vendredi 11 août 2017

Hunting season at the LHC

CERN - European Organization for Nuclear Research logo.

11 Aug 2017

Image above: Like hunters following the tracks of their prey, physicists compare real collision data with simulations of what they expect to see if a new particle is produced and decays in their detectors. (Supersymmetry simulation image: the CMS collaboration).

With the LHC now back smashing protons together at an energy of 13 TeV, what exotic beasts do physicists hope to find in this unfamiliar corner of the natural world?

Among the top priorities for the LHC experiments this year is the hunt for new particles suspected to lurk at the high-energy frontier: exotic beasts that do not fit within the Standard Model of particle physics and could lift the lid on an even deeper theory of nature’s basic workings.

Following the discovery of the Higgs boson five years ago, which was the final missing piece of the Standard Model of particle physics, physicists have good reason to expect that new particle species lie over the horizon. Among them is the mystery of what makes up dark matter, why the Standard Model particles of matter weigh what they do and come in three families of two, and, indeed, why the Higgs boson isn’t vastly heavier than it is – that is, why it isn't so heavy that it could have ended the evolution of the universe an instant after the Big Bang.

Casting the net wide

These outlandish prey are just a few of the known unknowns for physicists. To ensure that no corner of the new-physics landscape is left unturned, the LHC experiments also employ a model-independent approach to search for general features such as pairs of high-energy quarks and leptons or for unexplained sources of missing energy.

Image above: New particles predicted by specific models of physics beyond the Standard Model (Image: Daniel Dominguez, with permission from Hitoshi Murayama).

Their most elusive quarry might not light up their detectors at all, forcing the LHC exploration teams to adopt stealth approaches, such as making ultra-precise measurements of known Standard Model processes and seeing if they diverge from predictions. While physicists are hoping for a clear shot at any new particle species – a distinctive “bump” in the data that can only be explained by the presence of a new, heavy particle – they could be faced with a mere rustling in the undergrowth or other indirect signs that something is awry. This quest is not just the preserve of all of the LHC experiments, but also of numerous other experiments at CERN that are not linked to the LHC.

Either way, physicists exploring this uncharted territory of the high-energy frontier have to take extreme care not to get tricked by numerous Standard Model doppelgängers or be teased by inconclusive statistics. Even after an exotic new beast has been snared statistically and it seems that the LHC experiments have a discovery on their hands, so begins the task of identifying what the beast really is: a mere mutant or close relative of a species we already know? Or the first glimpse of a new subatomic kingdom?

Ranging from the bizarre to the mind-boggling, and in no particular order, below is a summary of some of the quantum creatures that are in the LHC experimentalists’ sights this year.

- Supersymmetric particles:


For more than 40 years, physicists have been beguiled by a hypothetical symmetry of space–time called supersymmetry (SUSY), which would imply that every particle in the Standard Model has a partner called a “sparticle”. Given that these have not yet been seen, they must be heavier than the standard version.


Considered by many to be mathematically beautiful, SUSY can settle some of the technical problems with the Standard Model and suggests ways in which the fundamental forces may be unified. The lightest SUSY particle is also a good candidate to explain what makes up dark matter.


SUSY could reveal itself in many ways in the LHC’s ATLAS and CMS experiments, for instance in events in which much of the energy is carried away by massive, weakly interacting sparticles. Like previous colliders, the LHC has so far found no evidence for supersymmetry, which rules out the existence of certain types of sparticles below a mass of 2 TeV.

- Higgs siblings:


The Standard Model demands just one type of Higgs boson, and so far it seems that the observed Higgs particle fits the requirements. However, many theories suggest that this standard Higgs is one of a wider family of Higgs particles with slightly different properties – SUSY predicts no less than five of them.


Since the Higgs boson, which gives the Standard Model particles their masses, is a fundamentally different “scalar” object compared to all other known particles, it could open the door to new physics domains.


Exotic cousins of the Higgs have different electrical charges and other properties, especially their mass, forcing them to decay differently to the standard Higgs in ways that should be relatively easy to spot.

- New vector bosons:


At the quantum level, nature’s fundamental forces are mediated by elementary particles called vector bosons: the neutral photon for electromagnetism, and the neutral Z or charged W bosons for the weak nuclear force responsible for radioactive decay. In principle, additional vector bosons – known as W’ and Z’ – could exist, too.


Finding such particles would constitute the discovery of a fifth force of nature, radically changing our view of the universe and extending the structure of the Standard Model.


Experimental signatures of new vector bosons, which presumably are heavier than the W and Z, otherwise they would have been spotted by now, range from direct production in ATLAS and CMS to more subtle signs of lepton flavour violation in LHCb.

- Extra dimensions:


The possible existence of additional dimensions of space beyond the three we know of was put forward in the late 1990s to nurse some of the Standard Model’s ills. In this picture, the entire universe could merely be a 3D “brane” floating through a higher-dimensional bulk, to which the Standard model particles are forever shackled while leaving the force of gravity to propagate freely in the bulk, or there could be additional microscopic dimensions at extremely small scales.

If true, it would allow physicists to study gravitons and other gravitational phenomena in the lab, as it would shift the scale of quantum gravity by many orders of magnitude, right down to the TeV scale where the LHC operates.


The presence of extra dimensions could produce a clear missing-energy signal in the ATLAS and CMS detectors and lead to “resonances”, like notes on a guitar string, that correspond to invisible relatives of the hypothetical carrier of gravity: the graviton.

- Quantum black holes:


If extra dimensions exist, implying gravity is stronger than we thought, it is possible for very light black-holes to exist – mathematically resembling a conventional astrophysical black hole but trillions and trillions of times lighter. Such a state is predicted to evaporate more or less as soon as it formed and therefore poses no danger. After all, if such creatures are created at high energies, then they are also created all the time in collisions between cosmic rays and the upper atmosphere without doing any apparent harm.

The discovery of a miniature black hole would revolutionise physics and accelerate efforts to create a quantum theory of gravity that unites quantum mechanics with Einstein’s general theory of relativity.


Miniature black holes would decay or “evaporate” instantly into other particles, revealing themselves as events containing multiple particles.

- Dark matter:


The Standard Model, while passing every test on Earth, can only account for 5% of the matter observed in the universe as a whole. It is presumed that the dark matter known to exist from astronomical observations is made of some kind of particle, perhaps a supersymmetric particle, but precisely which type is a still a mystery.

In addition to explaining a large fraction of the universe, the ability to study dark matter in the laboratory would open a rich and fascinating new line of experimental study.


Dark matter interacts very weakly, if at all, via the standard forces, and would leave a characteristic missing-energy signature in the ATLAS and CMS detectors.

- Leptoquarks:


The Standard Model contains two basic types of matter: quarks, which make up protons and neutrons; and leptons, such as electrons and neutrinos. Leptoquarks are hypothetical particles that are a bit of both, allowing quarks and leptons to transform into one another.

