After Strong El Niño Winter, NASA Model Sees Return to Normal

NASA - Goddard Space Flight Center logo.

Sept. 13, 2016

Not too hot, not too cold – instead, water temperatures in the equatorial Pacific Ocean should be just around normal for the rest of 2016, according to forecasts from the Global Modeling and Assimilation Office, or GMAO. With these neutral conditions, scientists with the modeling center at NASA’s Goddard Space Flight Center say there is unlikely to be a La Niña event in late 2016.

Last winter saw an extremely strong El Niño event, in which warmer-than-normal water sloshed toward the eastern Pacific Ocean. Historically, some of the larger El Niño events are followed by a La Niña event, in which deep, colder-than-normal water surfaces in the eastern Pacific Ocean, off the coast of South America.

Animation above: Sea surface temperature patterns of the 2015 El Niño in the Pacific Ocean unfolded differently than those seen in the 1997-1998 El Niño. Animation Credits: NASA.

"We are consistently predicting a more neutral state, with no La Niña or El Niño later this year," said Steven Pawson, chief of the GMAO. "Our September forecast continues to show the neutral conditions that have been predicted since the spring."

As part of a research and development project, GMAO contributes experimental seasonal forecasts each month to the North American Multi-Model Ensemble (NMME) and other centers. MME produces a forecast by combining the individual forecasts of a number of participating institutions, which helps to reduce the uncertainty involved in forecasting events nine to twelve months in advance. The NMME prediction system delivers forecasts based on the National Oceanic and Atmospheric Administration (NOAA) operational schedule and is used by many operational forecasters in predicting El Niño and La Niña events.

For GMAO, the seasonal forecasts are one way to use NASA satellite data to improve near-term climate predictions of the Earth system.

"We’re really trying to bring as much NASA observational data as possible into these systems," Pawson said.

The scientists with GMAO feed a range of NASA satellite data and other information into the seasonal forecast model to predict if an El Niño or La Niña event will occur in the nine months – information on the aerosols and ozone in the atmosphere, sea ice, winds, sea surface heights and temperatures, and more. The models are run on supercomputers at the NASA Center for Climate Simulation – 9 terabytes of data each month.

For much of this spring and summer, however, the Goddard group’s forecast of neutral conditions looked like an outlier. Most other forecasts originally called for a La Niña event, but then shifted to more neutral outlooks in August. But the GMAO forecasts produced in January 2016, which look nine months ahead, saw the Pacific Ocean reverting to normal temperatures after last year’s El Niño, and even getting a little colder than normal. Still, the water wouldn’t get cold enough to be considered a La Niña, according to the GMAO forecasts.

It’s not the first time in recent memory that GMAO was an outlier. "The big El Niño that peaked in November 2015, we actually began forecasting that back in March, and our forecast was in excellent agreement with the real event," said Robin Kovach, a research scientist at GMAO. While the strength of the 2015-2016 El Niño predicted by the model seemed at first to be excessive, it was borne out in subsequent observations.

The GMAO models aren’t always right, though, Kovach said. In 2014 the group forecast a large El Niño that didn’t materialize.

"There’s a fair degree of uncertainty when you start predicting for nine months ahead," Pawson said. But the group is constantly upgrading their systems, and is currently working to improve the resolution and bring in new types of satellite observations, such as soil moisture information from the Soil Moisture Active Passive mission, which launched in 2015.

GMAO scientists are also investigating how to incorporate observations of ocean color into the seasonal forecast model. Shades of green can tell researchers about how much phytoplankton is in a region, which in turn can provide information about fish populations.

"So if there’s another big El Niño in five years or so, we could be able to do online predictions of phytoplankton," he said, "and help fishermen predict where fish might be."

For more information, visit: https://gmao.gsfc.nasa.gov/

For NOAA’s El Niño and La Niña information and forecasts, visit: https://www.climate.gov/enso

Animation (mentioned), Text, Credits: NASA’s Goddard Space Flight Center/Kate Ramsayer/Karl Hille.

Greetings, Orbiter.ch

A Streamlined Form in Lethe Vallis, Mars

NASA - Mars Reconnaissance Orbiter (MRO) patch.

