vendredi 16 mars 2012

Glittering Jewels of Messier 9













ESA - Hubble Space Telescope logo.

16 March 2012

 Hubble image of Messier 9

The NASA/ESA Hubble Space Telescope has produced the most detailed image so far of Messier 9, a globular star cluster located close to the centre of the galaxy. This ball of stars is too faint to see with the naked eye, yet Hubble can see over 250 000 individual stars shining in it.

Messier 9, pictured here, is a globular cluster, a roughly spherical swarm of stars that lies around 25 000 light-years from Earth, near the centre of the Milky Way, so close that the gravitational forces from the galactic centre pull it slightly out of shape.

Globular clusters are thought to harbour some of the oldest stars in our galaxy, born when the Universe was just a small fraction of its current age. As well as being far older than the Sun — around twice its age — the stars of Messier 9 also have a markedly different composition, and are enriched with far fewer heavier elements than the Sun.

Wide-field view of Messier 9 (ground-based image)

In particular, the elements crucial to life on Earth, like oxygen and carbon, and the iron that makes up our planet’s core, are very scarce in Messier 9 and clusters like it. This is because the Universe’s heavier elements were gradually formed in the cores of stars, and in supernova explosions. When the stars of Messier 9 formed, there were far smaller quantities of these elements in existence.

Messier 9, as its name suggests, was discovered by the great French astronomer Charles Messier in 1764. Even through the most advanced telescopes of the day, none of the stars in the cluster could be seen individually. Messier, seeing only a faint smudge, therefore classified the object as a nebula — or “cloud” in Latin. It was only later in the 18th century that astronomers, most notably William Herschel, began to spot stars within the cluster.

video
Zoom into Messier 9

The contrast between Messier’s equipment and the tools at the disposal of today’s astronomers is stark. Hubble’s image, the highest resolution image yet made of Messier 9, is able to resolve individual stars, right into the crowded centre of the cluster. Over 250 000 of them are neatly focused on the detector of Hubble’s Advanced Camera for Surveys, in an image which covers an area no bigger than the size of the head of a pin held at arm’s length.

As well as showing the individual stars, Hubble’s image clearly shows the different colours of the stars. A star’s colour is directly related to its temperature — counter-intuitively, perhaps, the redder it is, the cooler it is; and the bluer it is, the hotter. The wide range of stellar temperatures here is clearly displayed by the broad palette of colours visible in Hubble’s image of Messier 9.

video
Pan across Messier 9

Messier 9’s neighbourhood is interesting too, and is marked by two vast and dark nebulae. These pitch-black clouds of interstellar dust are known as Barnard 259 (to the south-east of Messier 9) and Barnard 64 (to the west), and are clearly visible in wide-field images of the cluster.
Notes

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

Link:

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

Images, Text, Credits: NASA / ESA / Digitized Sky Survey 2 (Acknowledgement: Davide De Martin) / Videos: NASA / ESA / Digitized Sky Survey 2 / N. Risinger (skysurvey.org).

Best regards, Orbiter.ch

Solar flares over, Venus Express restarts science investigations













ESA - Venus Express Mission patch.

16 March 2012

ESA’s Venus Express spacecraft has returned to routine operation after its startracker cameras were temporarily blinded last week by radiation from a pair of large solar flares.

Science observations by ESA’s Venus Express were temporarily suspended on 7 March after the two startrackers – used to help navigate and orient the spacecraft – were overwhelmed by excessive proton radiation.

Venus Express

The proton storm stemmed from the Coronal Mass Ejections (CMEs) emitted by the Sun, which were associated with a pair of massive solar flares that occurred early in the morning on 7 March.

With the startrackers unable to function properly, mission controllers at ESOC, ESA’s European Space Operations Centre, Darmstadt, had to place the spacecraft into a special mode to ride out the storm. 

This meant that all instruments were switched off and routine scientific observations and data gathering were stopped.

Source of Venus Express trouble: Active sun spot group AR1429

“As the radiation faded, the startrackers began functioning normally again on 9 March,” said Octavio Camino, ESA’s Spacecraft Operations Manager.

“After taking some time to conduct a series of thorough spacecraft health checks, Venus Express returned to regular science operations on 12 March at 20:20 GMT.”

Waiting out the storm

This month, Venus Express is going through ‘quadrature’: a period of about five weeks during which the Sun-spacecraft-Earth angle is between 75° and 95°. They occur twice every 19 months.

During quadrature, the spacecraft must maintain a special orientation so that certain instruments are not over-exposed to sunlight and the radio antenna can still be pointed to Earth.

“At any time, if a problem is autonomously detected onboard, the spacecraft might place itself into ‘safe mode’,” says Octavio.

However, if a safe mode were to happen during quadrature operations, and the startrackers were not operating, it would be much more difficult to return the spacecraft to normal operations.

“To be very cautious, we simply stopped science activities to wait out the proton storm,” says Octavio.

The mission operations team used the gyroscopes to maintain a safe attitude while waiting for the startrackers to return to normal.

Venus Express: a very robust mission

“There were no permanent effects; Venus Express is in excellent condition and the operations team performed very well,” said Paolo Ferri, responsible for interplanetary mission operations at ESOC.

“Yes, orbiting Venus means we’re closer to the Sun – and in a potentially hazardous environment.”

“But we have a very robust mission that is once again returning a large amount of valuable scientific data.”