Leptoquarks appear in certain extensions of the Standard Model, in particular in attempts to unify the strong, weak and electromagnetic interactions.


Since they are expected to decay into a lepton and a quark, searches at the LHC look for characteristic bumps in the mass distributions of decay products.

- Quark substructure:


All the experimental evidence so far indicates that the six types of quarks we know of are indivisible, but history has shown us to be wrong on this front with other particles, not least the atom. Exploring matter at smaller scales, it is natural to ask: are quarks really the smallest entities, or do they possess components inside them?


If found, quark substructure would prove that there is a whole new layer of the subatomic world that we do not yet know about. The existence of “preons” has been postulated to give an explanation at a more fundamental level to the table of elementary particles and forces, with the aim of replicating the successful ordering of the periodic table.


The experimental signature of the compositeness of quarks can be the detection of the decay of a quark in an excited state into ordinary quarks and gluons, which will in turn produce two streams of highly-energetic collimated particles called jets.

- Heavy sterile neutrinos:


The Standard Model involves three types of light neutrinos – electron, muon and tau neutrinos – but several puzzles, such as the very small mass of regular neutrinos, suggest that there might be additional, sterile neutrinos, much heavier than the regular ones.


If found, a heavy sterile neutrino can help solve the problem of matter-antimatter asymmetry in the universe. It could also be a candidate for dark matter, in addition to accounting for the small masses of the regular, non-sterile neutrinos, which cannot be otherwise explained in the framework of the Standard Model.


The mass of sterile neutrinos is theoretically unknown, but their presence could be revealed when they “oscillate” into regular, flavoured neutrinos.

- Long-lived particles:


New particles produced in a particle collision are generally assumed to decay immediately, almost precisely at their points of origin, or to escape undetected. However, many models of new physics include heavy particles with lifetimes large enough to allow them to travel distances ranging from a few micrometres to a few hundred thousand kilometres before decaying into ordinary matter.


Heavy, long-lived particles can help explaining many of the unsolved questions of the Standard Model, such as the small mass of the Higgs boson, dark matter, and perhaps the imbalance of matter and antimatter in the universe.


Long-lived particles could appear like a stream of ordinary matter spontaneously appearing out of nowhere (“displaced vertices”). Other ways to search for them include looking for a large “dE/dx”, long time of flight or tracks disappearing in the detector.


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.

Related links:

LHC experiments:

Large Hadron Collider (LHC):

Standard Model:

Higgs boson:

For more information about European Organization for Nuclear Research (CERN), Visit:

Images (mentioned), Text, Credits: CERN/Matthew Chalmers, Stefania Pandolfi.

Best regards,

Weather Forecast for Monday’s Planned Launch of SpaceX CRS-12

SpaceX - CRS-12 Dragon Mission patch.

August 11, 2017

Meteorologists with the U.S. Air Force 45th Space Wing are predicting a 70 percent chance of favorable weather for liftoff of the SpaceX Falcon 9 rocket carrying a Dragon spacecraft. Launch of the company’s twelfth commercial resupply mission to the International Space Station is scheduled for Monday, Aug. 14 at 12:31 p.m. EDT from Launch Pad 39A at NASA’s Kennedy Space Center in Florida.

Image above: On June 3, 2017, a SpaceX Falcon 9 rocket lifted off from Launch Complex 39A on the company’s 11th commercial resupply services mission to the International Space Station. Photo credits: NASA/Tony Gray.

Rain and thunderstorms are expected today and through the weekend, especially in the afternoon – a familiar summer weather pattern for Florida’s Space Coast. Heading into Monday, cumulus clouds and flight through precipitation are forecasters’ primary launch weather concerns, but the early afternoon launch time is helpful.7

Related links:

NASA Television:


Cargo Resupply (CRS):

Image (mentioned), Text, Credits: NASA/Anna Heiney.


Hubble Displays a Dwarf Spiral Galaxy

NASA - Hubble Space Telescope patch.

Aug. 11, 2017

The subject of this NASA/ESA Hubble Space Telescope image is a dwarf galaxy named NGC 5949. Thanks to its proximity to Earth — it sits at a distance of around 44 million light-years from us, placing it within the Milky Way’s cosmic neighborhood — NGC 5949 is a perfect target for astronomers to study dwarf galaxies.

With a mass of about a hundredth that of the Milky Way, NGC 5949 is a relatively bulky example of a dwarf galaxy. Its classification as a dwarf is due to its relatively small number of constituent stars, but the galaxy’s loosely-bound spiral arms also place it in the category of barred spirals. This structure is just visible in this image, which shows the galaxy as a bright yet ill-defined pinwheel. Despite its small proportions, NGC 5949’s proximity has meant that its light can be picked up by fairly small telescopes, something that facilitated its discovery by the astronomer William Herschel in 1801.

Astronomers have run into several cosmological quandaries when it comes to dwarf galaxies like NGC 5949. For example, the distribution of dark matter within dwarfs is quite puzzling (the “cuspy halo” problem), and our simulations of the Universe predict that there should be many more dwarf galaxies than we see around us (the “missing satellites” problem).

Hubble Space Telescope

For images and more information about Hubble, visit:

Image, Animation, Credits: ESA/Hubble & NASA/Text Credits: European Space Agency/NASA/Karl Hille.

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TRAPPIST-1 is Older Than Our Solar System

Jet Propulsion Laboratory (JPL) logo.

August 11, 2017

Image above: This illustration shows what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Image Credits: NASA/JPL-Caltech.

If we want to know more about whether life could survive on a planet outside our solar system, it's important to know the age of its star. Young stars have frequent releases of high-energy radiation called flares that can zap their planets' surfaces. If the planets are newly formed, their orbits may also be unstable. On the other hand, planets orbiting older stars have survived the spate of youthful flares, but have also been exposed to the ravages of stellar radiation for a longer period of time.

Scientists now have a good estimate for the age of one of the most intriguing planetary systems discovered to date -- TRAPPIST-1, a system of seven Earth-size worlds orbiting an ultra-cool dwarf star about 40 light-years away. Researchers say in a new study that the TRAPPIST-1 star is quite old: between 5.4 and 9.8 billion years. This is up to twice as old as our own solar system, which formed some 4.5 billion years ago.

The seven wonders of TRAPPIST-1 were revealed earlier this year in a NASA news conference, using a combination of results from the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, NASA's Spitzer Space Telescope, and other ground-based telescopes. Three of the TRAPPIST-1 planets reside in the star's "habitable zone," the orbital distance where a rocky planet with an atmosphere could have liquid water on its surface. All seven planets are likely tidally locked to their star, each with a perpetual dayside and nightside.