Sept. 13, 2016

This image shows a portion of Lethe Vallis, an outflow channel that also transported lava. The image was acquired at 15:16 local Mars time on May 6, 2016, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. Another investigation of this area (Balme et al., 2011) discovered a repeat pattern of dune-like forms in the channel interpreted as fluvial dunes (or, giant current ripples) which are dunes formed by flowing water.

This is one of only a few places on Mars where these pristine-appearing landforms have been identified. The channel formed by catastrophic floods, during which it produced the prominent crater-cored, teardrop-shaped island in the middle. The island has the blunter end pointing upstream and the long tail pointing downstream.

Both the island and the fluvial dunes were formed by these extreme floods and their size is an indicator of the enormous discharges required to create them. The margins of the channel also show the terminal front of a pristine lava flow unit that inundated the channel from the south and the dunes show the remnants of another older lava flow. The top of the island displays polygonal patterned ground texture, which is a characteristic of periglacial processes in ice-rich ground.

The dark materials from the channel and island walls are probably dark sand being eroded from an underlying horizontal basaltic (lava) layer. The crater at the core of the island has elongated dunes and reticulate dust ridges inside. This single image thus contains features formed by periglacial, volcanic, fluvial, impact, aeolian and mass wasting processes, all in one place.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

Additional image data: HiRISE, University of Arizona: http://www.uahirise.org/ESP_045833_1845

Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

Image, Text, Credits: NASA/JPL/University of Arizona/Caption: Henrik Hargitai and Ginny Gulick/Sarah Loff.

Greetings, Orbiter.ch

First physics experiment at HIE-ISOLDE begins

CERN - European Organization for Nuclear Research logo.

Sept. 13, 2016

Image above: Miniball is one of two detection stations receiving beams from HIE-ISOLDE. It’s a very efficient gamma detector array, and will be permanently linked to the beams from HIE-ISOLDE (Image: CERN).

This weekend the first physics experiment started running using radioactive beams from the newly upgraded HIE-ISOLDE facility. ISOLDE, the nuclear research facility at CERN, allows many different experiments to study the properties of atomic nuclei.

The upgrade means the machine can now reach an energy of 5.5MeV per nucleon (MeV/u.), making ISOLDE the only facility in the world capable of investigating nuclei from the middle to heavy end of this energy range.

The experiment is ready to go after the second of two cryomodules (containing the accelerating cavities)was installed – marking the end of the installation of phase one of HIE-ISOLDE.

The HIE-ISOLDE (High Intensity Energy-ISOLDE) Project is a major upgrade of the ISOLDE facility, which will increase the energy, intensity and quality of the beams delivered to scientists.

“It’s a major breakthrough. This is the result of eight years of development and manufacturing. This would not have been possible without the dedication of the technical staff at CERN. But what makes us most proud isn’t that we built a machine, but that we have attracted enthusiastic users to do forefront physics. We are looking forward to this exciting high intensity period,” says Yacine Kadi , leader of the HIE-ISOLDE project.

Image above: The tunnel at HIE-ISOLDE now contains two cryomodules – a unique set up that marks the end of phase one for the HIE-ISOLDE installation. By Spring 2018 the project will have four cryomodules installed and will be able to reach higher energy up to 10 MeV/u a broader range of nuclear physics (Image: Erwin Siesling/ CERN).

This is the second physics run of the project (the first radioactive beam was run on 22 October 2015) but then the machine only had one cryomodule and was capable of running at an energy of just 4.3MeV/u.

Now, with the second cryostat coupled on, the machine is capable of reaching up to 5.5 MeV/u and can investigate the structure of heavier isotopes.

“It is a universal machine that can accelerate and investigate all nuclei from mass number 6 to mass 224 or more and at variable energies,” explains Maria Borge, leader of the ISOLDE group. “This year we’re investigating nuclei with mass number from 9 to 142 – these experiments can only be done at this moment at ISOLDE. At CERN.”

HIE-ISOLDE will be capable of investigating nuclei of all masses when the additional two cryomodules are installed in 2018, as the machine will be able to accelerating them up to energies of 10MeV/u.

The further upgrades mean that, while ISOLDE can currently collect information about the collective properties of isotopes, eventually researchers will be able to use the machine at higher intensities to investigate the properties of individual particles. This can be done at the moment for lower masses, but has never been done before for heavier isotopes.