Related links:

Venus Express operations: http://www.esa.int/SPECIALS/Operations/SEM7QMQJNVE_0.html

The Sun now: http://www.esa.int/esaCP/ASE08Y9KOYC_Protecting_0.html

Space Situational Awareness: http://www.esa.int/esaMI/SSA/index.html

ESA/NASA SOHO homepage: http://sohowww.estec.esa.nl/

Images, Text, Credits: ESA / Michel Breitfellner, Miguel Pérez Ayúcar, Manuel Castillo - ESAC.

Greetings, Orbiter.ch

jeudi 15 mars 2012

Abell 383: An Elusive Subject












NASA - Chandra X-ray Observatory patch.

03.15.12


Two teams of astronomers have used data from NASA's Chandra X-ray Observatory and other telescopes to map the distribution of dark matter in a galaxy cluster known as Abell 383, which is located about 2.3 billion light years from Earth. Not only were the researchers able to find where the dark matter lies in the two dimensions across the sky, they were also able to determine how the dark matter is distributed along the line of sight.

Dark matter is invisible material that does not emit or absorb any type of light, but is detectable through its gravitational effects. Several lines of evidence indicate that there is about six times as much dark matter as "normal," or baryonic, matter in the Universe. Understanding the nature of this mysterious matter is one of the outstanding problems in astrophysics.

Galaxy clusters are the largest gravitationally-bound structures in the universe, and play an important role in research on dark matter and cosmology, the study of the structure and evolution of the universe. The use of clusters as dark matter and cosmological probes hinges on scientists' ability to use objects such as Abell 383 to accurately determine the three-dimensional structures and masses of clusters.

The recent work on Abell 383 provides one of the most detailed 3-D pictures yet taken of dark matter in a galaxy cluster. Both teams have found that the dark matter is stretched out like a gigantic football, rather than being spherical like a basketball, and that the point of the football is aligned close to the line of sight.

The X-ray data (purple) from Chandra in the composite image show the hot gas, which is by far the dominant type of normal matter in the cluster. Galaxies are shown with the optical data from the Hubble Space Telescope (HST), the Very Large Telescope, and the Sloan Digital Sky Survey, colored in blue and white.

Both teams combined the X-ray observations of the "normal matter" in the cluster with gravitational lensing information determined from optical data. Gravitational lensing -- an effect predicted by Albert Einstein -- causes the material in the galaxy cluster, both normal and dark matter, to bend and distort the optical light from background galaxies. The distortion is severe in some parts of the image, producing an arc-like appearance for some of the galaxies. In other parts of the image the distortion is subtle and statistical analysis is used to study the distortion effects and probe the dark matter.

A considerable amount of effort has gone into studying the center of galaxy clusters, where the dark matter has the highest concentration and important clues about its behavior might be revealed. Both of the Abell 383 studies reported here continue that effort.

The team of Andrea Morandi from Tel Aviv University in Israel and Marceau Limousin from Université de Provence in France and University of Copenhagen in Denmark concluded that the increased concentration of the dark matter toward the center of the cluster is in agreement with most theoretical simulations. Their lensing data came from HST images.

The team led by Andrew Newman of the California Institute of Technology and Tommaso Treu of University of California, Santa Barbara (UCSB) used lensing data from HST and the Japanese telescope Subaru, but added Keck observations to measure the velocities of stars in the galaxy in the center of the cluster, allowing for a direct estimate of the amount of matter there. They found evidence that the amount of dark matter is not peaked as dramatically toward the center as the standard cold dark matter model predicts. Their paper describes this as being the "most robust case yet" made for such a discrepancy with theory.

Chandra X-ray Observatory

The contrasting conclusions reached by the two teams most likely stem from differences in the data sets and the detailed mathematical modeling used. One important difference is that because the Newman et al. team used velocity information in the central galaxy, they were able to estimate the density of dark matter at distances that approached as close as only 6,500 light years from the center of the cluster. Morandi and Limousin did not use velocity data and their density estimates were unable to approach as close to the cluster's center, reaching to within 80,000 light years.

Another important difference is that Morandi and Limousin used a more detailed model for the 3-D map of dark matter in the cluster. For example, they were able to estimate the orientation of the dark matter "football" in space and show that it is mostly edge-on, although slightly tilted with respect to the line of sight.

As is often the case with cutting-edge and complex results, further work will be needed to resolve the discrepancy between the two teams. In view of the importance of resolving the dark matter mystery, there will undoubtedly be much more research into Abell 383 and other objects like it in the months and years to come.

If the relative lack of dark matter in the center of Abell 383 is confirmed, it may show that improvements need to be made in our understanding of how normal matter behaves in the center of galaxy clusters, or it may show that dark matter particles can interact with each other, contrary to the prevailing model.

The Newman et al. paper was published in the February 20, 2011 issue of the Astrophysical Journal Letter and the Morandi and Limousin paper has been accepted for publication in the Monthly Notices of the Royal Astronomical Society. Other members of the Newman et al. team were Richard Ellis from Caltech, and David Sand from Las Cumbres Global Telescope Network and UCSB.

Read more/access all images: http://chandra.harvard.edu/photo/2012/a383/

Image, Text, Credits: X-ray: NASA/CXC/Caltech/A.Newman et al/Tel Aviv/A.Morandi & M.Limousin; Optical: NASA/STScI, ESO/VLT, SDSS.

Greetings, Orbiter.ch

mercredi 14 mars 2012

NASA Releases New WISE Mission Catalog Of Entire Infrared Sky









NASA - WISE Mission patch.

March 14, 2012

NASA unveiled a new atlas and catalog of the entire infrared sky today showing more than a half billion stars, galaxies and other objects captured by the Wide-field Infrared Survey Explorer (WISE) mission.

