A ground-penetrating radar instrument that NASA helped develop for the European Space Agency’s Mars Express orbiter has completed a five-month campaign of observing subsurface layering in the north polar ice cap of Mars. The campaign is a highlight of the orbiter’s extended mission. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) made observations from altitudes as low as about 233 miles (375 kilometers) during several hundred passes over the pole. The MARSIS team is analyzing the data and plans to publish findings.

More…

The very first stars in our universe were not the behemoths scientists had once thought, according to new simulations performed at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

Astronomers “grew” stars in their computers, mimicking the conditions of our primordial universe. The simulations took weeks. When the scientists’ concoctions were finally done, they were shocked by the results — the full-grown stars were much smaller than expected.

Until now, it was widely believed that the first stars were the biggest of all, with masses hundreds of times that of our sun. The new research shows they are only tens of times the mass of sun; for example, the simulations produced one star that was as little as 43 solar masses.

“The first stars were definitely massive, but not to the extreme we thought before,” said Takashi Hosokawa, an astronomer at JPL and lead author of the new study, appearing online Friday, Nov. 11 in the journal Science. “Our simulations reveal that the growth of these stars is stunted earlier than expected, resulting in smaller final sizes.”

The early universe consisted of nothing more than thin clouds of hydrogen and helium atoms. A few hundred million years after its birth, the first stars began to ignite. How these first stars formed is still a mystery.

Astronomers know that all stars form out of collapsing clouds of gas. Gravity from a growing “seed” at the center of the cloud attracts more and more matter. For so-called normal stars like our sun, this process is aided by heavier elements such as carbon, which help to keep the gas falling onto the budding star cool enough to collapse. If the cloud gets too hot, the gas expands and escapes.

But, in the early universe, stars hadn’t yet produced heavy elements. The very first stars had to form out of nothing but hydrogen and helium. Scientists had theorized that such stars would require even more mass to form, to compensate for the lack of heavy elements and their cooling power. At first, it was thought the stars might be as big as one thousand times the mass of our sun. Later, the models were refined and the first stars were estimated to be hundreds of solar masses.

“These stars keep getting smaller and smaller over time,” said Takashi. “Now we think they are even less massive, only tens of solar masses.”

The team’s simulations reveal that matter in the vicinity of the forming stars heats up to higher temperatures than previously believed, as high as 50,000 Kelvin (90,000 degrees Fahrenheit), or 8.5 times the surface temperature of the sun. Gas this hot expands and escapes the gravity of the developing star, instead of falling back down onto it. This means the stars stop growing earlier than predicted, reaching smaller final sizes.

“This is definitely going to surprise some folks,” said Harold Yorke, an astronomer at JPL and co-author of the study. “It was standard knowledge until now that the first stars had to be extremely massive.”

The results also answer an enigma regarding the first stellar explosions, called supernovae. When massive stars blow up at the end of their lives, they spew ashes made of heavier elements into space. If the very first stars were the monsters once thought, they should have left a specific pattern of these elements imprinted on the material of the following generation of stars. But, as much as astronomers searched the oldest stars for this signature, they couldn’t find it. The answer, it seems, is that it simply is not there. Because the first stars weren’t as massive as previously thought, they would have blown up in a manner akin to the types of stellar explosions that we see today.

“I am sure there are more surprises in store for us regarding this exciting period of the universe,” said Yorke. “NASA’s upcoming James Webb Space Telescope will be a valuable tool to observe this epoch of early star and galaxy formation.”

More…

NASA’s Cassini spacecraft successfully completed its closest-ever pass over Saturn’s moon Dione on Monday, Dec. 12, slaloming its way through the Saturn system on its way to tomorrow’s close flyby of Titan. Cassini is expected to glide about 2,200 miles (3,600 kilometers) over the Titan surface on Dec. 13.

In the selection of the raw images obtained during the Cassini Dione flyby, Dione is sometimes joined by other moons. Mimas appears just beyond the dark side of Dione in one view. In another view, Epimetheus and Pandora appear together, along with Saturn’s rings.

