vendredi 11 mars 2016
NASA & USGS - Landsat-7 Mission patch.
March 11, 2016
An estimated 3 million shipwrecks are scattered across the planet’s oceans. Most maritime mishaps take place close to shore where hazards to navigation — such as rocks, reefs, other submerged objects and vessel congestion — are abundant. While there is a romantic association of shipwrecks and buried treasure, it is desirable to know where they are located for many other practical reasons. The ships may be of historical significance or, if the hard substrate of the ship has created a reef, of ecological significance. Modern-era shipwrecks are also commonly sources of pollution, leaking onboard fuel and corroded heavy metals. Nearshore shipwrecks can be navigational hazards themselves.
Image above: In this natural color Landsat OLI image, long sediment plumes extend from the wreck sites of the SS Sansip and SS Samvurn. Insets show elevation models (created by a multibeam echosounder) of the wrecks on the seafloor. Image Credits: NASA/USGS Landsat/Jesse Allen/NASA Earth Observatory/Matthias Baeye et al.
Researchers have found that shipwrecks near the coast can leave sediment plumes at the sea’s surface that help reveal their location. Using data from the NASA/USGS Landsat 8 satellite, researchers have detected plumes extending as far as 4 kilometers (about 2.5 miles) downstream from shallow shipwreck sites. This discovery demonstrates for the first time how Landsat and Landsat-like satellites may be used to locate the watery graves of coastal shipwrecks.
A quarter of all shipwrecks may rest in the North Atlantic. In the narrow southern end of the North Sea, where the English coast is only 100 miles from the shores of Belgium and the Netherlands, World War II-era shipwrecks are plentiful. In this area, mines, submarines, other submersibles and warships targeted cargo ships sailing between Allied countries and Dutch and Belgian ports. The potential negative environmental impacts of these modern-era shipwrecks are substantial enough that the Council of Europe’s Parliamentary Assembly has recommended they be mapped and monitored.
Images above: Elevation models show the SS Sansip (left) and the SS Samvurn (right) as imaged by a multibeam echosounder. Both of these ships leave sediment plumes detectable by Landsat 8 during ebb and flood tides. Images Credits: Matthias Baeye et al.
While airborne lidar (which uses light pulses to measure distance) can be used to detect shipwrecks close to shore and multibeam echosounders and other sound-based methods can be used anywhere deep enough for a survey vessel to sail, the former method requires clear water and cost prohibits both methods from being used to conduct exhaustive coastal surveys.
A new study published in the Journal of Archaeological Science by authors Matthias Baeye and Michael Fettweis, from the Royal Belgian Institute of Natural Sciences; Rory Quinn from Ulster University in Northern Ireland; and Samuel Deleu from Flemish Hydrography, Agency for Maritime and Coastal Services, aims to change things. The authors have found a way to use freely available Landsat satellite data to detect shipwrecks in sediment-laden coastal waters.
Their study, conducted in a coastal area off of the Belgium port of Zeebrugge, relied on a detailed multibeam echosounder survey of wreck sites, previously conducted by the Flemish government. This part of the Belgian coast is strewn with shipwrecks, in often sediment-laden waters.
Image above: A Liberty ship, SS George Washington Carver, launches in 1943. By 1944, wartime production of these "ugly duckling" cargo steamers took an average of 42 days. Image Credits: E.F. Joseph/The New York Public Library/Photographs and Prints Division.
The researchers started with the known location of four fully submerged shipwrecks in their study site: the SS Sansip, which the authors explain was a 135 m (443 foot) U.S. Liberty ship that sank after striking a mine in December 1944; the SS Samvurn, a similar ship that met the same fate the very next month; as well as the SS Nippon, a ship that sank after a maritime collision in 1938; and the SS Neutron, a small 51 m (167 foot) steel cargo vessel that fell victim to an uncharted navigation hazard, presumed to be the SS Sansip.
Using 21 Landsat 8 images and tidal models, the researchers mapped sediment plumes extending from the wreck locations. They found that the two ships with substantial portions of their structure unburied created sediment plumes that could be traced downstream during ebb and flood tides.
The authors postulate that the exposed structure of these ships created scour pits that then fill with fine sediments (sand, clay, organic matter, etc.) during slack tides (the period of relatively still currents between ebb and flood tides). These scour pits then serve as sediment repositories from which sediments are re-suspended during flood and ebb tides. When these sediments reach the surface, they create their telltale plumes.
Uncharted shipwrecks could be located by using the researchers’ methodology in reverse — i.e., mapping sediment plumes during various tidal stages and then following the plumes upstream to their point of origin.
Image above: The SS Marad, a U.S. Liberty cargo ship at sea, steams along between 1941-42. Liberty ships were an essential part of the U.S. wartime merchant fleet during World War II. Over 2,700 Liberty ships were produced in five years. The SS Sansip was a U.S. Liberty ship and the SS Samvurn had similar dimensions. Image Credits: U.S. Library of Congress.
The study looked at shipwrecks in waters as deep as 15 m (50 feet); depth is an essential consideration as the re-suspended sediment plumes must reach the surface to be detected by optical satellites like Landsat.
Given that coastal waters are typically shallow, often sediment-laden, and where most shipwrecks occur, this new shipwreck detection method could prove useful for marine archaeologists.
The Landsat Program is a series of Earth observing satellite missions jointly managed by NASA and the U.S. Geological Survey. Landsat satellites have been consistently gathering data about our planet since 1972. Landsat 8, designed with many evolutionary advances, launched in 2013.
View satellite imagery of the shipwrecks from NASA’s Earth Observatory: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=87651
NASA’s Landsat website: http://www.nasa.gov/landsat
USGS’ Landsat website: http://landsat.usgs.gov/
Council of Europe’s Parliamentary Assembly: http://assembly.coe.int/nw/xml/XRef/Xref-XML2HTML-en.asp?fileid=18077&lang=en
Images (mentioned), Text, Credits: NASA/Goddard Space Flight Center/Laura Rocchio/Karl Hille.
Publié par Orbiter.ch à 15:05
NASA - New Horizons Mission logo.
March 11, 2016
Far in the western hemisphere, scientists on NASA’s New Horizons mission have discovered what looks like a giant “bite mark” on Pluto’s surface. They suspect it may be caused by a process known as sublimation—the transition of a substance from a solid to a gas. The methane ice-rich surface on Pluto may be sublimating away into the atmosphere, exposing a layer of water-ice underneath.
In this image, north is up. The southern portion of the left inset above shows the cratered plateau uplands informally named Vega Terra (note that all feature names are informal). A jagged scarp, or wall of cliffs, known as Piri Rupes borders the young, nearly crater-free plains of Piri Planitia. The cliffs break up into isolated mesas in several places.