At the time of its discovery, scientists believed the TRAPPIST-1 system had to be at least 500 million years old, since it takes stars of TRAPPIST-1's low mass (roughly 8 percent that of the Sun) roughly that long to contract to its minimum size, just a bit larger than the planet Jupiter. However, even this lower age limit was uncertain; in theory, the star could be almost as old as the universe itself. Are the orbits of this compact system of planets stable? Might life have enough time to evolve on any of these worlds?

"Our results really help constrain the evolution of the TRAPPIST-1 system, because the system has to have persisted for billions of years. This means the planets had to evolve together, otherwise the system would have fallen apart long ago," said Adam Burgasser, an astronomer at the University of California, San Diego, and the paper's first author. Burgasser teamed up with Eric Mamajek, deputy program scientist for NASA's Exoplanet Exploration Program based at NASA's Jet Propulsion Laboratory, Pasadena, California, to calculate TRAPPIST-1's age. Their results will be published in The Astrophysical Journal.

It is unclear what this older age means for the planets' habitability. On the one hand, older stars flare less than younger stars, and Burgasser and Mamajek confirmed that TRAPPIST-1 is relatively quiet compared to other ultra-cool dwarf stars. On the other hand, since the planets are so close to the star, they have soaked up billions of years of high-energy radiation, which could have boiled off atmospheres and large amounts of water. In fact, the equivalent of an Earth ocean may have evaporated from each TRAPPIST-1 planet except for the two most distant from the host star: planets g and h. In our own solar system, Mars is an example of a planet that likely had liquid water on its surface in the past, but lost most of its water and atmosphere to the Sun's high-energy radiation over billions of years.

Image above: TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its seven planets orbit very close to it. Image Credits: NASA/JPL-Caltech.

However, old age does not necessarily mean that a planet's atmosphere has been eroded. Given that the TRAPPIST-1 planets have lower densities than Earth, it is possible that large reservoirs of volatile molecules such as water could produce thick atmospheres that would shield the planetary surfaces from harmful radiation. A thick atmosphere could also help redistribute heat to the dark sides of these tidally locked planets, increasing habitable real estate. But this could also backfire in a "runaway greenhouse" process, in which the atmosphere becomes so thick the planet surface overheats - as on Venus.

"If there is life on these planets, I would speculate that it has to be hardy life, because it has to be able to survive some potentially dire scenarios for billions of years," Burgasser said.

Fortunately, low-mass stars like TRAPPIST-1 have temperatures and brightnesses that remain relatively constant over trillions of years, punctuated by occasional magnetic flaring events. The lifetimes of tiny stars like TRAPPIST-1 are predicted to be much, much longer than the 13.7 billion-year age of the universe (the Sun, by comparison, has an expected lifetime of about 10 billion years).

"Stars much more massive than the Sun consume their fuel quickly, brightening over millions of years and exploding as supernovae," Mamajek said. "But TRAPPIST-1 is like a slow-burning candle that will shine for about 900 times longer than the current age of the universe."

Some of the clues Burgasser and Mamajek used to measure the age of TRAPPIST-1 included how fast the star is moving in its orbit around the Milky Way (speedier stars tend to be older), its atmosphere's chemical composition, and how many flares TRAPPIST-1 had during observational periods. These variables all pointed to a star that is substantially older than our Sun.

Future observations with NASA's Hubble Space Telescope and upcoming James Webb Space Telescope may reveal whether these planets have atmospheres, and whether such atmospheres are like Earth's.

"These new results provide useful context for future observations of the TRAPPIST-1 planets, which could give us great insight into how planetary atmospheres form and evolve, and persist or not," said Tiffany Kataria, exoplanet scientist at JPL, who was not involved in the study.

Future observations with Spitzer could help scientists sharpen their estimates of the TRAPPIST-1 planets' densities, which would inform their understanding of their compositions.

For more information about TRAPPIST-1, visit:

Images (mentioned), Text, Credits: NASA/JPL/Elizabeth Landau.

Best regards,

25 Years of Global Sea Level Data, and Counting

Jet Propulsion Laboratory (JPL) logo.

August 11, 2017

Animation above: Changes in sea level height from 1993 to 2017 compared with a long-term mean of the data. Blue and purple are lower than the mean; red, yellow and white are higher. Animation Credits: NASA/JPL-Caltech.

Today marks the 25th anniversary of the launch of a revolutionary ocean research vessel -- a space "ship." As the NASA/CNES Topex-Poseidon satellite ascended into orbit, it ushered in a new era of oceanography with the first highly accurate, global measurements of sea levels. That mission and its three successors, all named Jason, have continuously mapped global ocean currents and tides; opened our eyes to the global reach of El Niño and other climate events; created a quarter-century-long, extraordinarily precise record of global and regional sea level rise; and enabled improved forecasts of extreme weather events such as hurricanes, floods and droughts.

A new slideshow celebrates this important data set -- a fundamental measurement for the study of the oceans and climate -- and the longstanding U.S.-French collaboration that brought it about.


Image above: Topex-Poseidon illustration. Image Credits: NASA/JPL-Caltech.

In 1992, when Topex-Poseidon launched, no one foresaw that its record of precision ocean height measurements would continue through three decades and four spacecraft. In fact, many oceanographers at the time weren't convinced that Topex-Poseidon's sensors would be accurate enough to reveal the signal of sea level rise out of the noise of waves, tides and other changes. But the radar altimeter and radiometer measurement system outperformed expectations from the start. In 25 years of continuous operation, Topex-Poseidon and its successors have recorded 2.8 inches (7 centimeters) of global average sea level rise.

Our planet's oceans are too vast and complex to be fully measured by any single satellite, or even by any single nation. Topex-Poseidon and its successor Jason satellite missions are shining examples of the power of a sustained, long-term international partnership, led by the U.S. and French space agencies, NASA and CNES.  For nearly three decades, NASA and CNES scientists and engineers have pooled their expertise, talents and insights to design and construct an integrated spaceborne measurement system far more powerful than the sum of its parts. NASA and CNES have worked together, applying advanced technology to collect measurements of remarkable precision and accuracy, and then making those measurements freely and openly available. With this effort, they have provided humanity with unprecedented views of the global oceans, how they change on time scales of days to decades, and how the oceans influence -- and respond to -- weather and climate.

"For more than a generation, NASA and CNES scientists and engineers have collaborated to make exquisitely accurate measurements of the ocean surface from space, providing insights into the workings and interactions of our planet's two great fluid systems, the oceans and the atmosphere," said Michael Freilich, director of NASA's Earth Science Division in Washington.

Ocean Currents
Perpetual Ocean

Video above: This is an animation of ocean surface currents from June 2005 to December 2007 from NASA satellites. Video Credits: NASA/GSFC/SVS.