"Today, WISE delivers the fruit of 14 years of effort to the astronomical community," said Edward Wright, WISE principal investigator at UCLA, who first began working on the mission with other team members in 1998.

WISE launched Dec. 14, 2009, and mapped the entire sky in 2010 with vastly better sensitivity than its predecessors. It collected more than 2.7 million images taken at four infrared wavelengths of light, capturing everything from nearby asteroids to distant galaxies. Since then, the team has been processing more than 15 trillion bytes of returned data. A preliminary release of WISE data, covering the first half of the sky surveyed, was made last April.


The WISE catalog of the entire sky meets the mission's fundamental objective. The individual WISE exposures have been combined into an atlas of more than 18,000 images covering the sky and a catalog listing the infrared properties of more than 560 million individual objects found in the images. Most of the objects are stars and galaxies, with roughly equal numbers of each. Many of them have never been seen before.

WISE observations have led to numerous discoveries, including the elusive, coolest class of stars. Astronomers hunted for these failed stars, called "Y-dwarfs," for more than a decade. Because they have been cooling since their formation, they don't shine in visible light and could not be spotted until WISE mapped the sky with its infrared vision.

WISE also took a poll of near-Earth asteroids, finding there are significantly fewer mid-size objects than previously thought. It also determined NASA has found more than 90 percent of the largest near-Earth asteroids.


Other discoveries were unexpected. WISE found the first known "Trojan" asteroid to share the same orbital path around the sun as Earth. One of the images released today shows a surprising view of an "echo" of infrared light surrounding an exploded star. The echo was etched in the clouds of gas and dust when the flash of light from the supernova explosion heated surrounding clouds. At least 100 papers on the results from the WISE survey already have been published. More discoveries are expected now that astronomers have access to the whole sky as seen by the spacecraft.

"With the release of the all-sky catalog and atlas, WISE joins the pantheon of great sky surveys that have led to many remarkable discoveries about the universe," said Roc Cutri, who leads the WISE data processing and archiving effort at the Infrared and Processing Analysis Center at the California Institute of Technology in Pasadena. "It will be exciting and rewarding to see the innovative ways the science and educational communities will use WISE in their studies now that they have the data at their fingertips."

NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., manages and operates WISE for NASA's Science Mission Directorate in Washington. The mission was competitively selected under NASA's Explorers Program, which is managed by NASA's Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah, and the spacecraft was built by Ball Aerospace and Technologies Corp., in Boulder, Colo. Science operations, data processing and archiving take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

For a collection of WISE images released to date, visit: http://wise.ssl.berkeley.edu/gallery_images.html

An introduction and quick guide to accessing the WISE all-sky archive for astronomers is online at: http://wise2.ipac.caltech.edu/docs/release/allsky/

For more information about WISE, visit: http://www.nasa.gov/wise

Images, Text, Credits: NASA / JPL-Caltech.

Greetings, Orbiter.ch

The Feeding Habits of Teenage Galaxies













ESO - European Southern Observatory logo.

14 March 2012

 Teenage galaxies in the distant Universe

New observations made with ESO’s Very Large Telescope are making a major contribution to understanding the growth of adolescent galaxies. In the biggest survey of its kind astronomers have found that galaxies changed their eating habits during their teenage years - the period from about 3 to 5 billion years after the Big Bang. At the start of this phase smooth gas flow was the preferred snack, but later, galaxies mostly grew by cannibalising other smaller galaxies.

Astronomers have known for some time that the earliest galaxies were much smaller than the impressive spiral and elliptical galaxies that now fill the Universe. Over the lifetime of the cosmos galaxies have put on a great deal of weight but their food, and eating habits, are still mysterious. A new survey of carefully selected galaxies has focussed on their teenage years — roughly the period from about 3 to 5 billion years after the Big Bang.

Teenage galaxies in the distant Universe (unannotated)

By employing the state-of-the-art instruments on ESO’s Very Large Telescope an international team is unravelling what really happened. In more than one hundred hours of observations the team has collected the biggest ever set of detailed observations of gas-rich galaxies at this early stage of their development [1].

“Two different ways of growing galaxies are competing: violent merging events when larger galaxies eat smaller ones, or a smoother and continuous flow of gas onto galaxies. Both can lead to lots of new stars being created,” explains Thierry Contini (IRAP, Toulouse, France), who leads the work.

Teenage galaxies in the distant Universe and the motions of their gas

The new results point toward a big change in the cosmic evolution of galaxies, when the Universe was between 3 and 5 billion years old. Smooth gas flow (eso1040) seems to have been a big factor in the building of galaxies in the very young Universe, whereas mergers became more important later.

“To understand how galaxies grew and evolved we need to look at them in the greatest possible detail. The SINFONI instrument on ESO’s VLT is one of the most powerful tools in the world to dissect young and distant galaxies. It plays the same role that a microscope does for a biologist,” adds Thierry Contini.

A Wide-field view of the sky around a field studied in the MASSIV survey

Distant galaxies like the ones in the survey are just tiny faint blobs in the sky, but the high image quality from the VLT used with the SINFONI instrument [2] means that the astronomers can make maps of how different parts of the galaxies are moving and what they are made of. There were some surprises.

“For me, the biggest surprise was the discovery of many galaxies with no rotation of their gas. Such galaxies are not observed in the nearby Universe. None of the current theories predict these objects,” says Benoît Epinat, another member of the team.

video
Zooming in on teenage galaxies in the distant Universe

“We also didn’t expect that so many of the young galaxies in the survey would have heavier elements concentrated in their outer parts — this is the exact opposite of what we see in galaxies today,” adds Thierry Contini.