Cutting diagonally across the mottled plans is the long extensional fault of Inanna Fossa, which stretches eastward 370 miles (600 kilometers) from here to the western edge of the great nitrogen ice plains of Sputnik Planum.
Compositional data from the New Horizons spacecraft’s Ralph/Linear Etalon Imaging Spectral Array (LEISA) instrument, shown in the right inset, indicate that the plateau uplands south of Piri Rupes are rich in methane ice (shown in false color as purple). Scientists speculate that sublimation of methane may be causing the plateau material to erode along the face of the cliffs, causing them to retreat south and leave the plains of Piri Planitia in their wake.
Compositional data also show that the surface of Piri Planitia is more enriched in water ice (shown in false color as blue) than the higher plateaus, which may indicate that Piri Planitia’s surface is made of water ice bedrock, just beneath a layer of retreating methane ice. Because the surface of Pluto is so cold, the water ice is rock-like and immobile. The light/dark mottled pattern of Piri Planitia in the left inset is reflected in the composition map, with the lighter areas corresponding to areas richer in methane – these may be remnants of methane that have not yet sublimated away entirely.
The inset at left shows about 650 feet (200 meters) per pixel; the image measures approximately 280 miles (450 kilometers) long by 255 miles (410 kilometers) wide. It was obtained by New Horizons at a range of approximately 21,100 miles (33,900 kilometers) from Pluto, about 45 minutes before the spacecraft’s closest approach to Pluto on July 14, 2015.
The LEISA data at right was gathered when the spacecraft was about 29,000 miles (47,000 kilometers) from Pluto; best resolution is 1.7 miles (2.7 kilometers) per pixel.
For more information about New Horizons mission, visit: http://www.nasa.gov/mission_pages/newhorizons/main/index.html
Images, Text, Credits: NASA/JHUAPL/SwRI/Tricia Talbert.
Publié par Orbiter.ch à 14:42
NASA - Mars Science Laboratory (MSL) logo.
March 11, 2016
Image above: Patches of Martian sandstone visible in the lower-left and upper portions of this March 9, 2016, view from the Mast Camera of NASA's Curiosity Mars rover have a knobbly texture due to nodules apparently more resistant to erosion than the host rock in which some are still embedded. Image Credits: NASA/JPL-Caltech/MSSS.
NASA has selected 28 researchers as participating scientists for the Curiosity Mars rover mission, including six newcomers to the rover's science team.
The six new additions work in Alabama, Colorado, Indiana, Pennsylvania, Michigan and Tennessee. Eighty-nine scientists around the world submitted research proposals for using data from Curiosity and becoming participating scientists on the Mars Science Laboratory Project, which built and operates the rover. The 28 selected by NASA are part of a science team that also includes about 120 other members, mainly the principal investigators and co-investigators for the rover's 10 science instruments, plus about 320 science-team collaborators, such as the investigators’ associates and students.
An initial group of Mars Science Laboratory participating scientists was chosen before Curiosity's 2012 landing on Mars, and several of those scientists were selected again in the latest round. Participating scientists on the mission play active roles in the day-to-day science operations of Curiosity, involving heavy interaction with rover engineers at NASA's Jet Propulsion Laboratory, Pasadena, California. JPL manages the mission for NASA.
Image above: The nodule in the center of this image from the Mars Hand Lens Imager (MAHLI) on NASA's Curiosity Mars rover shows individual grains of sand and (on the left) laminations from the sandstone deposit in which the nodule formed. Image Credits: NASA/JPL-Caltech/MSSS.
The six participating scientists who are new to the mission are: Barbara Cohen, of NASA Marshall Space Flight Center, Huntsville, Alabama; Christopher Fedo of the University of Tennessee, Knoxville; Raina Gough of the University of Colorado, Boulder; Briony Horgan of Purdue University, West Lafayette, Indiana; Christopher House of Pennsylvania State University, University Park; and Mark Salvatore of the University of Michigan, Dearborn.
Seven other newly selected participating scientists have participated in the Curiosity mission previously in other roles: Christopher Edwards, U.S. Geological Survey, Flagstaff, Arizona; Abigail Fraeman, JPL; Scott Guzewich, Universities Space Research Association, Greenbelt, Maryland; Craig Hardgrove, Arizona State University, Tempe; Amy McAdam, NASA Goddard Space Flight Center, Greenbelt, Maryland; Melissa Rice, Western Washington University, Bellingham; and Kathryn Stack Morgan, JPL.
Image above: This view shows nodules exposed in sandstone that is part of the Stimson geological unit on Mount Sharp, Mars. The nodules can be seen to consist of grains of sand cemented together. Curiosity's Mars Hand Lens Imager (MAHLI) took this image on March 10, 2016. Image Credits: NASA/JPL-Caltech/MSSS.
Fifteen researchers who had been selected previously as Mars Science Laboratory participating scientists were selected again in this round: Raymond Arvidson, Washington University, St. Louis, Missouri; John Bridges, University of Leicester, United Kingdom; Bethany Ehlmann, California Institute of Technology, Pasadena; Jennifer Eigenbrode, NASA Goddard; Kenneth Farley, Caltech; John Grant, Smithsonian Institution, Washington; Jeffrey Johnson, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland; Richard Léveillé, McGill University, Montreal, Quebec, Canada; Kevin Lewis, Johns Hopkins University; Scott McLennan, State University of New York, Stony Brook; Ralph Milliken, Brown University, Providence, Rhode Island; John Moores, York University, Toronto, Ontario, Canada; David Rubin, University of California, Santa Cruz; Mariek Schmidt, Brock University, St. Catherines, Ontario, Canada; Rebecca Williams, Planetary Science Institute, Madison, Wisconsin.
Image above: This map shows the route driven by NASA's Curiosity Mars rover from where it landed in 2012 to its location in early March 2016, approaching "Naukluft Plateau." As the rover continues up Mount Sharp, its science team has been refreshed by a second round of NASA participating-scientist selections. Image Credits: NASA/JPL-Caltech/Univ. of Arizona.
During Curiosity's prime mission, which was completed in 2014, the project met its main goal by finding evidence that ancient Mars offered environmental conditions with all the requirements for supporting microbial life, if any ever existed on Mars. In Curiosity's first extended mission, researchers are using the rover on the lower portion of a layered mountain to study how Mars' ancient environment changed from wet conditions favorable for microbial life to harsher, drier conditions. For more information about Curiosity, visit: http://mars.jpl.nasa.gov/msl
Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Guy Webster.
Publié par Orbiter.ch à 14:33
NASA - Hubble Space Telescope patch.
March 11, 2016
Peering deep into the early universe, this picturesque parallel field observation from the NASA/ESA Hubble Space Telescope reveals thousands of colorful galaxies swimming in the inky blackness of space. A few foreground stars from our own galaxy, the Milky Way, are also visible.