The Topex-Poseidon mission was the first to monitor the changing patterns of major ocean surface currents in a comprehensive way. Ocean current locations are revealed by large-scale hills and valleys on the ocean surface, which can vary by more than 6 feet (2 meters) in height. The peaks and dips defining the ocean's topography are caused by variations in water temperature and pressure.  Large-scale currents like the Gulf Stream tend to flow along contours of constant ocean height, following the sides of the hills and valleys.  The steepness of a slope indicates the speed of the current. Unlike terrain on land, however, the liquid "landscape" shifts with changes in winds, temperature and other factors, causing shifts in the locations and speeds of the currents. The only way to monitor these changes over the entire surface of Earth's ocean is to make precise measurements of the height of the ocean surface from orbiting satellites.

Measuring the ocean shape over nearly the entire globe every 10 days, Topex-Poseidon gave the first quantitative view of how ocean currents change with the seasons. Topex/Poseidon and the Jason-1, Jason-2 and Jason-3 missions have provided unique insights into how ocean circulation affects climate by moving heat from place to place on our planet.

Heat Storage in the Ocean

Image above: NOAA's annual assessment of the heat in the upper ocean (2015 shown), a measure of global warming, draws on Topex series data. Image Credit: NOAA.

More than 90 percent of the heat from global warming is stored in the ocean, which means oceans are key players in global climate. Heat causes ocean water to expand, adding to sea level rise. Measuring both long-term sea level trends and the shape of the ocean surface related to currents, Topex-Poseidon and the Jason series provide two basic ingredients for understanding the ocean's role in global climate variations.

"As human-caused global warming drives sea levels higher and higher, we are literally contributing to the reshaping of the surface of our planet," said Josh Willis, NASA project scientist for Jason-3 at NASA's Jet Propulsion Laboratory in Pasadena, California. "The precision altimetric satellite missions tell us how much and how fast."

El Niño, La Niña, and More

Image above: Among Topex-Poseidon's early achievements was recording the full extent of a record El Niño in 1997 and the succeeding La Niña in 1999. Darker colors are sea levels lower than normal, lighter and white colors are higher than normal. Image Credits: NASA/JPL-Caltech.

For decades, scientists could not predict how El Niño and other year-to-year ocean variations changed regional weather. That was partly because, using only ships and buoys, they couldn't observe the genesis and growth of these changes far out in the equatorial Pacific. Topex-Poseidon and the Jason satellites have given the first frequent, global views of the full extent and life cycles of El Niño and La Niña events. Lee-Lueng Fu of JPL -- project scientist for the first two ocean altimetry missions -- pointed out, "Topex-Poseidon allowed us to follow their evolution and showed that these events weren't limited to just the tropics. It also gave us evidence of even longer-lasting ocean variations." One of these is the Pacific Decadal Oscillation, similar to El Niño and La Niña in character but with phases lasting up to several decades.

In the last 25 years, with the help of altimetry data, scientists have pinpointed many global connections between these multi-year ocean variations and weather consequences such as drought and flooding throughout the globe. While these events have by no means yielded all their secrets, they are better understood and better forecast than before global spaceborne observations began.

Tides on the Open Ocean

Image above: A numerical model of daily global tides using sea level data from Topex-Poseidon. Image Credit: ESR.

Before satellite measurements, deep-ocean tide measurements were difficult to make, expensive and sparse. Topex-Poseidon made the first global maps of tides, which changed scientists' understanding of how tides dissipate. The data show that a third of tidal energy dissipates in the open ocean, playing important and previously unknown roles in mixing water within the ocean.


Topex-Poseidon had a three-year prime mission, but long before that time was up, oceanographers and other Earth scientists recognized the value of continuing its measurements as long as possible. Fu explained, "Sea surface height is a fundamental measure of the Earth system, so it was a no-brainer that scientists would want to have this kind of information indefinitely." With strong community support, Jason-1 was constructed by NASA and CNES and launched in December 2001. For three years, Topex-Poseidon and Jason-1 flew in coordinated orbits that allowed scientists to cross-calibrate their measurements and then combine the data sets to observe the global oceans more frequently. Each succeeding mission has also overlapped its predecessor, ensuring a consistent data record.

So far, each of the ocean altimetry missions has proven to be long-lived. Topex-Poseidon was eventually decommissioned in 2005 after 13 years in orbit. Jason-1 survived almost 12 years, until July 2013. Nine-year-old Jason-2 and Jason-3 (launched in January 2016) are still in operation.


Image above: Lee Fu (left) was the project scientists for Topex Poseidon and Jason-1 and -2. Josh Willis is the current project scientist for Jason-2 and -3. Image Credits: NASA/JPL-Caltech.

With the launch of Jason-2 in June 2008, the focus of spaceborne ocean altimetry transitioned from research objectives to data applications providing tangible benefits to society. Mission operations moved from the research agencies NASA and CNES to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT); indeed, satellite altimeter measurements are used routinely in NOAA's El Niño forecasts. NASA and CNES continue to provide science teams, instrument design, and science-focused, specialized data management.


Image above: Jason-1 data contributed to this forecast of Hurricane Rita's track across the Gulf of Mexico in 2005. The storm track appears as a black line. Jason-1 observed a tongue of very warm water (red) in the gulf, 13-23 inches ( 35-60 centimeters) higher than surrounding water. Ocean heat can strengthen hurricane intensity. Image Credits: NASA/JPL-Caltech/University of Colorado.

On smaller space and time scales, satellite altimetry measurements provide information directly useful for marine storm prediction. Hurricanes are fueled by heat stored in the ocean below, and since the upper ocean expands and contracts as it heats and cools, sea level height is a marker for water temperature and heat content. So it is hardly surprising that ocean altimetry data are routinely used in forecasting hurricane strength.

In 2014, an unexpected forecasting use for altimetry data became operational. Bangladesh, whose 46-year history has encompassed death-dealing river floods, uses Jason-2 measurements of river levels in its flood forecasting and warning system. Within the first year using these data, Bangladesh's system enabled the most accurate, long-lead flood warnings ever given for that nation.


Image above: The U.S. Navy uses the ocean altimetry satellites' data to aid surface and underwater navigation. Image Credit: U.S. Navy.

Civilian sailors and the U.S. Navy use the series' near-real-time data on currents, eddies, winds and waves to aid surface and underwater navigation. Information on eddy currents in the Gulf of Mexico has been used by marine operators to schedule offshore drilling operations, with significant cost savings.


Video above: Artist's rendering of Jason-3. Video Credits: NASA/JPL-Caltech.

When Jason-3 launched in 2016, NASA project scientist Willis commented, "This mission has big shoes to fill. Its predecessors have built one of the clearest records we have of our changing climate." Jason-3 has performed flawlessly in continuing the global record of precise sea-surface topography measurements and is now halfway through its prime mission.

A New Role for Jason-2

Image above: Jason-2's new, lower orbit will allow scientists -- such as Walter H. Smith (NOAA) and David Sandwell (Scripps Institution of Oceanography), who produced this map -- to improve their understanding of features on the global seafloor. Image Credit: NOAA.