The team are only just starting to explore their rich set of observations. They plan to also observe the galaxies with future instruments on the VLT as well as using ALMA to study the cold gas in these galaxies. Looking further into the future the European Extremely Large Telescope will be ideally equipped to extend this type of study deeper into the early Universe.

Notes:

[1] The name of the survey is MASSIV: Mass Assembly Survey with SINFONI in VVDS. The VVDS is the VIMOS-VLT Deep Survey. VIMOS is the VIsible imaging Multi-Object Spectrograph, a powerful camera and spectrograph on the VLT that was used to find the galaxies used in the MASSIV work, and measure their distances and other properties.

[2] SINFONI is the Spectrograph for INtegral Field Observations in the Near Infrared. It is the instrument on the VLT that was used for the MASSIV survey. SINFONI is a near-infrared (1.1-2.45 µm) integral field spectrograph using adaptive optics to improve the image quality.

More information:

This research was presented in four papers describing the MASSIV survey that will appear in the journal Astronomy & Astrophysics.

The team is composed of T. Contini (Institut de Recherche en Astrophysique et Planétologie [IRAP], CNRS & Université de Toulouse, France), B. Epinat (Laboratoire d'Astrophysique de Marseille, CNRS & Université d'Aix-Marseille, France [LAM]), D. Vergani (Istituto di Astrofisica Spaziale e Fisica Cosmica-INAF, Bologna, Italy [IASF BO-INAF]), J. Queyrel (IRAP), L. Tasca (LAM), B. Garilli (Istituto di Astrofisica Spaziale e Fisica Cosmica-INAF, Milan, Italy [IASF MI-INAF]), O. Le Fevre (LAM), M. Kissler-Patig (ESO), P. Amram (LAM), J. Moultaka (IRAP), L. Paioro (IASF MI-INAF), L. Tresse (LAM), C. López-Sanjuan (LAM), E. Perez-Montero (Instituto de Astrofísica de Andalucía, Granada, Spain), C. Divoy (IRAP) and V. Perret (LAM).

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. 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 the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

    Research papers in A&A:

    Paper I: http://www.eso.org/public/archives/releases/sciencepapers/eso1212/eso1212a.pdf
    Paper II: http://www.eso.org/public/archives/releases/sciencepapers/eso1212/eso1212b.pdf
    Paper III: http://www.eso.org/public/archives/releases/sciencepapers/eso1212/eso1212c.pdf
    Paper IV: http://www.eso.org/public/archives/releases/sciencepapers/eso1212/eso1212d.pdf

    MASSIV website: http://www.ast.obs-mip.fr/users/contini/MASSIV/

    Photos of the VLT: http://www.eso.org/public/images/archive/category/paranal/

    Article about MASSIV in ESO Messenger: http://www.eso.org/public/archives/releases/sciencepapers/eso1212/eso1212e.pdf

Images, Text, Credits: ESO / CFHT / Digitized Sky Survey 2. Acknowledgment: Davide De Martin / Video: ESO / A. Fujii / Digitized Sky Survey 2 / CFHT. Music: John Dyson (from the album Moonwind).

Best regards, Orbiter.ch

Compact Planetary System













NASA - Kepler Mission patch.

March 14, 2012


This artist's concept depicts a planetary system so compact that it's more like Jupiter and its moons than a star and its planets. Astronomers using data from NASA's Kepler mission and ground-based telescopes recently confirmed that the system, called KOI-961, hosts the three smallest exoplanets currently known to orbit a star other than our sun. An exoplanet is a planet that resides outside of our solar system.

The star, which is located about 130 light-years away in the Cygnus constellation, is a red dwarf that is one-sixth the size of the sun, or just 70 percent bigger than Jupiter. The star is also cooler than our sun, and gives off more red light than yellow.

The smallest of the three planets, called KOI-961.03, is actually located the farthest from the star, and is pictured in the foreground. This planet is about the size of Mars, with a radius of 0.57 times that of Earth. The next planet to the upper right is KOI-961.01, which is 0.78 times the radius of Earth. The planet closest to the star is KOI-961.02, with a radius 0.73 times the Earth's.

All three planets whip around the star in less than two days, with the closest planet taking less than half a day. Their close proximity to the star also means they are scorching hot, with temperatures ranging from 350 to 836 degrees Fahrenheit (176 to 447 degrees Celsius). The star's habitable zone, or the region where liquid water could exist, is located far beyond the planets.

The ground-based observations contributing to these discoveries were made with the Palomar Observatory, near San Diego, Calif., and the W.M. Keck Observatory atop Mauna Kea in Hawaii.

For more information about Kepler Mission , visit: http://kepler.nasa.gov/

Image, Text, Credit: NASA / JPL-Caltech.

Cheers, Orbiter.ch

mardi 13 mars 2012

NASA and CSA Robotic Operations Advance Satellite Servicing

NASA / CSA-ASC - STS-123 Mission "Dextre" patch.

March 13, 2012

NASA's Robotic Refueling Mission (RRM) experiment aboard the International Space Station has demonstrated remotely controlled robots and specialized tools can perform precise satellite-servicing tasks in space. The project marks a milestone in the use of the space station as a technology test bed.

"We and our partners are making important technological breakthroughs," NASA Administrator Charles Bolden said. "As we move ahead toward reaching our exploration goals, we will realize even more benefits from humans and robots working together in space."

The Canadian Space Agency's (CSA) robotic handyman, Dextre, successfully completed the tasks March 7-9 on the space station's external RRM module, designed to demonstrate the tools, technologies and techniques needed to robotically refuel and repair satellites.