This Dione encounter was intended primarily for Cassini’s composite infrared spectrometer and radio science subsystem. However, the imaging team did capture views of the distinctive, wispy fractures on the side of Dione that always trails in its orbit around Saturn. It also obtained images of a ridge called Janiculum Dorsa on the hemisphere of Dione that always leads in its orbit around Saturn. While other flybys produced more detailed views of the surface, the best resolved images from this flyby have scales ranging from about 1,100 feet (350 meters) to about 1,600 feet (500 meters) per pixel. Janiculum Dorsa will be imaged by Cassini at higher resolution in May 2012.

All of Cassini’s raw images can be seen at http://saturn.jpl.nasa.gov/photos/raw/ .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena manages the mission for the agency’s Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations team is based at the Space Science Institute in Boulder, Colo. JPL is a division of Caltech.

More…

NASA transferred title and ownership of space shuttle Enterprise to the Intrepid Sea, Air & Space Museum during a ceremony on Sunday, Dec. 11, at the museum in New York City. The transfer is the first step toward Intrepid receiving Enterprise in the spring of 2012.

“NASA is proud to transfer the title of space shuttle Enterprise to the Intrepid Sea, Air & Space Museum,” said NASA Administrator Charles F. Bolden. “The U.S.S. Intrepid had a rich history with NASA’s mission, and Enterprise – the pathfinder for the Space Shuttle Program – belongs in this historic setting. Enterprise, along with the rest of our shuttle fleet, is a national treasure and it will help inspire the next generation of explorers as we begin our next chapter of space exploration.”

Bolden announced April 12 that Intrepid was one of four institutions nationwide to receive a shuttle. Enterprise, which was the prototype vehicle and used in NASA’s approach and landings tests, will move from the Smithsonian National Air & Space Museum’s Udvar-Hazy Center to New York. The shuttle will be flown from Washington to JFK International Airport atop NASA’s 747 Shuttle Carrier Aircraft. It then will be transported during the summer of 2012 by barge to the Intrepid museum complex located at Pier 86 of the Hudson River Park, and placed on the Intrepid’s flight deck under a protective covering. The public will have the ability to see the shuttle while visiting the museum.

At the Dec. 11 ceremony, NASA Deputy Administrator Lori Garver said, “As we take our first steps on a path toward a new era of space exploration, we want to ensure that the treasures of our past achievements inspire generations of leaders – the people who will visit asteroids, walk on Mars and launch the next science satellites to explore our solar system and peer beyond it. It’s NASA’s pleasure to transfer to Intrepid the title to the space shuttle Enterprise. With the last flight of the Space Shuttle Program in July, the shuttle era came to an end, but that won’t stop these marvelous spacecraft from inspiring millions of people from around the world who will visit them in the geographically diverse areas that will house them. The orbiters won’t stop being part of the fabric of America.”

Enterprise rolled out of the Palmdale, Calif., manufacturing facility in September, 1976 and was used to test critical phases of landing and other aspects of shuttle preparations. The Approach and Landing Test, or ALT, program involved both ground tests and flight tests. Enterprise conducted 16 flight tests, from taxi to active free flight. The ground tests included taxi tests of the 747 shuttle carrier aircraft with the Enterprise mated to it to determine structural loads and responses and assess ground handling and control characteristics up to flight takeoff speed. The taxi tests also validated 747 steering and braking with the orbiter attached. A ground test of orbiter systems followed the unmanned captive tests. All orbiter systems were activated as they would be in atmospheric flight in final preparation for the manned captive flight phase. Five captive unmanned flights of the Enterprise mounted on its carrier with its systems inert were conducted to assess the structural integrity and performance handling qualities of the mated craft.

Three manned captive flights followed with astronauts operating the orbiter’s flight control systems while the Enterprise remained atop the 747. These flights were designed to exercise and evaluate all systems in the flight environment in preparation for the free flights.

NASA astronauts Fred Haise, Gordon Fullerton, Joe Engle and Dick Truly took turns flying the 150,000-pound spacecraft from February through November 1977 and demonstrated that the orbiter could fly in the atmosphere and land like an airplane.

At Marshall Space Flight Center between March 1978 and March 1979, Enterprise was mated with the external tank and solid rocket boosters and was subjected to a series of vertical ground vibration tests.