This year, Jason-2's onboard systems began to show signs of space radiation damage. The mission management decided to lower the satellite out of its shared orbit with Jason-3. At the urging of the science community, the satellite was lowered by 17 miles (27 kilometers), where it will collect data along a series of ground tracks only 5 miles (8 kilometers) apart, with a one-year repeat cycle.

Besides protecting Jason-3, the new orbit will allow Jason-2 to produce an improved, high-resolution estimate of Earth's average sea surface height. Because ocean topography is partly determined by the contours on the ocean bottom, the estimate is expected to enable scientists to improve maps of the seafloor, resolving currently unknown details of underwater features such as seamounts. These maps will permit advances in ocean modeling, tsunami wave forecasting and naval operations support.

Into the Future

Image above: Illustration of the upcoming Sentinel-6 mission. Image Credit: ESA.

The next ocean altimetry mission, expected to launch in 2020, is called Jason Continuity of Service (Jason-CS) on the Sentinel-6 mission. As the long name implies, it will carry on the proud Jason legacy, but with a new partner: the European Space Agency. EUMETSAT will lead the mission, and NASA's role will remain similar to its role in Jason-3. CNES will assess and evaluate the performance of the mission and provide precise orbit determination.

Satellites have already revolutionized oceanography, and soon they will do the same for hydrology -- the study of water on land. The French/U.S. Surface Water and Ocean Topography (SWOT) mission will be at the forefront, carrying an innovative interferometer dubbed KaRin that marks a break with today's technologies.

Fu notes that these changes show the value the world scientific community places on the ocean altimetry program. "The measurement is so important, and the technology is fully demonstrated," he said. "In the long haul, ocean altimetry is an international commitment."

Related links:









Jet Propulsion Laboratory (JPL):

Animation (mentioned), Images (mentioned), Videos (mentioned), Text, Credits: NASA, written by Carol Rasmussen/JPL/Alan Buis.


jeudi 10 août 2017

Eye Check Day on Station, Dragon Gets Ready For Launch

ISS - Expedition 52 Mission patch.

August 10, 2017

International Space Station (ISS). Animation Credit: NASA

The Expedition 52 crew members pulled out their medical hardware today for a variety of eye checks and other biomedical research. The station residents are also making space and packing up gear for next week’s cargo delivery aboard the SpaceX Dragon.

The crew each participated in a series of eye exams throughout Thursday working with optical coherence tomography (OCT) gear. OCT is a medical imaging technique that captures imagery of the retina using light waves. A pair of cosmonauts then peered into a fundoscope for a more detailed look at the eye’s interior. The regularly scheduled eye checks were conducted with real-time input from doctors on the ground.

SpaceX completed a static fire test of its Falcon 9 rocket today at NASA’s Kennedy Space Center. The Dragon cargo craft will be perched atop the Falcon 9 for a targeted launch Monday at 12:31 p.m. EDT.

Image above: The full moon is pictured from the International Space Station. Image Credit: NASA.

Once in space, Dragon will conduct a series of orbital maneuvers navigating its way to the station Wednesday morning. Finally, Dragon will reach its capture point ten meters away from the complex. From there, astronauts Jack Fischer and Paolo Nespoli will command the Canadarm2 to reach out and grapple Dragon. Next, ground controllers remotely guide Dragon still attached to the Canadarm2 and install it to the Harmony module.

The crew is clearing space on the International Space Station today and packing gear to stow on Dragon after it arrives next week. NASA TV begins its pre-launch coverage Sunday covering Dragon’s science payloads. Monday’s launch coverage begins at noon. NASA TV will also broadcast Dragon’s arrival Wednesday beginning at 5:30 a.m.

Related links:

Expedition 52:


Kennedy Space Center:

Launch coverage:

Space Station Research and Technology:

International Space Station (ISS):

Animation (mentioned), Image (mentioned), Text, Credits: NASA/Mark Garcia.

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Day to Night and Back Again: Earth’s Ionosphere During the Total Solar Eclipse

NASA - Solar Dynamics Observatory (SDO) patch.

Aug. 10, 2017

On Aug. 21, 2017, the Moon will slide in front of the Sun and for a brief moment, day will melt into a dusky night. Moving across the country, the Moon’s shadow will block the Sun’s light, and weather permitting, those within the path of totality will be treated to a view of the Sun’s outer atmosphere, called the corona.

But the total solar eclipse will also have imperceptible effects, such as the sudden loss of extreme ultraviolet radiation from the Sun, which generates the ionized layer of Earth’s atmosphere, called the ionosphere. This ever-changing region grows and shrinks based on solar conditions, and is the focus of several NASA-funded science teams that will use the eclipse as a ready-made experiment, courtesy of nature.

NASA is taking advantage of the Aug. 21 eclipse by funding 11 ground-based science investigations across the United States. Three of these will look to the ionosphere in order to improve our understanding of the Sun’s relationship to this region, where satellites orbit and radio signals are reflected back toward the Earth.

“The eclipse turns off the ionosphere’s source of high-energy radiation,” said Bob Marshall, a space scientist at University of Colorado Boulder and principal investigator for one of the studies. “Without ionizing radiation, the ionosphere will relax, going from daytime conditions to nighttime conditions and then back again after the eclipse.”

Animation above: During the total solar eclipse, the Moon will turn off the ionosphere’s source of extreme ultraviolet radiation: The ionosphere will go from daytime conditions to nighttime conditions. Animation Credits: NASA’s Goddard Space Flight Center/Katy Mersmann.

Stretching from roughly 50 to 400 miles above Earth’s surface, the tenuous ionosphere is an electrified layer of the atmosphere that reacts to changes from both Earth below and space above. Such changes in the lower atmosphere or space weather can manifest as disruptions in the ionosphere that can interfere with communication and navigation signals.

“In our lifetime, this is the best eclipse to see,” said Greg Earle, an electrical and computer engineer at Virginia Tech in Blacksburg, Virginia, who is leading another of the studies. “But we’ve also got a denser network of satellites, GPS and radio traffic than ever before. It’s the first time we’ll have such a wealth of information to study the effects of this eclipse; we’ll be drowning in data.”

Pinning down ionospheric dynamics can be tricky. “Compared to visible light, the Sun’s extreme ultraviolet output is highly variable,” said Phil Erickson, a principal investigator of a third study and space scientist at Massachusetts Institute of Technology’s Haystack Observatory in Westford, Massachusetts. “That creates variability in ionospheric weather. Because our planet has a strong magnetic field, charged particles are also affected along magnetic field lines all over the planet — all of this means the ionosphere is complicated.”

But when totality hits on Aug. 21, scientists will know exactly how much solar radiation is blocked, the area of land it’s blocked over and for how long. Combined with measurements of the ionosphere during the eclipse, they’ll have information on both the solar input and corresponding ionosphere response, enabling them to study the mechanisms underlying ionospheric changes better than ever before.

