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Sonntag, 21. Juli 2013 - 09:15 Uhr

Raumfahrt - Cassini-Sonde wird die Erde am 19.Juli vom Saturn-Orbit aus aufnehmen

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On July 19, 2013, NASA's Cassini spacecraft will take a picture of Earth from about 898 million (1.44 billion kilometers) away, or nearly 10 times the distance between Earth and the sun. It will be the first time Earthlings have had advance notice that their picture will be taken from interplanetary distances.

This simulated view from NASA's Cassini spacecraft shows the expected positions of Saturn and Earth on July 19, 2013, around the time Cassini will take Earth's picture. Cassini will be about 898 million miles (1.44 billion kilometers) away from Earth at the time. That distance is nearly 10 times the distance from the sun to Earth. Image credit: NASA/JPL-Caltech

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PASADENA, Calif. - NASA's Cassini spacecraft, now exploring Saturn, will take a picture of our home planet from a distance of hundreds of millions of miles on July 19. NASA is inviting the public to help acknowledge the historic interplanetary portrait as it is being taken.
Earth will appear as a small, pale blue dot between the rings of Saturn in the image, which will be part of a mosaic, or multi-image portrait, of the Saturn system Cassini is composing.
"While Earth will be only about a pixel in size from Cassini's vantage point 898 million [1.44 billion kilometers] away, the team is looking forward to giving the world a chance to see what their home looks like from Saturn," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We hope you'll join us in waving at Saturn from Earth, so we can commemorate this special opportunity."
Cassini will start obtaining the Earth part of the mosaic at 2:27 p.m. PDT (5:27 p.m. EDT or 21:27 UTC) and end about 15 minutes later, all while Saturn is eclipsing the sun from Cassini's point of view. The spacecraft's unique vantage point in Saturn's shadow will provide a special scientific opportunity to look at the planet's rings. At the time of the photo, North America and part of the Atlantic Ocean will be in sunlight.
Unlike two previous Cassini eclipse mosaics of the Saturn system in 2006, which captured Earth, and another in 2012, the July 19 image will be the first to capture the Saturn system with Earth in natural color, as human eyes would see it. It also will be the first to capture Earth and its moon with Cassini's highest-resolution camera. The probe's position will allow it to turn its cameras in the direction of the sun, where Earth will be, without damaging the spacecraft's sensitive detectors.
"Ever since we caught sight of the Earth among the rings of Saturn in September 2006 in a mosaic that has become one of Cassini's most beloved images, I have wanted to do it all over again, only better," said Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colo. "This time, I wanted to turn the entire event into an opportunity for everyone around the globe to savor the uniqueness of our planet and the preciousness of the life on it."
Porco and her imaging team associates examined Cassini's planned flight path for the remainder of its Saturn mission in search of a time when Earth would not be obstructed by Saturn or its rings. Working with other Cassini team members, they found the July 19 opportunity would permit the spacecraft to spend time in Saturn's shadow to duplicate the views from earlier in the mission to collect both visible and infrared imagery of the planet and its ring system.
"Looking back towards the sun through the rings highlights the tiniest of ring particles, whose width is comparable to the thickness of hair and which are difficult to see from ground-based telescopes," said Matt Hedman, a Cassini science team member based at Cornell University in Ithaca, N.Y., and a member of the rings working group. "We're particularly interested in seeing the structures within Saturn's dusty E ring, which is sculpted by the activity of the geysers on the moon Enceladus, Saturn's magnetic field and even solar radiation pressure."
This latest image will continue a NASA legacy of space-based images of our fragile home, including the 1968 "Earthrise" image taken by the Apollo 8 moon mission from about 240,000 miles (380,000 kilometers) away and the 1990 "Pale Blue Dot" image taken by Voyager 1 from about 4 billion miles (6 billion kilometers) away.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate in Washington, and designed, developed and assembled the Cassini orbiter and its two onboard cameras. The imaging team consists of scientists from the United States, the United Kingdom, France and Germany. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
Quelle: NASA
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Update: 4.07.2013
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A Day to Celebrate the Pale Blue Dot
On July 19, 2013, Cassini's cameras will be turned in the direction of the sun and will capture the Earth, alongside Saturn and its rings, in an event that will mark the first time Earthlings will know in advance their picture will be taken from a billion miles away. 
A full end-to-end mosaic of images of the ring system will be acquired over 4 hours on July 19. The Earth will be captured in a series of images taken between 21:27 to 21:42 UTC on that day, or 14:27 and 14:42 Pacific Daylight Time. LIGHT TRAVEL TIME IS ALREADY ACCOUNTED FOR IN THESE TIMES. This means you should be out and smiling, waving and celebrating at the indicated times, adjusted of course for your time zone. For people in the Pacific Daylight Time zone, that means 2:27 pm to 2:42 pm.
Quelle: NASA
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Update: 15.07.2013
 
Cassini bringt sich in Position für Aufnahme der Erde aus dem Saturn-Orbit
 
 
 