In October 2013 Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) began observing this portion of sky as part of the Frontier Fields program. This spectacular skyscape was captured during the study of the giant galaxy cluster Abell 2744, otherwise known as Pandora’s Box. While one of Hubble’s cameras concentrated on Abell 2744, the other camera viewed this adjacent patch of sky near to the cluster.
Hubble orbiting Earth
Containing countless galaxies of various ages, shapes and sizes, this parallel field observation is nearly as deep as the Hubble Ultra-Deep Field. In addition to showcasing the stunning beauty of the deep universe in incredible detail, this parallel field — when compared to other deep fields — will help astronomers understand how similar the universe looks in different directions.
Hubble’s Wide Field Camera 3 (WFC3): https://www.spacetelescope.org/about/general/instruments/wfc3/
Hubble’s Advanced Camera for Surveys (ACS): https://www.spacetelescope.org/about/general/instruments/acs/
Frontier Fields program: http://frontierfields.org/about/
Hubble Ultra-Deep Field: http://www.spacetelescope.org/science/deep_fields/
For images and more information about Hubble, visit:
Image, Video, Credits: NASA, ESA and the HST Frontier Fields team (STScI), Acknowledgement: Judy Schmidt/Text Credits: European Space Agency/NASA/Ashley Morrow.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 14:12
CERN - European Organization for Nuclear Research logo.
March 11, 2016
“Children’s fiction books were boring so I read all the science books,” says John Ellis, a theoretical physicist who worked on the “Higgs-strahlung process” that helped discover the Higgs boson in 2012.
Boring. That word stands out when talking to the theoretical physicists at CERN about how they got to where they are now.
Boring and complicated are words often associated with people’s impression of physics in general. For some theoreticians working at CERN, physics wasn’t the career they saw for themselves – their own lessons in the subject were dull and off-putting. Instead they imagined themselves as mathematicians, doctors and engineers.
Image above: What makes a theoretical physicist pursue their career? Camille Bonvin is one of the fellows at CERN looking at theories of cosmology. (Image: Sophia Bennett/CERN).
It took teachers with a true passion for the subject – who saw beyond the mathematics to the fundamental questions it answers about nature – to show these future physicists their true calling. For others, while it would take them time to discover theoretical physics, their love of the subject was ignited by childhood pleasures long before anyone could make it seem boring.
“I liked physics, but I found it a bit dry, a bit boring, so I decided to study medicine,” explains Camille Bonvin, a fellow now at the beginning of her career in the CERN theory department.
Bonvin was at university studying medicine when something she learnt at the end of her school days began playing on her mind: “Right at the end of school we got this fantastic teacher that started to talk about cosmology, general relativity and quantum mechanics, not going into details as we didn’t have the background, but explaining the ideas behind these strange theories I hadn’t heard of before.”
This teacher was a trigger, and six weeks into her degree Bonvin switched to physics. Now, she is looking to begin her new role as an Assistant Professor at the University of Geneva – where she gained her PhD in 2008.
Image above: John Ellis, of Kings College London, in his office at CERN surrounded by science books. It was these books that drew him into physics as a child, when he found that he couldn't check out "good fiction" from the library until he was 14 years old (Image: Sophia Bennett/CERN).
“It wasn’t that I disliked medicine, it's just that I thought if I continue to study medicine I will never get to learn more about general relativity and quantum physics and so on,” she shrugs.
Similarly, Gian Giudice, the new Head of CERN’s Theory department, fell into physics after a substitute lecturer with a passion for the subject showed him that physics in school is often boring because it is taught without the tools of mathematics – it is the mathematics that makes physics so exciting.
“My high-school teacher was good at lecturing in mathematics but he was most boring when he was getting to physics. He was just stating some laws: the subject sounded totally dull,” Giudice explains. “One day he fell ill and this young substitute teacher came into class and showed us how, from the laws of mechanics applied to a system of colliding particles, one can derive the laws of thermodynamics. It opened my eyes to a completely new perspective on the power of logical deduction in physics. It was one of the most fascinating experiences of my life!”
But for Michelangelo Mangano, who has worked in the CERN theory department for 22 years, his goal was set as a child as he stared into the night skies, seeing the depth of the universe and wondering what he could learn.
“I’m from the Apollo generation – I was a kid when the Apollo missions were going to the moon, so that attracted me to the cosmos. I always planned to do astronomy and astrophysics,” Mangano grins.
Image above: Camille Bonvin, a fellow in CERN's Theory department was six weeks into a medical degree before she swapped to physics, when the thought of never learning about general relativity or cosmology made her change. (Image: Sophia Bennett/CERN).
“But when I got to university working on astrophysics meant going from the naive approach of a young person who looks at the sky into number crunching. That took away the fascination.”
To preserve his own pleasure in star-gazing, he started looking into particle physics instead.
It was at university that many of these theoretical physicists discovered that particle physics, like all other sciences, helps to answer questions of the universe. But unlike other sciences it’s about looking at nature to interpret the logic behind it and seeing which physical laws apply.
“Physics is not a descriptive science in which you just observe nature and make a catalogue of the facts. The goal is to understand the logic behind the facts and discover nature's inner workings,” says Giudice.
What is theory?
By university, each of these scientists had narrowed down their future career options, from a childlike love of general science and a natural aptitude for mathematics, to studying for a physics degree. But within physics there are many branches, and experimental physics often captures the public’s imagination more easily, with its huge machines that seem to mimic science fiction.
"At first I found particle physics very cold. But then when you look at it from the mathematical perspective and you realize the incredible connection there is between mathematics and the structure of the universe, well that gave it an incredible appeal.” –Michelangelo Mangano.
Experiments have been crucial to this decade’s greatest physics discoveries, despite the machines looking for something that theory had predicted many decades before.
The Large Hadron Collider dominated the particle physics news-reel since the huge discovery in 2012 of the Higgs boson – and as recently as last month, a large-scale experiment in the US, the Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves 100 years after Einstein’s theory predicted their existence.
With these two discoveries, two theories – Einstein’s Theory of General Relativity and the Standard model – have proved themselves to be the best description of our world, yet neither explain the complete picture.
Until now, these theories told the experiments where to look and what they were looking for. Theory was so crucial to experimental physics that CERN’s theory department, led by Niels Bohr, was set up two years before the rest of CERN.
Then, in 1952, a group of theorists, many under the age of thirty, met in Copenhagen and had three goals; scientific research on the fundamental problems in nuclear physics, training young theoretical physicists and developing active co-operation between laboratories – the original CERN theory department.
To this day, at CERN the theory department is working on numerous theories, from supersymmetry to string theory. But now, it’s possible these theories and ideas could be led by the experiments as opposed to vice-versa.
So what makes a newly fledged physicist follow the path of theory over experiments?
Why choose theory?