At Kennedy Space Center, it was brought to the launch complex, stacked on the mobile launch platform and used to train for maintenance and crew escape procedures.

In later years, Enterprise made an appearance at the Paris Air Show, with stops in Germany, England, Italy and Canada. Enterprise also was put on display in April 1984 at the World’s Fair in New Orleans. Enterprise has been to more NASA centers and other places around the world than any other orbiter. In 1985, NASA transferred Enterprise to the National Air & Space Museum.

More…

In 16 years of data observations, the Solar Heliophysics Observatory (SOHO) — a joint European Space Agency and NASA mission –- made an unexpected claim for fame: the sighting of new comets at an alarming rate. SOHO has spotted over 2100 comets, most of which are from what’s known as the Kreutz family, which graze the solar atmosphere where they usually evaporate completely.

But on December 2, 2011, the discovery of a new Kreutz-family comet was announced. This comet was found the old-fashioned way: from the ground. Australian astronomer Terry Lovejoy spotted the comet, making this the first time a Kreutz comet has been found through a ground-based telescope since the 1970′s. The comet has been designated C/2011 W3 (Lovejoy).

Discovering a comet before it moves into view of space-based telescopes, gives scientists the opportunity to prepare the telescopes for the best possible observations. Indeed, since comet Lovejoy was visible from the ground, scientists have high hopes that this might be an exceptionally bright comet, making it all the easier to view and study. (Some Kreutz comets –- such as Ikeya-Seki in 1965 — are so bright they can be seen with the naked eye in the daytime, though this is extremely rare.)

The comet moved into view of the Solar Terrestrial Relations Observatory (STEREO) on Monday, December 12. It should be visible in SOHO by Wednesday, Dec 14.

Next up is Hinode, which will make observations at about 6 p.m. ET on Dec 15, as the comet moves towards its closest approach to the sun. Hinode’s solar optical telescope will take the highest resolution images of this close approach. As the comet passes through the sun’s atmosphere, the corona, an increase in particle collisions may produce X-rays, so Hinode may also capture X-ray images of the comet.

The comet will likely pass within some 87,000 miles of the sun, and disappear behind the northwest limb of the sun shortly after it is seen by Hinode.

More…

As parts of Central America and the U.S. Southwest endure some of the worst droughts to hit those areas in decades, scientists have unearthed new evidence about ancient dry spells that suggest the future could bring even more serious water shortages. Three researchers speaking at the annual meeting of the American Geophysical Union in San Francisco on Dec. 5, 2011, presented new findings about the past and future of drought.

Pre-Columbian Collapse

Ben Cook, a climatologist affiliated with NASA’s Goddard Institute for Space Studies (GISS) and Columbia University’s Lamont-Doherty Earth Observatory in New York City, highlighted new research that indicates the ancient Meso-American civilizations of the Mayans and Aztecs likely amplified droughts in the Yucatán Peninsula and southern and central Mexico by clearing rainforests to make room for pastures and farmland.

Converting forest to farmland can increase the reflectivity, or albedo, of the land surface in ways that affect precipitation patterns. “Farmland and pastures absorb slightly less energy from the sun than the rainforest because their surfaces tend to be lighter and more reflective,” explained Cook. “This means that there’s less energy available for convection and precipitation.”

Cook and colleagues used a high-resolution climate model developed at GISS to run simulations that compared how patterns of vegetation cover during pre-Columbian (before 1492 C.E.) and post-Columbian periods affected precipitation and drought in Central America. The pre-Columbian era saw widespread deforestation on the Yucatán Peninsula and throughout southern and central Mexico. During the post-Columbian period, forests regenerated as native populations declined and farmlands and pastures were abandoned.

Cook’s simulations include input from a newly published land-cover reconstruction that is one of the most complete and accurate records of human vegetation changes available. The results are unmistakable: Precipitation levels declined by a considerable amount — generally 10 to 20 percent — when deforestation was widespread. Precipitation records from stalagmites, a type of cave formation affected by moisture levels that paleoclimatologists use to deduce past climate trends, in the Yucatán agree well with Cook’s model results.