Quelle: NASA
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Update: 18.07.2013
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The First Interplanetary Photobomb
Consider it the first interplanetary photobomb. On July 19th, NASA's Cassini spacecraft will photograph Earth through the rings of Saturn--and NASA wants you to jump into the shot.
"Cassini has photographed Earth before, but this will be the first time Earthlings know in advance their picture will be taken from a billion miles away," says Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, CA.  "We hope that people around the world will go outside to wave at Saturn while the photo-shoot is underway."
Cassini's cameras will be trained on Earth during a 15 minute interval that begins at 2:27 p.m. PDT (5:27 p.m. EDT or 21:27 UTC).
"I am excited about this rare opportunity to send photons of all of us waving at Saturn," adds Spilker.  "I am encouraging my family and friends to wave at Saturn on that day also."
The circumstances of this photo-op are extraordinary.  From Cassini's point of view, the body of Saturn will eclipse the sun, so that the rings are magnificently backlit.  Earth will appear as a tiny blue speck just outside the E ring.
Opportunities to image Earth from the outer solar system are rare.  Since the Space Age began, there have been only two images of Earth from the outer solar system. The first and most distant was taken 23 years ago by NASA's Voyager 1 spacecraft beyond Neptune. The second was Cassini's image from the Saturn system in 2006.
Cassini's image of Earth in 2006 inspired Carolyn Porco, the Cassini imaging team lead at the Space Science Institute in Boulder, Colorado. "Ever since we caught sight of  Earth among the rings of Saturn in September 2006, I have wanted to do it all over again, only better," she says. "This time, I wanted to turn the event into an opportunity for people all over the globe to celebrate together the extraordinary achievements that have made such interplanetary photo sessions possible."
This photo-shoot will improve upon Cassini's previous effort in two ways:  The July 19, 2013, image will be the first to capture the Saturn system with Earth in natural color, as human eyes would see it. It also will be the first to capture Earth and its moon with Cassini's highest-resolution camera.
The Americas will be facing Saturn at the time of the image.   For North Americans, the event happens in broad daylight, so the best way to participate is to go outside, face east, and wave at the blue sky.
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North America and part of the Atlantic Ocean are expected to be illuminated when NASA's Cassini spacecraft takes a snapshot of Earth on July 19, 2013. This view is a close-up simulation. Image credit: NASA/JPL-Caltech
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Go outside again after sunset.  By that time, Saturn will have moved into the southwestern sky.  It pops out of the twilight, a slightly-golden pinprick about twice as bright as a first magnitude star.  Saturn is in the constellation Virgo, not far from the bright star Spica.
If you have a telescope, point it at Saturn.  Even inexpensive backyard optics will show you Saturn's rings and its biggest moon Titan.  Observers who see Saturn for the first time through the eyepiece of a telescope often gasp.  The view is Hubble-esque, but the experience is much more personal.  You’re seeing Saturn with your own eyes, a celestial wonder right out of the pages of an astronomy magazine.
From Cassini's point of view, Saturn's rings are too wide to capture in a single image, so the spacecraft will take a series of exposures.  These will be combined on Earth to produce a breathtaking mosaic.
"Seeing the whole mosaic of the backlit rings when it is put together will be incredible," says Spilker. "We will be looking for changes in Saturn's faint rings, especially the E ring, from the mosaic we took back in 2006."
The highlight of the day, however, will likely be our own planet. Says Porco, "It will be a day to celebrate life on the Pale Blue Dot."
Quelle: NASA
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PASADENA, Calif. -- Two NASA spacecraft, one studying the Saturn system, the other observing Mercury, are maneuvering into place to take pictures of Earth on July 19 and 20.
The image taken from the Saturn system by NASA's Cassini spacecraft will occur between 2:27 and 2:42 PDT (5:27 and 5:42 p.m. EDT, or 21:27 and 21:47 UTC) Friday, July 19. Cassini will be nearly 900 million miles (nearly 1.5 billion kilometers) away from Earth. NASA is encouraging the public to look and wave in the direction of Saturn at the time of the portrait and share their pictures via the Internet.
The Cassini Earth portrait is part of a more extensive mosaic -- or multi-image picture -- of the Saturn system as it is backlit by the sun. The viewing geometry highlights the tiniest of ring particles and will allow scientists to see patterns within Saturn's dusty rings. Processing of the Earth images is expected to take a few days, and processing of the full Saturn system mosaic will likely take several weeks.
Inspired in part by the Cassini team's plans to obtain a picture of Earth, scientists reexamined the planned observations of NASA's MESSENGER spacecraft in orbit around Mercury. They realized Earth is coincidentally expected to appear in some images taken in a search for natural satellites around Mercury on July 19 and 20. Those images will be taken at 4:49 a.m., 5:38 a.m. and 6:41 a.m. PDT (7:49 a.m., 8:38 a.m. and 9:41 a.m. EDT, or 11:49, 12:38, and 13:41 UTC) on both days. Parts of Earth not illuminated in the Cassini images, including all of Europe, the Middle East and Central Asia, will appear illuminated in the MESSENGER images. MESSENGER's images also will take a few days to process prior to release.
Quelle: NASA
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Update: 20.07.2013
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From its perch in the Saturn system, NASA's Cassini spacecraft took pictures of Earth from nearly 900 million miles (nearly 1.5 billion kilometers) today. To celebrate the first time the public has had advance notice that Earth's portrait was being taken from interplanetary distances, scientists and engineers at NASA's Jet Propulsion Laboratory and other Earthlings elsewhere gathered to wave at Saturn on July 19. Cassini took pictures of Earth between 2:27 and 2:42 p.m. PDT today.

The Earth images are part of a larger mosaic of the Saturn system that Cassini is taking while in Saturn's shadow. The mosaic will help scientists learn more about the fainter rings encircling Saturn.

The processing of the Earth image is expected to take a few days, and processing of the full Saturn system mosaic will likely take several weeks.

Quelle: NASA

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Update: 21.07.2013

W00083229.jpg was taken on July 20, 2013 and received on Earth July 20, 2013. The camera was pointing toward SATURN-ERING at approximately 623,956 miles (1,004,160 kilometers) away, and the image was taken using the CL1 and GRN filters. This image has not been validated or calibrated.

Quelle NASA


Tags: Wave at Saturn 

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Samstag, 20. Juli 2013 - 21:30 Uhr

Luftfahrt - NASA testet Steuerung für Unbemannte Flugzeuge

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NASA's communications experts have begun flight testing a prototype radio as part of the agency's contributions toward fully integrating civil and commercial Unmanned Aircraft Systems (UAS) into the National Airspace System (NAS).

This particular radio is one of the first steps to provide the critical communications link for UAS pilots on the ground to safely and securely operate their remotely piloted vehicles in flight even though they are many miles – if not continents or oceans – apart.

"So far the tests are going well and we're learning a lot about how this prototype radio operates under various conditions, but we still have much more testing to do on this radio and others that will come," said Jim Griner, a project engineer at NASA's Glenn Research Center in Cleveland.

Currently there is not a great deal of freedom for civilian uses of UAS over our nation's skies. Police and firefighters, for example, must use off-the-shelf systems and fly under special Federal Aviation Administration (FAA) approvals that restrict where and when remotely piloted vehicles can fly.

"There are some pretty good limitations on those operations, but the work we're doing to develop a new command and control radio for the UAS to use will help go beyond that," Griner said.

Built under a cooperative agreement between NASA and Rockwell Collins in Iowa, the current prototype radio is a platform to test operations at certain frequencies with specific radio waveforms that are unique to its particular task – in this case command and control of a remotely piloted vehicle.

Once testing concludes on the initial prototype, lessons learned will be applied to a second generation test radio, which is now scheduled to be delivered to NASA in September. Additional testing will follow, after which a final prototype design is to be delivered and tested in the 2015-2016 timeframe.

Ultimately the FAA will define the final requirements that will lead to certification of a UAS command and control radio for use in the NAS, but by building and testing prototype units now NASA is helping move the process along.

"Usually the requirements are defined first and then we try to build equipment based on those requirements. This short-circuits a number of years off the traditional process," Griner said.

The prototype radio was delivered to NASA Glenn on Feb. 28 and successfully put through its paces on a laboratory test bench. Flight tests in a NASA S-3 Viking twin-engine jet began in May and are expected to continue in June.

Tests of the prototype radio were preceded by a number of flights of the S-3 in which NASA researchers sought to characterize the way radio frequencies behave at the specific bandwidths assigned to civil UAS operations – something that had not been done before.

The way radio waves move through the air can be affected by a number of different things, including whether the ground is covered with leafy trees or snow and ice. Mountains, oceans, weather conditions, urban sprawl, skyscrapers and more can cause a change in a radio signal, for a good or bad.

These channel characterization flights began last December with the S-3 flying over areas of Ohio and Pennsylvania while a specially outfitted trailer with a 60-foot deployable antenna mast transmitted signals from the ground below.

With the prototype radio now in hand, the channel characterization and prototype radio tests will overlap a bit as there are plans for a visit to California this month to record data over coastal feature areas that include the ocean, mountains and desert.

NASA's UAS in the NAS Project is part of the Aeronautics Research Mission Directorate's Integrated Systems Research Program.

A NASA engineer standing on the trailer assists with raising the communications tower that transmits to the NASA research aircraft.
Image Credit: 

NASA / Michelle M.