“I always wanted to become a theorist, I studied physics, I did physics while I was at school, my intention was always to become a theorist. In fact at university I studied mathematics and theoretical physics and did no experiments while I was at university at all.” – John Ellis.
“There are so many details involved in building an experiment. Checking all the magnets, or coiling 100 metres of wire, they’re not terribly exciting. Experimentalists have to have huge collaborations just to share out these boring repetitive tasks, but they also share the fun. In theory, we get to focus more on the conceptual side of things,” another CERN theorist, Slava Rychkov, explains why he chose this specific physics path – caveating that they also get to share the fun that comes with seeing a huge experiment being built.
Rychkov’s decision to become a theorist was easy, for him the choice was actually between mathematics and physics.
Where theoretical physicists say “ok, this is 99% true, lets move forward”, a mathematician could spend decades trying to complete that 1% to make it 100% true. That’s a big price to pay.”
Image above: “I was a double major at my university in Moscow. It just so happened I started doing research in pure mathematics, then much later I got the chance to try theoretical physics. I found I had all the fun I had in math, but in addition you have a feeling you’re really studying the fundamental questions of nature.” Slava Rychkov (Image: Sophia Bennett/CERN).
Like notable theorist Richard Feynman, who famously discussed his aptitude for electronics and tinkering with radios as a child, one thing many of the CERN theoreticians had in common was their complete lack of practical ability.
“I’m completely useless with my hands,” laughs John Ellis from in front of the mountains of papers and books that fill his office. “My wife finally got me doing some painting in the house for the first time in 30 years, just the day before yesterday!”
Giudice had the same problem, grinning, he explains that without his laboratory partners he never would have passed the practical lessons at university. “I was terrible. I was always a disaster in the lab, I had no clue what to do. Thankfully there were other people doing everything for me, because I’m not a practical man.”
While Mangano was useless with electronics, he disagrees this implies a lack of practicality, as he discusses his amateur carpentry, masonry and woodwork.
Wolfgang Lerche, in contrast, greatly enjoyed playing with electronics as a teenager, boasting that he could beat many of his experimental colleagues in terms of practical ability.
Image above: Wolfgang Lerche (right) works on the deeply mathematical aspects of string theory, despite his practical nature. Here, he is interviewed by Harriet Jarlett for this series of articles (Image: Sophia Bennett/CERN).
As a student in Germany his university didn’t teach particle physics. Instead he learnt about it in 1979 when, as a summer student at CERN, he found a whole new world of physics open up, and was lured into the realm of theoretical physics.
Lerche knows that, while the skills needed for both experimental and theoretical physics are different, there’s always some overlap.
“Much of any physicist’s time is spent trying to find out why something doesn’t work. The tolerance to deal with frustration, and the patience needed for solving “impossible” problems, belong to the basic skills that are needed by both groups.”
The next article in our In Theory series, on rival groups within the theory department, will be published next week. You can read the first article here:
CERN - In theory: Welcome to the Theory corridor:
CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.
The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.
Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.
Higgs boson: http://home.cern/topics/higgs-boson
Gravitational waves: http://home.cern/about/updates/2016/02/cern-congratulates-discoverers-gravitational-waves
Standard model: http://home.cern/about/physics/standard-model
Large Hadron Collider (LHC): http://home.cern/topics/large-hadron-collider
CERN's "Group of Theoretical Studies": http://home.cern/cern-people/opinion/2014/10/theory-cern-turns-62
For more information about the European Organization for Nuclear Research (CERN), visit: http://home.web.cern.ch/
Images (mentioned), Text, Credits: CERN/Harriet Jarlett.
Publié par Orbiter.ch à 08:08
ESA - Rosetta Mission patch.
11 March 2016
ESA’s Rosetta spacecraft has revealed a surprisingly large region around its host comet devoid of any magnetic field.
When ESA’s Giotto flew past Comet Halley three decades ago, it found a vast magnetic-free region extending more than 4000 km from the nucleus. This was the first observation of something that scientists had until then only thought about but had never seen.
Magnetic field-free cavity at comet
Interplanetary space is pervaded by the solar wind, a flow of electrically charged particles streaming from the Sun and carrying its magnetic field across the Solar System. But a comet pouring lots of gas into space obstructs the solar wind.
At the interface between the solar wind and the coma of gas around the active comet, particle collisions as well as sunlight can knock out electrons from the molecules in the coma, which are ionised and picked up by the solar wind. This process slows the solar wind, diverting its flow around the comet and preventing it from directly impacting the nucleus.
Along with the solar wind, its magnetic field is unable to penetrate the environment around the comet, creating a region devoid of magnetic field called a diamagnetic cavity.
Prior to Rosetta arriving at Comet 67P/Churyumov-Gerasimenko, scientists had hoped to observe such a magnetic field-free region in the environment of this comet. The spacecraft carries a magnetometer as part of the Rosetta Plasma Consortium suite of sensors (RPC-MAG), whose measurements were already used to demonstrate that the comet nucleus is not magnetised.
However, since Rosetta’s comet is much less active than Comet Halley, the scientists predicted that a diamagnetic cavity could form only in the months around perihelion – the closest point to the Sun on the comet’s orbit – but that it would extend only 50–100 km from the nucleus.
Comet on 26 July 2015
During 2015, the increased amounts of dust dragged into space by the outflowing gas became a significant problem for navigation close to the comet. To keep Rosetta safe, trajectories were chosen such that by the end of July 2015, a few weeks before perihelion, it was some 170 km away from the nucleus. As a result, scientists considered that detecting signs of the magnetic field-free bubble would be impossible.
“We had almost given up on Rosetta finding the diamagnetic cavity, so we were astonished when we eventually found it,” says Charlotte Götz of the Institute for Geophysics and extraterrestrial Physics in Braunschweig, Germany.
Charlotte is the lead author of a new study, published in the journal Astronomy and Astrophysics, presenting the detection of a diamagnetic cavity obtained by RPC-MAG on 26 July. The paper describes one of the most spectacular measurements from almost 700 detections of regions with no magnetic field made by Rosetta at the comet since June 2015.
“We were able to detect the cavity, and on many occasions, because it is much bigger and dynamic than we had expected,” adds Charlotte.
Discovery of diamagnetic cavity
To investigate why the magnetic field-free cavity is so much bigger than predicted, Charlotte and her colleagues looked at measurements performed around the same time by other instruments, such as Rosetta's scientific camera, OSIRIS, and the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument, ROSINA, to verify whether any anomalous changes in the comet's activity could be pushing the cavity away from the nucleus.
While one of the cavity detections, on 29 July, occurred in conjunction with a strong outburst of gas and dust recorded by other instruments on Rosetta, this seems to be an isolated case. Almost all of the other observations of magnetic field-free regions, including the one recorded on 26 July, were not accompanied by any appreciable increase of outgassing.
