vendredi 21 août 2015

NASA-Funded MOSES-2 Sounding Rocket to Investigate Coronal Heating









NASA / MSU  - MOSES logo.

Aug. 21, 2015

A NASA-funded sounding rocket is getting ready to launch to give insight into one of the biggest mysteries in solar physics—the fact the sun's atmosphere is some 1,000 times hotter than its surface. The mission, developed by scientists and students at Montana State University in Bozeman, Montana, will make a 15-minute journey into space on a Black Brant IX suborbital sounding rocket.  During its trip, it will take images of the sun in the extreme ultraviolet, or EUV, which can't be seen from the ground due to Earth’s EUV-blocking atmosphere.


Image above: Engineers work on the final steps of integrating the MOSES-2 sounding rocket payload. The rocket, which will launch from White Sands Missile Range in New Mexico August 25, is carrying an instrument called the Multi-Order Solar EUV Spectrograph, or MOSES-2. This instrument will be used to take images of the sun in extreme ultraviolet light on its 15-minute flight into space. Taking these kinds of images is impossible from the ground, since Earth’s atmosphere blocks all extreme ultraviolet light. Image Credit: NASA.

The Multi-Order Solar EUV Spectrograph, or MOSES-2, launch will be investigating the transition region of the sun, the layer of material where the photosphere—the layer of the sun we see—becomes the corona.

“The transition region is a pretty interesting place,” said Charles Kankelborg, principal investigator for MOSES-2 at Montana State University, Bozeman, Montana.

The so-called coronal heating problem is based in the fact that the sun produces energy by fusing hydrogen at its center -- so material generally gets cooler as you move outward from that incredibly hot core. The one exception is the sun’s atmosphere, the corona. Though the corona is farther from the core than any other part of the sun, it is unexpectedly hotter than many of the layers below. Scientists have proposed several theories to explain this mystery heating, ranging from the possibility of thousands of mini solar flares to complicated magnetic wave processes.


Graphic above: This graphic shows a model of the layers of the Sun, with approximate mileage ranges for each layer: for the inner layers, the mileage is from the sun's core; for the outer layers, the mileage is from the sun's surface. Image Credit: National Solar Observatory.

Kankelborg and his team are hoping to catch images of an explosive event in the transition region, one possible cause of coronal heating. Similar to a solar flare, such explosive events are thought to be caused by magnetic reconnection, a sometimes violent process in which magnetic field lines disconnect and reconfigure, releasing energy and heat. The MOSES team says that watching magnetic reconnection may well be easier in the transition region that it is in the larger solar flares.

“It’s very difficult to see the actual magnetic reconnection in a solar flare,” said Kankelborg. “Solar flares happen in the sun's upper atmosphere, the corona, where material is relatively sparse, so there’s not much stuff there to let off light and show us what’s happening.”

On the other hand, the transition region is relatively dense, meaning that researchers have a chance to observe magnetic reconnection more directly if they catch an explosive event.

The MOSES-2 instrument is finely tuned to see material in this region. Because different elements emit light at different temperatures and wavelengths, scientists can focus on a particular temperature—and therefore a particular layer of material—by taking images in a corresponding wavelength. MOSES-2 is configured to take pictures at 465 Angstroms, which represents material at a temperature of about 900,000 degrees Fahrenheit.

MOSES-2 will begin taking data when the rocket reaches a height of around 100 miles, 107 seconds after launch. Even 100 miles above the surface, there is still enough atmosphere that only about half of the sun’s EUV light is visible. However, at the peak of the rocket’s flight, nearly 187 miles in altitude, there is so little atmospheric material that any EUV light blocking is negligible. The total flight time is around 15 minutes, with about five minutes of data collection.

Though the period of data collection is short, sounding rockets are a valuable way to access space for a low cost.


Image above: The MOSES-2 sounding rocket payload undergoes final testing in preparation for its August 25 launch from White Sands Missile Range in New Mexico. The sounding rocket will fly for 15 minutes, carrying the Multi-Order Soalr EUV Spectrograph, or MOSES-2, instrument. MOSES-2 will take images of the sun in extreme ultraviolet light from outside Earth’s atmosphere. It is impossible to take these kinds of images from Earth, since Earth’s atmosphere blocks all extreme ultraviolet light. Image Credit: NASA.

“For about one percent of the cost of a satellite mission, you can spend five minutes taking data in space,” said Kankelborg. “It’s a great way to demonstrate cutting-edge instruments and new ways of doing science.”

The lower budget and shorter timeline of sounding rocket missions also make them ideal for university and student involvement.

“In a university setting, it’s easier to run a research program based on sounding rocket missions than satellite missions,” said Kankelborg. “You can get students involved in building instruments hands-on.” Three students from the Montana State University MOSES-2 team will attend the launch at White Sands Missile Range in New Mexico.

The launch window for MOSES-2 opens on Aug. 25, and the team will wait for favorable weather conditions before launching. This is the second flight for the MOSES instrument. In 2006, MOSES flew on a sounding rocket to make similar observations of the sun, but in a different wavelength. The team plans to fly MOSES a third time in 2018 along with a new spectrograph to make more observations of the transition region.

The MOSES-2 launch is supported through NASA’s Sounding Rocket Program at the Goddard Space Flight Center’s Wallops Flight Facility in Virginia. NASA’s Heliophysics Division manages the sounding rocket program.

