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Sonntag, 17. November 2013 - 10:46 Uhr

Astronomie - Die Erkundung der dritten Dimension von Cassiopeia A

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Exploring the Third Dimension of Cassiopeia A

One of the most famous objects in the sky - the Cassiopeia A supernova remnant - will be on display like never before, thanks to NASA's Chandra X-ray Observatory and a new project from the Smithsonian Institution. A new three-dimensional (3D) viewer, being unveiled this week, will allow users to interact with many one-of-a-kind objects from the Smithsonian as part of a large-scale effort to digitize many of the Institutions objects and artifacts.

Scientists have combined data from Chandra, NASA's Spitzer Space Telescope, and ground-based facilities to construct a unique 3D model of the 300-year old remains of a stellar explosion that blew a massive star apart, sending the stellar debris rushing into space at millions of miles per hour. The collaboration with this new Smithsonian 3D project will allow the astronomical data collected on Cassiopeia A, or Cas A for short, to be featured and highlighted in an open-access program -- a major innovation in digital technologies with public, education, and research-based impacts.

To coincide with Cas A being featured in this new 3D effort, a specially-processed version of Chandra's data of this supernova remnant is also being released. This new image shows with better clarity the appearance of Cas A in different energy bands, which will aid astronomers in their efforts to reconstruct details of the supernova process such as the size of the star, its chemical makeup, and the explosion mechanism. The color scheme used in this image is the following: low-energy X-rays are red, medium-energy ones are green, and the highest-energy X-rays detected by Chandra are colored blue.

Cas A is the only astronomical object to be featured in the new Smithsonian 3D project. This and other objects in the collection - including the Wright brothers plane, a 1,600-year-old stone Buddha, a gunboat from the Revolutionary War, and fossil whales from Chile -- were being showcased in the Smithsonian X 3D event, taking place on November 13th and 14th at the Smithsonian in Washington, DC. In addition to new state-of-the-art 3D viewer, the public will be able to explore these objects through original videos, online tours, and other supporting materials.

Cas A is the only supernova remnant to date to be modeled in 3D. In order to create this visualization, unique software that links the fields of astrophysics and medical imaging (known as "astronomical medicine") was used. Since its initial release in 2009, the 3D model has proven a rich resource for scientists as well as an effective tool for communicating science to the public. Providing this newly formatted data in an open source framework with finely-tuned contextual materials will greatly broaden awareness and participation for general public, teacher, student and researcher audiences.

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

Quelle: NASA


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Samstag, 16. November 2013 - 18:19 Uhr

Mars-Chroniken - Sanfte Hügellandschaft und breite Täler in Ismeniae Fossae

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Mit sanften, gerundeten Landschaftsformen präsentiert sich die Region Ismeniae Fossae auf dem Mars, die auf den aktuellen Bildern der vom Deutschen Zentrum für Luft- und Raumfahrt (DLR) betriebenen hochauflösenden Stereokamera HRSC an Bord der ESA-Raumsonde Mars Express zu sehen ist. Die meisten Krater und Abhänge sind komplett von einer Schicht aus feinkörnigem Material überzogen, das vermutlich der Wind dorthin transportiert hat.

Dabei befindet sich Ismeniae Fossae an der Grenze vom südlichen Hochland zu den ausgedehnten, im Norden angrenzenden Ebenen des Tieflands auf dem Mars: eine Landschaft, die eher von kantigen, zerfurchten Restbergen und tief eingeschnittenen Tälern geprägt ist. Der Übergang vom Hoch- zum Tiefland erfolgt hier entlang einer schmalen Zone, in der die Erosion durch Wasserläufe, Wind, Eis und Grundwasser eine markante Landschaft geschaffen hat. Diese topographische Zweiteilung in ein nördliches Gebiet mit Tiefebenen und ein älteres südliches Hochland mit zahlreichen Einschlagskratern ist eines der auffälligsten Merkmale unseres Nachbarplaneten.

Im Süden der Bilder 1, 4 und 5 zeigt die Marsoberfläche auffallend wenig topographisches Relief. Die Geländekanten sind als Folge von Erosionsprozessen und der Ablagerung eines "Mantels" aus Sand und Staub geglättet und abgerundet. Ein etwa 20 Kilometer großer, alter Einschlagskrater, der durch eine talförmige Vertiefung durchtrennt ist, ist fast nur noch in seinen Umrissen erkennbar.

Zeugenberge in ehemaligem Krater

In der topographischen Übersichtskarte (Bild 2) ist der Großteil der Ismeniae Fossae-Region zu erkennen. Im Süden fällt deutlich ein grabenartiges Tal auf, das im Nordosten an dem 130 Kilometer großen Krater Moreux in mehreren grabenartigen Verzweigungen ("Fossae") endet. Der Name Ismeniae leitet sich von dem Fluss Ismenius im antiken Böotien ab, einem Landstrich nordwestlich von Athen. In den Bildern 1, 4 und 5 ist rechts unten der westliche Rand des Kraters Moreux zu sehen (benannt nach dem französischen Astronomen Louis-Théophile Moreux, 1867-1954). Das Landschaftsbild in der Übersichtskarte verrät, dass Ismeniae Fossae wahrscheinlich komplett aus den erodierten Überresten eines einstmals gefüllten Kraters mit bis zu 470 Kilometern Durchmesser besteht.

Die Gestalt und Beschaffenheit der freigelegten Überreste im Innern dieses Beckens, aber auch im Gebiet der breiten Taleinschnitte, ähneln einem geologischen Landschaftstypus auf dem Mars, den man als "Chaotic Terrain" (chaotisches Gebiet) bezeichnet. Solche Gebiete (dazu zählen zum Beispiel auch Iani Chaos, Aureum Chaos oder Aram Chaos) sind extrem zerklüftete, von der Erosion geprägte Oberflächen, in der einzelne Felsblöcke und Hügel eine wirre Struktur von "Zeugenbergen" in chaotischer Anordnung bilden. Vermutlich entstand es, als Eis im Untergrund schmolz und die entstandenen Hohlräume in sich zusammenstürzten.

Blockgletscher hinterließen ihre Spuren

Ausgehend von diesem chaotischen Gebiet führt eine lange, schmale talförmige Senke sichelförmig in die Region hinein, die im oberen Teil von Bild 1 zu sehen ist. Diese Senke ist stellenweise bis zu zwei Kilometer tief, ihre Flanken sind weich und ihr Rand ist gewellt. Sie beinhaltet ein Material, auf dessen Oberfläche ein Muster von Furchen und schlierigen Strukturen zu sehen ist, die parallel zu den Abhängen verlaufen, von denen die Täler begrenzt werden.