The effect is most noticeable over the Yucatán Peninsula and southern Mexico, areas that overlapped with the centers of the Mayan and Aztec civilizations and had high levels of deforestation and the most densely concentrated populations. Rainfall levels declined, for example, by as much as 20 percent over parts of the Yucatán Peninsula between 800 C.E. and 950 C.E.

Cook’s study supports previous research that suggests drought, amplified by deforestation, was a key factor in the rapid collapse of the Mayan empire around 950 C.E. In 2010, Robert Oglesby, a climate modeler based at the University of Nebraska, published a study in the Journal of Geophysical Research that showed that deforestation likely contributed to the Mayan collapse. Though Oglesby and Cook’s modeling reached similar conclusions, Cook had access to a more accurate and reliable record of vegetation changes.

During the peak of Mayan civilization between 800 C.E. and 950 C.E., the land cover reconstruction Cook based his modeling on indicates that the Maya had left only a tiny percentage of the forests on the Yucatán Peninsula intact. By the period between 1500 C.E. and 1650 C.E., in contrast, after the arrival of Europeans had decimated native populations, natural vegetation covered nearly all of the Yucatán. In modern times, deforestation has altered some areas near the coast, but a large majority of the peninsula’s forests remain intact.

“I wouldn’t argue that deforestation causes drought or that it’s entirely responsible for the decline of the Maya, but our results do show that deforestation can bias the climate toward drought and that about half of the dryness in the pre-Colonial period was the result of deforestation,” Cook said.

Northeastern Megadroughts

The last major drought to affect the Northeast occurred in the 1960s, persisted for about three years and took a major toll on the region. Dorothy Peteet, a paleoclimatologist also affiliated with NASA GISS and Columbia University, has uncovered evidence that shows far more severe droughts have occurred in the Northeast.

By analyzing sediment cores collected from several tidal marshes in the Hudson River Valley, Peteet and her colleagues at Lamont-Doherty have found evidence that at least three major dry spells have occurred in the Northeast within the last 6,000 years. The longest, which corresponds with a span of time known as the Medieval Warm Period, lasted some 500 years and began around 850 C.E. The other two took place more than 5,000 years ago. They were shorter, only about 20 to 40 years, but likely more severe.

“People don’t generally think about the Northeast as an area that can experience drought, but there’s geologic evidence that shows major droughts can and do occur,” Peteet said. “It’s something scientists can’t ignore. What we’re finding in these sediment cores has big implications for the region.”

Peteet’s team detected all three droughts using a method called X-ray fluorescence spectroscopy. They used the technique on a core collected at Piermont Marsh in New York to search for characteristic elements — such as bromine and calcium — that are more likely to occur at the marsh during droughts.

Fresh water from the Hudson River and salty water from the Atlantic Ocean were both predominant in Piermont Marsh at different time periods, but saltwater moves upriver during dry periods as the amount of fresh water entering the marsh declines. Peteet’s team detected extremely high levels of both bromine and calcium, both of them indicators of the presence of saltwater and the existence of drought, in sections of the sediment cores corresponding to 5,745 and 5,480 years ago.

During the Medieval Warm Period, the researchers also found striking increases in the abundance of certain types of pollen species, especially pine and hickory, that indicate a dry climate. Before the Medieval Warm Period, in contrast, there were more oaks, which prefer wetter conditions. They also found a thick layer of charcoal demonstrating that wildfires, which are more frequent during droughts, were common during the Medieval Warm Period.

“We still need to do more research before we can say with confidence how widespread or frequent droughts in the Northeast have been,” Peteet said. There are certain gaps in the cores Peteet’s team studied, for example, that she plans to investigate in greater detail. She also expects to expand the scope of the project to other marshes and estuaries in the Northeast and to collaborate with climate modelers to begin teasing out the factors that cause droughts to occur in the region.

The Future of Food

Climate change, with its potential to redistribute water availability around the globe by increasing rainfall in some areas while worsening drought in others, might negatively impact crop yields in certain regions of the world.