For more information about NASA's Sounding Rocket Program, visit:
https://www.nasa.gov/soundingrockets

Related link:

Montana State University - MOSES/ESIS - Mission Overview: http://ssel.montana.edu/moses.html

Images (mentioned), Text, Credits: NASA’s Goddard Space Flight Center/Sarah Frazier/Holly Zell.

Best regards, Orbiter.ch

CERN - ALICE precisely compares light nuclei and antinuclei












CERN - European Organization for Nuclear Research logo.

August 21, 2015

The ALICE experiment at the Large Hadron Collider (LHC) at CERN has made a precise measurement of the difference between ratios of the mass and electric charge of light nuclei and antinuclei. The result, published today in Nature Physic (http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3432.html), confirms a fundamental symmetry of nature to an unprecedented precision for light nuclei. The measurements are based on the ALICE experiment’s abilities to track and identify particles produced in high-energy heavy-ion collisions at the LHC.


Image above: The ALICE detector on CERN's Large Hadron Collider. (Image: A Saba/CERN).

The ALICE collaboration has measured the difference between mass-to-charge ratios for deuterons (a proton, or hydrogen nucleus, with an additional neutron) and antideuterons, as well as for helium-3 nuclei (two protons plus a neutron) and antihelium-3 nuclei. Measurements at CERN, most recently by the BASE experiment, have already compared the same properties of protons and antiprotons to high precision. The study by ALICE takes this research further as it probes the possibility of subtle differences between the way that protons and neutrons bind together in nuclei compared with how their antiparticle counterparts form antinuclei.

“The measurements by ALICE and by BASE have taken place at the highest and lowest energies available at CERN, at the LHC and the Antiproton Decelerator, respectively,” says CERN Director-General Rolf Heuer. “This is a perfect illustration of the diversity in the laboratory’s research programme.”

The measurement by ALICE comparing the mass-to-charge ratios in deuterons/antideuterons and in helium-3/antihelium-3 confirms the fundamental symmetry known as CPT in these light nuclei. This symmetry of nature implies that all of the laws of physics are the same under the simultaneous reversal of charges (charge conjugation C), reflection of spatial coordinates (parity transformation P) and time inversion (T). The new result, which comes exactly 50 years after the discovery of the antideuteron at CERN and in the US, improves on existing measurements by a factor of 10-100.


Graphic above: Measurements of energy loss in the time-projection chamber enable the ALICE experiment to identify antinuclei (upper curves on the left) and nuclei (upper curves on the right) produced in the lead-ion collisions at the LHC. (Image: ALICE).

The ALICE experiment records high-energy collisions of lead ions at the LHC, enabling it to study matter at extremely high temperatures and densities. The lead-ion collisions provide a copious source of particles and antiparticles, and nuclei and the corresponding antinuclei are produced at nearly equal rates. This allows ALICE to make a detailed comparison of the properties of the nuclei and antinuclei that are most abundantly produced. The experiment makes precise measurements of the curvature of particle tracks in the detector’s magnetic field and of the particles’ time of flight, and uses this information to determine the mass-to-charge ratios for the nuclei and antinuclei.

“The high precision of our time-of-flight detector, which determines the arrival time of particles and antiparticles with a resolution of 80 picoseconds, associated with the energy-loss measurement provided by our time-projection chamber, allows us to measure a clear signal for deuterons/antideuterons and helium-3/antihelium-3 over a wide range of momentum”, says ALICE spokesperson Paolo Giubellino.

The measured differences in the mass-to-charge ratios are compatible with zero within the estimated uncertainties, in agreement with expectations for CPT symmetry. These measurements, as well as those that compare the protons with antiprotons, may further constrain theories that go beyond the existing Standard Model of particles and the forces through which they interact.

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:

BASE compares protons to antiprotons with high precision: http://orbiterchspacenews.blogspot.ch/2015/08/base-compares-protons-to-antiprotons.html

Related links:

ALICE experiment: http://home.web.cern.ch/about/experiments/alice

Large Hadron Collider (LHC): http://home.web.cern.ch/topics/large-hadron-collider

BASE experiment: http://www.nature.com/nature/journal/v524/n7564/full/nature14861.html

Standard Model of particles: http://home.web.cern.ch/about/physics/standard-model

High-energy heavy-ion collisions: http://home.web.cern.ch/about/physics/heavy-ions-and-quark-gluon-plasma

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

Image & Graphic (mentioned), Text, Credits: CERN/Cian O'Luanaigh.

Greetings, Orbiter.ch

Crew Explores Life Science While Waiting for Japanese Delivery










ISS - Expedition 44 Mission patch.

August 21, 2015

The Expedition 44 crew was back at work today continuing a series of biomedical studies, physics experiments and maintenance tasks. Meanwhile, more science is on its way to the International Space Station aboard Japan’s fifth space freighter.


Image above: Hurricane Danny was pictured over the central Atlantic Ocean from the International Space Station early Friday morning. Image Credit: NASA TV.

Three cosmonauts studied magnetics, human digestion then participated in ultrasound scans and blood pressure checks today. The trio, consisting of Commander Gennady Padalka and Flight Engineers Mikhail Kornienko and Oleg Kononenko, also subjected themselves to vision checks for the ongoing Ocular Health study.