"The Hubble servicing missions taught us the importance and value of getting innovative, cutting-edge technologies to orbit quickly to deliver great results," said Frank Cepollina, a veteran leader of five Hubble Space Telescope servicing missions and associate director of the Satellite Servicing Capabilities Office (SSCO) at NASA's Goddard Space Flight Center in Greenbelt, Md. "The impact of the space station as a useful technology test bed cannot be overstated. Fresh satellite-servicing technologies will be demonstrated in a real space environment within months instead of years. This is huge. It represents real progress in space technology advancement."

Before a satellite leaves the ground, technicians fill its fuel tank through a valve that is sealed, covered and designed never to be accessed again. The RRM experiment demonstrates a remote-controlled robot can remove these barriers and refuel such satellites in space.

video
Highlights from the RRM Gas Fittings Removal Task, Part 1

Video above: The Robotic Refueling Mission (RRM) Gas Fittings Removal (GFR) task marked the first use of RRM tools in orbit and represents a milestone in the use of the International Space Station as a technology test bed. During GFR operations on March 7-9, 2012, the 12-foot (3.7-meter) Canadian Dextre robot removed, inspected, and re-stowed three RRM tools, resulting a clean bill of health for each. Dextre then used the RRM Multifunction Tool to remove the launch locks that kept four tool adapters secure in their receptacles during the shuttle launch of RRM to space. Finally, Dextre performed the most intricate task ever attempted by a space robot: cutting two separate 'lock wires' 20 thousandths of an inch (0.5 millimeters) in diameter using the RRM Wire Cutter Tool (WCT). Deftly maneuvered by ground-based mission operators and Dextre, the WCT smoothly slid its hook under the individual wires and severed them with only a few millimeters of clearance.

Dextre successfully retrieved and inspected RRM tools, released safety launch locks on tool adapters, and used an RRM tool to cut extremely thin satellite lock wire. These operations represent the first use of RRM tools in orbit and Dextre's first participation in a research and development project.

RRM was developed by SSCO and is a joint effort between NASA and CSA. During the next two years, RRM and Dextre will conduct several servicing tasks using RRM tools on satellite parts and interfaces inside and covering the cube-shaped RRM module.

NASA expects the RRM results to reduce the risks associated with satellite servicing. It will encourage future robotic servicing missions by laying the foundation for them. Such future missions could include the repair, refueling and repositioning of orbiting satellites.

"We are especially grateful to CSA for their collaboration on this venture," Cepollina said. "CSA has played a pivotal role in the development of space robotics, from the early days of the space shuttle to the work they are doing with Dextre on space station."

Dextre description

During the three-day RRM Gas Fittings Removal task, the 12-foot (3.7-meter) Dextre performed the most intricate task ever attempted by a space robot: cutting two separate "lock wires" 20 thousandths of an inch (0.5 millimeters) in diameter using the RRM Wire Cutter Tool (WCT). Deftly maneuvered by ground-based mission operators and Dextre, the WCT smoothly slid its hook under the individual wires and severed them with only a few millimeters of clearance. This wire-cutting activity is a prerequisite to removing and servicing various satellite parts during any future in-orbit missions.

RRM operations are scheduled to resume in May 2012 with the completion of the gas fittings removal task. The RRM Refueling task is scheduled for later this summer. NASA and CSA will present RRM results at the Second International Workshop on on-Orbit Servicing, hosted by Goddard May 30-31, 2012.

Dextre and RRM are an example of how robots are changing operations in space. Another is Robonaut 2, or R2, a project of NASA and General Motors. R2, the first human-like robot, was launched into space in 2011 and is a permanent resident of the International Space Station.

For more information about RRM or the On-Orbit Servicing Workshop, visit: http://ssco.gsfc.nasa.gov

For information about NASA and agency programs, visit: http://www.nasa.gov

Image, Video, Text, Credit: NASA / CSA-ASC / MDA.

Greetings, Orbiter.ch

Herschel's new view on giant planet formation













ESA - Herschel Mission patch.

13 Mar 2012

Astronomers have used ESA's Herschel Space Observatory to observe 2M1207, a peculiar brown dwarf with its own circumstellar disc and a planetary companion five times more massive than Jupiter. These new data provide the first image of this system taken at sub-millimetre wavelengths and show that the disc's mass amounts to a few times the mass of Jupiter. The presence of such a massive disc around this ten-million-year old brown dwarf suggests that its planetary companion formed directly from the disc's fragmentation. This reopens the debate on how giant planets form around stellar and sub-stellar objects.

Brown dwarfs are a puzzling class of objects suspended between stellar and planetary status. Not massive enough to ignite hydrogen fusion in their cores, like stars do, they are more massive than planets and thus able – unlike planets – to burn deuterium for a brief period in their interiors. Since the first brown dwarf was discovered, in 1995, astronomers have detected hundreds of them in our Galaxy, the Milky Way, and have speculated about the origin of these curious celestial bodies.

Artist's impression of the brown dwarf 2M1207. Credit: ESA

Like stars, a number of brown dwarfs are surrounded by discs of gas and dust, very similar to circumstellar discs seen around young stars. A handful of them are also known to possess planetary companions with the properties of gas giants and masses similar to or larger than Jupiter's. Since the separation between these planetary-mass objects and their parent bodies is larger than the typical values observed for most gas giant exoplanets, these brown dwarf planetary companions are valuable when investigating how giant planets form at rather large distances from their parent bodies.