Quelle: NASA


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Samstag, 20. Juli 2013 - 14:30 Uhr

Raumfahrt - Mapheus-4: Röntgenaufnahmen aus der Schwerelosigkeit

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Start der Höhenforschungsrakete Mapheus-4

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DLR startet Höhenforschungsrakete mit Experimenten der Materialphysik

Fast vier Minuten Schwerelosigkeit herrschten in der Höhenforschungsrakete Mapheus-4, die am 15. Juli 2013 um 7.53 Uhr vom schwedischen Raketenstartplatz Esrange startete. An Bord: zwei materialphysikalische Experimente des Deutschen Zentrums für Luft- und Raumfahrt (DLR). Unter Weltraumbedingungen zeichnete erstmals eine Röntgenröhre die Diffusion von Aluminium und Nickel noch während des Flugs auf. Zudem untersuchten die Wissenschaftler des DLR-Instituts für Materialphysik im Weltraum, wie sich granulare Gase in der Schwerelosigkeit verhalten. Durchgeführt wurde der Start vom Team der Mobilen Raketenbasis (MORABA) des DLR.

Gerade einmal 83 Sekunden nach dem Start waren die richtigen Bedingungen für den Experimentstart erreicht - im Inneren der Höhenforschungsrakete konnten von nun an die Experimente MIDAS (Measuring InterDiffusion in Alloys and Semiconductors) und MEGraMA (Magnetically Excited Granular Matter) ohne die störenden Einflüsse der Gravitation ablaufen. Die Rakete flog dabei bis in eine Höhe von über 154 Kilometern.

Experimente in der Schwerelosigkeit

Bereits vor dem Start hatte ein kleiner Ofen die sechs Materialproben, die aus unterschiedlichen Anteilen von Aluminium und Nickel bestanden, auf  900 Grad Celsius vorgeheizt. Seine Premiere hatte der Ofen bereits auf der Mapheus-3-Mission im November 2012, bei dem die Wissenschaftler seinen Einsatz auf einer Höhenforschungsrakete testeten. Nach Eintritt der Schwerelosigkeit wurden unterschiedliche Metallproben durch eine Bewegung im Inneren des Ofens miteinander in Kontakt gebracht, um so die geschmolzenen Aluminium-Nickel-Proben diffundieren zu lassen. Die kompakte und vollständig gegen Strahlungsaustritt abgeschirmte Röntgenradiographieanlage nahm dabei pro Sekunde eine Aufnahme in Echtzeit auf. "Die Diffusion in metallischen Flüssigkeiten ist ein Prozess, der bis heute noch nicht zu 100 Prozent verstanden ist", sagt Dr. Florian Kargl, wissenschaftlicher Projektleiter für die Mapheus-4-Mission. Die gewonnenen Daten aus der Schwerelosigkeit werden mit Modellrechnungen und Daten aus dem irdischen Labor verglichen; diese Ergebnisse können unter anderem dazu beitragen, in der Industrie Gießprozesse beispielsweise von Turbinenschaufeln zu optimieren.

Um das Verhalten von granularen Gasen besser zu verstehen, schickten die Wissenschaftler des DLR-Instituts für Materialphysik im Weltraum kleine Metallkügelchen in die Schwerelosigkeit. Während des Fluges wurden diese von vier Magneten zur Bewegung angeregt - zwei  Hochgeschwindigkeitskameras zeichneten anschließend mit zu bis 500 hochaufgelösten Bildern pro Sekunde auf, wie die Teilchen gegeneinander stießen und welchen zeitlichen Verlauf die Geschwindigkeitsverteilung nahm. Mit den Ergebnissen können die Forscher analysieren, wie granulare Gase - zum Beispiel Schüttgut wie Pillen - dichter und stabiler gepackt werden können. "Die Schwerelosigkeit beim Flug mit der Höhenforschungsrakete erlaubt es uns, diese Vorgänge zu untersuchen, ohne dass sich die Teilchen durch den Einfluss der Schwerkraft ablagern."

Bergung mit dem Hubschrauber

Nach dem insgesamt zehnminütigen Flug landete der Behälter mit den Experimenten an Bord in rund 60 Kilometern Entfernung vom Startplatz und wurde mit einem Hubschrauber geborgen. Für die Konzeption der einstufigen Trägerrakete und den Missionsbetrieb war die Abteilung Mobile Raketenbasis des DLR verantwortlich. Nach den erfolgreichen Vorgängerflügen Mapheus-1 bis Mapheus-3 hatte sie den brasilianisch-deutschen Raketenmotor S30  für Mapheus-4 adaptiert, um die Nutzlastkapazität und die Flughöhe deutlich zu steigern. "Bei einer Gesamtnutzlastmasse von 272 Kilogramm erreichte Mapheus-4 eine Flughöhe von 154 Kilometern" berichtet Frank Scheuerpflug, verantwortlich für die Mapheus-Mission bei der MORABA,  nach dem Flug.

Die Wissenschaftler und Ingenieure des Mapheus-Teams können nun bereits auf die Resultate und Erfahrungen von vier ergebnisreichen Flügen zurückblicken. "Mapheus ist ein hervorragendes Beispiel für hochaktuelle Materialforschung unter Schwerelosigkeit, die von der Effizienz und Flexibilität der Forschungsraketen profitiert", betont Projektleiter Martin Siegl vom DLR-Institut für Raumfahrtsysteme. Das Mapheus-Programm wird im kommenden Jahr fortgesetzt.

Quelle: DLR


Tags: Mapheus-4 

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Samstag, 20. Juli 2013 - 14:00 Uhr

Raumfahrt - China startet Langer-Marsch-C4 Rakete mit 3 Satelliten

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China’s Long March-4C carrier rocket successfully orbited three satellites for scientific experiments on Saturday, the state-run Xinhua news agency reported.

The launch took place at 3:37 Moscow time on Saturday [23:37 GMT on Sunday] from the launch pad in the Taiyuan Satellite Launch Center in Taiyuan, capital of north China's Shanxi Province.

The three satellites - Chuangxin-3, Shiyan-7 and Shijian-15 - will be used “mainly for conducting scientific experiments on space maintenance technologies,” the agency reported.

It was the 179th launch for a Long March rocket.

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China “secretly” launch three satellites via Long March 4C

In what was one of the most secretive Chinese missions in recent years, a Long March 4C launched three military satellites. The launch, which occurred at 23:37 UTC from the Taiyuan Satellite Launch Center on Friday, was the subject of a state media blackout, with news leaking via social media just hours before lift-off.

 

Chinese Launch:

Chinese media refer to the new mission as launching three technological satellites: namely the Chuang Xin-3, the Shiyan Weixing-7 and the Shijian-15.

The first Chung Xin (‘Innovation’) sats were experimental telecommunications microsatellites designed and built by the China Academy of Sciences.

Shiyan Weixing satellites are usually used to test new technologies as well as the Shijian (‘Practice’) satellites used for technological demonstration. Shijian-15 probably will test a Chinese robotic arm, a mission that has been planned and announced for some time, while Shiyan-7 will scan for orbital debris.

This was the 179th successful launch of a Chang Zheng (Long March) launch vehicle, the 42nd successful orbital launch from Taiyuan and the first from Taiyuan this year. It was also the fifth successful orbital Chinese launch in 2012.

Launch Vehicle and Launch Site:

With its main commonality matched to the Long March 4B, the first stage has a 24.65 meter length with a 3.35 meter diameter, consuming 183,340 kg of N2O4/UDMH (gross mass of first stage is 193.330 kg).