Image above: Cosmonauts Mikhail Kornienko, Gennady Padalka and Oleg Kononenko speak to the Russian Prime Minister Dmitri Medvedev Friday morning. Image Credit: NASA TV.

NASA astronaut Scott Kelly collected blood and urine samples and stored them in a science freezer for the Fluid Shifts study. New Flight Engineers Kimiya Yui and Kjell Lindgren continued practicing the robotic techniques they will use Monday morning to capture a new cargo craft and berth it to the Harmony module. Lindgren also checked out spacewalking tools.


Image above: Astronauts Kimiya Yui and Kjell Lindgren train for the robotic capture of Japan’s “Kounotori” HTV-5 cargo craft. Image Credit: NASA TV.

The “Kounotori” H-II Transfer Vehicle-5 (HTV-5) from the Japan Aerospace Exploration Agency is delivering more than 9,500 pounds of research and supplies for the six-person station crew. NASA TV will begin live coverage of the HTV-5 arrival Monday at 5:15 a.m. EDT with capture due at about 6:55 a.m.

Related links:

Magnetics study: http://www.energia.ru/en/iss/researches/popular/02.html

Human digestion study: http://www.energia.ru/en/iss/researches/human/09.html

Ocular Health study: http://www.nasa.gov/mission_pages/station/research/experiments/204.html

Fluid Shifts study: http://www.nasa.gov/mission_pages/station/research/experiments/1257.html

HTV-5 arrival live coverage: http://www.nasa.gov/multimedia/nasatv/index.html

For more information on the International Space Station and its crews, visit: http://www.nasa.gov/station

Images (mentioned), Text, Credits: NASA.

Greetings, Orbiter.ch

A Hubble Cosmic Couple











NASA - Hubble Space Telescope patch.

Aug. 21, 2015


Here we see the spectacular cosmic pairing of the star Hen 2-427 — more commonly known as WR 124 — and the nebula M1-67 which surrounds it. Both objects, captured here by the NASA/ESA Hubble Space Telescope are found in the constellation of Sagittarius and lie 15,000 light-years away.

The star Hen 2-427 shines brightly at the very center of this explosive image and around the hot clumps of surrounding gas that are being ejected into space at over 93,210 miles (150,000 km) per hour.

Hen 2-427 is a Wolf–Rayet star, named after the astronomers Charles Wolf and Georges Rayet. Wolf–Rayet are super-hot stars characterized by a fierce ejection of mass.

The nebula M1-67 is estimated to be no more than 10,000 years old — just a baby in astronomical terms — but what a beautiful and magnificent sight it makes.

video
Hubble and the sunrise over Earth

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington. 

For images and more about this study and the Hubble Space Telescope, visit:

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

Image, video, Text, Credits: ESA/Hubble & NASA, Ashley Morrow. Acknowledgement: Judy Schmidt, Text credit: European Space Agency (ESA).

Best regards, Orbiter.ch

DAICHI-2 Emergency Observations of Sakurajima Volcano












JAXA - ALOS-2 (DAICHI-2) Mission logo.

August 21, 2015

The Japan Aerospace Exploration Agency (JAXA) has been observing the volcanic activity of Sakurajima, Japan using the Advanced Land Observing Satellite-2 “DAICHI-2” (ALOS-2) following a request from the Japan Meteorological Agency (JMA)'s Coordinating Committee for Prediction of Volcanic Eruptions. JAXA was asked to perform an emergency observation as there had been a warning of an eruption since August 16, 2015.

The acquired data are being immediately provided to the Geospatial Information Authority of Japan (GSI) and other related disaster preparation organizations, and being analyzed for crustal deformation. For details of the analysis results by GSI and JAXA, please refer to the following websites respectively:

- GSI Analysis results (in Japanese): http://www.gsi.go.jp/BOUSAI/H27-sakurajima.html

- JAXA Earth Observation and Research Center analysis results (in Japanese): http://www.eorc.jaxa.jp/ALOS-2/img_up/jpal2_sakurajima_20150816-17.htm


Image above: SAR interferometric analysis* image of Sakurajima, Japan acquired by DAICHI-2 (analyzed by JAXA).

The image shows the comparison result of the data acquired on January 4 and August 16, 2015. The deformation of up to about 16 cm closer toward the satellite was observed at the area on the east side of the Minamidake Summit of Sakurajima (indicated by the white square).

DAICHI-2 (ALOS-2) satellite

*SAR interferometric analysis

The Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) aboard the DAICHI-2 (ALOS-2) can measure deformation of the land surface (how much the land surface moves) by observing the same place twice and comparing the data. Such an analysis method is called “SAR interferometry (InSAR)”. The observed difference is indicated by colors. When the land surface comes closer to the satellite, the color coordination (coloration) moves from green, red, blue to green, and when it goes away from the satellite, the coloration moves from green, blue red, to green.

JAXA continues observations by the DAICHI-2 to contribute to disaster preparation organizations monitoring Sakurajima.

Related links:

- Organization for disaster preparation and monitoring through satellites (in Japanese): http://www.sapc.jaxa.jp/work/antidisaster/

- About SAR interferometric analysis (in Japanese): http://www.eorc.jaxa.jp/ALOS-2/img_up/jpal2_howto_insar.htm
   
- About DAICHI-2: http://global.jaxa.jp/projects/sat/alos2/

Images, Text, Credits: National Research and Development Agency and Japan Aerospace Exploration Agency (JAXA).