Two main physical mechanisms are known to result in the formation of giant gaseous planets around stars: the 'standard' scenario of core accretion and the 'alternative' one invoking disc fragmentation. In the core accretion mechanism, a rocky core forms first from the coagulation of dust grains in the disc, and only later does this solid core start accreting gas from its surroundings, eventually growing into a giant gaseous planet. In the disc fragmentation model, the circumstellar disc collapses due to its own weight into smaller fragments, whose minimum mass depends on the disc's total mass, thus forming proto-planets that later evolve into proper planets. Both mechanisms could well be at play around brown dwarfs as well.

Theory suggests that disc fragmentation is more efficient at forming giant planets at large radial distances from the parent body: brown dwarfs with planetary companions are thus a crucial testbed to probe the validity of this alternative model for giant planet formation. For this purpose, a team of astronomers led by Basmah Riaz from the University of Hertfordshire, UK, have exploited ESA's Herschel Space Observatory to study a peculiar brown dwarf which is known to possess both a disc and a planetary companion.

Named 2MASSW J1207334-393254, or 2M1207 for short, this brown dwarf is quite evolved, with an age of about 10 million years, and has a mass that amounts to 25 times that of Jupiter. It is located at a distance of about 170 light years from us and belongs to the low-density group of stars known as the TW Hydrae association. The brown dwarf's planetary companion, a gaseous giant five times more massive than Jupiter, was the first extrasolar planet to have been directly imaged and lies at a very large distance from 2M1207 – the projected distance between the two bodies measuring 55 astronomical units (AU).

"We have been looking forward to using SPIRE, the long-wavelength instrument on Herschel, to obtain the first view of this brown dwarf in the sub-millimetre portion of the spectrum," explains Riaz. By tracing emission from cold dust, sub-millimetre observations provide crucial information about the disc around 2M1207. Although only a trace component in terms of the disc's mass, which mainly consists of gas, cold dust extends out to the far reaches of the disc and thus allows astronomers to probe its entire extent. "After modelling the system with the new data, we find that the disc's total mass amounts to about 3 to 5 times the mass of Jupiter and that its radius ranges between 50 and 100 AU," she adds.

Since 2M1207 is the oldest known brown dwarf possessing a disc, the astronomers inquired into a possible correlation between disc masses and the age of their parent brown dwarfs. "Interestingly, the mass of 2M1207's disc is similar to those of other discs observed around much younger brown dwarfs, with ages of only 1 million years," notes Riaz. This suggests that dissipation processes of discs around brown dwarfs may take place on much slower time scales as opposed to discs around fully-fledged stars, where a trend of decreasing disc masses for increasingly older objects is recorded.

Artist's impression of the Herschel Space Telescope. Credit: ESA

By knowing the mass and size of the disc around this brown dwarf, the astronomers have also gained crucial insight into the origin of its planetary companion. "We knew that the planetary companion to 2M1207 did not form through core accretion, because such a process would have taken much longer than the system's age," explains Riaz. For the first time, the new Herschel data allowed the alternative formation scenario to be tested quantitatively. "The mass of the disc indicates that this planetary-mass body has likely arisen directly from fragmentation of the disc, which may have been more massive in the brown dwarf's early days," she adds.

The system comprising 2M1207 and its companion represents the first evidence showing that planetary-mass bodies can indeed originate from disc fragmentation, thus challenging the currently leading scenario for the formation of giant planets. However, there are also other possible scenarios that could explain the formation of this system – for example, both the brown dwarf and its planetary-mass companion might have formed at the same time as a binary system – and the issue remains open.

"This is the first detection of the brown dwarf 2M1207 in the sub-millimetre range", comments Göran Pilbratt, ESA's Herschel Project Scientist. "The present study showcases Herschel's capability to investigate the mechanisms that lead to the formation of planetary-mass companions to stellar and sub-stellar objects."

Notes for editors:

The results presented here are based on observations of the brown dwarf 2MASSW J1207334-393254, or 2M1207 for short, that have been performed with the SPIRE instrument on Herschel at wavelengths of 250, 350 and 500 micron. The observations have been performed as part of the Herschel Open Time Programme "Disk masses for ~10 Myr old brown dwarf disks" of which B. Riaz is Principal Investigator. The other astronomers involved in this study are G. Lodato (Dipartimento di Fisica, Università degli Studi di Milano, Italy), D. Stamatellos (School of Physics and Astronomy, Cardiff University, UK) and J.E. Gizis (Department of Physics and Astronomy, University of Delaware, USA).

The system consists of 2M1207A, a brown dwarf with a mass of 25 Jupiter masses, and 2M1207B, a planetary companion with a mass of 5 Jupiter masses. The two bodies have a projected separation of 55 astronomical units (AU). To date, 2M1207A is the oldest brown dwarf known to possess a circumstellar disc.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The SPIRE instrument contains an imaging photometer (camera) and an imaging spectrometer. The camera operates in three wavelength bands centred on 250, 350 and 500 µm, and so can make images of the sky simultaneously in three sub-millimetre colours. SPIRE has been developed by a consortium of institutes led by Cardiff Univ. (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC (UK); and NASA (USA).

Related publications:

B. Riaz, et al., "First sub-millimeter detection of the TWA brown dwarf disc 2MASSW J1207334-393254", 2012, Monthly Notices of the Royal Astronomical Society: Letters, doi:10.1111/j.1745-3933.2012.01225.x, in press.

For more information about Herschel Space Telescope, visit: http://www.esa.int/SPECIALS/Herschel/index.html

Images, Text, Credit: ESA / Göran Pilbratt / Centre for Astrophysics Research University of Hertfordshire Hatfield, United Kingdom / Basmah Riaz.