“The community has grown a lot recently, as people are attracted by the possibilities new higher energies bring. It’s a energy domain that’s not explored much, since no other facility in world can deliver pure beams at these energies,” Borge says.

HIE-ISOLDE will run from now until mid-November. All but one of the seven different experiments planned during this time will use the Miniball detection station. The first experiment will investigate Tin, a special element with two double magic isotopes.

HIE-ISOLDE: nuclear physics now at higher energies

Video above: Eight years since the start of the HIE-ISOLDE project, a new accelerator is in place taking nuclear physics at CERN to higher energies. The first physics run last year marked the start of the project, but after a new cryomodule was installed physicists are able to reach a greater energy of up to 5.5.MeV/u. With physicists setting their sights on even higher energies of 10 MeV/u in the future, they will continue to commission more HIE-ISOLDE accelerating cavities and beamlines in the years to come. (Video: Christoph Madsen/CERN).

Note:

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 article:

Upgraded nuclear physics facility starts up
http://orbiterchspacenews.blogspot.ch/2015/11/upgraded-nuclear-physics-facility.html

Related links:

HIE-ISOLDE facility: http://home.cern/about/experiments/isolde

For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/

Images (mentioned), Video (mentioned), Text, Credits: CERN/Harriet Jarlett.

Greetings, Orbiter.ch

Astronomers observe star reborn in a flash

ESA - Hubble Space Telescope logo.

13 September 2016

Stingray Nebula and SAO 244567

An international team of astronomers using Hubble have been able to study stellar evolution in real time. Over a period of 30 years dramatic increases in the temperature of the star SAO 244567 have been observed. Now the star is cooling again, having been reborn into an earlier phase of stellar evolution. This makes it the first reborn star to have been observed during both the heating and cooling stages of rebirth.

Even though the Universe is constantly changing, most processes are too slow to be observed within a human lifespan. But now an international team of astronomers have observed an exception to this rule. “SAO 244567 is one of the rare examples of a star that allows us to witness stellar evolution in real time”, explains Nicole Reindl from the University of Leicester, UK, lead author of the study. “Over only twenty years the star has doubled its temperature and it was possible to watch the star ionising its previously ejected envelope, which is now known as the Stingray Nebula.”

SAO 244567, 2700 light-years from Earth, is the central star of the Stingray Nebula and has been visibly evolving between observations made over the last 45 years. Between 1971 and 2002 the surface temperature of the star skyrocketed by almost 40 000 degrees Celsius. Now new observations made with the Cosmic Origins Spectrograph (COS) on the NASA/ESA Hubble Space Telescope have revealed that SAO 244567 has started to cool and expand.

SAO 244567

This is unusual, though not unheard-of [1], and the rapid heating could easily be explained if one assumed that SAO 244567 had an initial mass of 3 to 4 times the mass of the Sun. However, the data show that SAO 244567 must have had an original mass similar to that of our Sun. Such low-mass stars usually evolve on much longer timescales, so the rapid heating has been a mystery for decades.

Back in 2014 Reindl and her team proposed a theory that resolved the issue of both SAO 244567’s rapid increase in temperature as well as the low mass of the star. They suggested that the heating was due to what is known as a helium-shell flash event: a brief ignition of helium outside the stellar core [2].

This theory has very clear implications for SAO 244567’s future: if it has indeed experienced such a flash, then this would force the central star to begin to expand and cool again — it would return back to the previous phase of its evolution. This is exactly what the new observations confirmed. As Reindl explains: “The release of nuclear energy by the flash forces the already very compact star to expand back to giant dimensions — the born-again scenario.”

Evolution of SAO 244567

It is not the only example of such a star, but it is the first time ever that a star has been observed during both the heating and cooling stages of such a transformation.

Yet no current stellar evolutionary models can fully explain SAO 244567’s behaviour. As Reindl elaborates: “We need refined calculations to explain some still mysterious details in the behaviour of SAO 244567. These could not only help us to better understand the star itself but could also provide a deeper insight in the evolution of central stars of planetary nebulae.”

Until astronomers develop more refined models for the life cycles of stars, aspects of SAO 244567’s evolution will remain a mystery.