Greetings, Orbiter.ch

Chasing ice










ESA - Sentinel-1 Mission logo / ESA - Sentinel-2 Mission logo.

21 August 2015

Chasing glacier retreat

Satellite images show that the fastest moving glacier in the world shed a chunk of ice measuring around 12.5 sq km this week – one of the most significant calving events on record.

Radar images from Sentinel-1A captured the Jakobshavn glacier in western Greenland before and after the event, which took place between 14 and 16 August.

Comparing images taken on 27 July, and 13 and 19 August, the new face of the glacier has been pushed inland by several kilometres to what appears to be its furthest easterly location since monitoring began in the mid-1880s.

The image time series suggests that between 27 July and 13 August, the glacier advanced westward before the calving caused rapid retreat of the ice front to its position on 19 August.

It is estimated that the glacier lost a total area of 12.5 sq km. Assuming the ice is about 1400 m deep, this equates a volume of 17.5 cubic km – which could cover the whole of Manhattan Island by a layer of ice about 300 m thick.

The history of this last calving event is also revealed in images taken by Sentinel-2A on 6 and 16 August.

Jakobshavn glacier drains 6.5% of the Greenland ice sheet, producing around 10% its icebergs. This amounts to some 35 billion tonnes of ice that calve every year.

Jakobshavn glacier calving

Other similar events have been documented where the glacier parted with 7 sq km of ice, both earlier this year and back in 2010.

Icebergs are often so large that they cannot float away easily. They remain, sometimes for years, stuck on the bottom in shallower areas of the fjord until they finally melt enough to disperse, break into pieces or are pushed out by icebergs coming up from behind.

Sentinel-1A satellite

Studied for over 250 years, the Jakobshavn glacier has helped to develop our understanding of the importance of ice streams and glaciers in climate change, icecap glaciology, and how they affect sea level.

Sentinel-1A and Sentinel-2A are the first two satellites in orbit for Europe’s Copernicus programme. While Sentinel-1A is an all-weather, day-and-night radar imaging mission, Sentinel-2A carries a multispectral imager.

Sentinel-2A satellite

Since radar can ‘see’ through clouds and in the dark, Sentinel-1A it is particularly useful for maritime surveillance, ship safety, sea-ice charting and ice-sheet monitoring. Sentinel-2A also demonstrates here that it is also valuable for ice and climate monitoring.

Together, these and future Sentinels, in particular the upcoming Sentinel-3 mission, will add further complementary measurements for operational applications and scientific purposes.

Related links:

Sentinel-1A: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1

Sentinel-2A: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-2

Sentinel data access & technical information: https://sentinel.esa.int/web/sentinel/home

European Commission Copernicus site: http://www.copernicus.eu/

Images, Text, Credits: ESA/Copernicus Sentinel data (2015).

Greetings, Orbiter.ch

The tumultuous heart of our Galaxy












ESA - XMM-Newton Mission patch.

21 August 2015

X-ray view of the Galactic Centre

This new image of powerful remnants of dead stars and their mighty action on the surrounding gas from ESA's XMM-Newton X-ray observatory reveals some of the most intense processes taking place at the centre of our galaxy, the Milky Way.

The bright, point-like sources that stand out across the image trace binary stellar systems in which one of the stars has reached the end of its life, evolving into a compact and dense object – a neutron star or black hole. Because of their high densities, these compact remnants devour mass from their companion star, heating the material up and causing it to shine brightly in X-rays.

The central region of our galaxy also contains young stars and stellar clusters, and some of these are visible as white or red sources sprinkled throughout the image, which spans about one thousand light-years.

Most of the action is occurring at the centre, where diffuse clouds of gas are being carved by powerful winds blown by young stars, as well as by supernovas, the explosive demise of massive stars.

The supermassive black hole sitting at the centre of the Galaxy is also responsible for some of this action. Known as Sagittarius A*, this black hole has a mass a few million times that of our Sun, and it is located within the bright, fuzzy source to the right of the image centre.

While black holes themselves do not emit light, their immense gravitational pull draws in the surrounding matter that, in the process, emits light at many wavelengths, most notably X-rays. In addition, two lobes of hot gas can be seen extending above and below the black hole.

Astronomers believe that these lobes are caused either directly by the black hole, which swallows part of the material that flows onto it but spews out most of it, or by the cumulative effect of the numerous stellar winds and supernova explosions that occur in such a dense environment.

This image, showing us an unprecedented view of the Milky Way's energetic core, was put together in a new study by compiling all observations of this region that were performed with XMM-Newton, adding up to about one and a half months of monitoring in total.

The Galactic Centre through the emission of heavy elements

The large, elliptical structure to the lower right of Sagittarius A* is a super-bubble of hot gas, likely puffed up by the remnants of several supernovas at its centre. While this structure was already known to astronomers, this study confirms for the first time that it consists of a single, gigantic bubble rather than the superposition of several, individual supernova remnants along the line of sight.

Another huge pocket of hot gas, designated the 'Arc Bubble' due to its crescent-like shape, can be seen close to the image centre, to the lower left of the supermassive black hole. It is being inflated by the forceful winds of stars in a nearby stellar cluster, as well as by supernovae; the remnant of one of these explosions, a candidate pulsar wind nebula, was detected at the core of the bubble.