Best regards, Orbiter.ch

lundi 12 mars 2012

Record-Setting Astronaut Lopez-Alegria Departs NASA











NASA logo.

Mar. 12, 2012

Michael Lopez-Alegria, NASA's most experienced spacewalker and the American holding the record for the single longest spaceflight mission, has left the agency.

Lopez-Alegria flew on four missions and performed 10 spacewalks during his career. He most recently served in the Flight Crew Operations Directorate at NASA's Johnson Space Center in Houston as assistant director for the International Space Station (ISS).

"Mike has faithfully served the Flight Crew Operations Directorate for many years," said Janet Kavandi, director of Flight Crew Operations at Johnson. "His unique background and diplomatic skills have made him an outstanding FCOD assistant director for space station and lead for the Multilateral Crew Operations Panel. Mike's tireless dedication to the safety and well-being of space station crews is well known. We will miss him and wish him well in his future endeavors."

Astronaut Michael Lopez-Alegria

During his career, Lopez-Alegria logged more than 257 days in space, including 215 days as commander of the Expedition 14 mission to the ISS, which stands as the single longest spaceflight by an American. Lopez-Alegria also logged more than 67 hours during his 10 spacewalks, more than any other American, and second only in the record books to Russian cosmonaut Anatoly Solovyev.

"Mike has been a huge asset to the astronaut office during the course of his career," said Peggy Whitson, chief of the Astronaut Office at Johnson. "His contributions in spacewalking, shuttle, space station and Soyuz operations are notable and very distinguished. Personally, we will miss his humor and insights and wish him all the best."

Lopez-Alegria flew on three space shuttle missions. The first, STS-73 in 1995, focused on science experiments. He then served as NASA's director of operations at the Yuri Gagarin Cosmonaut Training Center in Star City, Russia, where he was in charge of American astronauts training for flights to the Russian space station Mir and the ISS. Lopez-Alegria later flew on STS-92 in 2000 and STS-113 in 2002, delivering critical truss elements to the station.

Expedition 14 Commander Lopez-Alegria and his crew launched to the ISS on a Soyuz spacecraft from the Baikonur Cosmodrome in Kazakhstan on Sept. 18, 2006. This fourth and final mission earned Lopez-Alegria the spaceflight record. The crew conducted a seven-month mission to operate, maintain, build and use the station and its science facilities. During the expedition, two uncrewed Russian Progress cargo vehicles arrived and departed the station and a space shuttle assembly mission reconfigured the station's power supply. Lopez-Alegria's mission ended with a Soyuz landing on the Kazakh steppe on April 21, 2007.

For Lopez-Alegria's complete biography, visit: http://www.jsc.nasa.gov/Bios/htmlbios/lopez-al.html

Image, Text, Credit: NASA.

Greetings, Orbiter.ch

Building Vega meant testing materials to their limits













Aerospace Engineering / ESA / Arianespace - VEGA Launcher logo.

March 12, 2012

 Liftoff of Vega VV01

When the first of Europe’s Vega rockets thundered skywards on 13 February, it was a new design based on some novel materials. Such novelty called for rigorous technical risk management by ESA’s materials specialists.

Vega is aimed at carrying small and medium satellites, increasing the flexibility and competitiveness of Europe’s launcher family. It incorporates a wide range of new materials to keep its own mass low: the lighter Vega is, the more payload it can haul to orbit.

Vega’s design is guided by decades of experience building and flying Ariane launchers, with its first three solid-fuel stages derived from Ariane 5’s strap-on boosters.

A reignitable liquid-propellant fourth stage completes delivery of Vega payloads into orbit as well as hosting the avionics and thrusters to oversee the entire stack’s roll control throughout its flight. 

Vega's four stages

Like any other ESA project, the Vega team had at their service the specialist engineering teams and laboratories at ESA’s technical centre ESTEC in Noordwijk, the Netherlands.

Materials experts focused on choosing and qualifying materials for the demanding space environment and worked closely with the Vega project team as the launcher took shape.

“It has been out of the ordinary to work on a launcher,” says Tommaso Ghidini, Head of the Materials Technology Section at ESTEC.

“Instead of hardware that has to go on operating in space for years on end, Vega’s working lifetime lasts slightly more than an hour – but it still has to function without flaw throughout that time.

Vega second stage

“Launcher materials really get stressed to their limits: extremely high temperatures combine with high pressures and additional stresses due to shock, vibration, aerodynamic and acoustic forces.

“So the principle is the same, and we assisted the project and the industry side when they ran into difficulties.

“We carried out testing on their behalf, investigated when particular materials didn’t perform as planned and advised on alternatives if necessary.”

Starting at the bottom

ESA’s materials specialists made contributions to various elements of Vega – starting at the very bottom.

Vega third stage

The nozzles of the new rocket face some of the most demanding performance requirements of all. Vega’s Zefiro-23 second stage and Zefiro-9 third stage both have nozzles made from carbon phenolic composite material.

This composite has a tendency to ‘ablate’ – flake away – at very high temperatures, so much so that it is sometimes used as a heatshield for re-entering spacecraft: this flaking effect comes in handy as a way of dumping frictional heat.

“Carbon phenolic is a difficult material to test because it loses mass at high temperature – it starts getting thinner,” Tommaso recalls.

Carbon phenolic testing for Vega nozzles

“The challenge was allowing for this in real-world testing while still gaining insight into its mechanical properties under stress.

“We use grips to introduce pull stress, but that would be no use if the material then thins out so much it tears once it is heated.

