NASA Study Points to Infrared-Herring in Apparent Amazon Green-Up

For the past eight years, scientists have been working to make sense of why some satellite data seemed to show the Amazon rain forest "greening-up" during the region's dry season each year from June to October. The green-up indicated productive, thriving vegetation in spite of limited rainfall.
Now, a new NASA study published today in the journal Nature shows that the appearance of canopy greening is not caused by a biophysical change in Amazon forests, but instead by a combination of shadowing within the canopy and the way that satellite sensors observe the Amazon during the dry season.
Correcting for this artifact in the data, Doug Morton, of NASA's Goddard Space Flight Center in Greenbelt, Md., and colleagues show that Amazon forests, at least on the large scale, maintain a fairly constant greenness and canopy structure throughout the dry season. The findings have implications for how scientists seek to understand seasonal and interannual changes in Amazon forests and other ecosystems.
"Scientists who use satellite observations to study changes in Earth's vegetation need to account for seasonal differences in the angles of solar illumination and satellite observation," Morton said.
Isolating the apparent green-up mechanism
The MODIS, or Moderate Resolution Imaging Spectroradiometer, sensors that fly aboard NASA's Terra and Aqua satellites make daily observations over the huge expanse of Amazon forests. An area is likely covered in green vegetation if sensors detect a relatively small amount of red light – absorbed in abundance by plants for photosynthesis – but see a large amount of near-infrared light, which plants primarily reflect. Scientists use the ratio of red and near-infrared light as a measure of vegetation "greenness."
Numerous hypotheses have been put forward to explain why Amazon forests appear greener in MODIS data as the dry season progresses. Perhaps young leaves, known to reflect more near-infrared light, replace old leaves? Or, possibly trees add more leaves to capture sunlight in the dry season when the skies are less cloudy.
Unsettled by the lack of definitive evidence explaining the magnitude of the green-up, Morton and colleagues set out to better characterize the phenomenon. They culled satellite observations from MODIS and NASA's Ice Cloud and land Elevation Satellite (ICESat) Geosciences Laser Altimeter System (GLAS), which can provide an independent check on the seasonal differences in Amazon forest structure.
The team next used a theoretical model to demonstrate how changes in forest structure or reflectance properties have distinct fingerprints in MODIS and GLAS data. Only one of the hypothesized mechanisms for the green-up, changes in sun-sensor geometry, was consistent with the satellite observations.
"We think we have uncovered the mechanism for the appearance of seasonal greening of Amazon forests – shadowing within the canopy that changes the amount of near-infrared light observed by MODIS," Morton said.
Seeing the Amazon in a new light
In June, when the sun is as low and far north as it will get, shadows are abundant. By September, around the time of the equinox, Amazon forests at the equator are illuminated from directly overhead. At this point the forest canopy is shadow-free, highly reflective in the infrared, and therefore very green according to some satellite vegetation indices.
 Around the equinox, the MODIS sensor takes the 'perfect picture' with no shadows," Morton said. "The change in shadows is amplified in MODIS data because the sun is directly behind the sensor at the equinox. This seasonal change in MODIS greenness has nothing to do with how forests are changing."
In fact, accounting for the changing geometry between the sun and satellite sensor paints a picture of the Amazon that, as a whole, doesn't change much through the dry season.
"Additional work is needed to verify these results with field measurements, and to explore the influence of drought on corrected vegetation indices," said Scott Goetz, an ecologist at Woods Hole Research Center in Woods Hole, Mass., who was not involved with the Nature study. "But past interpretations of productivity changes need to be reconsidered in light of these new results."
Looking forward, Morton sees the results as a reminder and opportunity for remote sensing scientists to work more closely with ground-based ecosystem scientists.
"Scaling our knowledge of forest canopies from measurements of individual leaves to satellite observations of the entire Amazon basin requires a deep understanding of both forest ecology and remote sensing science," Morton said. "This interdisciplinary collaboration is critical to improve our understanding of the patterns and processes driving changes in vegetation productivity."

Space Station Live: Studying the Immune System In Space

An experiment on the International Space Station explores why astronauts' immune systems become suppressed in microgravity. NASA Public Affairs Officer Lori Meggs talks about the experiment, T-Cell Activation in Aging, with Principal Investigator and former shuttle astronaut Millie Hughes Fulford.