Ein solches Muster findet man in vielen ähnlichen Tälern mit kastenförmigem Profil - die Geologen sprechen von "linearen Talfüllungen". Die Oberflächenbeschaffenheit legt nahe, dass hier einst Eis vorhanden war, möglicherweise ein so genannter Blockgletscher: Das ist ein von Schutt bedeckter Eisstrom, der sich langsam die Senke hinunterschob. Zahlreiche schmale, verzweigte Täler westlich des Moreux-Kraters deuten darauf hin, dass hier auch einmal Wasser über die Marsoberfläche geflossen ist.

Ein weiteres, ungewöhnliches Landschaftsmerkmal dieser Gegend sind Gruppen von runden bis ellipsenförmigen, teilweise miteinander verbundenen Vertiefungen auf der Hochfläche, die links auf den Bildern 1, 4 und 5 zu sehen ist. Dabei handelt es sich entweder um eine Anhäufung von Sekundärkratern, also Einschlägen, die durch den auf die Marsoberfläche niedergehenden Auswurf eines größeren Einschlags in der Umgebung zurückzuführen sind, oder um Senken und Gruben, die entstanden sind, nachdem Eis an oder unmittelbar unter der Oberfläche verdampft ist.

Bildverarbeitung und das HRSC-Experiment der Mars Express-Mission

Die Aufnahmen mit der HRSC (High Resolution Stereo Camera) entstanden am 16. Juni 2013 während Orbit 11.709 von Mars Express. Die Bildauflösung beträgt etwa 20 Meter pro Bildpunkt (Pixel). Die Abbildungen zeigen einen Ausschnitt bei etwa 40 Grad nördlicher Breite und 42 Grad östlicher Länge.
Die Farbdraufsicht (Bild 1) wurde aus dem senkrecht auf die Marsoberfläche gerichteten Nadirkanal und den Farbkanälen der HRSC erstellt; die perspektivische Schrägansicht (Bild 3) wurde aus den Stereokanälen der HRSC berechnet. Das Anaglyphenbild (Bild 4), das bei Betrachtung mit einer Rot-Blau- oder Rot-Grün-Brille einen dreidimensionalen Eindruck der Landschaft vermittelt, wurde aus dem Nadirkanal und einem Stereokanal abgeleitet. Die in Regenbogenfarben kodierte Aufsicht (Bild 5) beruht auf einem digitalen Geländemodell der Region, von dem sich die Topographie der Landschaft ableiten lässt.

Die High Resolution Stereo Kamera wurde am Deutschen Zentrum für Luft- und Raumfahrt (DLR) entwickelt und in Kooperation mit industriellen Partnern gebaut (EADS Astrium, Lewicki Microelectronic GmbH und Jena-Optronik GmbH). Das Wissenschaftsteam unter Leitung des Principal Investigator (PI) Prof. Dr. Ralf Jaumann besteht aus 40 Co-Investigatoren, die aus 33 Institutionen und zehn Nationen stammen. Die Kamera wird vom DLR-Institut für Planetenforschung in Berlin-Adlershof betrieben. Die hier gezeigten Darstellungen wurden vom Institut für Geologische Wissenschaften der FU Berlin in Zusammenarbeit mit dem DLR-Institut für Planetenforschung in Berlin erstellt.

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Quelle: DLR


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Samstag, 16. November 2013 - 17:52 Uhr

Astronomie - Messenger-Sonde beobachtet Komet ENCKE und ISON bei Merkur

 

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Nov. 15, 2013:  What are the odds? On Nov. 18th and 19th not one but two comets will fly by the planet Mercury.

"This is a unique coincidence," says Ron Vervack an astronomer at the Johns Hopkins University Applied Physics Lab and a member of the science team for NASA's MESSENGER spacecraft, "and a golden opportunity to study two comets passing close to the sun.”

On Nov. 18th Comet Encke will pass within 0.025 AU of Mercury, followed a day later by Comet ISON at 0.24 AU (1 AU is the distance between the sun and Earth, 150 million km).   The MESSENGER spacecraft, which is orbiting Mercury, will turn its sensors toward the passing comets for a point-blank investigation of both.The double flyby is exciting, says Vervack, but "it makes things a little crazy. We have to rush to complete our observations of Comet Encke, then do it all over again for Comet ISON. Everything is happening at more or less the same time."

MESSENGER was designed to study Mercury, not comets, “but it is a capable spacecraft with a versatile instrument package,” he adds. “We hope to get some great data.” Onboard spectrometers will analyze the chemical makeup of the two comets while MESSENGER's cameras snap pictures of atmospheres, jets and tails. Comet Encke is less well known, but no less interesting.  For one thing, it is the source of the Taurid meteor shower, a slow display of midnight fireballs that occurs every year in early- to mid-November. Comet Encke dips inside the orbit of Mercury every 3.3 years, so it is regularly exposed to solar activity.

"We'll be catching Comet Encke just days before its closest approach to the sun (0.3 AU)," Vervack  says, "so we get to see it at its most active."

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Dates acquired: 2013 (UT): Nov. 6, 7, 8 (Encke) and Nov. 9, 10, 11 (ISON)
Image Mission Elapsed Time (MET): 26100552, 26190552, 26276500 (Encke), 26330792, 26417208, 26503610 (ISON)
Image ID: 1026100552, 1026190552, 1026276500 (Encke), 1026330792, 1026417208, 1026503610 (ISON)
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: Filter 2 (700 nm)
Resolution: 38 seconds of arc per pixel for Encke, 76 for ISON
Scale: Each tile: 2.85 deg. wide by 0.745 deg. high (Encke), 5.7 deg. wide by 1.49 deg. high (ISON)

Of Interest: As the new comet C/2012 S1 (ISON) and the well-known short-period comet 2P/Encke both approach their closest distances to the Sun later this month, they are also passing close to the MESSENGER spacecraft now orbiting the innermost planet Mercury. Just this week, both comets have brightened sufficiently to be captured in images by MESSENGER’s wide-angle camera. This figure shows, on the left, images of Encke on three successive days from November 6 to November 8; on the right, images of ISON are shown for three successive days from November 9 to November 11. Both comets appear to brighten each day (top to bottom).

Green circles indicate some of the brighter cataloged background stars in each image; yellow marks bracket the comets. The background stars are fixed in each image from top to bottom, so the motion of the comet relative to the stars is clear in each case. The images have been smoothed slightly to diminish the distracting sharp edges of the pixels.

MESSENGER is viewing these comets from a vantage point that is very different from that of observers on Earth. Comet Encke was approximately 0.5 AU from the Sun and 0.2 AU from MESSENGER when these images were taken; the same distances were approximately 0.75 AU and 0.5 AU, respectively, for ISON. More images will be obtained starting on November 16 when the comets should be both brighter and closer to Mercury.

The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System's innermost planet. During the first two years of orbital operations, MESSENGER acquired more than 150,000 images and extensive other data sets. MESSENGER is scheduled to continue orbital operations until late March 2015.
 