The vehicle is equipped with a YF-21B engine capable of a ground thrust of 2,971 kN and a ground specific impulse of 2,550 Ns/kg. The second stage has a 10.40 meter length with a 3.35 meter diameter and 38,326 kg, consuming 35,374 kg of N2O4/UDMH.

It includes a YF-22B main engine capable of a vacuum thrust of 742 kN and four YF-23B vernier engines with a vacuum thrust of 47.1 kN (specific impulses of 2,922 Ns/kg and 2,834 Ns/kg, respectively).

The third stage has a 4.93 meter length with a 2.9 meter diameter, consuming 12,814 kg of N2O4/UDMH. Having a gross mass of 14,560 kg, it is equipped with a YF-40 engine capable of a vacuum thrust of 100.8 kN and a specific impulse in vacuum of 2,971 Ns/kg.

Situated in the Kelan County on the northwest part of the Shanxi Province, the Taiyuan Satellite Launch Center (TSLC) is also known by the Wuzhai designation. It is used mainly for polar launches (meteorological, Earth resources and scientific satellites).

The center is at an altitude of 1400-1900m above sea level, and is surrounded by mountains to the east, south and north, with the Yellow River to its west. The annual average temperature is 4-10 degrees C, with maximum of 28 degrees C in summer and minimum of -39 degrees C in winter.

TSLC is suitable for launching a range of satellites, especially for low earth and sun-synchronous orbit missions. The center has state-of-the-art facilities for launch vehicle and spacecraft testing, preparation, launch and in-flight tracking and safety control, as well as for orbit predictions.

Quelle: NSC


2845 Views

Samstag, 20. Juli 2013 - 10:30 Uhr

Astronomie - Gigantisch koronaler Ausbruch über der Sonne Nordpol

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The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT.

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The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT. Coronal holes are dark, low density regions of the sun’s outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.

Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun’s activity cycle. The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013. During this portion of the cycle, the number of coronal holes decreases. During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment. The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again.  At such times, coronal holes have appeared that are even larger than this one.

The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it’s unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.

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Quelle: NASA


Tags: SOHO 

3022 Views

Freitag, 19. Juli 2013 - 21:58 Uhr

Raumfahrt - Falsch eingebaute Sensoren sorgen für Absturz von Proton-M-Rakete

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Proton-M Rocket Downed by Reversed Sensors – Roscosmos

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A Russian Proton-M rocket that exploded after launch on July 2was lost because its angular velocity sensors were installed upside-down, the country’s space agency said Thursday.

The mistake affected three of six yaw angular velocity sensors on the unmanned rocket, said deputy head of Roscosmos, Alexander Lopatin, citing a state commission’s investigation of the crash.

The mistake could have been the fault of either the worker who installed the sensors or the engineer who drew up the construction blueprints, Lopatin said at a press conference.

“Installing these devices is complicated and awkward work,” Lopatin said.

The wrongly installed sensors bore the trace of being forced into place, he added.

There is no provision for spotting such a mistake in current pre-launch procedures, Lopatin said. The commission is drafting a set of measures to rectify the situation, including possible filming of sensor installation procedures for pre-launch review.

The sensors were produced by the Academician Pilyugin Center and installed at the Khrunichev space center, which assembled the rocket in 2011. Both enterprises are state-owned and Moscow-based.

The Proton-M, which was carrying three satellites for the Glonass satellite navigation system – Russian answer to America's GPS – tipped over and rolled before it blew up 12 seconds after takeoff from Baikonur spaceport in Kazakhstan.

The combined cost of the lost rocket and satellites is 4.4 billion rubles ($136 million), according to official state tender data.

Russia's Prosecutor General’s Office will look into the Roscomos investigation’s findings, as will the government, Lopatin said. The Cabinet is planning a reform of Russia’s space industry, which has been plagued by a series of failed launches in recent years, several involving Proton rockets.

Quelle: RIANOVOSTI

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A Russian Proton rocket veers out of control seconds after launch from the Baikonur Cosmodrome in Kazakhstan. (Credit: YouTube)


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Freitag, 19. Juli 2013 - 17:15 Uhr

Raumfahrt - US-NAVY startet erfolgreich MUOS (Mobile User Objective System) mit Atlas-V-Rakete