Animation above: The Moon’s shadow will dramatically affect insolation — the amount of sunlight reaching the ground — during the total solar eclipse. Animation Credits: NASA's Scientific Visualization Studio.

Tying the three studies together is the use of automated communication or navigation signals to probe the ionosphere’s behavior during the eclipse. During typical day-night cycles, the concentration of charged atmospheric particles, or plasma, waxes and wanes with the Sun.

“In the daytime, ionospheric plasma is dense,” Earle said. “When the Sun sets, production goes away, charged particles recombine gradually through the night and density drops. During the eclipse, we’re expecting that process in a much shorter interval.”

Image above: During typical day-night cycles, the ionosphere — shown in purple and not-to-scale in this image — waxes and wanes with the Sun. The total solar eclipse will cut off this region’s source of ionizing radiation. Image Credits: NASA's Goddard Space Flight Center/Duberstein.

The denser the plasma, the more likely these signals are to bump into charged particles along their way from the signal transmitter to receiver. These interactions refract, or bend, the path taken by the signals. In the eclipse-induced artificial night the scientists expect stronger signals, since the atmosphere and ionosphere will absorb less of the transmitted energy.

“If we set up a receiver somewhere, measurements at that location provide information on the part of the ionosphere between the transmitter and receiver,” Marshall said. “We use the receivers to monitor the phase and amplitude of the signal. When the signal wiggles up and down, that’s entirely produced by changes in the ionosphere.”

Using a range of different electromagnetic signals, each of the teams will send signals back and forth across the path of totality. By monitoring how their signals propagate from transmitter to receiver, they can map out changes in ionospheric density. The teams will also use these techniques to collect data before and after the eclipse, so they can compare the well-defined eclipse response to the region’s baseline behavior, allowing them to discern the eclipse-related effects.

Probing the Ionosphere 

Image above: A layer of charged particles, called the ionosphere, surrounds Earth, extending from about 50 to 400 miles above the surface of the planet. Image Credits: NASA's Goddard Space Flight Center/Duberstein.

The ionosphere is roughly divided into three regions in altitude based on what wavelength of solar radiation is absorbed: the D, E and F, with D being the lowermost region and F, the uppermost. In combination, the three experiment teams will study the entirety of the ionosphere.

Marshall and his team, from the University of Colorado Boulder, will probe the D-region’s response to the eclipse with very low frequency, or VLF, radio signals. This is the lowest and least dense part of the ionosphere — and because of that, the least understood.

“Just because the density is low, doesn’t mean it’s unimportant,” Marshall said. “The D-region has implications for communications systems actively used by many military, naval and engineering operations.”

Marshall’s team will take advantage of the U.S. Navy’s existing network of powerful VLF transmitters to examine the D-region’s response to changes in solar output. Radio wave transmissions sent from Lamoure, North Dakota, will be monitored at receiving stations across the eclipse path in Boulder, Colorado, and Bear Lake, Utah. They plan to combine their data with observations from several space-based missions, including NOAA’s Geostationary Operational Environmental Satellite, NASA’s Solar Dynamics Observatory and NASA’s Ramaty High Energy Solar Spectroscopic Imager, to characterize the effect of the Sun’s radiation on this particular region of the ionosphere.

Erickson and team will look further up, to the E- and F-regions of the ionosphere. Using over 6,000 ground-based GPS sensors alongside powerful radar systems at MIT’s Haystack Observatory and Arecibo Observatory in Puerto Rico, along with data from several NASA space-based missions, the MIT-based team will also work with citizen radio scientists who will send radio signals back and forth over long distances across the path.

MIT’s science team will use their data to track travelling ionospheric disturbances — which are sometimes responsible for space weather patterns in the upper atmosphere — and their large-scale effects. These disturbances in the ionosphere are often linked to a phenomenon known as atmospheric gravity waves, which can also be triggered by eclipses.

“We may even see global-scale effects,” Erickson said. “Earth’s magnetic field is like a wire that connects two different hemispheres together. Whenever electrical variations happen in one hemisphere, they show up in the other.”

Image above: Earth's limb at night, seen from the International Space Station, with air glow visual composited into the image. Image Credit: NASA.

Earle and his Virginia Tech-based team will station themselves across the country in Bend, Oregon; Holton, Kansas; and Shaw Air Force Base in Sumter, South Carolina. Using state-of-the-art transceiver instruments called ionosondes, they will measure the ionosphere’s height and density, and combine their measurements with data from a nation-wide GPS network and signals from the ham radio Reverse Beacon Network. The team will also utilize data from SuperDARN high frequency radars, two of which lie along the eclipse path in Christmas Valley, Oregon, and Hays, Kansas.

“We’re looking at the bottom side of the F-region, and how it changes during the eclipse,” Earle said. “This is the part of the ionosphere where changes in signal propagation are strong.” Their work could one day help mitigate disturbances to radio signal propagation, which can affect AM broadcasts, ham radio and GPS signals.

Ultimately, the scientists plan to use their data to improve models of ionospheric dynamics. With these unprecedented data sets, they hope to better our understanding of this perplexing region.

“Others have studied eclipses throughout the years, but with more instrumentation, we keep getting better at our ability to measure the ionosphere,” Erickson said. “It usually uncovers questions we never thought to ask.”

For more information on the upcoming total solar eclipse:

Related links:​

NASA Looks to Solar Eclipse to Help Understand Earth’s Energy System:

Chasing the Total Solar Eclipse from NASA’s WB-57F Jets:

Solar Dynamics Observatory (SDO):

GOES (Geostationary Environmental Operational Satellites):

RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager):

Images (mentioned), Animations (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Lina Tran.

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Watch Martian Clouds Scoot, Thanks to NASA's Curiosity

NASA - Mars Science Laboratory (MSL) patch.

Aug. 10, 2017

Animation above: Wispy clouds float across the Martian sky in this accelerated sequence of enhanced images taken on July 17, 2017, by the Navcam on NASA's Curiosity Mars rover. Animation Credits: NASA/JPL-Caltech/York University.

Wispy, early-season clouds resembling Earth's ice-crystal cirrus clouds move across the Martian sky in some new image sequences from NASA's Curiosity Mars rover.

These clouds are the most clearly visible so far from Curiosity, which landed five years ago this month about five degrees south of Mars' equator. Clouds moving in the Martian sky have been observed previously by Curiosity and other missions on the surface of Mars, including NASA's Phoenix Mars Lander in the Martian arctic nine years ago.

Researchers used Curiosity's Navigation Camera (Navcam) to take two sets of eight images of the sky on an early Martian morning last month. For one set, the camera pointed nearly straight up. For the other, it pointed just above the southern horizon. Cloud movement was recorded in both and was made easier to see by image enhancement. A midday look at the sky with the same camera the same day showed no clouds.