The rich data set compiled in this study contains observations that span the full range of X-ray energies covered by XMM-Newton; these include some energies corresponding to the light emitted by heavy elements such as silicon, sulphur and argon, which are produced primarily in supernova explosions. By combining these additional information present in the data, the astronomers obtained another, complementary view of the Galactic Centre, which reveals beautifully the lobes and bubbles described earlier on.

ESA's XMM-Newton


In addition, this alternative view also displays the emission, albeit very faint, from warm plasma in the upper and lower parts of the image. This warm plasma might be the collective macroscopic effect of outflows generated by star formation throughout this entire central zone.

Another of the possible explanations for such emission links it to the turbulent past of the now not-so-active supermassive black hole. Astronomers believe that, earlier on in the history of our galaxy, Sagittarius A* was accreting and ejecting mass at a much higher rate, like the black holes found at the centre of many galaxies, and these diffuse clouds of warm plasma could be a legacy of its ancient activity. 

Related scientific papers:

The XMM-Newton view of the central degrees of the Milky Way, by G. Ponti et al.: http://mnras.oxfordjournals.org/content/453/1/172.short?rss=1

The Galactic Centre XMM-Newton monitoring project is supported by the Bundesministerium für Wirtschaft und Technologie/Deutsches Zentrum für Luft- und Raumfahrt (BMWI/DLR, FKZ 50 OR 1408) and the Max Planck Society.

For more information about XMM-Newton mission, visit: http://sci.esa.int/xmm-newton/

More about...

XMM-Newton overview: http://www.esa.int/Our_Activities/Space_Science/XMM-Newton_overview

XMM-Newton image gallery: http://xmm.esac.esa.int/external/xmm_science/gallery/public/index.php

In depth:

XMM-Newton in-depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=23

Images, Text, Credits: ESA/XMM-Newton/G. Ponti et al. 2015.

Best regards, Orbiter.ch

Cassini's Final Breathtaking Close Views of Dione












NASA - Cassini Mission to Saturn patch.

August 21, 2015


Image above: This view from NASA's Cassini spacecraft looks toward Saturn's icy moon Dione, with giant Saturn and its rings in the background, just prior to the mission's final close approach to the moon on August 17, 2015. Image Credit: NASA/JPL-Caltech/Space Science Institute.

A pockmarked, icy landscape looms beneath NASA's Cassini spacecraft in new images of Saturn's moon Dione taken during the mission's last close approach to the small, icy world. Two of the new images show the surface of Dione at the best resolution ever.


Image above: Dione hangs in front of Saturn and its icy rings in this view, captured during Cassini's final close flyby of the icy moon. Image Credit: NASA/JPL-Caltech/Space Science Institute.

Cassini passed 295 miles (474 kilometers) above Dione's surface at 11:33 a.m. PDT (2:33 p.m. EDT) on Aug. 17. This was the fifth close encounter with Dione during Cassini's long tour at Saturn. The mission's closest-ever flyby of Dione was in Dec. 2011, at a distance of 60 miles (100 kilometers).


Image above: Saturn's moon Dione hangs in front of Saturn's rings in this view taken by NASA's Cassini spacecraft during the inbound leg of its last close flyby of the icy moon. Image Credit: NASA/JPL-Caltech/Space Science Institute.

"I am moved, as I know everyone else is, looking at these exquisite images of Dione's surface and crescent, and knowing that they are the last we will see of this far-off world for a very long time to come," said Carolyn Porco, Cassini imaging team lead at the Space Science Institute, Boulder, Colorado. "Right down to the last, Cassini has faithfully delivered another extraordinary set of riches. How lucky we have been."

Raw, unprocessed images from the flyby are available at: http://saturn.jpl.nasa.gov/mission/flybys/dione20150817/


Image above: NASA's Cassini spacecraft captured this parting view showing the rough and icy crescent of Saturn's moon Dione following the spacecraft's last close flyby of the moon on Aug. 17, 2015. Image Credit: NASA/JPL-Caltech/Space Science Institute.

The main scientific focus of this flyby was gravity science, not imaging. This made capturing the images tricky, as Cassini's camera was not controlling where the spacecraft pointed.

"We had just enough time to snap a few images, giving us nice, high resolution looks at the surface," said Tilmann Denk, a Cassini participating scientist at Freie University in Berlin. "We were able to make use of reflected sunlight from Saturn as an additional light source, which revealed details in the shadows of some of the images."


Image above: NASA's Cassini spacecraft gazes out upon a rolling, cratered landscape in this oblique view of Saturn's moon Dione. Image Credit:NASA/JPL-Caltech/Space Science Institute.

Cassini scientists will study data from the gravity science experiment and magnetosphere and plasma science instruments over the next few months as they look for clues about Dione's interior structure and processes affecting its surface.

Only a handful of close flybys of Saturn's large, icy moons remain for Cassini. The spacecraft is scheduled to make three approaches to the geologically active moon Enceladus on Oct. 14 and 28, and Dec. 19. During the Oct. 28 flyby, the spacecraft will come dizzyingly close to Enceladus, passing a mere 30 miles (49 kilometers) from the surface. Cassini will make its deepest-ever dive through the moon's plume of icy spray at this time, collecting valuable data about what's going on beneath the surface. The December Enceladus encounter will be Cassini's final close pass by that moon, at an altitude of 3,106 miles (4,999 kilometers).