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17.07.2013

The U.S. Navy is planning to loft its second in a series of next-generation narrowband communications satellites on Friday, July 19.
The United Launch Alliance Atlas V is slated to boost the second Mobile User Objective System (MUOS) spacecraft during a 44-min. launch window that opens at 8:48 a.m. EDT from Cape Canaveral. The launch vehicle is an Atlas V 551, meaning it will use a 5-meter fairing and five strap-on, solid-rocket boosters.
The first MUOS was launched Feb. 24, 2012, and began limited operations late last year. The constellation, ultimately planned for four operational satellites, is built by Lockheed Martin.
MUOS contains a legacy ultra-high frequency communications payload, built by Boeing, as well as one using the newer Wideband Code Division Multiple Access (WCDMA) standard. Full capability of the new WCDMA payload will not be reached until this second satellite is in orbit and checked out. At that point, officials will validate its functionality, including use of the new payload, with satellites and ground systems.
The WCDMA payload is intended to provide soldiers with voice, data and video services similar to those offered by commercial smart phones. Today’s narrowband system requires soldiers to be stationary to receive a signal; MUOS was designed to allow soldiers to move around the battlefield while also accessing data rates up to 10 times higher than those provided by today’s constellation.
Lockheed Martin is working on a MUOS development contract worth up to $3.3 billion; the program has slipped at least two years.
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The U.S. Navy’s Mobile User Objective System (MUOS)-2 satellite, encapsulated with its payload fairing, is transferred from the Vertical Integration Facility to SLC-41 and its awaiting Atlas V 551 launch vehicle on 8 July 2013. Photo Credit: United Launch Alliance
Quelle: US-NAVY/ULA
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Update: 18.07.2013
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They are the U.S. military's heaviest spacecraft looking for rides to orbit -- the Navy's next-generation satellites providing communications to forces on the move -- and the United Launch Alliance's mightiest version of the Atlas 5 will do the heavy lifting Friday morning to deploy the second bird in the series.
Liftoff of the Mobile User Objective System satellite No. 2 is scheduled for 8:48 a.m. EDT (1248 GMT) from Cape Canaveral on Florida's east-central coast.
"At nearly 15,000 pounds, MUOS 2 marks the heaviest satellite launched to date by an Atlas 5," said Jim Sponnick, ULA's vice president of Atlas and Delta programs.
The 206-foot-tall rocket, riding aboard its mobile launch platform, was rolled out from the assembly building to the Complex 41 pad Wednesday morning.
At the same time, other ULA workers just down the road at Complex 37 were conducting a countdown dress rehearsal and fueling test on a Delta 4 rocket for its launch of the Air Force's sixth Wideband Global SATCOM satellite on August 7.
Atlas clocks begin ticking early Friday for the seven-hour countdown. Weather officials will be monitoring isolated showers and thunderstorms coming ashore from the Atlantic, a forecast that gives a 40 percent chance of acceptable conditions during the 44-minute launch window.
With five powerful solid rocket motors mounted to the first stage, the Atlas 5 will thunder skyward in its most energetic configuration, which has been employed only three times before to launch the first MUOS satellite and hurl NASA space probes to Jupiter and Pluto.
The Atlas 5, making its 39th flight in 11 years, is a modular launcher that enables mission designers to mix and match the number of solids and various nose cone selections to meet the needs of a given payload. The highly sophisticated and hefty MUOS series takes all the power.
The spacecraft is packaged atop the rocket for a three-hour climb into its preliminary orbit, a highly elliptical dropoff point that requires three firings by the Centaur upper stage to achieve.
From there, controllers will spend about eight days maneuvering the craft into a circular geosynchronous orbit 22,300 miles above the planet, then three days commanding the craft to spread its power-generating wings and unfurl two giant antennas on the ends of extension booms.
"With the launch of the second MUOS spacecraft, we take the next large step toward providing truly global narrowband communications for our deployed warfighters around the world," said Navy Capt. Paul Ghyzel, manager of the Satellite Communications Program Office.
At the heart of the MUOS satellite's communications payload are two gold mesh, umbrella-like antenna reflectors, one to provide the same type of UHF communications like previous Navy spacecraft and the other offering modernized capabilities that the new system will create.
"MUOS will deliver unparalleled high-speed communications access to mobile users for decades," said Iris Bombelyn, vice president of Narrowband Communications at satellite-builder Lockheed Martin.
"With over 20,000 terminals that are capable of connecting to this secure mobile (satellite communications) system, we are at the cusp of our potential. The MUOS satellite provides not only ongoing support for the legacy UHF Follow-On users in the field but a myriad of new services, bandwidth, capacity and applications to mobile users."
Coverage to legacy users will transmit through a 17.7-foot-diameter reflector on the bottom of the MUOS craft and the advanced, multi-beam features of MUOS to significantly increase the transmission capacity over the Navy's previous satellites will use a large 46-foot reflector atop MUOS.
All U.S. military forces rely upon Navy satellites for Ultra High Frequency narrowband communications. UHF offers small, portable units that forces can carry into battle and the frequency enables communications in urban canyons and mountainous terrain, penetrating foliage and transmitting through bad weather.
Each MUOS satellite has 16 times the capacity of the aging UHF satellite constellation.
What's more, the new satellites not only support the current user terminals in operation but also creates a new "rugged smartphone" network to provide 3G-like cellular telephone and data services across the globe.
"One of the way we frequently describe the new capabilities that MUOS brings is think of a cellphone," Ghyzel said.
"The architecture that we've built with the satellite constellation and with the global ground network, the satellite is the celltower. Anybody that is using a radio that is capable of communicating with MUOS, when they speak their transmission is picked up by the satellite and then routed like a cellular system would route to wherever it needs to be to talk to the guy on the other end.
"So if you are driving down the interstate and you walk to talk to a guy one county over, you may be using the same tower. For Bob to talk to Jim.
"But if Bob is in Florida and wants to talk to his wife in Seattle, he can pick up a cellphone, the tower next to the interstate he is driving on is going to pick up that call, but then it is going to go through a fiber optic network to get to a celltower that is closest to his wife in Seattle and that tower is going to send that call to her cellphone.
"Much like for us in MUOS, if you got somebody that's in Hawaii that needs to talk to a ship that's 200 miles off Hawaii, that traffic is going to go through the satellite that is over the Pacific.
"But if that ship commander needs to talk to somebody that is in Afghanistan, then they are going to transmit over MUOS, the satellite over the Pacific is going to up that transmission, but (it is) then routed through the rest of the MUOS network to the satellite that's going to be over the Indian Ocean, eventually, and then down into Afghanistan.
"You can think of the satellites as the celltowers in the sky. That's a really good way to think of how the system works."
The MUOS craft were built on Lockheed Martin's A2100 satellite design used by dozens of previous communications spacecraft. All five MUOS craft are clones to each other, with four slated to be operational satellites in the constellation and one considered an on-orbit spare.
MUOS 1 was successfully launched on Feb. 24, 2012. MUOS 3 is eyeing a launch in about 12 months, followed by MUOS 4 in the summer of 2015 and MUOS 5 some time after that.
The Atlas rocket has been the expendable launch vehicle of choice for the Navy's narrowband UHF communications satellites dating back several spacecraft generations to the 1970s, exclusively carrying the entire Fleet Satellite Communications System, Ultra High Frequency Follow On series and now MUOS. A variety of Atlas-Centaur versions have been employed on the previous 20 flights since 1978, all from Cape Canaveral. 
Quelle: SN
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Update: 19.07.2013
Erfolgreicher Start von Atlas-Rakete mit MUOS
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The US Navy’s MUOS-2 satellite was launched on Friday morning aboard a United Launch Alliance Atlas V. Liftoff from Space Launch Complex 41 at Cape Canaveral was re-scheduled to 13:00 UTC (09:00 local time) after an earlier upper level winds constraints. The spacecraft is currently being delivered to its initial destination via the Centaur Upper Stage.

 

 


Atlas V Launch:

MUOS-2 is the second in a series of five planned Mobile User Objective System (MUOS) satellites, part of a six billion dollar program to replace the UHF Follow-On (UFO) satellites currently used by the US Navy.

The prime contractor for the MUOS program is Lockheed Martin, with the spacecraft based around the A2100M satellite bus. At a gross mass of around 6,740 kilograms (14,900 lb), MUOS are among the heaviest unclassified spacecraft ever placed into geosynchronous orbit. A BT-4 liquid rocket motor, produced by IHI Corporation of Japan, will be used to perform on-orbit maneuvers.

The satellite’s 14-metre (46-foot) reflector antennae are produced in Melbourne, Florida by Harris Corporation, while part of the communications payload is constructed by Boeing IDS. General Dynamics and Ericsson are responsible for developing the ground segment of the MUOS system.

The first MUOS satellite, MUOS-1, was launched in February 2012, also by an Atlas V. That spacecraft completed initial on-orbit testing on 17 July last year, ahead of acceptance testing by the US military.

A Navy program, MUOS is one of several series of communications satellites operated by the US military. The US Air Force operates the Wideband Global Satcom and Advanced Extremely High Frequency program, both of which are expected to see launches in the next two months.

The National Reconnaissance Office also has its own communications satellites, the Satellite Data System (SDS), and several other spacecraft, such as the mysterious PAN satellite, have been launched. The US military was also reported to have bought the AMC-14 satellite from SES after it failed to achieve geostationary orbit in 2008.

The rocket that launched MUOS-2 was an Atlas V 551, tail number AV-040. Friday’s launch marked the fourth flight of the 551 configuration, which is the most powerful version of the Atlas V, and the thirty-ninth Atlas V launch overall.

First flown in 2002, the Atlas V is, along with the Delta IV, one of two Evolved Expendable Launch Vehicles (EELVs) developed to meet the requirements of the US military. Both the Atlas V and Delta IV are operated by United Launch Alliance, which was formed in December 2006 to take over operations of the EELV fleet and Boeing’s older Delta II rocket.

In its thirty-eight flights to date, the Atlas V has achieved a near-perfect success record, with only one partial failure – a fuel leak caused by a valve failure led to AV-009 placing the USA-194 spacecraft into a lower-than-planned orbit in 2007.

Atlas is one of the most reliable rockets flying – its last outright failure occurred over 20 years ago, when in March 1993 the UFO-1 satellite was placed into an unusable orbit after an engine failure. That launch used an Atlas I.