Animation above: Clouds drift across the sky above a Martian horizon in this accelerated sequence of enhanced images taken on July 17, 2017, by the Navcam on NASA's Curiosity Mars rover. Animation Credits: NASA/JPL-Caltech/York University.

Mars' elliptical orbit makes that planet's distance from the Sun vary more than Earth's does. In previous Martian years, a belt of clouds has appeared near the equator around the time Mars was at its farthest from the Sun. The new images of clouds were taken about two months before that farthest point in the orbit, relatively early in the season for the appearance of this cloud belt.

"It is likely that the clouds are composed of crystals of water ice that condense out onto dust grains where it is cold in the atmosphere," said Curiosity science-team member John Moores of York University, Toronto, Canada. "The wisps are created as those crystals fall and evaporate in patterns known as 'fall streaks' or 'mare's tails.' While the rover does not have a way to ascertain the altitude of these clouds, on Earth such clouds form at high altitude."

Animation above: Wispy clouds float across the Martian sky in this accelerated sequence of early-morning images taken on July 17, 2017, by the Navcam on NASA's Curiosity Mars rover. Animation Credits: NASA/JPL-Caltech/York University.

York's Charissa Campbell produced the enhanced-image sequences by generating an "average" of all the frames in each sequence, then subtracting that average from each frame, emphasizing any frame-to-frame changes. The moving clouds are also visible, though fainter, in a sequence of raw images.

The Curiosity mission has been investigating the environmental conditions of ancient and modern Mars since the rover landed on Aug. 5, 2012, PDT (Aug. 6, EDT and Universal Time). For more about Curiosity, visit:

Animations (mentioned), Text, Credits: NASA/Laurie Cantillo/Dwayne Brown/Tony Greicius/JPL/Guy Webster.


A Starburst with the Prospect of Gravitational Waves

NASA - Chandra X-ray Observatory patch.

Aug. 10, 2017

In 1887, American astronomer Lewis Swift discovered a glowing cloud, or nebula, that turned out to be a small galaxy about 2.2 billion light years from Earth. Today, it is known as the “starburst” galaxy IC 10, referring to the intense star formation activity occurring there.

More than a hundred years after Swift’s discovery, astronomers are studying IC 10 with the most powerful telescopes of the 21st century. New observations with NASA’s Chandra X-ray Observatory reveal many pairs of stars that may one day become sources of perhaps the most exciting cosmic phenomenon observed in recent years: gravitational waves.

By analyzing Chandra observations of IC 10 spanning a decade, astronomers found over a dozen black holes and neutron stars feeding off gas from young, massive stellar companions. Such double star systems are known as “X-ray binaries” because they emit large amounts of X-ray light. As a massive star orbits around its compact companion, either a black hole or neutron star, material can be pulled away from the giant star to form a disk of material around the compact object. Frictional forces heat the infalling material to millions of degrees, producing a bright X-ray source.

When the massive companion star runs out fuel, it will undergo a catastrophic collapse that will produce a supernova explosion, and leave behind a black hole or neutron star. The end result is two compact objects: either a pair of black holes, a pair of neutron stars, or a black hole and neutron star. If the separation between the compact objects becomes small enough as time passes, they will produce gravitational waves. Over time, the size of their orbit will shrink until they merge. LIGO has found three examples of black hole pairs merging in this way in the past two years.

Starburst galaxies like IC 10 are excellent places to search for X-ray binaries because they are churning out stars rapidly. Many of these newly born stars will be pairs of young and massive stars. The most massive of the pair will evolve more quickly and leave behind a black hole or a neutron star partnered with the remaining massive star. If the separation of the stars is small enough, an X-ray binary system will be produced.

This new composite image of IC 10 combines X-ray data from Chandra (blue) with an optical image (red, green, blue) taken by amateur astronomer Bill Snyder from the Heavens Mirror Observatory in Sierra Nevada, California. The X-ray sources detected by Chandra appear as a darker blue than the stars detected in optical light.

The young stars in IC 10 appear to be just the right age to give a maximum amount of interaction between the massive stars and their compact companions, producing the most X-ray sources. If the systems were younger, then the massive stars would not have had time to go supernova and produce a neutron star or black hole, or the orbit of the massive star and the compact object would not have had time to shrink enough for mass transfer to begin. If the star system were much older, then both compact objects would probably have already formed. In this case transfer of matter between the compact objects is unlikely, preventing the formation of an X-ray emitting disk.

Chandra X-ray Observatory

Chandra detected 110 X-ray sources in IC 10. Of these, over forty are also seen in optical light and 16 of these contain “blue supergiants”, which are the type of young, massive, hot stars described earlier. Most of the other sources are X-ray binaries containing less massive stars. Several of the objects show strong variability in their X-ray output, indicative of violent interactions between the compact stars and their companions.

A pair of papers describing these results were published in the February 10th, 2017 issue of The Astrophysical Journal and is available online here and here. The authors of the study are Silas Laycock from the UMass Lowell’s Center for Space Science and Technology (UML); Rigel Capallo, a graduate student at UML; Dimitris Christodoulou from UML; Benjamin Williams from the University of Washington in Seattle; Breanna Binder from the California State Polytechnic University in Pomona; and, Andrea Prestwich from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Read More from NASA's Chandra X-ray Observatory:

For more Chandra images, multimedia and related materials, visit:

Image, Animation, Text,  Credits: X-ray: NASA/Lee Mohon/CXC/UMass Lowell/S. Laycock et al.; Optical: Bill Snyder Astrophotography.


Preserving the stress of volcanic uprise on Mars

ESA - Mars Express Mission patch.

10 August 2017

Thaumasia mountains

An ancient mountain range on Mars preserves a complex volcanic and tectonic past imprinted with signs of water and ice interactions. 

The images, taken on 9 April by the high-resolution stereo camera on ESA’s Mars Express, show the Thaumasia mountains and Coracis Fossae, which fringe the huge Solis Planum volcanic plateau from the south.

Thaumasia mountain range in context

The region lies to the south of the vast Valles Marineris canyon system and towering Tharsis volcanoes, and is strongly linked to the tectonic stresses that played out during their formation over 3.5 billion years ago.

As the Tharsis bulge swelled with magma during the planet’s first billion years, the surrounding crust was stretched, ripping apart and eventually collapsing into troughs. While Valles Marineris is one of the most extreme results, the effects are still seen even thousands of kilometres away, such as in the Coracis Fossae region observed in this image where near-parallel north–south faults are visible primarily to the left.

Thaumasia mountain topography

Tectonic structures like these can control the movement of magma, heat and water in the subsurface, leading to hydrothermal activity and the production of minerals.

Light-toned deposits, which might be clay minerals formed in the presence of water, stand out in the right part of the colour image and at the rim of the large crater. Similar deposits were identified in the nearby Lampland crater.

