 146.98 km on the ground. The IRS-1A satellite, with its LISS-I and LISS-II sensors, quickly enabled India to map, monitor and manage its natural resources at coarse and medium spatial resolutions. The operational availability of data products to the user organisations further strengthened the operationalisation of remote sensing applications and management in the country.

IRS-1A was followed by the launch of IRS-1B, an identical satellite, in 1991. IRS-1A and 1B in tandem provided 11-day repetivity. These two satellites in the IRS series have been the workhorses for generating natural resources information in a variety of application areas, such as agriculture, forestry, geology and hydrology etc.

From then onwards, series of IRS spacecraft was launched with enhanced capabilities in payloads and satellite platforms. The whole gamut of the activities from the evolution of IRS missions by identifying the user requirements to the utilisation of data from these missions by user agencies is monitored by National Natural Resources Management System (NNRMS), which is the nodal agency for natural resources management and infrastructure development using remote sensing data in the country.

IRS-1A being lowered into Thermovac Chamber for Simulation Tests at ISRO Satellite Centre, Bangalore (1987-88)

Apart from meeting the general requirements, definition of IRS missions based on specific thematic applications like natural resources monitoring, ocean and atmospheric studies and cartographic applications resulted in the realisation of theme based satellite series, namely, (i) Land/water resources applications (RESOURCESAT series and RISAT series); (ii) Ocean/atmospheric studies (OCEANSAT series, INSAT-VHRR, INSAT-3D, Megha-Tropiques and SARAL); and (iii) Large-scale mapping applications (CARTOSAT series).

IRS-1A development was a major milestone in the IRS programme. On this occasion of 30 years of IRS-1A and fruitful journey of Indian remote sensing programme, it is important to look back at the achievements of Indian Space Programme particularly in remote sensing applications, wherein India has become a role-model for the rest to follow.  Significant progress continued in building and launching the state-of-the-art Indian Remote Sensing Satellite as well as in the operational utilisation of the data in various applications to the nation.

The “VOSTOK” ready for Lift-off with IRS-1A on board (March 17, 1988)

Today, the array of Indian Earth Observation (EO) Satellites with imaging capabilities invisible, infrared, thermal and microwave regions of the electromagnetic spectrum, including hyperspectral sensors, have helped the country in realising major operational applications. The imaging sensors have been providing spatial resolution ranging from 1 km to better than 1m; repeat observation (temporal imaging) from 22 days to every 15 minutes and radiometric ranging from 7 bit to 12 bit, which has significantly helped in several applications at the national level. In the coming years, the Indian EO satellites are heading towards further strengthened and improved technologies, taking cognizance of the learnings/ achievements made in the yesteryears, while addressing newer observational requirements and the technological advancements including high agility spacecraft.

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Where do old satellites go when they die?

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Like every other machine, satellites do not last forever. Whether their job is to observe weather, measure greenhouse gases in the atmosphere, or point away from Earth to study the stars, eventually all satellites grow old, wear out, and die, just like old washing machines and vacuum cleaners.Cartoon of old, worn out spacecraft, with long grey beard and patches on solar panels.

So what happens when a trusty satellite’s time has come? These days there are two choices, depending on how high the satellite is. For the closer satellites, engineers will use its last bit of fuel to slow it down. That way, it will fall out of orbit and burn up in the atmosphere.

The second choice is to send the satellite even farther away from Earth. It can take a lot of fuel for a satellite to slow down enough to fall back into the atmosphere. That is especially true if a satellite is in a very high orbit. For many of these high satellites, it takes less fuel to blast it farther into space than to send it back to Earth.

Burning metal and “spacecraft cemeteries”

Getting rid of the smaller satellites in low orbits is simple. The heat from the friction of the air burns up the satellite as it falls toward Earth at thousands of miles per hour. Ta-da! No more satellite.

What about bigger things like space stations and larger spacecraft in low orbit? These objects might not entirely burn up before reaching the ground. There is a solution—spacecraft operators can plan for the final destination of their old satellites to make sure that any debris falls into a remote area. This place even has a nickname—the Spacecraft Cemetery! It’s in the Pacific Ocean and is pretty much the farthest place from any human civilization you can find.Simple map of Pacific Ocean and surround land masses. Area in South Pacific is circled in red and labeled spacecraft cemetery.