Station Crew Conducts Science While Awaiting Next Cargo Launch

While awaiting the launch of the next shipment of supplies to the International Space Station, the six-person Expedition 38 crew participated in a wide range of experiments studying the effects of long-duration spaceflight on the human body Tuesday.
Flight Engineer Mike Hopkins spent much of his morning participating in the Body Measures experiment, which collects anthropometric data to help researchers understand the magnitude and variability of the changes to body measurements during spaceflight. Predicting these changes will maximize crew performance, prevent injury and reduce time spent altering or adjusting spacesuits and workstations. The investigation also could help scientists understand the effects of prolonged bed rest, which produces physiological changes similar to those experienced in microgravity. Flight Engineer Koichi Wakata assisted Hopkins throughout the experiment session, setting up the calibration tape, collecting data and taking photographs.
Wakata also conducted an ultrasound scan on Flight Engineer Rick Mastracchio for the ongoing Spinal Ultrasound investigation. Medical researchers have observed that astronauts grow up to three percent taller during their long duration missions aboard the station and return to their normal height when back on Earth. The Spinal Ultrasound investigation seeks to understand the mechanism and impact of this change while advancing medical imaging technology by testing a smaller and more portable ultrasound device aboard the station.
 Wakata took a break from his work to talk with students from Fukuoka Prefecture and Kyushu University in his home country of Japan.
Hopkins and Wakata spent the afternoon loading the Orbital Sciences’ Cygnus cargo craft with trash for disposal when that vehicle departs the station on Feb. 18 for a destructive re-entry over the Pacific Ocean. Cygnus delivered over 2,700 pounds of cargo including crew provisions and scientific gear when it arrived at the station Jan. 13.
Hopkins also read up on procedures and gathered hardware for his upcoming session with the BP Reg experiment. This is a Canadian medical study that seeks to understand the causes of fainting and dizziness seen in some astronauts when they return to Earth following a long-duration mission. Results from this experiment will not only help researchers understand dizziness in astronauts, but it also will have direct benefits for people on Earth – particularly those predisposed to falls and resulting injuries, as seen in the elderly.

Mastracchio meanwhile changed out a recycle tank in the station’s Water Recovery System, which recycles condensation and urine into drinkable water, thereby reducing the amount of fresh water that must be sent to the crew aboard resupply ships.
On the Russian side of the complex, Commander Oleg Kotov conducted a biochemical analysis of his blood for the Splanh experiment, which is taking a look at the effects of long-duration spaceflight on the digestive system. The commander also performed the Seiner ocean-observation study, documenting color bloom patterns in the oceans’ waters for the fishing industry.
Flight Engineer Sergey Ryazanskiy downloaded data from an earthquake-monitoring experiment known as Seismoprognoz. He and Kotov installed the hardware for Seismoprognoz on the exterior of the station during a spacewalk on Dec. 27.
 The third Russian cosmonaut aboard the station, Mikhail Tyurin, set up a camera to record the operation of the Kaplya-2 experiment, which is studying the fluid motion and heat transfer of monodisperse drop flows in space. Tyurin also collected dosimeter readings for the Matryoshka experiment. Named after the traditional Russian nesting dolls, Matryoshka analyzes the radiation environment onboard the station.
Meanwhile at the Baikonur Cosmodrome in Kazakhstan, preparations continue for the launch of the ISS Progress 54 cargo craft Wednesday at 11:23 a.m. EST (10:23 p.m. Baikonur time) for an accelerated 6-hour, 4-orbit journey to the station.  When the new Progress docks with the station’s Pirs docking compartment at 5:25 p.m., it will deliver 1,764 pounds of propellant, 110 pounds of oxygen, 926 pounds of water and 2,897 pounds of spare parts, experiment hardware and other supplies to the orbiting complex.

Space Station Live: Space Diet to Prevent Bone Mineral Loss

Space Station Live commentator Pat Ryan conducts an interview with Dr. Scott M. Smith, the principal investigator of the Pro K experiment. The experiment is NASA's first evaluation of a dietary countermeasure to lessen bone loss of astronauts. Pro K proposes that a flight diet with a decreased ratio of animal protein to potassium will lead to decreased loss of bone mineral. Read more...