Perspective view of crater in Thaumasia mountain range

There is also evidence for valley formation by groundwater erosion and surface runoff occurring at the same time as when the active tectonics shaped the landscape. The water-based erosion means the troughs have been partially buried and heavily modified.

The region was later modified by glacial processes, seen in the flow-like lineated patterns in the flat floors of the large craters.

Thaumasia mountains in 3D

As a representative of the ancient highlands of Mars, this region holds a wealth of information about the Red Planet’s geological history.

Related links:

Mars Express:

Mars Webcam:

Robotic exploration of Mars:

Mars Express overview:

Mars Express in-depth:

ESA Planetary Science archive (PSA):

High Resolution Stereo Camera:

HRSC data viewer:

Behind the lens...

Frequently asked questions:

Images, Text, Credits: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO/NASA MGS MOLA Science Team.

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mercredi 9 août 2017

Station Boosts Orbit, Dragon Launch Slips a Day

ISS - Expedition 52 Mission patch.

August 9, 2017

Moon Rise From the Space Station

Image above: From his vantage point aboard the International Space Station, NASA astronaut Randy Bresnik pointed his camera toward the rising Moon and captured this beautiful image on August 3, 2017. Bresnik wrote, "Gorgeous moon rise! Such great detail when seen from space. Next full moon marks #Eclipse2017. We’ll be watching from @Space_Station." Image Credit: NASA.

A docked Russian cargo craft fired its engines today slightly raising the orbit of the International Space Station. The orbital boost sets up next month’s crew swap. The SpaceX Dragon cargo craft also received a new target launch date while the crew gets ready for a spacewalk next week.

NASA astronauts Peggy Whitson and Jack Fischer will return to Earth on Sept. 2 with cosmonaut Fyodor Yurchikhin wrapping up their Expedition 52 mission. Fischer and Yurchikhin will each have lived 135 consecutive days in space while Whitson will have 289 days. The next crew, with cosmonaut Alexander Misurkin and astronauts Mark Vande Hei and Joe Acaba, launches Sept. 13 to begin a 167-day mission in space.

Image above: Astronaut Peggy Whitson works on the Combustion Integrated Rack in the U.S. Destiny laboratory module. Image Credit: NASA.

SpaceX announced a one-day launch slip of its Dragon cargo craft atop a Falcon 9 rocket. Dragon is now targeted to launch Monday at 12:31 p.m. EDT from Kennedy Space Center. Fischer and astronaut Paolo Nespoli of the European Space Agency are training for Dragon’s arrival and capture planned for Wednesday at 7 a.m.

Two cosmonauts are also gearing up for a spacewalk amidst the cargo mission and crew swap preparations. The experienced Russian spacewalkers, Yurchikhin with eight career spacewalks and Sergey Ryazanskiy with three, performed leak checks, installed batteries and sized up their Orlan spacesuits and ahead of their Aug. 17 spacewalk.

Related links:

Combustion Integrated Rack:

SpaceX Dragon:

Commercial Resupply:

Expedition 52:

Space Station Research and Technology:

International Space Station (ISS):

Images (mentioned), Text, Credits: NASA/Mark Garcia/Sarah Loff.

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Cassini to Begin Final Five Orbits Around Saturn

NASA - Cassini Mission to Saturn patch.

Aug. 9, 2017

Image above: This artist's rendering shows Cassini as the spacecraft makes one of its final five dives through Saturn's upper atmosphere in August and September 2017. Image Credits: NASA/JPL-Caltech.

Cassini spacecraft will enter new territory in its final mission phase, the Grand Finale, as it prepares to embark on a set of ultra-close passes through Saturn’s upper atmosphere with its final five orbits around the planet.

Cassini will make the first of these five passes over Saturn at 12:22 a.m. EDT Monday, Aug. 14. The spacecraft's point of closest approach to Saturn during these passes will be between about 1,010 and 1,060 miles (1,630 and 1,710 kilometers) above Saturn's cloud tops.

The spacecraft is expected to encounter atmosphere dense enough to require the use of its small rocket thrusters to maintain stability – conditions similar to those encountered during many of Cassini's close flybys of Saturn's moon Titan, which has its own dense atmosphere.

"Cassini's Titan flybys prepared us for these rapid passes through Saturn's upper atmosphere," said Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory (JPL) in California. "Thanks to our past experience, the team is confident that we understand how the spacecraft will behave at the atmospheric densities our models predict."

Maize said the team will consider the Aug. 14 pass nominal if the thrusters operate between 10 and 60 percent of their capability. If the thrusters are forced to work harder – meaning the atmosphere is denser than models predict – engineers will increase the altitude of subsequent orbits. Referred to as a "pop-up maneuver,” thrusters will be used to raise the altitude of closest approach on the next passes, likely by about 120 miles (200 kilometers).

If the pop-up maneuver is not needed, and the atmosphere is less dense than expected during the first three passes, engineers may alternately use the "pop-down" option to lower the closest approach altitude of the last two orbits, also likely by about 120 miles (200 kilometers). Doing so would enable Cassini's science instruments, especially the ion and neutral mass spectrometer (INMS), to obtain data on the atmosphere even closer to the planet's cloud tops.

Cassini Grand Finale. Animation Credits: NASA/JPL-Caltech

"As it makes these five dips into Saturn, followed by its final plunge, Cassini will become the first Saturn atmospheric probe," said Linda Spilker, Cassini project scientist at JPL. "It's long been a goal in planetary exploration to send a dedicated probe into the atmosphere of Saturn, and we're laying the groundwork for future exploration with this first foray."

Other Cassini instruments will make detailed, high-resolution observations of Saturn's auroras, temperature, and the vortexes at the planet's poles. Its radar will peer deep into the atmosphere to reveal small-scale features as fine as 16 miles (25 kilometers) wide – nearly 100 times smaller than the spacecraft could observe prior to the Grand Finale.

On Sept. 11, a distant encounter with Titan will serve as a gravitational version of a large pop-down maneuver, slowing Cassini’s orbit around Saturn and bending its path slightly to send the spacecraft toward its Sept. 15 plunge into the planet.

During the half-orbit plunge, the plan is to have seven Cassini science instruments, including INMS, turned on and reporting measurements in near real time. The spacecraft is expected to reach an altitude where atmospheric density is about twice what it encountered during its final five passes. Once Cassini reaches that point, its thrusters will no longer be able to work against the push of Saturn’s atmosphere to keep the spacecraft's antenna pointed toward Earth, and contact will permanently be lost. The spacecraft will break up like a meteor moments later, ending its long and rewarding journey.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate in Washington. JPL designed, developed and assembled the Cassini spacecraft.

For more information about the Cassini-Huygens mission visit and The Cassini imaging team homepage is at and ESA's website:

Animation (mentioned), Image (mentioned), Text, Credits: NASA/Felicia Chou/Katherine Brown/JPL/Preston Dyches.

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