“To account for such a big cavity in the simulations, we would need the outgassing rate to be 10 times higher than was measured at the comet by ROSINA,” says co-author Karl-Heinz Glassmeier from Technische Universität Braunschweig, Germany, principal investigator of RPC-MAG.
The most likely explanation seems to lie, instead, in the dynamical nature of the cavity boundary.
Comet on 26 July 2015
Boundaries between plasma regions with different properties are often unstable, and small oscillations can arise in the pile-up region of the solar wind, where it encounters the magnetic field-free region, on the Sun-facing side of the comet. If these oscillations propagate and get amplified along the boundary, in the direction opposite the Sun, they could easily cause the cavity to grow in size.
Such a moving instability would also explain why the measurements of magnetic field-free regions are sporadic and mainly span several minutes, with the 26 July one lasting 25 minutes and the longest one, recorded in November, about 40 minutes. The short duration of the detections is not a result of Rosetta crossing the cavity – the spacecraft moves much too slowly with respect to the comet – but of the magnetic field-free regions repeatedly passing through the spacecraft.
“What we are seeing is not the main part of the cavity but the smaller pockets at the cavity boundary, which are occasionally pushed farther away from the nucleus by the waves propagating along the boundary,” adds Charlotte.
Scientists are now busy analysing all the magnetic field-free events recorded by Rosetta, to learn more about the properties of the plasma in the comet environment and its interaction with the solar wind. After perihelion, as the comet moved away from the Sun and its outgassing and dust production rate declined, the spacecraft was able to move closer to the nucleus, and the magnetometer continued detecting magnetic field-free regions for several months, until the latest detection in February 2016.
Comet Halley close up
“Three decades ago, Giotto’s detection at Comet Halley was a great success, because it was the first confirmation of the existence of a diamagnetic cavity at a comet,” says Matt Taylor, Rosetta Project Scientist at ESA.
“But that was only one measurement, while now we have seen the cavity at Rosetta’s comet come and go hundreds of times over many months. This is why Rosetta is there, living with the comet and studying it up close.”
Notes for Editors:
“First detection of a diamagnetic cavity at comet 67P/Churyumov-Gerasimenko,” by C. Götz et al. is published in the journal Astronomy & Astrophysics. The results will be presented at the 50th ESLAB Symposium “From Giotto to Rosetta”, held 14–18 March in Leiden, the Netherlands: http://dx.doi.org/10.1051/0004-6361/201527728
For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta
Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview
Rosetta in depth: http://sci.esa.int/rosetta
Rosetta at Astrium: http://www.astrium.eads.net/en/programme/rosetta-1go.html
Rosetta at DLR: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10394/
Ground-based comet observation campaign: http://www.rosetta-campaign.net/home
Rosetta factsheet: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_factsheet
Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions
Images, Animation, Text, Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/RPC/IGEP/IC/C.Carreau/Markus Bauer/Matt Taylor/Institute for Geophysics and extraterrestrial Physics Technische Universität Braunschweig/Karl-Heinz Glassmeier/Charlotte Götz.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 06:45
jeudi 10 mars 2016
NASA's Goddard Space Flight Center logo.
March 10, 2016
NASA has demonstrated the success of advanced technology for making precise measurements of Earth’s orientation and rotation – information that helps provide a foundation for navigation of all space missions and for geophysical studies of our planet.
The technology includes a new class of radio antenna and electronics that provide broadband capabilities for Very Long Baseline Interferometry, or VLBI. This technique is used to make precise measurements of Earth in space and time.
VLBI measurements have been conducted for decades using a worldwide network of stations that carry out coordinated observations of very distant astronomical objects called quasars. To meet the demand for more precise measurements, a new global network of stations, called the VLBI Global Observing System, or VGOS, is being rolled out to replace the legacy network.
Image above: The new 12-meter (39-foot) antenna at the Kōke‘e Park Geophysical Observatory in Hawaii achieved “first light” – its first time observing radio sources as a single dish – and its first interferometric fringes in early February 2016. Image Credits: MIT Haystack Observatory/Ganesh Rajagopalan.
NASA is participating in this next-generation network and just completed the installation of a joint NASA-U.S. Naval Observatory VGOS station at NASA’s Kōke‘e Park Geophysical Observatory in Hawaii. NASA has two other developmental VGOS stations operating at the Goddard Geophysical and Astronomical Observatory at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and at the Massachusetts Institute of Technology's Haystack Observatory in Westford, Massachusetts.
With this preliminary network, NASA passed a crucial milestone on February 5: conducting the first demonstration anywhere in the world of broadband observations for VLBI over a long baseline.
Using Quasars to Measure the Earth: A Brief History of VLBI
Video above: Originally developed to study distant astronomical objects called quasars, the technique called Very Long Baseline Interferometry provides information about the relative locations of observing stations and about Earth’s rotation and orientation in space. Video Credits: NASA Goddard Space Flight Center.
“The successful tests demonstrate the viability of the new broadband antenna technology for making the kinds of observations needed for improved accuracy in measurements of the very fine-scale shape of Earth,” said Benjamin R. Phillips, who leads NASA’s Earth Surface and Interior Focus Area at NASA Headquarters in Washington, D.C.
The coordinated observation was verified by detection of fringes – an interference pattern indicating that all three stations were receiving and could combine the signals from the quasar they observed.
“The testing has been a concerted effort involving many team members at all three stations, as well as the MIT correlator facility,” said Pedro Elosegui of the Haystack Observatory, which leads the NASA development of the VGOS signal chain.
Several technical hurdles had to be cleared to carry out the long-baseline demonstration. One issue is that the effects of the ionosphere – a layer of Earth’s upper atmosphere that impacts the behavior of radio waves – and of the local weather are quite different at the three sites. Another factor, which applies in any VLBI measurement, is that stations have to contend with interference from nearby radio and cell towers and other sources.
“These and other technical issues have been dealt with,” said Goddard’s Stephen Merkowitz, manager of NASA’s Space Geodesy Project. “We have a few more challenges down the road, but they are manageable. We now know that the new global system can be used the way it was intended.”
The broadband antenna and electronics provide improved sensitivity in a scaled-down package. With dish sizes of 12 to 13 meters (about 39 to 42 feet), the next-generation antennas are designed to be smaller than most of the current system’s dishes, which are typically 20 to 30 meters (about 65 to 100 feet). The scaled-down size allows an antenna to move quickly, conducting up to 100 observations in an hour compared to about 12 observations in an hour for the current VLBI system. This type of antenna is also much less expensive than the larger antennas, making it more economical to deploy and operate a global network.