Notes:

[1] The other star thought to have experienced the same type of helium flash event (see
[2]) is FG Sagittae, located in the constellation Sagitta, making SAO 244567 the second of its kind. However, other objects undergoing similar “born-again” scenarios are known, including Sakurai’s Object, located in Sagittarius.

[2] Helium flash events, also known as late thermal pulses, occur late in the evolution of about 25% of low- to medium-mass stars. After evolving off the main sequence, these stars enter the red giant phase, where the star expands dramatically. Various changes occur in the star’s chemical and physical composition during this phase, until it has burnt most of the helium available in its core, which is by then composed of carbon and oxygen. Helium fusion continues in a thin shell around the core, but then turns off as the helium becomes depleted. This allows hydrogen fusion to start in a layer above the helium layer. After enough additional helium accumulates, helium fusion is reignited, leading to a thermal pulse which eventually causes the star to expand, cool and brighten temporarily.

More information:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The results will be presented in the paper “Breaking news from the HST: The central star of the Stingray Nebula is now returning towards the AGB”, published in the Monthly Notices of the Royal Astronomical Society (MNRAS).

The international team of astronomers in this study consists of Nicole Reindl (University of Leicester, UK; Eberhard Karls University, Germany), T. Rauch (Eberhard Karls University, Germany), M. M. Miller Bertolami (UNLP-CONICET, Argentina), H. Todt (University of Potsdam, Germany), K. Werner (Eberhard Karls University, Germany)

Links:

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Link to science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1618/heic1618a.pdf

For more information about the Hubble Space Telescope, visit:

http://hubblesite.org/
http://www.nasa.gov/hubble
https://www.spacetelescope.org/

Images, Text, Credits: ESA/Hubble & NASA/Video: ESA/Hubble, L. Calçada.

Best regards, Orbiter.ch

NASA’s THEMIS Sees Auroras Move to the Rhythm of Earth’s Magnetic Field

NASA - THEMIS Mission patch.

Sept. 12, 2016

The majestic auroras have captivated humans for thousands of years, but their nature – the fact that the lights are electromagnetic and respond to solar activity – was only realized in the last 150 years. Thanks to coordinated multi-satellite observations and a worldwide network of magnetic sensors and cameras, close study of auroras has become possible over recent decades. Yet, auroras continue to mystify, dancing far above the ground to some, thus far, undetected rhythm.

Using data from NASA’s Time History of Events and Macroscale Interactions during Substorms, or THEMIS, scientists have observed Earth’s vibrating magnetic field in relation to the northern lights dancing in the night sky over Canada. THEMIS is a five-spacecraft mission dedicated to understanding the processes behind auroras, which erupt across the sky in response to changes in Earth’s magnetic environment, called the magnetosphere.

Animation above: These aurora images were taken in 2013 from the ground looking up with a network of all-sky cameras spread across Canada, studying auroras in collaboration with THEMIS. Taking images of aurora from the ground in conjunction with satellite data taken from above the atmosphere gives scientists a more comprehensive picture of how and why auroras form. Animation Credits: NASA/CSA/University of California, Berkeley/University of Calgary/NSF.

These new observations allowed scientists to directly link specific intense disturbances in the magnetosphere to the magnetic response on the ground. A paper on these findings was published in Nature Physics on Sept. 12, 2016.

“We’ve made similar observations before, but only in one place at a time – on the ground or in space,” said David Sibeck, THEMIS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who did not participate in the study. “When you have the measurements in both places, you can relate the two things together.”

Understanding how and why auroras occur helps us learn more about the complex space environment around our planet. Radiation and energy in near-Earth space can have a variety of effects on our satellites – from disrupting their electronics to increasing frictional drag and interrupting communication or navigation signals. As our dependence on GPS grows and space exploration expands, accurate space weather forecasting becomes ever more important.

The space environment of our entire solar system, both near Earth and far beyond Pluto, is determined by the sun’s activity, which cycles and fluctuates through time. The solar system is filled with solar wind, the constant flow of charged particles from the sun. Most of the solar wind is deflected from Earth by our planet’s protective magnetosphere.

However, under the right conditions, some solar particles and energy can penetrate the magnetosphere, disturbing Earth’s magnetic field in what’s known as a substorm. When the solar wind’s magnetic field turns southward, the dayside, or sun-facing side, of the magnetosphere contracts inward. The back end, called the magnetotail, stretches out like a rubber band. When the stretched magnetotail finally snaps back, it starts to vibrate, much like a spring moving back and forth. Bright auroras can occur during this stage of the substorm.