New research conducted by Princeton University hydrologist Justin Sheffield shows that areas of the developing world that are drought-prone and have growing population and limited capabilities to store water, such as sub-Saharan Africa, will be the ones most at risk of seeing their crops decrease their yields in the future.

Sheffield and his team ran hydrological model simulations for the 20th and 21st centuries and looked at how drought might change in the future according to different climate change scenarios. They found that the total area affected by drought has not changed significantly over the past 50 years globally.

However, the model shows reductions in precipitation and increases in evaporative demand are projected to increase the frequency of short-term droughts. They also found that the area across sub-Saharan Africa experiencing drought will rise by as much as twofold by mid-21st century and threefold by the end of the century.

When the team analyzed what these changes would mean for future agricultural productivity around the globe, they found that the impact on sub-Saharan Africa would be especially strong.

Agricultural productivity depends on a number of factors beyond water availability including soil conditions, available technologies and crop varieties. For some regions of sub-Saharan Africa, the researchers found that agricultural productivity will likely decline by over 20 percent by mid-century due to drying and warming.

More…

Testing continues at NASA Langley Research Center as the 18,000-pound (8,164.6 kg) Orion test article took its seventh splash into the Hydro Impact Basin Dec. 1.

Orion, NASA’s next deep space exploration vehicle, will carry astronauts into space, provide emergency abort capability, sustain the crew during space travel, and ensure safe re-entry and landing.

The testing, which began in this summer, simulates different water landing scenarios and takes into account different velocities, parachute deployments, entry angles, wave heights and wind conditions that Orion may face when landing in the Pacific Ocean.

“We are doing several of these tests to look at the operational envelope for the Orion landing conditions and the analysts need as much data as we can possibly give them,” said Lynn Bowman, SPLASH project manager. “In order to do it in as few cases possible, we have to look at these critical cases, which is not your average landing scenario or sea condition.”

The Dec. 1 test was all about the heat shield and how much it would flex after hitting the water at a slightly different angle. Sea conditions simulated a low-wind swell case.

The test article was only two feet above the water before it dropped pancake-style into the water. It traveled about 7 mph (11.26 kph).

There are more than 150 sensors on the test article that record data during each test drop. The results of these initial tests will help improve the design for the actual flight vehicle.

The last drop of the year is tentatively scheduled for Tuesday, Dec. 13.

More…

Plants are critical in supporting life on Earth, and with help from an experiment that flew onboard space shuttle Discovery’s STS-131 mission, they also could transform living in space.

NASA’s Kennedy Space Center partnered with the University of Florida, Miami University in Ohio and Samuel Roberts Noble Foundation to perform three different experiments in microgravity.

The studies concentrated on the effects microgravity has on plant cell walls, root growth patterns and gene regulation within the plant Arabidopsis thaliana. Each of the studies has future applications on Earth and in space exploration.

“Any research in plant biology helps NASA for future long-range space travel in that plants will be part of bioregenerative life support systems,” said John Kiss, one of the researchers who participated in the BRIC-16 experiment onboard Discovery’s STS-131 flight in April 2010 and a distinguished professor and chair of the Department of Botany at Miami University in Ohio.

The use of plants to provide a reliable oxygen, food and water source could save the time and money it takes to resupply the International Space Station (ISS), and provide sustainable sources necessary to make long-duration missions a reality. However, before plants can be effectively utilized for space exploration missions, a better understanding of their biology under microgravity is essential.

Kennedy partnered with the three groups for four months to provide a rapid turnaround experiment opportunity using the BRIC-16 in Discovery’s middeck on STS-131. And while research takes time, the process was accelerated as the end of the Space Shuttle Program neared.

Howard Levine, a program scientist for the ISS Ground Processing and Research Project Office and the science lead for BRIC-16, said he sees it as a new paradigm in how NASA works spaceflight experiments. The rapid turnaround is quite beneficial to both NASA and the researchers, saving time and money.

Each of the three groups was quite impressed with the payload processing personnel at Kennedy.

Kiss said the staff at the Space Life Sciences Lab at Kennedy did an outstanding job and that the experienced biologists and engineers were extremely helpful with such a quick turnaround. Kiss and his group published a paper on their initial findings of plant growth in microgravity in the October 2011 issue of the journal Astrobiology.