Image above: This view from NASA's Cassini spacecraft shows terrain on Saturn's moon Dione that is entirely lit by reflected light from Saturn, called Saturnshine. Image Credit: NASA/JPL-Caltech/Space Science Institute.

After December, and through the mission's conclusion in late 2017, there are a handful of distant flybys planned for Saturn's large, icy moons at ranges of less than about 30,000 miles (50,000 kilometers). Cassini will, however, make nearly two dozen passes by a menagerie of Saturn's small, irregularly shaped moons -- including Daphnis, Telesto, Epimetheus and Aegaeon -- at similar distances during this time. These passes will provide some of Cassini's best-ever views of the little moons.


Image above: This view of Dione from Cassini includes the mission's highest-resolution view of the icy moon's surface as an inset at center left. Image Credit: NASA/JPL-Caltech/Space Science Institute.

During the mission's final year -- called its Grand Finale -- Cassini will repeatedly dive through the space between Saturn and its rings.


Image above: A region on Dione where features in shadow are illuminated by reflected light from Saturn. Inset above center is one of Cassini's highest-resolution views of Dione's surface. Image Credit: NASA/JPL-Caltech/Space Science Institute.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about Cassini, visit:

http://www.nasa.gov/cassini

http://saturn.jpl.nasa.gov

http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Images (mentioned), Text, Credits: NASA/JPL/Preston Dyches.

Greetings, Orbiter.ch

Ariane 5’s fourth launch of 2015


















Arianespace - Flight VA 225 Mission poster.


21 August 2015

Ariane 5 liftoff on flight VA225

An Ariane 5 lifted off tonight from Europe’s Spaceport in Kourou, French Guiana, and delivered two telecom satellites into their planned orbits.

The launch of flight VA225 occurred on 20 August at 20:34 GMT (22:34 CEST, 17:34 local time).

Eutelsat-8 West B, with a mass of 5782 kg and mounted in the upper position atop Ariane’s Sylda dual-payload carrier, was the first to be released about 28 minutes into the mission.

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Ariane 5 flight VA225 liftoff

Following a series of burns controlled by Ariane’s computer, the Sylda structure encasing the 3300 kg Intelsat-34 was then jettisoned. Intelsat-34 was released into its own transfer orbit about 13 minutes after the first satellite.

Artist's rendering of Intelsat 34

Eutelsat-8 West B, owned and operated by Eutelsat, will operate from 8°W in geostationary orbit. It will provide HD and Ultra HD direct-to-home TV broadcast services to the Middle East and North Africa, and telecommunications services in Africa and the eastern part of South America. The satellite has a design life of about 15 years.

Artist's rendering of Eutelsat 8 West B

Intelsat-34, owned and operated by Intelsat, will be positioned at 304.5°E in geostationary orbit to provide media distribution services for Latin America and host a leading Brazilian direct-to-home platform. It will also support advanced broadband services to maritime and aeronautical providers serving the North Atlantic. It has a design life of 15 years.

The payload mass for this launch was 9912 kg. The satellites totalled about 9082 kg, with payload adapters and carrying structures making up the rest.

Flight VA225 was the 81st Ariane 5 mission.

For more information about Arianespace, visit: http://www.arianespace.com/index/index.asp

Images, Video, Text, Credits: ESA/Arianespace/Gunter's Space Page.

Best regards, Orbiter.ch

mercredi 19 août 2015

NASA Mars Rover Moves Onward After 'Marias Pass' Studies












NASA - Mars Science Laboratory (MSL) patch.

Aug. 19, 2015


Image above: This low-angle self-portrait of NASA's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin." The MAHLI camera on Curiosity's robotic arm took multiple images on Aug. 5, 2015, that were stitched together into this selfie. Image Credits: NASA/JPL-Caltech/MSSS.

NASA's Curiosity Mars rover is driving toward the southwest after departing a region where for several weeks it investigated a geological contact zone and rocks that are unexpectedly high in silica and hydrogen content. The hydrogen indicates water bound to minerals in the ground.

In this "Marias Pass" region, Curiosity successfully used its drill to sample a rock target called "Buckskin" and then used the camera on its robotic arm for multiple images to be stitched into a self-portrait at the drilling site. The new Curiosity selfie from a dramatically low angle is online at:

http://www.jpl.nasa.gov/spaceimages/details.php?id=pia19808


Image above: This version of a self-portrait of NASA's Curiosity Mars rover at a drilling site called "Buckskin" is presented as a stereographic projection, which shows the horizon as a circle. The MAHLI camera on Curiosity's robotic arm took dozens of component images for this selfie on Aug. 5, 2015. Image Credits: NASA/JPL-Caltech/MSSS.

The rover finished activities in Marias Pass on Aug. 12 and headed onward up Mount Sharp, the layered mountain it reached in September 2014. In drives on Aug. 12, 13, 14 and 18, it progressed 433 feet (132 meters), bringing Curiosity's total odometry since its August 2012 landing to 6.9 miles (11.1 kilometers).

Curiosity is carrying with it some of the sample powder drilled from Buckskin. The rover's internal laboratories are analyzing the material. The mission's science team members seek to understand why this area bears rocks with significantly higher levels of silica and hydrogen than other areas the rover has traversed.