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/Southwest Research Institute

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ironically, the fact that MESSENGER is designed to study a rocky planet could prove advantageous for the icy comets.  MESSENGER's x-ray spectrometer, in particular, could detect signs of ‘comet dirt’.

"We hope to obtain the first definitive detections of x-ray emissions from silicon, magnesium and aluminum," he explains. "If you think of a comet as a dirty snowball, these are elements that make up the dirt.  Close to the sun is where we expect the dirt to be vaporized."

In total, Vervack expects MESSENGER to gather 15 hours’ worth of data on Comet Encke and another 25 hours on Comet ISON.  With that kind of observing time, discoveries are a distinct possibility.

Vervack says the first images will be beamed back and released to the public within days of the flybys.  “There are no guarantees,” he cautions, “but I can’t wait to see the pictures.”

Quelle: NASA


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Samstag, 16. November 2013 - 11:44 Uhr

Mars-Chroniken - Forscher entwickeln Algorithmus, um einzelne Sandkörner in planetarischen Ablagerungen zu identifizieren

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Researchers develop algorithm to identify individual grains of Mars soil

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Instruments on the Curiosity Mars rover not only measure the chemistry of rocks, elemental abundances of soils and wind speeds, but also take an incredible number of images from both mast-mounted cameras and up-close imaging systems mounted to robotic arms. The process of analyzing soil images can be daunting, particularly when there are thousands of images and when the particles can be on the order of only 5-10 pixels wide. A team of researchers, led by Suniti Karunatillake at LSU’s Department of Geology and Geophysics, and including Stony Brook University, USGS-Flagstaff AZ, and Rider University, developed an image analysis and segmentation algorithm specifically to aid planetary scientists with this very basic, but often difficult, task.

Planetary scientists use images to identify the distribution of grain sizes of large-scale (centimeter or larger diameter) rocks and small-scale (less than 1 cm) grains. These grain sizes tell scientists about the processes that distributed the particles from their source regions to where they are now. For example, were they derived from a water source, blown by wind, or show hydrodynamic sorting?

The algorithm, implemented in Mathematica, uses a variety of image processing steps to segment the image, first into coarser (foreground) and finer (background) grains. The image is then further segmented until most grains are outlined. The code processes a single image within 1 to 5 minutes.

The semi-automated algorithm, while comparing favorably with manual (human) segmentation, provides better consistency across multiple images than a human. The researchers are exploring the use of this algorithm to quantify grain sizes in the images from the Mars Exploration Rovers Microscopic Imager (MI) as well as Curiosity’s Mars Hand Lens Imager (MAHLI). The grain size distributions identified in those images have the potential to reveal subtle trends with composition not considered previously. Ability to identify most of the grains in images also makes detailed, area-weighted, sedimentology possible. Applications extend to terrestrial data from less accessible sites such as deep lake basins or undisturbed river bed sediments.

Quelle: LSU Department of Research Communications


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Freitag, 15. November 2013 - 23:06 Uhr

Raumfahrt - Airline pilot sah Soyus-Kapsel-Rückkehr mit ISS-Crew-37 zur Erde

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Update after we confirmed the image below shows the Soyuz spacecraft returning to Earth Captain Wijker sent us this message:

Just reflecting on what I saw; watched like millions of others many times animated footage of space capsules returning to earth and this is almost routine and you can take this in without too much emotion. Now having seen this fire ball shooting across the sky knowing there are actually 3 people inside that fire ball that are back safe on earth 20 minutes later is breathtaking.

Very privileged that I was lucky enough to see this.

British Airways pilot Captain Simon Wijker caught this image of the Soyuz TMA-09M spacecraft, shortly before it landed in Kazakhstan. Inside the spacecraft were ESA astronaut Luca Parmitano, NASA’s Karen Nyberg, Russian commander Fyodor Yurchikhin and the Olympic torch.

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Captain Wijker contacted ESA, thinking that this might have been ESA’s Earth-monitoring satellite GOCE that was predicted to fall back to Earth around the same time.

Captain Wijker first wrote to ESA’s Communications Office in ESTEC:

“On 11 November around 02:30z I was the Captain of the BA15 from London to Singapore. Our position was over Russia near Rostov, N42.22.7 E048.53.4, heading east.  We spotted an object south of us that we could not identify. When it came closer it became a white ball of fire travelling at very high speed following roughly the curvature of the Earth disappearing over the horizon to the North. I was able to take some pictures of the vapour trail left behind that I thought might be of your interest.”

We asked the GOCE team, and space debris experts soon confirmed that it was not GOCE but suggested that there was a much more likely candidate.

“02:30 UTC means it could not be GOCE as it had impacted two hours before that time. What about the other major activity in space of that day?” said Rune Floberhagen, ESA’s GOCE mission manager.

ESA’s Space Debris office at ESOC in Darmstadt added:

“As GOCE had already re-entered at that time, I assume this is a sighting of Soyuz TMA-09M that landed 02:49 GMT on 11 November 2013 in Kazakhstan. The reported position is over the Caspian Sea which would match the spacecraft landing around 10 to 20 minutes later in Kazakhstan.”

Roland Luettgens, ESA Mission Director for Luca Parmitano’s Volare mission in the Soyuz at ESA’s Columbus Control Centre, near Munich, soon confirmed:

“Here is what I could reconstruct based on the data we have. Based on this, I think we can confirm that this is the Soyuz 35S.”

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Spacecraft launches and re-entries are always conducted in collaboration with air traffic controllers that designate no-fly zones for all commercial aircraft.

The British Airways aircraft was at a safe distance from the re-entry and was in no danger from witnessing this unique spectacle.

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Soyuz TMA-09M seen from BA15. Notice aircraft cockpit reflection. Credit: Simon Wijker

Quelle:Erica Rolfe
ESA Chief Online Publisher


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Freitag, 15. November 2013 - 17:34 Uhr

Raumfahrt - LASERSTRAHL VON ALPHASAT-SATELLIT ERREICHT VORGESEHENES ZIEL

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The Optical Communication Terminal is one of four ESA Technology Demonstration Payloads carried by Alphasat and created by German space agency DLR and German company TESAT. It relays Earth observation data from low-Earth orbit (LEO) to geostationary orbit (GEO) through laser transmission. A Ka-band transmitter then forwards the data to a ground station.