They found that roots of space-grown seedlings exhibited a significant difference compared to the ground controls in overall growth patterns in that they skewed in one direction. Their hypothesis is that an endogenous response in plants causes the roots to skew and that this default growth response is largely masked by the normal gravity experienced on the Earth’s surface.

“The rapid turnaround was quite challenging, but it was a lot of fun,” said Anna-Lisa Paul, research associate professor in the Department of Horticultural Sciences at the University of Florida. “The ability to conduct robust, replicated science in a time frame is comparable to the way we conduct research in our own laboratories, which is fundamentally a very powerful system.”

Paul’s research and that of her colleague Robert Ferl, professor at the University of Florida and co-principal investigator on the BRIC-16 experiment, focused on comparing patterns of gene expression between Arabidopsis seedlings and undifferentiated Arabidopsis cells, which lack the normal organs that plants use to sense their environment – like roots and leaves. Paul and Ferl found that even undifferentiated cells “know” they are in a microgravity environment, and further, that they respond in a way that is unique compared to plant seedlings.

Elison Blancaflor, associate professor at the Samuel Roberts Noble Foundation, discovered that plant genes encoding cell-wall structural proteins were significantly affected by microgravity.

“This is exciting because this research has given us the tools to begin working on designing plants that perform better on Earth and in space,” Blancaflor said.

Blancaflor has now extended his findings from BRIC-16 to generate new hypotheses to explain basic plant-cell function. For example, the BRIC-16 results led the Noble Foundation team to identify novel components of the molecular machinery that allow plant cells to grow normally.

According to Levine, plants could contribute to bioregenerative life support systems on long-duration space missions by automatically scrubbing carbon dioxide, creating oxygen, purifying water and producing food.

“There is also a huge psychological benefit of growing plants in space,” said Levine. “When you have a crew floating around in a tin can, a plant is a little piece of home they can bring with them.”

More…

The Visible Infrared Imager Radiometer Suite (VIIRS) onboard NASA’s newest Earth-observing satellite, NPP, acquired its first measurements on Nov. 21, 2011. This high-resolution image is of a broad swath of Eastern North America from Canada’s Hudson Bay past Florida to the northern coast of Venezuela. The VIIRS data were processed at the NOAA Satellite Operations Facility (NSOF) in Suitland, Md.

VIIRS is one of five instruments onboard the National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) satellite that launched from Vandenberg Air Force Base, Calif., on Oct. 28. Since then, NPP reached its final orbit at an altitude of 512 miles (824 kilometers), powered on all instruments and is traveling around the Earth at 16,640 miles an hour (eight kilometers per second).

“This image is a next step forward in the success of VIIRS and the NPP mission,” said James Gleason, NPP project scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md.

VIIRS will collect radiometric imagery in visible and infrared wavelengths of the Earth’s land, atmosphere, and oceans. By far the largest instrument onboard NPP, VIIRS weighs about 556 pounds (252 kilograms). Its data, collected from 22 channels across the electromagnetic spectrum, will be used to observe the Earth’s surface including fires, ice, ocean color, vegetation, clouds, and land and sea surface temperatures.

“VIIRS heralds a brightening future for continuing these essential measurements of our environment and climate,” said Diane Wickland, NPP program scientist at NASA headquarters in Washington. She adds that all of NPP’s five instruments will be up and running by mid-December and NPP will begin 2012 by sending down complete data.

“NPP is right on track to ring in the New Year,” said Ken Schwer, NPP project manager at NASA Goddard. “Along with VIIRS, NPP carries four more instruments that monitor the environment on Earth and the planet’s climate, providing crucial information on long-term patterns to assess climate change and data used by meteorologists to improve short-term weather forecasting.”

NPP serves as a bridge mission from NASA’s Earth Observing System (EOS) of satellites to the next-generation Joint Polar Satellite System (JPSS), a National Oceanic and Atmospheric Administration (NOAA) program that will also collect weather and climate data. NASA Goddard manages the NPP mission for the Earth Science Division of the Science Mission Directorate at NASA Headquarters in Washington. The JPSS program provides the NPP ground system and NOAA provides operational support.