Silica, monitored with Curiosity's laser-firing Chemistry and Camera (ChemCam) instrument, is a rock-forming chemical containing silicon and oxygen, commonly found on Earth as quartz. Hydrogen in the ground beneath the rover is monitored by the rover's Dynamic Albedo of Neutrons (DAN) instrument. It has been detected at low levels everywhere Curiosity has driven and is interpreted as the hydrogen in water molecules or hydroxyl ions bound within or absorbed onto minerals in the rocks and soil.


Image above: This low-angle self-portrait of NASA's Curiosity Mars rover from Aug. 5, 2015, shows the vehicle above the "Buckskin" rock target in the "Marias Pass" area of lower Mount Sharp. The MAHLI camera on Curiosity's robotic arm took dozens of images that were stitched together into this sweeping panorama. Image Credits: NASA/JPL-Caltech/MSSS.

"The ground about 1 meter beneath the rover in this area holds three or four times as much water as the ground anywhere else Curiosity has driven during its three years on Mars," said DAN Principal Investigator Igor Mitrofanov of Space Research Institute, Moscow. DAN first detected the unexpectedly high level of hydrogen using its passive mode. Later, the rover drove back over the area using DAN in active mode, in which the instrument shoots neutrons into the ground and detects those that bounce off the subsurface, but preferentially interacting with hydrogen. The measurements confirmed hydrated material covered by a thin layer of drier material.

Curiosity initially noted the area with high silica and hydrogen on May 21 while climbing to a site where two types of sedimentary bedrock lie in contact with each other. Such contact zones can hold clues about ancient changes in environment, from conditions that produced the older rock type to conditions that produced the younger one. This contact is the lure that led the rover team to choose Marias Pass as a route toward higher layers of Mount Sharp. Pale mudstone, like bedrock the mission examined for the first several months after reaching Mount Sharp at an area called "Pahrump Hills," forms one side of the contact. The overlying side is darker, finely bedded sandstone.


Image above: This view of a test rover at NASA's Jet Propulsion Laboratory in California results from advance testing of arm positions and camera pointings for taking a low-angle selfie of NASA's Curiosity Mars rover. Image Credits: NASA/JPL-Caltech/MSSS.

Curiosity examined the Marias Pass contact zone closely with instruments mounted on its mast and arm. The unusual levels of silica and hydrogen in rocks passed during the climb prompted a choice to backtrack to examine that area and acquire a drilled sample.

Buckskin was the first rock drilled by Curiosity since an electrical circuit in the drill's percussion mechanism exhibited a small, transient short circuit in February during transfer of sample powder from the third target drilled in the Pahrump Hills area.


Image above: Curiosity's DAN instrument for checking hydration levels in the ground beneath the rover detected an unusually high amount at a site near "Marias Pass," prompting repeated passes over the area to map the hydrogen amounts. This map shows color-coded results from multiple traverses over the area. Image Credits: NASA/JPL-Caltech/Russian Space Research Institute.

"We were pleased to see no repeat of the short circuit during the Buckskin drilling and  sample transfer," said Steven Lee, deputy project manager for Curiosity at NASA's Jet Propulsion Laboratory, Pasadena, California. "It could come back, but we have made changes in fault protection to continue safely drilling even in the presence of small shorts. We also improved drill percuss circuit telemetry to gain more diagnostic information from any future occurrences."

Curiosity reached the base of Mount Sharp after two years of fruitfully investigating outcrops closer to its landing site and trekking to the mountain. The main mission objective now is to examine layers of lower Mount Sharp for ancient habitable environments and evidence about how early Mars environments evolved from wetter to drier conditions.

JPL, a division of the California Institute of Technology in Pasadena, built the rover and manages the project for NASA's Science Mission Directorate in Washington. For more information about Curiosity, visit: http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/

You can follow the mission on Facebook and Twitter at: http://www.facebook.com/marscuriosity and http://www.twitter.com/marscuriosity

Images (mentioned), Text, Credits: NASA/JPL/Guy Webster/Tony Greicius.

Best regards, Orbiter.ch

NASA: There is No Asteroid Threatening Earth










Asteroid Watch logo.

Aug. 19, 2015

Numerous recent blogs and web postings are erroneously claiming that an asteroid will impact Earth, sometime between Sept. 15 and 28, 2015. On one of those dates, as rumors go, there will be an impact -- "evidently" near Puerto Rico -- causing wanton destruction to the Atlantic and Gulf coasts of the United States and Mexico, as well as Central and South America.

That's the rumor that has gone viral -- now here are the facts.

"There is no scientific basis -- not one shred of evidence -- that an asteroid or any other celestial object will impact Earth on those dates," said Paul Chodas, manager of NASA's Near-Earth Object office at the Jet Propulsion Laboratory in Pasadena, California.

In fact, NASA's Near-Earth Object Observations Program says there have been no asteroids or comets observed that would impact Earth anytime in the foreseeable future.  All known Potentially Hazardous Asteroids have less than a 0.01% chance of impacting Earth in the next 100 years.

Artist concept of asteroid approaching the Earth. Image Credit: NASA

The Near-Earth Object office at JPL is a key group involved with the international collaboration of astronomers and scientists who keep watch on the sky with their telescopes, looking for asteroids that could do harm to our planet and predicting their paths through space for the foreseeable future. If there were any observations on anything headed our way, Chodas and his colleagues would know about it.