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Das Laser-Kommunikationsterminal (LCT) an Bord des Alphasat-Satelliten hat am 4. November zum ersten Mal einen Laserstrahl planungsgemäß zur Bodenstation der ESA auf der Kanareninsel Teneriffa gesendet. Damit ist der Beweis gelungen, dass das Terminal präzise genug ausgerichtet werden kann, um einen Zielpunkt in über 36.000 Kilometer Entfernung zu treffen.
Im Rahmen des LCT-Testlaufs zielte und beamte das Terminal seinen Laser aus dem geostationären Orbit erfolgreich auf die Bodensensoren. Diese letzte Stufe der Inbetriebnahme der „gastierenden“ Nutzlast hat bewiesen, dass sie funktionstüchtig und bereit für die nächste Testphase ist: die Verlinkung mit der Bodenstation und den Datenaustausch.
Diese Technologieerprobungs-Nutzlast ist ein optisches Kommunikations- und Ka-Band-Downlink-System, welches von der in Deutschland ansässigen Firma TESAT gebaut und vom Deutschen Zentrum für Luft- und Raumfahrt (DLR) zur Verfügung gestellt wurde. Es soll das lasergestützte Sammeln von Informationen aus den verkehrsreichen erdnahen Umlaufbahnen sowie die anschließende Übermittlung dieser Informationen von ihrer weitaus höher gelegenen Position in einer geostationären Umlaufbahn an die Bodenstation testen.
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Laser von der optischen Bodenstation auf Teneriffa
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Im Rahmen des LCT-Testlaufs zielte und beamte das Terminal seinen Laser aus dem geostationären Orbit erfolgreich auf die Bodensensoren. Diese letzte Stufe der Inbetriebnahme der „gastierenden“ Nutzlast hat bewiesen, dass sie funktionstüchtig und bereit für die nächste Testphase ist: die Verlinkung mit der Bodenstation und den Datenaustausch.
Laser haben den Vorteil, dass sie große Datenmengen weitaus schneller übertragen können; so kann dieses Terminal eine Nutzdatenrate von bis zu 1,8 Gigabit pro Sekunde (Gbit/s) bewältigen. Das ist in etwa vergleichbar mit der 5.000-fachen Durchschnittsgeschwindigkeit einer in herkömmlichen Haushalten verwendeten Hochgeschwindigkeits-Internetverbindung. Über das Terminal können Daten von mehreren Satelliten gesammelt und anschließend weitergeleitet werden, ohne dass riesige und kostspielige Bodenantennen benötigt werden.
 „Die Laserkommunikation ebnet den Weg in eine Zukunft datenintensiver Telekommunikation“, so Christoph Hohage, Projektdirektor des DLR-Raumfahrtmanagements. „Ihr Marktpotenzial ist enorm, denn dank des europäischen Know-hows können bessere Dienstleistungen für Breitband-Nutzer sowie hochwertige Arbeitsplätze in Europa geschaffen werden.“
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ESA's Optical Ground Station (OGS) is 2400 m above sea level on the volcanic island of Tenerife. Visible green laser beams are used for stabilising the sending and receiving telescopes on the two islands. The invisible infrared single photons used for quantum teleportation are sent from the neighbouring island La Palma and received by the 1 m Telescope located under the dome of the OGS. Initial experiments with entangled photons were performed in 2007, but teleportation of quantum states could only be achieved in 2012 by improving the performance of the set-up. 
Aside from inter-island experiments for quantum communication and teleportation, the OGS is also used for standard laser communication with satellites, for observations of space debris or for finding new asteroids. The picture is a multiple exposure also including Tenerife's Teide volcano and the Milky Way in the background.
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Die Nutzlast befindet sich an Bord des von Inmarsat beauftragten Alphasat, dem größten europäischen Telekommunikationssatelliten, der je gebaut wurde. Bei seinem Start am 25. Juli betrug sein Gewicht über 6,6 Tonnen. Aktuell befindet sich Alphasat in seiner endgültigen Orbitalposition und hat die In-Orbit-Testphase abgeschlossen. Der Satellit zählt außerdem zu den größten öffentlich-privaten Partnerschaften der ESA, an der nicht nur die ESA, Inmarsat und die europäische Industrie, sondern auch drei weitere Technologieerprobungs-Nutzlasten beteiligt sind.
Stephane Lascar, Leiter der ESA-Telekommunikationsprojekte, fügt hinzu: „Dies ist ein bedeutender Meilenstein für Alphasat und die Zukunft europäischer Telekommunikationssatelliten. Es ist ein Wegbereiter des europäischen Datenrelaisübertragungssystems (EDRS), welches vorläufig Datenrelais-Dienste für die vier Sentinel-Erdbeobachtungssatelliten ausführen wird.
Das EDRS wird Dienste ermöglichen, die eine schnelle Übermittlung von großen Datenmengen erfordern, beispielsweise für Rettungskräfte während eines Notfalls, für Regierungs- und Sicherheitsdienste oder Einsatzkräfte in abgelegenen Gebieten.“
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The Optical Communication Terminal is one of four ESA Technology Demonstration Payloads carried by Alphasat and created by German space agency DLR and German company TESAT. It relays Earth observation data from low-Earth orbit (LEO) to geostationary orbit (GEO) through laser transmission. A Ka-band transmitter then forwards the data to a ground station.
Here, its signal is detected for the first time by ESA's Tenerife ground station in the Canary Islands during an illumination test.
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Quelle: ESA

2731 Views

Freitag, 15. November 2013 - 16:00 Uhr

Astronomie - Der Donnerstein von Ensisheim Anno 1492

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7.11.2013

Es war am Mittag des 7. November 1492, als ein
Steinmeteor mit einem gewaltigen Knall in ein Weizenfeld zwischen
Ensisheim und Battenheim im Elsass stürzte. Kräftige Männer eilten
herbei und holten den Meteoriten, aus seinem Loch. Sie brachten den
"Donnerstein" in die hiesige Kirche, wo der der Meteorit in Ketten
gelegt und aufgehängt wurde; so wie dies bei Teufelszeug zu tun war,
um weiteres Unheil zu vermeiden. 
Der sogenannte Ensisheim-Meteorit ist der älteste bezeugte
Meteoritenfall Europas und dementsprechend wertvoll: Der Großmeister
der Bruderschaft, die den Meteoriten im Museum des "Palais de la
Régence" in Ensisheim bewacht, wird den 53,83 kg schweren Donnerstein
für die Dauer von vier Tagen nach Wien bringen, wo das Stück in
seiner historischen Vitrine (von ca. 1870) im Meteoritensaal des
Naturhistorischen Museums von 15. bis 18. November 2013 zu sehen ist.
Für den Donnerstein von Ensisheim ist das die zweitlängste Reise,
die er bisher angetreten hat: Nach seinem milliardenkilometerlangen
Fall auf die Erde, ist er noch nie so weit gereist, wie jetzt nach
Wien. Interessantes Detail am Rande: Ensisheim war 1492 Teil der
Habsburgermonarchie. Obwohl der Stein also lange auf österreichischem
Staatsgebiet war, kommt er jetzt erstmals nach Österreich. 
Parallel zum Meteoriten werden einige historische Darstellungen
sowie Faksimiles dieses ältesten Meteoritenfalles in Europa zusammen
mit den "kleinen" Stücken des Ensisheim-Meteoriten aus der Sammlung
des NHM Wien gezeigt. Diese Objekte werden bis zum 3. Februar 2014 zu
sehen sein.
Pressekonferenz: Der Meteorit von Ensisheim
 Datum:   15.11.2013, um 10:30 Uhr
 Ort:     Naturhistorisches Museum Wien
          Burgring 7, 1010 Wien
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Quelle: OTS
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Update: 14.11.2013
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Streng bewachter Meteorit vier Tage in Wien

14.11.2013 - 11:18 | aktualisiert: vor 2 Stunden | Kommentieren

Der Meteorit von Ensisheim wird streng bewacht. Er ist der einzige Stein mit einer Leibgarde, die 24 Stunden aufpasst, dass auch nicht ein Bröserl von dem 54 Kilogramm schweren Brocken wegkommt.