The Atlas V 551 was first used for the 2006 launch of the New Horizons spacecraft bound for Pluto, with subsequent launches deploying the Juno probe to Jupiter and the MUOS-1 satellite.

The first stage of the Atlas V is a Common Core Booster, powered by a single RD-180 engine burning RP-1 and liquid oxygen. Derived from the RD-170 engine developed for the Soviet Union’s Energia and Zenit rockets, the RD-180 first flew in 2000 on the maiden flight of the Atlas III, and Friday’s launch marked its 45th flight.

Ignition of the RD-180 came  2.7 seconds ahead of the scheduled launch time, allowing the engine to reach launch-ready thrust by T-0, at which point five Aerojet solid rocket motors attached to the first stage also ignited.

Liftoff occurred at T+1.1 seconds, with the rocket pitching over and performing a roll and yaw maneuver to attain its launch azimuth around 2.8 seconds later at an altitude of 26 metres (85 feet).

Forty-four seconds after liftoff, the rocket passed through the area of maximum dynamic pressure, or Max-Q. Burnout and separation of the solid rocket motors, which augment the RD-180′s thrust during the early phases of the flight, occurred around a minute later; the first two boosters separating 103.3 seconds after launch, and the remaining three followed a second and a half later.

Separation of the payload fairing came at T+191.5 seconds, with the Forward Load Reactor separating five seconds later, however the exact times were dependent on atmospheric conditions and heating.

Six different payload fairings are offered for the Atlas V; three four-meter variants and three five-meter fairings. For Friday’s launch a medium length five-metre fairing was used. This was 23.4 meters (76.8 feet) long with a diameter of 5.4 meters (17.7 feet).

The five-meter fairings encapsulate the upper stage along with the payload, with a Forward Load Reactor, attached near the top of the upper stage, used to dampen vibrations in the fairing to provide a better acoustic environment for the payload.

The upper stage of the Atlas V is a Centaur, a descendent of a stage first flown in 1962 which made its 200th flight on the last MUOS launch in 2012. For the Atlas V both single and dual-engine Centaurs are available, however only the single-engine configuration has been flown to date.

The engine used on the Atlas V Centaur is an RL10A-4-2, which is fuelled by cryogenic propellant; liquid hydrogen and liquid oxygen. Centaur is expected to make three burns during Friday’s launch.

Following depletion of its propellant, the Common Core Booster’s engine cut off around four minutes and 21 seconds after launch. Six seconds later, the Centaur separated and begin its prestart procedure. RL10 ignition occurred 9.9 seconds after staging.

The Centaur’s first burn lasted seven minutes and 46.9 seconds, before the flight entered a seven-minute and 59-second coast phase. Following the coast, the second burn lasted five minutes and 55.7 seconds.

After the second burn, the launch entered an extended coast phase, lasting 142 minutes and 36.1 seconds. The final burn, which will follow this, is expected to last just 59.1 seconds. Three minutes and 39 seconds later, MUOS-2 will separate from its carrier rocket.

The target orbital parameters for the deployment of MUOS-2 are an apogee of 35,787 kilometers (19,323 nautical miles, 22,237 statute miles); a perigee of 3802 km (2,053 nmi, 2,362 mi); inclination of 19.1 degrees to the equator, and an argument of perigee of 179.0 degrees. MUOS-2 will then use its own propulsion system to maneuver to geostationary orbit.

AV-040 was the sixtieth rocket to launch from Space Launch Complex 41 (SLC-41) of the Cape Canaveral Air Force Station.

Built during the 1960s for the Titan IIIC as part of the Titan Integrate-Transfer-Launch Complex, LC-41 as it was then designated saw its first launch in December 1965 when a Titan launched the LES-3 and 4 satellites, along with Oscar-4 and OV2-3.

A Vertical Integration Building (VIB), shared with LC-40, was used to stack the rockets before they were rolled out to the launch pad for payload installation in a cleanroom atop the pad’s Mobile Service Tower (MST). The MST was demolished in 1999, while the VIB was demolished in 2006 following the end of Titan launches from SLC-40.

In total, twenty-seven Titan launches took place from SLC-41; ten Titan IIICs, seven Titan IIIEs, and ten Titan IVs – all Titan IVAs except for the final Titan to launch from the pad; a Titan IV(402)B which failed to place a DSP satellite into geosynchronous orbit. The last Titan IVA launch from the pad also failed due to a guidance problem. These two launches were part of a run of three consecutive launch failures which the Titan IV suffered during 1998-99.

The Atlas V has made 33 of its 39 launches from SLC-41, beginning with its maiden flight in 2002. A new Vertical Integration Facility, located closer to the pad than the old building, is used to assemble the rockets, including their payloads, with rollout to the pad occurring a few days before launch.

Friday’s launch was the ninth US orbital launch attempt of 2013, and the thirty-eighth or thirty-ninth overall for the world, depending on a rumored Iranian launch failure believed to have occurred around 17 February.

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Quelle: NASA


Tags: Mobile User Objective System ULA-Launch MUOS 

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Freitag, 19. Juli 2013 - 09:26 Uhr

Mars-Chroniken - Curiosity findet den Nachweis über den Verlust eines Großteils der ursprünglichen Atmosphäre des Mars.

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This picture shows a lab demonstration of the measurement chamber inside the Tunable Laser Spectrometer, an instrument that is part of the Sample Analysis at Mars investigation on NASA's Curiosity rover.
Image Credit: NASA/JPL-Caltech
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PASADENA, Calif. – A pair of new papers report measurements of the Martian atmosphere's composition by NASA's Curiosity rover, providing evidence about loss of much of Mars' original atmosphere.
Curiosity's Sample Analysis at Mars (SAM) suite of laboratory instruments inside the rover has measured the abundances of different gases and different isotopes in several samples of Martian atmosphere. Isotopes are variants of the same chemical element with different atomic weights due to having different numbers of neutrons, such as the most common carbon isotope, carbon-12, and a heavier stable isotope, carbon-13.
SAM checked ratios of heavier to lighter isotopes of carbon and oxygen in the carbon dioxide that makes up most of the planet's atmosphere. Heavy isotopes of carbon and oxygen are both enriched in today's thin Martian atmosphere compared with the proportions in the raw material that formed Mars, as deduced from proportions in the sun and other parts of the solar system. This provides not only supportive evidence for the loss of much of the planet's original atmosphere, but also a clue to how the loss occurred.
"As atmosphere was lost, the signature of the process was embedded in the isotopic ratio," said Paul Mahaffy of NASA Goddard Space Flight Center, Greenbelt, Md.  He is the principal investigator for SAM and lead author of one of the two papers about Curiosity results in the July 19 issue of the journal Science.
Other factors also suggest Mars once had a much thicker atmosphere, such as evidence of persistent presence of liquid water on the planet's surface long ago even though the atmosphere is too scant for liquid water to persist on the surface now. The enrichment of heavier isotopes measured in the dominant carbon-dioxide gas points to a process of loss from the top of the atmosphere -- favoring loss of lighter isotopes -- rather than a process of the lower atmosphere interacting with the ground.
Curiosity measured the same pattern in isotopes of hydrogen, as well as carbon and oxygen, consistent with a loss of a substantial fraction of Mars' original atmosphere. Enrichment in heavier isotopes in the Martian atmosphere has previously been measured on Mars and in gas bubbles inside meteorites from Mars. Meteorite measurements indicate much of the atmospheric loss may have occurred during the first billion years of the planet's 4.6-billion-year history. The Curiosity measurements reported this week provide more precise measurements to compare with meteorite studies and with models of atmospheric loss.
The Curiosity measurements do not directly measure the current rate of atmospheric escape, but NASA's next mission to Mars, the Mars Atmosphere and Volatile Evolution Mission (MAVEN), will do so. "The current pace of the loss is exactly what the MAVEN mission now scheduled to launch in November of this year is designed to determine," Mahaffy said.
The new reports describe analysis of Martian atmosphere samples with two different SAM instruments during the initial 16 weeks of the rover's mission on Mars, which is now in its 50th week. SAM's mass spectrometer and tunable laser spectrometer independently measured virtually identical ratios of carbon-13 to carbon-12. SAM also includes a gas chromatograph and uses all three instruments to analyze rocks and soil, as well as atmosphere.
"Getting the same result with two very different techniques increased our confidence that there's no unknown systematic error underlying the measurements," said Chris Webster of NASA's Jet Propulsion Laboratory, Pasadena, Calif. He is the lead scientist for the tunable laser spectrometer and the lead author for one of the two papers. "The accuracy in these new measurements improves the basis for understanding the atmosphere's history."
Curiosity landed inside Mars' Gale Crater on Aug. 6, 2012 Universal Time (on Aug. 5 PDT). The rover this month began a drive of many months from an area where it found evidence for a past environment favorable for microbial life, toward a layered mound, Mount Sharp, where researchers will seek evidence about how the environment changed.   
Quelle: NASA