"If there were any object large enough to do that type of destruction in September, we would have seen something of it by now," he stated.

Another thing Chodas and his team do know -- this isn't the first time a wild, unsubstantiated claim of a celestial object about to impact Earth has been made, and unfortunately, it probably won’t be the last.  It seems to be a perennial favorite of the World Wide Web.

In 2011 there were rumors about the so-called “doomsday” comet Elenin, which never posed any danger of harming Earth and broke up into a stream of small debris out in space. Then there were Internet assertions surrounding the end of the Mayan calendar on Dec. 21, 2012, insisting the world would end with a large asteroid impact. And just this year, asteroids 2004 BL86 and 2014 YB35 were said to be on dangerous near-Earth trajectories, but their flybys of our planet in January and March went without incident -- just as NASA said they would.

"Again, there is no existing evidence that an asteroid or any other celestial object is on a trajectory that will impact Earth," said Chodas. "In fact, not a single one of the known objects has any credible chance of hitting our planet over the next century."

NASA detects, tracks and characterizes asteroids and comets passing 30 million miles of Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes the physical nature of a subset of them, and predicts their paths to determine if any could be potentially hazardous to our planet. There are no known credible impact threats to date -- only the continuous and harmless infall of meteoroids, tiny asteroids that burn up in the atmosphere.

JPL hosts the office for Near-Earth Object orbit analysis for NASA's Near Earth Object Observations Program of the Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.

More information about asteroids and near-Earth objects is at:

http://neo.jpl.nasa.gov

http://www.jpl.nasa.gov/asteroidwatch and on Twitter: @asteroidwatch

Image (mentioned), Text, Credits: NASA/JPL/DC Agle/Tony Greicius.

Greetings, Orbiter.ch

Sibling Stars












ESO - European Southern Observatory logo.

19 August 2015

The rich star cluster IC 4651

Open star clusters like the one seen here are not just perfect subjects for pretty pictures. Most stars form within clusters and these clusters can be used by astronomers as laboratories to study how stars evolve and die. The cluster captured here by the Wide Field Imager (WFI) at ESO’s La Silla Observatory is known as IC 4651, and the stars born within it now display a wide variety of characteristics.

The loose speckling of stars in this new ESO image is the open star cluster IC 4651, located within the Milky Way, in the constellation of Ara (The Altar), about 3000 light-years away. The cluster is around 1.7 billion years old — making it middle-aged by open cluster standards. IC 4651 was discovered by Solon Bailey, who pioneered the establishment of observatories in the high dry sites of the Andes, and it was catalogued in 1896 by the Danish–Irish astronomer John Louis Emil Dreyer.

The star cluster IC 4651 in the constellation of Ara

The Milky Way is known to contain over a thousand of these open clusters, with more thought to exist, and many have been studied in great depth. Observations of star clusters like these have furthered our knowledge of the formation and evolution of the Milky Way and the individual stars within it. They also allow astronomers to test their models of how stars evolve.

The stars in IC 4651 all formed around the same time out of the same cloud of gas [1]. These sibling stars are only bound together very loosely by their attraction to one another and also by the gas between them. As the stars within the cluster interact with other clusters and clouds of gas in the galaxy around them, and as the gas between the stars is either used up to form new stars or blown away from the cluster, the cluster’s structure begins to change. Eventually, the remaining mass in the cluster becomes small enough that even the stars can escape. Recent observations of IC 4651 showed that the cluster contains a mass of 630 times the mass of the Sun [2] and yet it is thought that it initially contained at least 8300 stars, with a total mass 5300 times that of the Sun.

Wide-field view of the sky around the bright star cluster IC 4651

As this cluster is relatively old, a part of this lost mass will be due to the most massive stars in the cluster having already reached the ends of their lives and exploded as supernovae. However, the majority of the stars that have been lost will not have died, but merely moved on. They will have been stripped from the cluster as it passed by a giant gas cloud or had a close encounter with a neighbouring cluster, or even simply drifted away.

A fraction of these lost stars may still be gravitationally bound to the cluster and surround it at a great distance. The remaining lost stars will have migrated away from the cluster to join others, or have settled elsewhere in the busy Milky Way. The Sun was probably once part of a cluster like IC 4651, until it and all its siblings were gradually separated and spread across the Milky Way.

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Zooming in on the star cluster IC 4651

This image was taken using the Wide Field Imager. This camera is permanently mounted at the MPG/ESO 2.2-metre telescope at the La Silla Observatory. It consists of several CCD detectors with a total of 67 million pixels and can observe an area as large as the full Moon. The instrument allows observations from visible light to the near infrared, with more than 40 filters available. For this image, only three of these filters were used.

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The rich star cluster IC 4651

Notes:

[1] Although many of the stars captured here belong to IC 4651, most of the very brightest in the picture actually lie between us and the cluster and most of the faintest ones are more distant.

[2] This quantity is in fact much larger than the numbers quoted by previous studies which surveyed smaller regions, leaving out many of the cluster’s stars that lie further from its core.

More information:

ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become "the world’s biggest eye on the sky".

For more information about European Southern Observatory (ESO), visit: http://www.eso.org/public/

Images, Text, Credits: ESO/IAU and Sky & Telescope/Digitized Sky Survey 2. Acknowledgement: Davide De Martin/Videos: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org).

Greetings, Orbiter.ch