(Image: Spacecraft cemetery in the South Pacific Ocean, far from where anyone lives. Source: NASA)

“Graveyard orbits”

What about those higher satellites we blast farther away? Those we send into a “graveyard orbit.” This is an orbit almost 200 miles farther away from Earth than the farthest active satellites. And it’s a whopping 22,400 miles above Earth!

So is that the end of it for these far-away satellites? As far as you and I are concerned it is! However, some of these satellites will remain in orbit for a very, very long time. Perhaps someday in the future, humans may need to send “space garbage trucks” to clean these up. But for now, at least, they will be out of the way.

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Laser Scans Reveal Maya “Megalopolis” Below Guatemalan Jungle

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In what’s being hailed as a “major breakthrough” in Maya archaeology, researchers have identified the ruins of more than 60,000 houses, palaces, elevated highways, and other human-made features that have been hidden for centuries under the jungles of northern Guatemala.

Using a revolutionary technology known as LiDAR (short for “Light Detection And Ranging”), scholars digitally removed the tree canopy from aerial images of the now-unpopulated landscape, revealing the ruins of a sprawling pre-Columbian civilization that was far more complex and interconnected than most Maya specialists had supposed.

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(Image: Laser technology known as LiDAR digitally removes the forest canopy to reveal ancient ruins, showing that Maya cities such as Tikal were much larger than ground-based research had suggested. Source: National Geographic)

The project mapped more than 800 square miles (2,100 square kilometres) of the Maya Biosphere Reserve in the Petén region of Guatemala, producing the largest LiDAR data set ever obtained for archaeological research.

The results suggest that Central America supported an advanced civilization that was, at its peak some 1,200 years ago, more comparable to sophisticated cultures such as ancient Greece or China than to the scattered and sparsely populated city-states that ground-based research had long suggested.

In addition to hundreds of previously unknown structures, the LiDAR images show raised highways connecting urban centres and quarries. Complex irrigation and terracing systems supported intensive agriculture capable of feeding masses of workers who dramatically reshaped the landscape.

The ancient Maya never used the wheel or beasts of burden, yet “this was a civilization that was literally moving mountains,” said Marcello Canuto, a Tulane University archaeologist and National Geographic Explorer who participated in the project.

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PSLV-C40 Succesfully Launches Cartosat-2 Series Satellite

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India’s Polar Satellite Launch Vehicle, in its 42nd flight (PSLV-C40), has launched the 710 kg Cartosat-2 Series Satellite for earth observation and 30 co-passenger satellites together weighing about 613 kg at lift-off. PSLV-C40 was launched from the First Launch Pad (FLP) of Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota. In its first mission of 2018, the Indian Space Research Organisation (ISRO) successfully launched its 100th satellite. The mission comes a little over four months after the space agency’s unsuccessful launch of IRNSS-1H. Prime Minister Narendra Modi, congratulating ISRO for its success, said the launch signifies the bright future of India’s space programme.

(PSLV-C40 on First Launch Pad – Evening View. Source: ISRO)

The co-passenger satellites comprise one Microsatellite and one Nanosatellite from India as well as 3 Microsatellites and 25 Nanosatellites from six countries, namely, Canada, Finland, France, Republic of Korea, UK and USA. The total weight of all the 31 satellites carried onboard PSLV-C40 is about 1323 kg.

The 28 International customer satellites are being launched as part of the commercial arrangements between Antrix Corporation Limited (Antrix), a Government of India company under Department of Space (DOS), the commercial arm of ISRO and the International customers.

Cartosat-2 Series Satellite is the primary satellite carried by PSLV-C40. This remote sensing satellite is similar in configuration to earlier satellites in the series and is intended to augment data services to the users.

The imagery sent by satellite will be useful for cartographic applications, urban and rural applications, coastal land use and regulation, utility management like road network monitoring, water distribution, creation of land use maps, change detection to bring out geographical and manmade features and various other Land Information System (LIS) as well as Geographical Information System (GIS) applications.

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