Tags: Curiosity Mars-atmospheric 

3023 Views

Freitag, 19. Juli 2013 - 09:04 Uhr

Astronomie - Schnee in einem jungen Planetensystem

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Eisige Grenze für die Entstehung von Planeten und Kometen

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Die sogenannte Schneegrenze bestimmt, bei welchen Abständen sich erdähnliche Planeten oder Gasriesen um einen jungen Stern bilden können. Jetzt ist es erstmals gelungen, diese Grenzregion um den sonnenähnlichen Stern TW Hydrae abzubilden. Dessen Schneegrenze kann uns nicht nur mehr über die Entstehung von Planeten und Kometen verraten, sowie über die Faktoren, die ihre chemische Zusammensetzung bestimmen, sondern sich auch die Vergangenheit unseres Sonnensystems beleuchten. Die Ergebnisse erscheinen heute online auf Science Express.
Astronomen haben mit dem Atacama Large Millimeter/submillimeter Array (ALMA) die erste Aufnahme der Schneegrenze in einem jungen Planetensystem gewonnen. Auf der Erde bildet sich die Schneegrenze in großen Höhen, wo niedrige Temperaturen Luftfeuchtigkeit in Schnee verwandeln. An Bergen ist dies dort, wo der schneebedeckte Gipfel in nacktes Gestein übergeht, deutlich erkennbar.
Die Schneegrenzen um junge Sterne bilden sich auf ähnliche Art und Weise in den kalten Außenbereichen der Gas- und Staubscheiben, in denen Planetensysteme entstehen. Mit zunehmendem Abstand vom Stern friert zunächst Wasser (H2O) aus und bildet die erste Schneegrenze. Weiter draußen, bei noch kühleren Temperaturen, frieren weitere Stoffe aus und werden zu Schnee, wie zum Beispiel Kohlenstoffdioxid (CO2), Methan (CH4) und Kohlenstoffmonoxid (CO). In festem Zustand umgeben diese Stoffe Staubkörner mit einer Art klebriger Hülle. Sie spielen daher eine entscheidende Rolle beim Wachstum der Staubkörner: Sie verhindern, dass die Staubkörner bei Kollisionen auseinanderbrechen und ermöglichen ihnen so, zu den Grundbausteinen von Planeten und Kometen zu werden. Der Schnee vergrößert zusätzlich den Anteil fester Materie in der Scheibe und könnte dadurch den Prozess der Planetenentstehung beschleunigen.
Jede einzelne dieser Schneegrenzen – für Wasser, Kohlenstoffdioxid, Methan und Kohlenmonoxid – könnte mit der Entstehung bestimmter Typen von Planeten zusammenhängen [1]. Um einen sonnenähnlichen Stern, in einem Planetensystem wie dem unsrigen, würde die Wasser-Schneegrenze dem Bereich zwischen den Umlaufbahnen von Mars und Jupiter entsprechen, während die Kohlenstoffmonoxid-Schneegrenze etwa bei der Umlaufbahn des Planeten Neptun läge.
ALMA hat jetzt einen ersten Blick auf die Kohlenstoffmonoxid-Schneegrenze um den jungen Stern TW Hydrae geworfen, der 175 Lichtjahre von der Erde entfernt ist. Die Astronomen gehen davon aus, dass dieses angehende Planetensystem ähnliche Eigenschaften aufweist wie unser eigenes Sonnensystem in einem Alter von nur wenigen Millionen Jahre.
„Dank ALMA haben wir jetzt das erste echte Bild der Schneegrenze um einen jungen Stern. Das verrät uns einiges über die erste Phase der Geschichte unseres eigenen Sonnensystems”, sagt Chunhua “Charlie” Qi vom Harvard-Smithsonian Center for Astrophysics in Cambridge (USA), einer der beiden Hauptautoren des Fachartikels, in dem die Beobachtungen vorgestellt werden. „Damit sind wir in der Lage Details über die eisigen Außenbereiche eines fernen, sonnensystem-ähnlichen Planetensystems zu erfahren, die uns zuvor verborgen geblieben sind.”
Tatsächlich könnte das Vorhandensein der Kohlenstoffmonoxid-Schneegrenze noch weitere Konsequenzen als nur die Entstehung von Planeten haben. Kohlenstoffmonoxid-Eis wird für die Entstehung von Methanol benötigt, einem der Grundbausteine komplexerer organischer Moleküle. Kometen könnten derartige Moleküle zu den im Entstehen begriffenen erdähnlichen Planeten weiter innen befördert haben. Auf diese Weise wären Zutaten, die für die Entstehung des Lebens notwendig sind, auf diese Planeten gelangt.Bis zu den neuen Beobachtungen war es nicht gelungen, die Schneegrenzen direkt abzubilden, da sie immer in einem relativ dünnen Bereich im Inneren der protoplanetaren Scheibe um den Stern entstehen. Ihre exakte Position und Ausdehnung ließ sich daher nicht bestimmen. Ober- und unterhalb der dünnen Schicht, in der die Schneegrenzen existieren, verhindert die vom Stern ausgehende Strahlung die Bildung von Eis. Durch die starke Konzentration von Gas und Staub in der zentralen Ebene wird dieser Bereich von der Strahlung abgeschirmt, so dass Kohlenstoffmonoxid und andere Gase abkühlen und ausfrieren können.
Das Astronomenteam konnte mit einem ausgeklügelten Trick aber dennoch in das Innere der Scheibe schauen: Anstatt nach dem Schnee selbst Ausschau zu halten, der nicht direkt beobachtet werden kann, suchten sie nach einem Molekül namens Diazenyl (N2H+), das im Millimeterbereich des elektromagnetischen Spektrums strahlt und daher mit ALMA hervorragend beobachtet werden kann. Dieses Molekül reagiert sehr leicht mit Kohlenstoffmonoxidgas und wird dabei zerstört. In nachweisbaren Mengen ist es also nur dort zu finden wo das Kohlenstoffmonoxid zu Schnee ausgefroren ist und das Diazenyl daher nicht länger zerstören kann. Auf diese Weise wird die Anwesenheit von Diazenyl der Schlüssel zum Nachweis von Kohlenstoffmonoxid-Schnee.
Die einzigartige Empfindlichkeit und das Auflösungsvermögen von ALMA ermöglichen es den Astronomen, das Vorhandensein und die Verteilung von Diazenyl zu untersuchen. Dabei sind sie auf eine scharfe Grenze bei einem Abstand von etwa 30 Astronomischen Einheiten (also dem 30-fachen Abstand Erde-Sonne) vom Stern gestoßen. Die Messungen entsprechen einer Art Negativbild der Verteilung von Kohlenstoffmonoxid-Schnee in der Scheibe um TW Hydrae. Die Kohlenstoffmonoxid-Schneegrenze befindet sich demnach genau dort, wo sie auch der Theorie nach liegen sollte – am Innenrand des Diazenyl-Rings.
„Für unsere Beobachtungen standen uns nur 26 der 66 Antennen von ALMA zur Verfügung. Anzeichen für den Nachweis der Schneegrenzen bei anderen Sternen haben sich inzwischen noch in weiteren ALMA-Daten gezeigt, und wir gehen daher davon aus, dass zukünftige Beobachtungen mit der gesamten Anlage noch viele weitere solcher Schneegrenzen werden nachweisen können. Uns erwarten viele spannende Einblicke in die Entstehung und Entwicklung von Planeten – wir müssen nur abwarten”, schließt Michiel Hogerheijde von der Sterrewacht Leiden in den Niederlanden.
Endnoten
[1] Trockene Gesteinsplaneten bilden sich beispielsweise innerhalb der Wasser-Schneegrenze (also besonders nahe am Stern), wo nur Staub existieren kann. Auf der anderen Seite entstehen die eisigen Gasriesen nur hinter der Kohlenstoffmonoxid-Schneelinie.
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Diese ALMA-Aufnahme zeigt den Bereich, in dem sich um den jungen Stern TW Hydrae CO-Schnee gebildet hat. Der Kohlenstoffmonoxid-Schnee ist grün dargestellt und wird ab einer Entfernung von 30 Astronomischen Einheiten um den Stern sichtbar. CO ist nicht nur für die Entstehung von Planeten und Kometen notwendig, sondern wird auch zur Erzeugung von Methanl benötigt, einem der wichtigsten Grundbausteine für die Entstehung des Lebens.
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Diese Aufnahme vom ALMA-Observatorium in Chile zeigt in grün den Bereich, in dem sich um den jungen Stern TW Hydrae (in der Mitte eingezeichnet) CO-Schnee gebildet hat. Vergleicht man das TW Hydrae-System mit unserem Sonnensystem, entspricht der blaue Kreis der Umlaufbahn des Planeten Neptun. Der Übergang zum CO-Eis markiert dabei auch den Beginn der Zone in der sich kleinere eisbedeckte Körper wie Kometen oder Zwergplaneten wie Pluto und Eris bilden können.
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Quelle: ESO