Image above: An artist’s rendering (not to scale) of a cross-section of the magnetosphere, with the solar wind on the left in yellow and magnetic field lines emanating from the Earth in blue. The five THEMIS probes were well-positioned to directly observe one particular magnetic field line as it oscillated back and forth roughly every six minutes. In this unstable environment, electrons in near-Earth space, depicted as white dots, stream rapidly down magnetic field lines towards Earth’s poles. There, they interact with oxygen and nitrogen particles in the upper atmosphere, releasing photons and brightening a specific region of the aurora. Image Credits: Emmanuel Masongsong/UCLA EPSS/NASA.

In this unstable environment, electrons in near-Earth space stream rapidly down magnetic field lines towards Earth’s poles. There, they interact with oxygen and nitrogen particles in the upper atmosphere, releasing photons to create swaths of light that snake across the sky.

To map the auroras’ electric dance, the scientists imaged the brightening and dimming aurora over Canada with all-sky cameras. They simultaneously used ground-based magnetic sensors across Canada and Greenland to measure electrical currents during the geomagnetic substorm. Further out in space, the five THEMIS probes were well-positioned to collect data on the motion of the disrupted field lines.

The scientists found the aurora moved in harmony with the vibrating field line. Magnetic field lines oscillated in a roughly six-minute cycle, or period, and the aurora brightened and dimmed at the same pace.

“We were delighted to see such a strong match,” said Evgeny Panov, lead author and researcher at the Space Research Institute of the Austrian Academy of Sciences in Graz. “These observations reveal the missing link in the conversion of magnetic energy to particle energy that powers the aurora.”

The brightening and dimming of the aurora corresponds to the motion of the electrons and magnetic field lines.

“During the course of this event, the electrons are flinging themselves Earthwards, then bouncing back off the magnetosphere, then flinging themselves back,” Sibeck said.

When waves crash on the beach, they splash and froth, and then recede. The wave of electrons adopt a similar motion. The aurora brightens when the wave of electrons slams into the upper atmosphere, and dims when it ricochets off.

Before this study, scientists hypothesized that oscillating magnetic field lines guide the aurora. But the effect had not yet been observed because it requires the THEMIS probes to be located in just the right place over the ground-based sensors, to properly coordinate the data. In this study, scientists collected THEMIS data at a time when the probes were fortuitously positioned to observe the substorm.

THEMIS Sees Magnetic Reconnection

Video above: In this animation, the THEMIS mission observes auroral brightening – a result of a substorm, in which solar particles and energy disturb Earth’s magnetic field. The THEMIS orbit is shown in golden lines, while magnetic field lines emanating from Earth are shown in blue. When solar material impacts the magnetosphere, the day side contracts inward, while the back end, called the magnetotail, stretches out like a rubber band. When the stretched magnetotail finally snaps back, it starts to vibrate, much like a spring moving back and forth. In this unstable environment, electrons in near-Earth space rapidly stream down magnetic field lines towards Earth’s poles. There, they interact with oxygen and nitrogen particles in the upper atmosphere, releasing photons to create the aurora. Video Credits: NASA Goddard's Conceptual Image Lab, Walt Feimer.

“Even after nearly 10 years, the probes are still in great health, and the growing network of magnetometers and all-sky cameras continue to generate high quality data,” said Vassilis Angelopoulos, co-author and THEMIS principal investigator at University of California, Los Angeles.

THEMIS is a mission of NASA’s Explorer program, which is managed by Goddard. University of California, Berkeley’s Space Sciences Laboratory oversees mission operations. The all-sky imagers and magnetometers are jointly operated by UC Berkeley, UCLA, University of Calgary and University of Alberta in Canada.

“The intention with THEMIS has always been that we would put these measurements together and make these observations,” Sibeck said. “This is an extremely satisfying study and a pleasure to see the right use of this mission data.”

Related Link:

NASA's THEMIS website: http://www.nasa.gov/themis

Animation (mentioned), Image (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center, by Lina Tran/Rob Garner.

Greetings, Orbiter.ch

Barely Bisected Rings

NASA - Cassini Mission to Saturn patch.