Streng bewacht wird der Meteorit, der nach Wien kommt. BILD: SN/SN
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Der Meteorit von Ensisheim ist der älteste bezeugte Meteoritenfall Europas. Der Stein schlug am 7. November 1492 nahe dem französischen Städtchen Ensisheim auf, damals eine Ortschaft der k. u. k. Monarchie.
Damals wusste man nicht, ob der Stein nicht vielleicht des Teufels sei, obwohl er vom Himmel gefallen war. Daher brachte man ihn vorsichtshalber in die Kirche und legte ihn dort in Ketten, damit er kein Unheil anrichtet.
 
Ab heute, Freitag, ist der Stein für vier Tage im Naturhistorischen Museum Wien zu bestaunen. Die Bruderschaft "Confrérie Saint-Georges des Gardiens de la Météorite d'Ensisheim", die den Meteoriten seit Jahrhunderten hütet, überlässt ihn ausnahmsweise den Wienern. Der Stein wird vom Großmeister begleitet.
Quelle: Salzburger Nachrichten
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Update: 15.11.2013
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Meteorit: "Donnerstein" in Wien zu sehen

Der Meteorit von Ensisheim im Naturhistorischen Museum
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Das Naturhistorische Museum in Wien präsentiert den ältesten bezeugten Meteoritenfall Europas.
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Ein seltener außerirdischer Gast macht kurz Halt im Naturhistorischen Museum (NHM) Wien. Für vier Tage ist dort der Meteorit von Ensisheim zu sehen, der älteste bezeugte Meteoritenfall Europas. Am 7. November 1492 stürzte der "Donnerstein" mit einem gewaltigen Knall auf ein Feld bei Ensisheim im Elsass (Frankreich). Der knapp 54 Kilo schwere Meteorit wird von einer eigenen Bruderschaft bewacht.
NHM-Direktor Christian Köberl verglich am Freitag bei der Präsentation des Meteoriten das Ereignis von 1492 mit der in zahlreichen Filmen dokumentierten Explosion des "Meteoriten von Tscheljabinsk" über Russland am 15. Februar dieses Jahres. Statt durch Videoaufnahmen wurde das Ereignis durch das Flugblatt "Von dem donnerstein gefallen im 1492 jar" des Autors und Humanisten Sebastian Brant, der sich zu jener Zeit im rund 40 Kilometer von Ensisheim entfernten Basel aufhielt, in ganz Europa bekannt. Kaiser Maximilian I. machte auf dem Weg nach Frankreich wenige Tage nach dem Meteoritenfall in Ensisheim, das damals zur Habsburgermonarchie gehörte, Halt. Er ordnete an, den Stein in Ketten zu legen und in der Kirche aufzuhängen.
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Zwei Vertreter der Bruderschaft des Ensisheim-Meteoriten
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Dürer dürfte Meteorit gesehen haben
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Auch Albrecht Dürer hielt sich zum Zeitpunkt des Meteoritenfalls in Basel auf. Einige Jahre später malte er auf die Rückseite seines Gemäldes "Büßender Heiliger Hieronymus" und 1514 auf einen Kupferstich einen explodierenden Himmelskörper. Man geht davon aus, dass Dürer in Basel den Meteoriten gesehen hat und dieses Ereignis in den Bildern darstellte. 1528 wurde der Meteorit vom berühmten Alchemisten Paracelsus untersucht, 1771 besuchte Johann Wolfgang von Goethe den Himmelskörper und berichtete darüber in seiner Autobiografie "Dichtung und Wahrheit".
300 Jahre hing der Meteorit in der Kirche von Ensisheim, erst während der Französischen Revolution wurde er in ein Museum nach Colmar gebracht. In dieser Zeit wurden von dem ursprünglich rund 130 Kilo schweren Meteoriten Teile abgeschlagen, die sich heute in verschiedenen Museen und Sammlungen befinden. Auch das NHM in Wien hat Stücke des "Donnersteins" in seiner Sammlung, die nun gemeinsam mit einigen historischen Darstellungen und Faksimiles des Meteoritenfalls gezeigt werden - und zwar bis 3. Februar 2014 und damit deutlich länger als das Original, das übrigens in einer historischen Vitrine aus 1840 präsentiert wird.
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"St. Georgs-Bruderschaft" bewacht Meteoriten
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Anfang des 19. Jahrhunderts wurde der Meteorit dann wieder in der Kirche von Ensisheim aufgehängt - wo er als wahrscheinlich einziger Meteorit zum zweiten Mal auf die Erde fiel, und zwar 1854 beim Einsturz des Kirchturms. Seither wurde er zunächst in der Schule und dann im Gemeindeamt von Ensisheim aufbewahrt, wo sich heute ein dem Meteoriten gewidmetes Museum befindet. Dort wird er von einer 1984 gegründeten "St. Georgs-Bruderschaft des Meteoriten von Ensisheim" in ihrer rot-weißen Tracht bewacht. Der Großmeister der Bruderschaft, Jean-Marie Blosser, hat den Meteoriten nun nach Wien gebracht und wird ihn auch hier nicht aus den Augen lassen.
Die Präsentation erfolgt pünktlich zum ersten Geburtstag des im Vorjahr eröffneten Meteoritensaales im NHM, das die älteste und größte Meteoritensammlung der Welt beherbergt. Die Zusammensetzung des Meteoriten von Ensisheim sei nicht außergewöhnlich, es handle sich um einen 4,6 Mrd. Jahre alten "gewöhnlichen Chondriten", sagte Köberl. Der überhaupt älteste bisher dokumentierte Meteoritenfall dürfte 861 in Südjapan stattgefunden haben, in einem Tempel in Nogata auf der Insel Kyushu werde jedenfalls ein Meteorit in einer Schatulle aufbewahrt, in der dieses Falldatum eingraviert ist, so der NHM-Direktor.
Quelle: diepresse

3079 Views

Freitag, 15. November 2013 - 09:00 Uhr

Raumfahrt - Endeavour STS-61 - Die Rettung des Hubble Space Telescope 1993

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Space Shuttle Endeavour astronauts discussed their 1993 mission to repair the ailing Hubble Space Telescope. From left: mission specialist Tom Akers, pilot Ken Bowersox, mission commander Dick Covey, mission specialist and AeroAstro professor Jeff Hoffman, and payload commander Story Musgrave.