During NPP’s five-year life, the mission will extend more than 30 key long-term datasets that include measurements of the atmosphere, land and oceans. NASA has been tracking many of these properties for decades. NPP will continue measurements of land surface vegetation, sea surface temperature, and atmospheric ozone that began more than 25 years ago.

“The task now for the science community is to evaluate VIIRS performance and determine the accuracy of its data products,” said Chris Justice a professor of geography at the University of Maryland, College Park, who will be using VIIRS data in his research.

“These long-term data records are critical in monitoring how the Earth’s surface is changing – either from human activity or through climate change.”

More…

In between recess, geography class and eating the lunch their moms packed, NASA scientists have found the time to help validate Earth-observing satellites.

These scientists are the younger variety — students in NASA’s S’COOL project (Students’ Cloud Observations On-Line), a worldwide effort to collect cloud observations from the ground.

The students make observations like a NASA scientist and submit reports for their area to NASA. In return, the students receive a corresponding cloud observation from a NASA satellite to help them compare and learn.

This week, the S’COOL program received its 100,000th cloud observation, prompting a look into what NASA has been doing with all of these cloud observations.

“We often hear about how NASA satellite data helps students, but there are also quite a few things the students do for us,” says Lin Chambers, the lead for the S’COOL program, which is based out of NASA’s Langley Research Center in Hampton, Va.

According to Chambers, the most common way S’COOL ground observations help scientists is by confirming the presence of clouds in areas and under conditions that are challenging for satellite instruments.

For example, in a number of instances, students submitted cloud observations that reported a single layer of clouds in their area while the corresponding satellite was reporting a clear sky.

When the S’COOL team looked further into this discrepancy, they found that students were reporting small amounts of thin cirrus clouds, which are not detectable by the Clouds and Earth’s Radiant Energy System (CERES)/Imager algorithm for the Tropical Rainforest Measuring Mission (TRMM) spacecraft or the CERES/Imager algorithms for the Terra and Aqua satellites. With these student observations, scientists can now quantify how often satellites overlook cirrus clouds.

“The data are most useful to help confirm the cloud scenes that we know are difficult to detect with passive remote sensing,” says David Young, a NASA climate scientist who served as the first S’COOL science advisor. “You can’t see through layers, so you often miss low clouds that are under high clouds. It has been useful to get these data to see how often that occurs.”

Other tricky circumstances for satellites are observing clouds in areas with bright surfaces, such as snow, and complex surfaces, such as mountains.

Strong agreement between satellite data and student observations from snowy or icy areas helped NASA scientists confirm that the CERES instrument can in fact make cloud observations when surfaces are bright. To analyze satellite capabilities in areas with complex backgrounds, scientists looked instead toward student observations that reported clear skies.

“Seeing a completely clear sky from the satellite can be a challenge in certain circumstances, given the variable background of the Earth’s surface,” explained Chambers. “Once again, S’COOL observers helped scientists make sure that their satellites were making accurate observations.”

Student observations have also provided a more accurate approach for comparing cloud cover between the ground and the satellite. This improvement came as a result of another inconsistency found between satellite and S’COOL observations — students were reporting clear skies while satellites were reporting overcast skies.

“The S’COOL team found this difference often occurred when observers were located on the edge of a longitude and latitude line, and in many cases, student observations were being compared to satellite data that covered a different grid region than their actual location,” explains Chambers.

Additional studies are currently underway comparing S’COOL student reports to new data on cloud layers from the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and CloudSat satellites in NASA’s A-Train satellite constellation. A fifth edition of CERES will also be launching October 2011 on the NPOESS Preparatory Project (NPP) satellite, providing another opportunity for S’COOL observers to coordinate cloud observations.

While science goals were never the primary goal of the S’COOL program, Young explains that he and other scientists are proud that these results have been published, especially since these science outcomes are not very common with student outreach projects.

“People often ask why we don’t just use the data from trained cloud observers at the weather stations and airports,” says Young. “The answer is that we do. However, the S’COOL measurements are valuable because they are timed to coincide with the CERES measurements, and they provide observations from a wide variety of locations all over the world.”

More…