“So we had to design a more dynamic kind of test, with grip jigs kept cold and heating applied to those parts of the sample where we needed it. We applied the results to a new structural model of the motor for further diagnosis.”

The model supported the structural design of the nozzle which then passed a full-scale static firing test at Italy’s Salto di Quirra test range in Sardinia, enduring the equivalent of nearly 120 tonnes of force and flame temperatures of up to 3000 K.

Vega second stage firing test

“This was the first time that carbon phenolic underwent such detailed testing in Europe,” adds Tommaso.

“We appreciate very much our cooperation with ESA,” agrees Francesco Betti of Avio, prime contractor for the first three Vega stages. “Their technical expertise and the fact that we could use the ESA labs have helped us significantly.”

Vega - facing a corrosive environment

Vega VV01 on launch pad

Another type of testing was less dramatic but equally necessary to understand how Vega would cope with its environment in the days, weeks or perhaps months a launcher might wait to be flown.

“Vega’s launch site in French Guiana is one of the worst locations you could think of in terms of corrosion,” Tommaso explains.

“It is very warm and humid, with salty sea air, and wind that blows from a single direction so the same section is always getting affected.

“And then there are other launches taking place in the vicinity producing hydrochloric acid in their exhaust with the potential to accelerate corrosion.” 

Vega samples immersed for testing

ESA literally wrote the book on many types of corrosion testing, drafting shared standards used throughout Europe’s space industry through an initiative called the European Cooperation for Space Standardization (ECSS).

“We performed various types of standard corrosion and stress corrosion testing,” says Tommaso, the latter needed because the tendency for environment-driven degradation increases markedly when the material is under stress.

“For instance, we performed 'alternate immersion testing' where a sample is placed in salty water for 10 minutes at a time then taken out for 50 minutes, repeatedly for 30 days on end.”

Shipment test

Additional tests roamed further from the lab. For instance, some ‘stringers’ – the structural bones onto which the launcher’s skin is attached – and separation springs in the interstage joining the second and third stages were taken from Vega’s initial qualification model to be put on the same journey Vega itself would make.

“With the stringers we also carried out a shipment test,” Tommaso adds. “This means carrying them in the same container, on the same ship as Vega would be carried in, then have them experience the French Guiana environment.

“This shipment test confirmed directly the structure was fit for purpose.”

Getting the shakes

Vega's AVUM fourth stage

ESTEC’s materials team also contributed to Vega’s topmost stage, the Attitude and Vernier Upper Module (AVUM). This is the smallest of the stages, because it requires much less power to steer the remaining segment of rocket outside Earth’s atmosphere. Unlike the solid stages, its liquid-propellant motor is throttleable and even reignitable in nature.

AVUM also hosts the majority of avionics used to oversee the launcher’s flight, as well as the batteries serving as Vega’s onboard power source.

“In the case of the satellites we normally work with, launcher payloads can expect some degree of dampening from the vibration and shock of launch,” says Tommaso.

Preparing radiation test

“Obviously that can’t be the case with the actual launcher electronics – they have to endure all the forces put their way.”

The specialists assessed the qualification of the printed circuit boards and surface mounting technology, as well as examining the initially fault-prone ‘tabs’ linking the batteries with Vega’s avionics.

And with those avionics becoming potentially susceptible to space radiation as they rise above the shielding effects of the atmosphere, extensive radiation effects evaluation was performed in ESTEC’s Materials and Electrical Components Laboratories.

A dedicated components examination board was set up with representatives of Vega’s European Launch Vehicle company and ESA’s components division as permanent members, receiving assistance from other experts as needed.

This board had responsibility for selecting, procuring, evaluating and qualifying all Vega’s components electrical, electronic and electro-mechanical (EEE) components - no simple task when the list of components involved runs to more than 600 pages. Some 42 meetings or teleconferences were carried out with component subcontractors over the course of the board’s work.

Tackling fuel tanks

They took a similar approach to AVUM’s quartet of Russian-made fuel tanks, containing fuel and oxidiser.

Microsection of AVUM fuel tank weld

“We examined the welding of the tanks in a similar fashion, to look for ways they could be improved,” says Tommaso.

They produced a full metallurgical analysis of the welds, and came up with new protocols to improve their microstructure – the improved tanks standing up to more than twice their intended operating pressures.

“For the tanks as a whole we sought to quantify the residual stresses introduced as part of the manufacturing process, potentially making them more vulnerable to other sources of damage during their lifetime.”

A successful payoff

Liftoff of Vega VV01

After close cooperation with the Vega team, the ESTEC specialists enjoyed the satisfaction of a job well done as the Vega launcher soared into orbit – the first of many to come.

“I’m grateful to the ESTEC experts for their intense, responsive and proactive support to the Vega team,” comments Stefano Bianchi, ESA’s Vega programme manager.

“The success of the maiden flight is the success of our Agency's technical expertise and rigour.”

Related links:

Avio: http://www.aviogroup.com/en/catalog/space

Vega launch special: http://www.esa.int/SPECIALS/Vega/index.html

Space Engineering:

Materials and Processes: http://www.esa.int/SPECIALS/Space_Engineering/SEM4VN0P0WF_0.html

Electronic Components: http://www.esa.int/SPECIALS/Space_Engineering/SEMJUN0P0WF_0.html

Materials and Electrical Components Laboratories: http://www.esa.int/SPECIALS/Space_Engineering/SEMNK00P0WF_0.html

Images, Text, Credits: ESA/J. Huart / S. Corvaja / CNES / Arianespace / Avio / Optique Video du CSG.

Greetings, Orbiter.ch