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Rescuing the Hubble Space Telescope
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NASA crewmembers reflect on the most complex space repair in history.
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In the past two decades, the Hubble Space Telescope has produced thousands of staggering images of the universe — capturing colliding galaxies, collapsing stars, and pillars of cosmic gas and dust with its high-precision cameras. These images have driven many scientific discoveries, and have made their way into popular culture, having been featured on album covers, fashion runways, and as backdrops for sci-fi television episodes. 
With Hubble’s advanced capabilities today, it’s hard to recall that the telescope was once gravely threatened. But shortly after its launch in 1990, scientists discovered a flaw that jeopardized Hubble’s entire endeavor. What followed was a political and public backlash against the $1 billion mission — and NASA, the agency that oversaw it. 
For the next three years, engineers scrambled to design a mission to repair the telescope in space — an ambitious plan that would result in the most complex Space Shuttle mission ever flown.
“[Hubble] was never meant to be a suspense story,” Jeffrey Hoffman, a member of the original astronaut crew charged with repairing the telescope, said this week at MIT. Nevertheless, at the time, the future of Hubble — and of NASA itself — seemed to hinge on the repair mission.
On Dec. 2, 1993, Hoffman and six other astronauts aboard Space Shuttle Endeavour began an 11-day mission, named STS-61, that involved five spacewalks — the most of any shuttle mission — to restore Hubble’s vision. 
This week, Hoffman, now a professor of the practice in MIT’s Department of Aeronautics and Astronautics, was joined by other members of the STS-61 crew in reflecting on Hubble’s rescue mission in an all-day symposium held in MIT’s Bartos Theatre. Talks and panel discussions — often with the air of a warm reunion — explored Hubble’s initial promise; its failure shortly after launch; and the planning, training, and execution of a rescue mission to fix the telescope. 
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Hubble’s backlash
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The first inkling of a problem came during a NASA press conference held to present the first image taken by Hubble from space: The image, of a far-off star, appeared fuzzy. Scientists soon discovered a “spherical aberration”: Due to a defect in the manufacturing process, the telescope’s primary mirror had been ground too flat, setting its curvature off by less than the width of a hair.  
“The unthinkable had become fact,” said James Crocker, then an optical engineer at NASA. 
Once word of the defect spread, Hoffman recalled that NASA and the astronomy community experienced “a maelstrom of public opprobrium,” mainly circling around the same question: “How did you screw up so badly?” 
To illustrate the public feeling at the time, John Logsdon, former director of the Space Policy Center at George Washington University, presented editorial cartoons deriding the mission with pictures of lemons in space and images of static, “courtesy of the Amazing Hubble Telescope.” Overall, Logsdon observed, public perception of the problem focused less on the defects in space than on the agency on the ground. 
“NASA was very much at risk,” Logsdon said. 
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Preparing a fix
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Following the discovery of Hubble’s defective mirror, engineers at NASA faced immense pressure to fix the problem. Crocker eventually experienced what he called a “eureka moment” in the most unlikely of places: a shower in Munich, where he had traveled to appeal to the European Space Agency for possible solutions. On a break in his hotel room, he was adjusting the showerhead — a European design that extends or retracts to accommodate one’s height — when an idea came to him: Why not outfit Hubble with corrected mirrors built on robotic arms that can extend into the telescope and retract into place, just like an adjustable showerhead? 
NASA engineers ran with the idea, building the Wide Field and Planetary Camera 2, or WFPC2, to replace Hubble’s defective mirror. Getting the piano-sized instrument into the satellite required 11 months of training by Hoffman and six other astronauts, who spent more than 230 hours in a water tank, choreographing intricate maneuvers and learning to use more than 150 tools. Meanwhile, engineers tested and retested the instruments to be installed on the telescope. 
Frank Cepollina, then NASA’s manager of space servicing capabilities, remembers that at the time there was “great turmoil in checking every socket and bolt.”
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A spacewalk to save NASA
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All preparations led up to Dec. 2, 1993, when the STS-61 crew launched. On the mission’s third day, the crew used the shuttle’s robotic arm to grab hold of the free-floating telescope, attaching it to the shuttle’s cargo bay, an event that prompted mission commander Dick Covey to announce: “We’ve got a firm handshake with Mr. Hubble’s telescope.”
The next day, Hoffman and payload commander Story Musgrave embarked on the mission’s first spacewalk, during which Hoffman, anchored to the robotic arm, replaced two gyroscopes on the telescope. 
Astronauts Kathryn Thornton and Thomas Akers set out on the second spacewalk to replace one of the telescope’s solar panels, which had begun to list. After the astronauts disengaged the panel from the telescope, Hoffman remembers watching the array drift off into space, “like some prehistoric bird floating away — we were mesmerized.” 
Hoffman and Musgrave performed the mission’s third spacewalk to swap out Hubble’s defective mirror with the 620-pound WFPC2 — the crux of the mission, and one that saw Hoffman anchored to the robotic arm, with Musgrave free-floating inside the telescope as Hoffman fed tools to him. 
“It was a little like working under a car,” recalled Hoffman, who said the procedure was so complex that the shuttle crew had to talk them through each step. The procedure was a success, as NASA’s ground controllers found that the new mirror passed all its initial tests. 
The remainder of the mission went largely according to plan, except for one hair-raising moment on the final spacewalk. On his previous outing, Hoffman had noticed that Hubble’s magnetometers, located at the very tip of the telescope, were flaking. To prevent more debris from possibly damaging equipment, pilot Kenneth Bowersox and mission specialist Claude Nicollier fabricated makeshift covers out of insulation to wrap around new magnetometers. 
During the fifth and final spacewalk, Hoffman and Musgrave replaced the telescope’s magnetometers with the insulated upgrades, a maneuver that required removing screws and placing them in a bag while removing one instrument. In the process, a screw got away, floating free of the astronauts’ grasp. While seemingly harmless, the 3-millimeter screw had the potential to dent the telescope or the shuttle. 
Hoffman, anchored to the shuttle’s arm, reached in vain for the screw, while Nicollier tried moving the arm farther out. But both the arm and the screw were moving at the same speed. In a spur-of-the-moment action, Bowersox reprogrammed the shuttle’s computer to reset the arm’s maximum speed, allowing Hoffman to reach the screw. From then on, the astronauts would refer to the escapade as “the Great Screw Chase.” 