Broadband capability makes it possible to conduct observations in four bands – that is, at four frequencies – at the same time, whereas current VLBI systems operate in two bands. With four bands, more bits can be recorded at once, so the broadband system can achieve data rates of 8 to 16 gigabits per second, which is about 1000 times the data rate for HDTV. (The current VLBI system has a typical rate of 256 megabits per second.) This leads to better sensitivity, even though the antenna is smaller.
Another new feature is that the four bands are selectable within a range of 2 gigahertz to roughly 14 gigahertz. This helps to avoid interference with other sources, such as radio and cellphone towers.
With the rollout of the VGOS network, existing VLBI stations are being replaced, or in some cases upgraded. More sites will be added in the future to provide more uniform coverage across the globe. Once fully implemented, the worldwide VGOS network is expected to yield position and Earth orientation measurements that improve precision by a factor of three or more, compared to current measurements.
“The next-generation VLBI system will expand our ability to make the kinds of measurements that will be needed for geophysical studies and navigation applications, which demand more precision all the time,” said Merkowitz.
For more information about NASA’s Space Geodesy Project, visit: http://space-geodesy.nasa.gov/
Image (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Elizabeth Zubritsky/Karl Hille.
Publié par Orbiter.ch à 16:07
ARISS - Amateur Radio on the International Space Station logo.
March 10, 2016
Amateur radio hits a milestone on the orbiting laboratory.
On Thursday, March 10, astronauts on the International Space Station logged their 1,000th educational contact with the ground. NASA astronaut Tim Kopra answered questions posed by the North Dakota Space Grant Consortium in Grand Forks, North Dakota. No matter how many times it happens, talking directly with someone orbiting above the Earth remains a thrill for students.
Amateur Radio on the International Space Station (ARISS) works through an international consortium of amateur radio organizations and space agencies in the United States, Russia, Canada, Japan and Europe. Amateur, or ham, radio operators set up hardware on the ground and call NA1SS, the space station’s radio call sign. The suspense is palpable as those on the ground await a reply from space.
Image above: NASA astronaut Kjell Lindgren participates in an amateur radio call with students while aboard the International Space Station during Expedition 45. Image Credit: NASA.
A few students prepare and ask questions while hundreds of others, along with teachers, parents and members of the community, listen in from classrooms or auditoriums. The overall goal of this long-running experiment is to interest young people in mathematics and science, and inspire the next generation of explorers.
Crew members typically answer from 10 to 20 questions. These frequently touch on current research and life aboard the station, along with a wide variety of topics from emergencies, whether a human heart beats faster or slower in space, how food is stored on the station, whether astronauts ever get fresh fruit and vegetables, and what returning to Earth is like.
One participant from the 1,000th call asked Kopra what kind of experiments he was conducting on the space station.
“We have lots of different kinds of experiments,” Kopra responded. “Many of our experiments have to do with the effect of zero gravity on the human body, because it can be hard on the body – our muscles, our bones and our eyes. We’d like to learn how to solve those problems so that we can stay healthy and go into deep space, perhaps go back to the Moon or Mars someday.”
Image above: NASA astronaut Sunita Williams participates in an amateur radio call with students while aboard the International Space Station during Expedition 14. Image Credit: NASA.
Another student asked what Kopra thought the future of amateur radio aboard the space station would be.
“Amateur radio is a great way for us to reach people on Earth, and try to share our experience when we can,” Kopra said.
ARISS accepts student applications to connect with the station during specific proposal cycles in the U.S. and Europe, with an open application process in other regions. Schools partner with an Amateur Radio Club or a ham radio operator to provide and operate equipment while teachers commit to having their students study space- and communications-related topics, including how amateur radio works.
“Approved applications go on a waiting list with a proposed week for contact,” explains Kenneth Ransom, ISS Ham radio project coordinator at NASA’s Johnson Space Center. “About a month out from that week, we predict when the station will pass over to see what might work for the school. That list gets prioritized and sent to NASA planners who try to fit a pass into the crew schedule.”
Image above: A crowd of students and community members gather as a select group of students in Huntsville, Alabama speak with NASA astronaut Tim Kopra over HAM radio as the space station flies overhead. Image Credits: NASA/Christopher Blair.
Fitting into the busy crew schedule can present a challenge. Setting up the antenna to receive and transmit radio signals also often proves challenging, and radio operators have braved snow storms and ice to do so.
But these efforts are worth it. Teachers report that talking with crew members in space inspires their students, and has launched many into space-related careers – including neuroscience, chemistry, physics, astronomy and engineering. The events bring entire schools and communities together. Many schools start amateur radio clubs after their ham radio experience.
Astronauts enjoy the contact as well. NASA astronaut Sunita Williams participated in events while a crew member on Expedition 32 in 2012.
“I get choked up every time I read a report about a Ham radio contact,” she said at the ISS R&D Conference in 2015. “You go through the questions and it sounds like only 10 kids, then you read a report about how many people were at that event and how much preparation and time the kids took. It is nice to know it makes such a huge impact.”
The speed at which the space station travels typically offers a window of about 10 minutes for contact, according to Ransom. The set-up varies at every ground station and so do the events.
“We call it an experiment, and sometimes experiments don’t go the way we want them to,” Ransom says. “We have had some that didn’t work, for a variety of reasons, some that were spectacular successes and some that were marginal successes.”
Image above: NASA astronaut Tim Kopra participated in ham radio calls during Expedition 20 in 2009, as seen here. He was back on the radio for the historic 1,000th ARISS call to the space station. Image Credit: NASA.
These 1,000 radio contacts have involved students from across the U.S., as well as 52 other countries from every continent and even a few islands.
Anyone with an amateur radio can listen in on scheduled contacts. Crew members on the space station also sometimes make general radio calls and talk to ham operators around the world.
ARISS: 1,000 Calls and Counting
Many ham contacts end with the earth-bound moderators saying, “We have shared a moment of history,” and for the moderator of the North Dakota call, it was especially significant. Ham operator Charlie Sufana choked back tears as he closed the event.
“I had the luck of the draw to be the control operator for ARISS contact number one back in December 21, 2000,” Sufana said in an emotional sign-off. “And once again, the luck of the draw allowed me to be the mentor moderator for the 1,000th contact. Here’s to the next 1,000.”
Kedr to Begin its Space Mission on Feb. 16:
International Space Station (ISS): http://www.nasa.gov/mission_pages/station/main/index.html
Space Station Research and Technology: http://www.nasa.gov/mission_pages/station/research/index.html
Amateur Radio on the International Space Station (ARISS): http://www.ariss.org/
Images (mentioned), Video, Text, Credits: NASA Johnson Space Center/International Space Station Program Office/Melissa Gaskill/Kristine Rainey.
Publié par Orbiter.ch à 15:27
NASA - DSCOVR Mission patch.