Kepler Finds a Very Wobbly Planet

Imagine living on a planet with seasons so erratic you would hardly know whether to wear Bermuda shorts or a heavy overcoat. That is the situation on a weird, wobbly world found by NASA's planet-hunting Kepler space telescope.
The planet, designated Kepler-413b, precesses, or wobbles, wildly on its spin axis, much like a child's top. The tilt of the planet's spin axis can vary by as much as 30 degrees over 11 years, leading to rapid and erratic changes in seasons. In contrast, Earth's rotational precession is 23.5 degrees over 26,000 years. Researchers are amazed that this far-off planet is precessing on a human timescale.
Kepler 413-b is located 2,300 light-years away in the constellation Cygnus. It circles a close pair of orange and red dwarf stars every 66 days. The planet's orbit around the binary stars appears to wobble, too, because the plane of its orbit is tilted 2.5 degrees with respect to the plane of the star pair's orbit. As seen from Earth, the wobbling orbit moves up and down continuously.
Kepler finds planets by noticing the dimming of a star or stars when a planet transits, or travels in front of them. Normally, planets transit like clockwork. Astronomers using Kepler discovered the wobbling when they found an unusual pattern of transiting for Kepler-413b.
"Looking at the Kepler data over the course of 1,500 days, we saw three transits in the first 180 days -- one transit every 66 days -- then we had 800 days with no transits at all. After that, we saw five more transits in a row," said Veselin Kostov, the principal investigator on the observation. Kostov is affiliated with the Space Telescope Science Institute and Johns Hopkins University in Baltimore, Md. The next transit visible from Earth's point of view is not predicted to occur until 2020. This is because the orbit moves up and down, a result of the wobbling, in such a great degree that it sometimes does not transit the stars as viewed from Earth.
Astronomers are still trying to explain why this planet is out of alignment with its stars. There could be other planetary bodies in the system that tilted the orbit. Or, it could be that a third star nearby that is a visual companion may actually be gravitationally bound to the system and exerting an influence.
"Presumably there are planets out there like this one that we're not seeing because we're in the unfavorable period," said Peter McCullough, a team member with the Space Telescope Science Institute and Johns Hopkins University. "And that's one of the things that Veselin is researching: Is there a silent majority of things that we're not seeing?"
Even with its changing seasons, Kepler-413b is too warm for life as we know it. Because it orbits so close to the stars, its temperatures are too high for liquid water to exist, making it inhabitable. It also is a super Neptune -- a giant gas planet with a mass about 65 times that of Earth -- so there is no surface on which to stand.
NASA's Ames Research Center at Moffett Field, Calif., is responsible for the Kepler mission concept, ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery mission and was funded by the agency's Science Mission Directorate.

Sun Emits Mid-Level Solar Flare

The sun emitted a mid-level solar flare, beginning at 11:57 p.m. EST on Feb. 3, 2014, and peaking at midnight EST. NASA released images of the flare as captured by NASA's Solar Dynamics Observatory.

 Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel.

Russian Cargo Craft Departure Clears Way for Next Delivery

The Expedition 38 crew said farewell to an unpiloted Russian cargo craft Monday morning while making preparations for the arrival of the next space freighter, which is set to make an expedited 6-hour journey to the International Space Station Wednesday.
The ISS Progress 52 cargo ship undocked from the Pirs docking compartment 11:21 a.m. EST, and backed away to a safe distance from the orbital complex to begin several days of tests to study thermal effects of space on its attitude control system.
Progress 52 delivered nearly three tons of supplies when it arrived at the station on July 27. Now filled with trash and other unneeded items, the Russian resupply ship will be commanded to re-enter the Earth’s atmosphere Feb. 11 and disintegrate harmlessly over the Pacific Ocean.
The departure of Progress 52 clears Pirs for the arrival of the next Russian cargo ship, ISS Progress 54, which rolled out to its launch pad early Monday morning at the Baikonur Cosmodrome in Kazakhstan as temperatures hovered around 17 below zero F.  The vehicle is scheduled to launch on Wednesday at 11:23 a.m. (10:23 p.m. Baikonur time) on an accelerated 4-orbit journey to dock to Pirs at 5:25 p.m.  The new Progress is loaded with 1,764 pounds of propellant, 110 pounds of oxygen, 926 pounds of water and 2,897 pounds of spare parts, experiment hardware and other supplies  for the Expedition 38 crew.
Station Commander Oleg Kotov and Flight Engineer Mikhail Tyurin spent Monday morning conducting a training session with the Telerobotically Operated Rendezvous Unit, or TORU, which could be used to remotely guide Progress 54 to its docking port in the event that its Kurs automated rendezvous system experiences a problem.
Along with Flight Engineer Sergey Ryazanskiy, Kotov also participated in the Splanh experiment, a Russian study of the effects of long-duration spaceflight on the digestive system.
Flight Engineer Rick Mastracchio, who began his day with a vision test, spent much of his morning installing and activating a NanoRacks platform and multi-gas monitor. NanoRacks provides lower-cost microgravity research facilities for small payloads utilizing a standardized “plug-and-play” interface. Mastracchio also connected a keyboard and video monitor for NanoRacks.
Meanwhile, Flight Engineer Koichi Wakata conducted an ultrasound scan of the calf and thigh of his right leg for the Sprint study.  This experiment is evaluating effectiveness of high-intensity, low-volume exercise training in minimizing the loss of muscle mass and bone density that occurs during long-term exposure to weightlessness. Flight Engineer Mike Hopkins assisted Wakata with the experiment session.
Wakata also participated in a vision check-up, as medical teams on the ground keep a watchful eye on the crew’s health.
Hopkins focused most of his attention on preparing the Multi-user Droplet Combustion Apparatus within the Combustion Integrated Rack for more experiments studying how different materials burn in microgravity. Hopkins replaced the fuel reservoirs, igniter tips and fiber arm inside the chamber insert assembly of the apparatus.