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Continuing success
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Since that first repair mission, astronomers have used Hubble to collect thousands of stunning images of the universe and make countless discoveries, with more than 11,000 published papers based on Hubble images. The telescope has undergone four more servicing missions to replace old instruments and add new capabilities. 
Of Hubble’s future, Cepollina said: “As long as the telescope can collect photons, and we can provide next-generation instruments, we should keep truckin’.”
For the astronauts who rescued Hubble, disengagement from the telescope was bittersweet. 
“It was a little sad to let the telescope go,” Bowersox recalled. “It was like saying goodbye to a friend. It was a great, magical time.”
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Quelle: Massachusetts Institute of Technology (MIT)
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Endeavour Heads to Launch Pad
A morning sky drenched in vibrant color welcomes the Space Shuttle Endeavour as it rolls out to Launch Pad 39A today. Endeavour is being readied for the STS-61 mission, targeted for liftoff in early December. During the 11-day flight, a seven-member crew will carry out the first servicing of the Hubble Space Telescope.
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Endeavour Changes Launch Pads
The Space Shuttle Endeavour is being rolled around from Launch Pad 39A to Launch Pad 39B. The rare pad switch was deemed necessary after contamination was discovered in the Payload Changeout Room at Pad A. The transfer began around noon and was completed about seven hours later. Still to come are the payloads for the upcoming STS-61 mission, the first servicing of the Hubble Space Telescope.
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Hubble's Repair Team Gets to Work
Astronaut F. Story Musgrave, anchored on the end of the Remote Manipulator System (RMS) arm, prepares to be elevated to the top of the Hubble Space Telescope (HST) to install protective covers on the magnetometers. Astronaut Jeffrey A. Hoffman inside payload bay, assisted Musgrave with final servicing tasks on the telescope, wrapping up five days of space walks.
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STS061-87-062 (5 Dec. 1993) --- Astronaut F. Story Musgrave (top right center) works with a restraint device near the Hubble Space Telescope (HST) during the first of five STS-61 extravehicular activities (EVA). Astronaut Jeffrey A. Hoffman, who joined Musgrave for three of the five spacewalks, is seen at the bottom of the frame preparing to work with fuse plugs. Photo credit: NASA
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STS-61 Crew photo with Commander Richard O. Covey, Pilot Kenneth D. Bowersox, Payload Commander F. Story Musgrave and Mission Specialists Kathryn C. Thornton, Claude Nicollier, Jeffrey A. Hoffman and Tom Akers.
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Launch originally scheduled to occur from Launch Pad 39A, but after rollout, contamination was found in the Pad 39A Payload Changeout Room and a decision was made to move the shuttle and payloads to Pad 39B. Rollaround occurred on Nov. 15. The first launch attempt on Dec. 1 was scrubbed due to out-of-limit weather conditions at the Shuttle Landing Facility in the event of a return-to-launch-site contingency. Launch on Dec. 2 occurred on schedule. 
Mission Highlights
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The final shuttle flight of 1993 was one of most challenging and complex manned missions ever attempted. During a record five back-to-back space walks totaling 35 hours and 28 minutes, two teams of astronauts completed the first servicing of the Hubble Space Telescope (HST). In many instances, tasks were completed sooner than expected and a few contingencies that did arise were handled smoothly.
Hubble rendezvous, grapple and berthing occurred on flight day three, with Nicollier using the remote manipulator system arm to position the 43-foot (13-meter) long Hubble upright in payload bay. Throughout mission, commands to Hubble issued from Space Telescope Operations Control Center (STOCC) at Goddard Space Flight Center. After each servicing task completed, STOCC controllers verified electrical interfaces between replacement hardware and telescope.
On flight day four, first EVA team of Musgrave and Hoffman performed EVA #1, replacing two Rate Sensing Units (RSUs), each housing pair of gyroscopes; two Electronic Control Units which direct the RSUs; and eight electrical fuse plugs. Only unexpected problem occurred when Hoffman and Musgrave had difficulty closing compartment doors after replacing RSUs. Seven-hour, 54-minute space walk second longest in U.S. history to date, topped only by STS-49 EVA lasting eight hours, 29 minutes. During EVAs, Nicollier operated robot arm carrying one of two EVA crew members.
One of primary servicing goals -- installation of new solar arrays -- accomplished during EVA #2, performed on flight day five by Thornton and Akers and lasting six hours, 35 minutes. Timeline was re-worked to accommodate jettison of one of two original solar arrays, which could not be fully retracted due to kink in framework. Other solar array stowed in payload bay and replacement pair -- set of modified spares -- were installed without difficulty.
Expected four-hour replacement of one of Hubble's five scientific instruments, Wide Field/Planetary Camera (WF/PC), completed in about 40 minutes by Hoffman and Musgrave during EVA #3 on flight day six. WF/PC II is upgraded spare modified to compensate for flaw in HST primary mirror. Also, two new magnetometers installed at top of telescope during the six-hour, 48-minute EVA.
EVA #4 performed on flight day seven by Thornton and Akers. High-Speed Photometer, one of Hubble scientific instruments, removed and replaced with Corrective Optics Space Telescope Axial Replacement (COSTAR) unit. Task took less time to complete than expected. COSTAR designed to redirect light to three of four remaining Hubble instruments to compensate for flaw in primary mirror of telescope. Thornton and Akers also installed co-processor to enhance memory and speed of Hubble computer. During six-hour, 50- minute EVA, Akers set new U.S. space-walking record of 29 hours, 39 minutes, topping Eugene Cernan's 20-year-old record of 24 hours, 14 minutes. Thornton is leading U.S. female space walker with total of 21 hours, 10 minutes.
Final EVA performed by Hoffman and Musgrave on flight day eight. During seven-hour, 21-minute-long EVA #5, Hoffman and Musgrave replaced Solar Array Drive Electronics (SADE) unit and installed Goddard High Resolution Spectrograph Redundancy (GHRS) kit; also installed two protective covers over original magnetometers. After space walk completed, the new solar arrays and two high-gain antennas were deployed by STOCC. HST was also re-boosted to a slightly higher orbit of 321 nautical miles (595 kilometers) on flight day eight prior to the last EVA.
Hubble was redeployed on flight day nine. Release was delayed several hours to allow troubleshooting of erratic data telemetry from Hubble subsystems monitor; problem had occurred before and was not related to servicing. President Clinton and Vice President Gore congratulated crew, and Swiss minister of internal affairs called the following day to congratulate Nicollier.
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Quelle: NASA
 