March 10, 2016
The Deep Space Climate Observatory (DSCOVR) was built to provide a distinct perspective on our planet. Yesterday, it added another first to its collection of unique snapshots. While residents of islands and nations in the Western Pacific looked up in the early morning hours to observe a total eclipse of the Sun, DSCOVR looked down from space and captured the shadow of the Moon marching across Earth’s sunlit face.
The animation above was assembled from 13 images acquired on March 9, 2016, by NASA’s Earth Polychromatic Imaging Camera (EPIC), a four-megapixel charge-coupled device (CCD) and Cassegrain telescope on the DSCOVR satellite. Click on the link below the animation to download the individual images from the series.
“What is unique for us is that being near the Sun-Earth line, we follow the complete passage of the lunar shadow from one edge of the Earth to the other,” said Adam Szabo, NASA’s project scientist for DSCOVR. “A geosynchronous satellite would have to be lucky to have the middle of an eclipse at noon local time for it. I am not aware of anybody ever capturing the full eclipse in one set of images or video.”
In this, the only total solar eclipse of 2016, the shadow of the new Moon starts crossing the Indian Ocean and marches past Indonesia and Australia into the open waters and islands of Oceania (Melanesia, Micronesia, and Polynesia) and the Pacific Ocean. Note how the shadow moves in the same direction as Earth rotates. The bright spot in the center of each disk is sunglint—the reflection of sunlight directly back at the EPIC camera.
Japan’s Himawari-8 satellite also captured a series of images showing the procession of the shadow during this eclipse, which you can view here: http://cimss.ssec.wisc.edu/goes/blog/archives/20899
From its position about 1.6 million kilometers (1 million miles) from Earth and toward the Sun, DSCOVR maintains a constant view of the sunlit face of the planet. EPIC acquires images using ten different spectral filters—from ultraviolet to near infrared—to produce a variety of science products. Natural-color images are generated by combining three separate monochrome exposures (red, green, and blue channels) taken in quick succession.
According to Szabo, the satellite normally collects images at all ten wavelengths about once every 108 minutes (with just one image at full resolution). For this eclipse, the EPIC team collected full-resolution images every 20 minutes on just the red, green, and blue channels. This allowed the satellite to collect 13 images spanning the entire four hours and twenty minutes of the eclipse.
Deep Space Climate Observatory (DSCOVR)
In addition to the EPIC camera, DSCOVR carries the National Institute of Standards and Technology Advanced Radiometer (NISTAR), an instrument that measures how much solar energy is being radiated back into space from Earth. In coming weeks, scientists will be analyzing NISTAR data to quantify how the eclipse changed the incoming and outgoing radiation for those few hours.
Situated in a stable orbit between the Sun and Earth, DSCOVR’s primary mission is to monitor the solar wind for space weather forecasters at the National Oceanic and Atmospheric Administration (NOAA). Its secondary mission is to provide daily color views of our planet as it rotates through the day. The satellite was built and launched through a partnership between NASA, NOAA, and the U.S. Air Force.
Deep Space Climate Observatory (DSCOVR): http://www.nesdis.noaa.gov/DSCOVR/
Earth Polychromatic Imaging Camera (EPIC): http://epic.gsfc.nasa.gov/epic.html
Charge-coupled device (CCD): https://en.wikipedia.org/wiki/Charge-coupled_device
National Institute of Standards and Technology Advanced Radiometer (NISTAR): http://www.nasa.gov/content/goddard/noaas-dscovr-nistar-instrument-watches-earths-budget/#.VuHG3FLe3Ps
Images, Text, Credits: NASA image courtesy of the DSCOVR EPIC team. NASA Earth Observatory animation by Joshua Stevens. Caption by Mike Carlowicz.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 15:05
NASA - Chandra X-ray Observatory patch.
March 10, 2016
Galaxy cluster MACS J0717, one of the most complex and distorted galaxy clusters known, is the site of a collision between four clusters. It is located about 5.4 billion light years away from Earth.
Astronomers are studying a half dozen galaxy clusters, including MACS J0717, through the "Frontier Fields" project. To learn more about clusters, including how they grow via collisions, astronomers have used some of the world’s most powerful telescopes, looking at different types of light.
Read More from NASA's Chandra X-ray Observatory: http://chandra.harvard.edu/photo/2016/frontier/
For more Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra
Image, Text, Credits: X-ray: NASA/CXC/SAO/van Weeren et al.; Optical: NASA/STScI; Radio: NSF/NRAO/VLA/Lee Mohon.
Publié par Orbiter.ch à 14:52
NASA - Mars Reconnaissance Orbiter (MRO) logo.
March 10, 2016
- NASA's Mars Reconnaissance Orbiter arrived at Mars on March 10, 2006.
- Of the seven missions currently active at Mars, MRO returns more data every week than the other six combined.
- The mission has shown how dynamic Mars remains today and how diverse its past environmental conditions were.
Image above: NASA's Mars Reconnaissance Orbiter, nearing the 10th anniversary of its arrival at Mars, used its High Resolution Imaging Science Experiment (HiRISE) camera to obtain this view of an area with unusual texture on the southern floor of Gale Crater. Image credits: NASA/JPL-Caltech/Univ. of Arizona.
True to its purpose, the big NASA spacecraft that began orbiting Mars a decade ago this week has delivered huge advances in knowledge about the Red Planet.
NASA's Mars Reconnaissance Orbiter (MRO) has revealed in unprecedented detail a planet that held diverse wet environments billions of years ago and remains dynamic today.
One example of MRO's major discoveries was published last year, about the possibility of liquid water being present seasonally on present-day Mars. It drew on three key capabilities researchers gained from this mission: telescopic camera resolution to find features narrower than a driveway; spacecraft longevity to track seasonal changes over several Martian years; and imaging spectroscopy to map surface composition.
Other discoveries have resulted from additional capabilities of the orbiter. These include identifying underground geologic structures, scanning atmospheric layers and observing the entire planet's weather daily. All six of the orbiter's science instruments remain productive in an extended mission more than seven years after completion of the mission's originally planned primary science phase.
Magnificent Mars: 10 Years of Mars Reconnaissance Orbiter
"This mission has helped us appreciate how much Mars -- a planet that has changed greatly over time -- continues to change today," said MRO Project Scientist Rich Zurek of NASA's Jet Propulsion Laboratory, Pasadena, California. JPL manages the mission.
Data from MRO have improved knowledge about three distinct periods on Mars. Observations of the oldest surfaces on the planet show that diverse types of watery environments existed -- some more favorable for life than others. More recently, water cycled as a gas between polar ice deposits and lower-latitude deposits of ice and snow, generating patterns of layering linked to cyclical changes similar to ice ages on Earth.
Dynamic activity on today's Mars includes fresh craters, avalanches, dust storms, seasonal freezing and thawing of carbon dioxide sheets, and summertime seeps of brine.