Sept. 12, 2016

Saturn's shadow stretched beyond the edge of its rings for many years after Cassini first arrived at Saturn, casting an ever-lengthening shadow that reached its maximum extent at the planet's 2009 equinox. This image captured the moment in 2015 when the shrinking shadow just barely reached across the entire main ring system. The shadow will continue to shrink until the planet’s northern summer solstice, at which point it will once again start lengthening across the rings, reaching across them in 2019.

Like Earth, Saturn is tilted on its axis. And, just as on Earth, as the sun climbs higher in the sky, shadows get shorter. The projection of the planet's shadow onto the rings shrinks and grows over the course of its 29-year-long orbit, as the angle of the sun changes with respect to Saturn's equator.

This view looks toward the sunlit side of the rings from about 11 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Jan. 16, 2015.

The view was obtained at a distance of approximately 1.6 million miles (2.5 million kilometers) from Saturn. Image scale is about 90 miles (150 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and ESA's website: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image, Text, Credit: NASA/JPL-Caltech/Space Science Institute/Tony Greicius.

Greetings, Orbiter.ch

Proba-3: set the controls for the verge of the Sun

ESA - European Space Agency patch.

12 September 2016

By converging in orbit, a pair of small satellites will open a new view on the source of the largest structure in the Solar System: the Sun’s ghostly atmosphere, extending millions of kilometres out into space.

The two satellites together are called Proba-3, set for launch in late 2019. Through precise formation flying, one will cast a shadow across the second to open up an unimpeded view of the inner area of the ‘corona’, which is a million times fainter than the blindingly brilliant solar disc.

 Proba-3 satellites form artificial eclipse

“When I first heard of the idea I said ‘Wow! That’s just what we need’,” said Andrei Zhukov of the Royal Observatory of Belgium, serving as Principal Investigator for Proba-3’s solar instrument.

“The best way to observe the corona from the ground is during a solar eclipse, although we still have to cope with stray light – we cannot correct for the influence of Earth’s atmosphere.

“The next best method is by using ‘coronagraphs’ to create an articifical eclipse, either on ground telescopes or inside Sun-watching satellites such as SOHO and Stereo.

Solar corona seen during terrestrial eclipses

“The problem is that stray light bending around the edge of the occulting disc limits our view of the most important inner portion of the corona. SOHO’s coronagraph, for instance, can observe no closer in than 1.1 Sun-diameters. Others can see closer, but with strong stray light making detailed observation impossible.

“With Proba-3 we aim to see extremely close to the solar surface in visible light, by flying the occulter and coronagraph on separate satellites some 150 m apart.  

“This should give us a ringside seat on the most interesting segment of the corona, where a lot of interesting physics is going on, where the solar wind is born and ‘coronal mass ejections’ originate – gigantic solar eruptions with the potential to affect our terrestrial infrastructure.”

A fiery solar explosion

While the Sun’s surface is a comparatively cool 6000ºC, the corona averages a sizzling million degrees. The mystery is how energy travels from the cool Sun to the hot corona, in apparent defiance of the laws of thermodynamics.

“By mapping the fine structure of the inner corona for a prolonged time – we are targeting around six hours – our hope is that we gain insight into the kind of energy flows that are taking place,” notes Dr Zhukov.

“Our standard observing mode will be once per minute, but we could speed that up to a few seconds within a selected field of view, for instance when tracing the rapid evolution of a mass ejection.

Proba-3's pair of satellites

“The ultimate goal is to be able to solve the physics of space weather, in order to forecast coronal mass ejections, which are known to have dramatic effects on terrestrial electricity grids and other infrastructure.”

Proba-3: Dancing with the stars

Proba-3 is first and foremost a technology demonstration, exploring the potential of precise formation flying in orbit, but achieving meaningful scientific results will also help to prove its approach works.   

Related links:

About Proba-3: http://www.esa.int/Our_Activities/Space_Engineering_Technology/Proba_Missions/About_Proba-3

Mission: http://www.esa.int/Our_Activities/Space_Engineering_Technology/Proba_Missions/Mission2

Images, Video, Text, Credits: ESA/P. Carril/Wendy Carlos & Fred Espenak/SOHO (ESA/NASA)/S. Hill.

Best regards, Orbiter.ch