3031 Views

Freitag, 19. Juli 2013 - 08:45 Uhr

Astronomie - SOFIA-Flüge über Neu-Seeland

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SOFIA will travel to Christchurch, New Zealand, from July 12 to Aug. 2, 2013, for three weeks of observations of the southern sky. The scientific targets for the southern deployment of SOFIA include the center of our Milky Way Galaxy, young stars, star forming regions, and supernova remnants in the southern Milky Way, the Milky Way's two satellite galaxies known as the Magellanic Clouds, and several nearby galaxies.
An International Collaboration
As a joint project between NASA and the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR), SOFIA operates a telescope with an effective diameter of 2.5 meters in a modified Boeing 747SP aircraft and is thus the world's largest airborne observatory. SOFIA flies at altitudes as high as 13,700 meters (45,000 feet) to provide access to astronomical signals at far-infrared wavelengths that would otherwise be blocked due to absorption by water vapor in the atmosphere.
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WASHINGTON -- NASA's SOFIA airborne observatory will be based in New Zealand for the next two weeks, taking advantage of the Southern Hemisphere's orientation to study celestial objects that are difficult or impossible to see in the northern sky.
SOFIA, formally known as the Stratospheric Observatory for Infrared Astronomy, deployed to the United States Antarctic Program's facilities at Christchurch International Airport last week and completed its first science flight at 4 a.m. local time July 18 (noon EDT July 17). A team of scientists, engineers, pilots and technicians from the United States and Germany are deployed with SOFIA to support as many as nine research flights through Aug. 1.
SOFIA is a modified Boeing 747SP aircraft that carries a telescope with an effective diameter of 100 inches (250 centimeters). It provides astronomers access to the visible, infrared and submillimeter spectrum.
On the first flight in New Zealand, astronomers used SOFIA to observe the disk of gas and dust orbiting the black hole at the center of our Milky Way galaxy, and two dwarf galaxies, the Large and Small Magellanic Clouds, which accompany the Milky Way. The Magellanic Clouds can be seen easily with the naked eye in the southern sky.
"SOFIA's deployment to the Southern Hemisphere shows the remarkable versatility of this observatory, which is the product of years of fruitful collaboration and cooperation between the U.S. and German space agencies," said Paul Hertz, director of NASA's Astrophysics Division in Washington. "This is just the first of a series of SOFIA scientific deployments envisioned over the mission's planned 20-year lifetime."
A vital part of the collaboration is a far-infrared spectrometer, the German Receiver for Astronomy at Terahertz Frequencies (GREAT). Mounted on SOFIA's telescope for the entire deployment, GREAT is especially suited for studies of interstellar gas and the life cycle of stars.
"The success of the GREAT spectrometer in addressing exciting scientific questions at far-infrared wavelengths was demonstrated during SOFIA's earlier, Northern Hemisphere flights," said Rolf Guesten of the Max Planck Institute for Radio Astronomy in Bonn, Germany, and leader of the German researchers who developed the spectrometer. "Now, we are turning the instrument to new frontiers such as the Magellanic Clouds, including the Tarantula Nebula -- that is the most active star-forming region known in the local group of galaxies."
SOFIA project scientist Pamela Marcum said the results anticipated from observations made during the aircraft's deployment will further scientists' understanding of star formation, stellar evolution and chemistry in stellar clouds.
"The deployment exemplifies the synergistic relationship between SOFIA's international partners, with NASA playing a crucial role in the planning and execution of the science observations," Marcum said.
SOFIA is a joint project of NASA and the German Aerospace Center, DLR. The aircraft is based at NASA's Dryden Flight Research Center's Aircraft Operations Facility in Palmdale, Calif. Dryden manages the program. NASA's Ames Research Center in Moffett Field, Calif., manages SOFIA's science and mission operations in cooperation with the Universities Space Research Association (USRA) of Columbia, Md., and the German SOFIA Institute (DSI) at the University of Stuttgart. The National Science Foundation's U.S. Antarctic Program provided vital support for SOFIA's deployment operations in Christchurch.
Quelle: NASA

Tags: SOFIA New Zealand 

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