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Donnerstag, 14. November 2013 - 22:47 Uhr

Astronomie - Durch Einsatz neuer Geräte entpuppt sich eine Galaxie im HIntergrund

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Surprising Image Provides New Tool for Studying a Galaxy
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Astronomers studying gas halos around nearby galaxies were surprised when detailed studies with the National Science Foundation's Karl G. Jansky Very Large Array (VLA) showed that one of their subjects is not a single galaxy, but rather two, nearly perfectly superimposed on the sky to masquerade as one. The discovery allowed them to use the alignment to learn otherwise-unobtainable facts about the nearer galaxy.
As part of a study of 35 galaxies, the astronomers observed one called UGC 10288, a spiral galaxy more than 100 million light-years distant that appears edge-on as seen from Earth. Their multiple VLA observations in 2011 and 2012 produced the best radio-telescope images of that galaxy ever made. The detailed images surprisingly revealed a more-distant galaxy, with strong radio emission, almost directly behind UGC 10288. In previous images, the two galaxies had been blended together.
The background galaxy is nearly 7 billion light-years from Earth.
"This changed the picture, quite literally," said Judith Irwin, of Queen's University in Ontario, Canada. "It changed our understanding of the characteristics of UGC 10288, but also gave us an unexpected new tool for learning more about that galaxy," Irwin added. The alignment of a foreground galaxy with such a strongly-emitting background galaxy with extended jets probably is the first such alignment found, the astronomers said.
The first insight gleaned from the improved images was that UGC 10288 is not forming stars as rapidly as the astronomers first thought. This is because much of the radio emission in the previous, blended images came from the background galaxy.
The new images also showed that the gas in the galaxy's "outskirts," high above its spiral disk of stars, is not a single, smooth halo-like envelope, but instead forms smaller, discrete features. One of these features is arc-like, rising more than 11,000 light-years above the disk.
The background galaxy, and the fact that it is aligned with its radio jets perpendicular to UGC 10288's disk, provides a valuable means of studying the nearer galaxy. "We can use the radio waves from the background galaxy, coming through the nearer one, as a way to measure the properties of the nearer galaxy," said Jayanne English, of the University of Manitoba.
Preliminary use of the more-distant galaxy in this manner has given the scientists some magnetic-field measurements of different portions of UGC 10288. The researchers plan to do additional analysis of their data to make more such measurements.
"We're getting a nice scientific reward from the unexpected discovery of the background galaxy," Irwin said. "Ironically, we would not have included UGC 10288 in our original study if its radio brightness had not been boosted by the background galaxy in the earlier images," she added.
Irwin and English worked with an international team of astronomers from North America, Europe, and India who are part of the Continuum Halos in Nearby Galaxies -- an EVLA Survey (CHANG-ES) consortium. The scientists reported their findings in the Astronomical Journal.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
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Image #1: The edge-on spiral galaxy UGC 10288 (horizontal) appeared to be a single object in previous radio telescope observations. However, new, detailed radio data (cyan in this image) from the NRAO's VLA reveals that the large perpendicular (vertical) extension really is a distant background galaxy with radio jets. The foreground image of UGC 10288 includes data from optical, infrared and radio telescopes.
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Image #2: This image of UGC 10288, the foreground spiral galaxy, includes data from NASA's WISE (far-infrared; orange) and Spitzer (near-infrared; yellow) space observatories, the Kitt Peak National Observatory's 0.9m telescope (ionized hydrogen; rose), and the Sloan Digital Sky Survey (optical; purplish-blue), and NRAO's VLA (radio; cyan).
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Image #3: This image of the background galaxy, CHANG-ES A, combines data from 2 radio frequency bands and different configurations of the VLA.
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Quelle: 
Science Credit: Judith Irwin (Queen's University), members of the CHANG-ES team, NRAO/AUI/NSF.
Image Credit: Jayanne English (U. of Manitoba), Judith Irwin (Queen's U.), Richard Rand (U. of New Mexico) and collaborators in the CHANG-ES consortium, NRAO VLA, NASA WISE & Spitzer missions, NOAO, and SDSS.

Tags: UGC 10288 

2958 Views

Donnerstag, 14. November 2013 - 22:34 Uhr

Astronomie - Hubble sieht unsere Milchstraße wie sie aussah in der Vergangenheit

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NASA's Hubble Space Telescope has revealed the first visual evidence of how our home galaxy, the Milky Way, assembled itself into the majestic pinwheel of stars we see today.
Astronomers used Hubble's deep-sky surveys to study the evolution of 400 galaxies similar to the Milky Way and noted their appearance at various stages of development over a time span of 11 billion years. Judging from images of these far-flung galaxies, they found the Milky Way likely began as faint, blue, low-mass object containing lots of gas. Gas is the fuel for star birth and the blue color is an indicator of rapid star formation.
They also found the Milky Way probably was a flat disk with a bulge in the middle, both of which grew simultaneously into the majestic spiral seen today. The sun and Earth reside in the disk and the bulge is both full of older stars and home to a supermassive black hole that probably grew along with the galaxy.
"For the first time, we have direct images of what the Milky Way looked like in the past," said study co-leader Pieter G. van Dokkum of Yale University in New Haven, Conn. "Of course, we can't see the Milky Way itself in the past. We selected galaxies billions of light-years away that will evolve into galaxies like the Milky Way. By tracing the Milky Way's siblings, we find that our galaxy built up 90 percent of its stars between 11 billion and 7 billion years ago, which is something that has not been measured directly before."
The Hubble telescope's superior resolving power, with which it can see extremely fine details, allowed the researchers to study how the structure of the Milky Way changed over time. At the peak of star formation, when the universe was about 4 billion years old, the Milky Way-like galaxies were pumping out about 15 stars a year. By comparison, the Milky Way today is creating only one star a year.
"You can see that these galaxies are fluffy and spread out," said study co-leader Shannon Patel of Leiden University in The Netherlands. "There is no evidence of a bulge without a disk, around which the disk formed later." Team member Erica Nelson, of Yale University, added: "These galaxies show us the whole Milky Way grew at the same time, unlike more massive elliptical galaxies, in which the central bulge forms first."
To identify the far-flung galaxies and study them in detail, the research team used three of the largest Hubble programs, the 3D-HST survey, the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and the Great Observatories Origins Deep Survey. These surveys combined spectroscopy with visible and near-infrared imaging by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys.
The research team's analysis involved measuring the distances and sizes of the galaxies. The astronomers calculated the mass of each galaxy from its brightness and colors. They selected the galaxies in their census from a catalog they compiled of more than 100,000 galaxies. The survey galaxies are consistent with computer models, which show at early stages, a majority of the bulges of spiral galaxies were built up at the same time as their corresponding disks.
"In these observations, we're capturing most of the evolution of the Milky Way," explained team member Joel Leja of Yale University. "These deep surveys allow us to see the smaller galaxies. In previous observations we could only see the most luminous galaxies in the distant past, and now we can look at more normal galaxies. Hubble gives us the shapes and colors of these spirals as well as their distances from Earth. We also can measure the rates at which each part of the galaxies grew. All of this is difficult to do from the ground."
The team’s results were published July 10 in The Astrophysical Journal Letters. A second paper appears in the Nov. 11 online edition of The Astrophysical Journal.
Quelle: NASA

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