The mission provides three types of crucial support for rover and stationary lander missions to Mars. Its observations enable careful evaluation of potential landing sites. They also help rover teams choose routes and destinations. Together with NASA's Mars Odyssey, which has been orbiting Mars since 2001, MRO relays data from robots on Mars' surface to NASA Deep Space Network antennas on Earth, multiplying the productivity of the surface missions.
The mission has been investigating areas proposed as landing sites for future human missions in NASA's Journey to Mars.
Map Projected Browse Image. Image Credits: NASA/JPL-Caltech/Univ. of Arizona.
"The Mars Reconnaissance Orbiter remains a powerful asset for studying the Red Planet, with its six instruments all continuing capably a decade after orbit insertion. All this and the valuable infrastructure support that it provides for other Mars missions, present and future, make MRO a keystone of the current Mars Exploration Program," said Zurek.
Arrival at Mars
On March 10, 2006, the spacecraft fired its six largest rocket engines for about 27 minutes, slowing it down enough for the gravity of Mars to catch it into orbit. Those engines had been used only once before, for 15 seconds during the first trajectory adjustment during the seven-month flight from Earth to Mars. They have been silent since arrival day. Smaller engines provide thrust for orbit adjustment maneuvers.
For its first three weeks at Mars, the spacecraft flew elongated, 35-hour orbits ranging as far as 27,000 miles (43,000 kilometers) from the Red Planet. During the next six months, a process called aerobraking used hundreds of carefully calculated dips into the top of the Martian atmosphere to gradually adjust the size of the orbit. Since September 2006, the craft has been flying nearly circular orbits lasting about two hours, at altitudes from 155 to 196 miles (250 to 316 kilometers).
The spacecraft's two large solar panels give MRO a wingspan the length of a school bus. That surface area helped with atmospheric drag during aerobraking and still cranks out about 2,000 watts of electricity when the panels face the sun. Generous power enables the spacecraft to transmit a torrent of data through its main antenna, a dish 10 feet (3 meters) in diameter. The total science data sent to Earth from MRO -- 264 terabits -- is more than all other interplanetary missions combined, past and present.
Mars Reconnaissance Orbiter (MRO. Image Credits: NASA/JPL
Lockheed Martin Space Systems, Denver, built the spacecraft with the capability to transmit copious data to suit the science goals of revealing Mars in great detail, which requires plenty of data.
For example, the mission's High Resolution Imaging Science Experiment (HiRISE) camera, managed by the University of Arizona, Tucson, has returned images that show features as small as a desk anywhere in observations that now have covered about 2.4 percent of the Martian surface, an area equivalent to two Alaskas, with many locations imaged repeatedly. The Context Camera (CTX), managed by Malin Space Systems, San Diego, has imaged more than 95 percent of Mars, with resolution showing features smaller than a tennis court. The Compact Reconnaissance Imaging Spectrometer (CRISM), managed by Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, also has imaged nearly 98 percent of the planet in multiple visual-light and infrared wavelengths, providing composition information at scales of 100 to 200 yards or meters per pixel.
For more information about MRO, visit:
For more information about NASA's journey to Mars, visit:
Images (mentioned), Video, Text, Credits: NASA/Dwayne Brown/Laurie Cantillo/JPL/Guy Webster.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 06:30
mercredi 9 mars 2016
NASA - Armstrong Flight Research Center patch.
March 9, 2016
An air data probe intended to improve investigation of sonic booms is flying on the F-15B aircraft at NASA's Armstrong Flight Research Center in California.
NASA's goal for sonic boom research is to find ways to control and lessen the noise from shockwaves so that federal regulators will allow commercial supersonic flight overland.
The current six-flight series is set to continue through about mid March, said Brett Pauer, F-15B project manager. Much like earlier flight tests in 2011 and 2014, the Eagle Aero Probe is flying on the F-15B's test fixture called the centerline instrument pylon. The pylon is located under the aircraft's fuselage.
Image above: A new supersonic probe seen affixed to a F-15B flight test fixture might one day measure the sonic booms of a new generation of supersonic aircraft. Image Credits: NASA Photo/Lauren Hughes.
Researchers will be evaluating the performance of the probe originally developed by Eagle Aeronautics of Hampton, Virginia, and redesigned by NASA for this phase. The probe will be tested in a flight environment and the results will be compared with a traditional NACA-style probe that was flown on the centerline instrumented pylon in 2012. In addition to obtaining air data measurements underneath the F-15B, the probe will measure the strength of a shockwave generated from, as of yet, an undetermined part of the F-15B aircraft structure.
"You want to have minimal lag in your measurement system in order to accurately characterize the intensity of the shockwave," said Mike Frederick, NASA Armstrong principal investigator of the Eagle Aero Probe. "With this probe, pressure changes are seen almost immediately because the pressure sensors are located within about four inches of the pressure ports on the nosecone. For comparison, on the F-15B nose boom, which has been used for air-to-air probing in the past, the pressure transducers are located back in the radome, approximately 15 feet behind the pressure ports."
Image above: From left, Mike Frederick and NASA interns Jack Ly and Kassidy McLaughlin monitor a flight. Image Credits: NASA Photo/Lauren Hughes.
A later phase of the testing will be to install the probe on either the nose of the F-15B, or on one of NASA's F-15D aircraft based at Armstrong, Pauer said. The Eagle Aero Probe will replace the current nose boom during shockwave probing research flights, he added.
The later flights will look at shockwaves generated by another nearby supersonic aircraft and are expected to obtain more accurate data than traditional probes, Pauer explained.
"If the flights go as planned, the Eagle Aero Probes could be used to measure the shockwaves generated by future supersonic aircraft," Pauer said. "This data could help improve aircraft design tools that would ultimately reduce the loudness of sonic booms."
Image above: Research on the Eagle Aero Probe is ongoing from an F-15B flight test fixture, as the aircraft flies missions over the high desert. Image Credits: NASA Photo/Jim Ross.
Previous generations of the Eagle Aero Probes flew on the F-15B as part of a continuing effort that began as a NASA Research Announcement effort in 2009. The probes were tested in the Unitary Plan Wind Tunnel at NASA's Langley Research Center in Hampton prior to flight research at NASA Armstrong.
From the data obtained during this current flight phase, a key deficiency with the previous generations of the probe appears to be solved, Frederick said. A heater control system added into the probe keeps the pressure transducer temperatures stable at 150 degrees F, minimizing temperature effects on the pressure transducers and resulting in more accurate pressure measurements.
Supersonic Flight: https://www.nasa.gov/subject/7566/supersonic-flight
Armstrong Flight Research Center: https://www.nasa.gov/centers/armstrong/home/index.html
Images (mentioned), Text, Credits: NASA Armstrong Flight Research Center/Jay Levine/Monroe Conner.
Publié par Orbiter.ch à 16:50