Blogarchiv

Sonntag, 20. Januar 2013 - 17:30 Uhr

Mars-Chroniken - Mars-Rover Opportunity Sol 027-033 Rückblick

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Microscopic Imager Non-linearized Full frame EDR acquired on Sol 27 of Opportunity's mission to Meridiani Planum at approximately at approximately 11:31:11 Mars local solar time, Microscopic Imager dust cover commanded to be OPEN. NASA/JPL/Cornell/USGS

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Right Panoramic Camera Non-linearized Full frame EDR acquired on Sol 27 of Opportunity's mission to Meridiani Planum at approximately 10:13:08 Mars local solar time, camera commanded to use Filter 2 (754 nm). NASA/JPL/Cornell

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Left Rear Hazard Camera Non-linearized Full frame EDR acquired on Sol 27 of Opportunity's mission to Meridiani Planum at approximately 13:20:47 Mars local solar time. NASA/JPL

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Right Front Hazard Camera Non-linearized Downsampled EDR acquired on Sol 27 of Opportunity's mission to Meridiani Planum at approximately 11:39:09 Mars local solar time. NASA/JPL

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Microscopic Imager Non-linearized Full frame EDR acquired on Sol 28 of Opportunity's mission to Meridiani Planum at approximately at approximately 12:26:38 Mars local solar time, Microscopic Imager dust cover commanded to be OPEN. NASA/JPL/Cornell/USGS

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Right Panoramic Camera Non-linearized Full frame EDR acquired on Sol 28 of Opportunity's mission to Meridiani Planum at approximately 10:13:34 Mars local solar time, camera commanded to use Filter 1 (436 nm). NASA/JPL/Cornell

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Right Front Hazard Camera Non-linearized Downsampled EDR acquired on Sol 28 of Opportunity's mission to Meridiani Planum at approximately 11:47:02 Mars local solar time. NASA/JPL

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Microscopic Imager Non-linearized Full frame EDR acquired on Sol 29 of Opportunity's mission to Meridiani Planum at approximately at approximately 12:17:43 Mars local solar time, Microscopic Imager dust cover commanded to be OPEN. NASA/JPL/Cornell/USGS

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Left Panoramic Camera Non-linearized Sub-frame EDR acquired on Sol 29 of Opportunity's mission to Meridiani Planum at approximately 13:20:39 Mars local solar time, camera commanded to use Filter 7 (432 nm). NASA/JPL/Cornell

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Right Panoramic Camera Non-linearized Sub-frame EDR acquired on Sol 29 of Opportunity's mission to Meridiani Planum at approximately 11:45:57 Mars local solar time, camera commanded to use Filter 1 (436 nm). NASA/JPL/Cornell

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Left Navigation Camera Non-linearized Full frame EDR acquired on Sol 29 of Opportunity's mission to Meridiani Planum at approximately 13:05:24 Mars local solar time. NASA/JPL

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Left Panoramic Camera Non-linearized Sub-frame EDR acquired on Sol 30 of Opportunity's mission to Meridiani Planum at approximately 11:49:26 Mars local solar time, camera commanded to use Filter 3 (673 nm). NASA/JPL/Cornell

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Left Front Hazard Camera Non-linearized Downsampled EDR acquired on Sol 30 of Opportunity's mission to Meridiani Planum at approximately 15:12:33 Mars local solar time. NASA/JPL

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Right Panoramic Camera Non-linearized Sub-frame EDR acquired on Sol 32 of Opportunity's mission to Meridiani Planum at approximately 09:44:59 Mars local solar time, camera commanded to use Filter 3 (803 nm). NASA/JPL/Cornell

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Left Panoramic Camera Non-linearized Full frame EDR acquired on Sol 32 of Opportunity's mission to Meridiani Planum at approximately 13:58:50 Mars local solar time, camera commanded to use Filter 7 (432 nm). NASA/JPL/Cornell

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Left Panoramic Camera Non-linearized Sub-frame EDR acquired on Sol 33 of Opportunity's mission to Meridiani Planum at approximately 10:44:18 Mars local solar time, camera commanded to use Filter 7 (432 nm). NASA/JPL/Cornell

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Left Navigation Camera Non-linearized Full frame EDR acquired on Sol 33 of Opportunity's mission to Meridiani Planum at approximately 13:17:06 Mars local solar time. NASA/JPL

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Left Navigation Camera Non-linearized Full frame EDR acquired on Sol 33 of Opportunity's mission to Meridiani Planum at approximately 13:15:26 Mars local solar time. NASA/JPL

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Right Navigation Camera Non-linearized Full frame EDR acquired on Sol 33 of Opportunity's mission to Meridiani Planum at approximately 13:02:26 Mars local solar time. NASA/JPL

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Left Navigation Camera Non-linearized Full frame EDR acquired on Sol 33 of Opportunity's mission to Meridiani Planum at approximately 12:58:20 Mars local solar time. NASA/JPL

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Left Front Hazard Camera Non-linearized Full frame EDR acquired on Sol 33 of Opportunity's mission to Meridiani Planum at approximately 12:53:17 Mars local solar time. NASA/JPL

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Fotos: NASA


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Sonntag, 20. Januar 2013 - 11:45 Uhr

Astronomie - Mond und Jupiter am Abendhimmel zu sehen wenn keine Wolken da sind

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Ungetrübter Blick auf Mond und Jupiter im Dezember 2011 (mehr Aufnahmen in der Astronomie-Galerie)

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3193 Views

Samstag, 19. Januar 2013 - 16:30 Uhr

Raumfahrt - JAXA´s SELENE-Mond-Mission

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Scenario of the Moon’s Geological Evolution
Developed from SELENE Observation Data
Current research on the moon’s origin and geological
evolution focuses on three main topics. The fi rst topic
relates to the magma ocean hypothesis, which posits
that in the past a giant impact event caused melting
to signifi cant depth on the moon. It is thought that
when the magma ocean cooled, plagioclase feldspars
emerged, forming the lunar crust. Is this hypothesis
correct? If so, we need to clarify the process through
which the moon’s crust and mantle were formed.
The second topic of research relates to the aforementioned
giant impact hypothesis, which states that
the moon was formed from debris left over from a collision
between the Earth and a body the size of Mars
approximately 4.5 billion years ago. Within the magma
ocean hypothesis, there is the problem of what could
have been the source of heat large enough to melt the
moon to a depth of several hundred meters. However,
under the giant impact hypothesis, the moon started
out in a molten state, hence this problem does not
require further explanation. Nevertheless, we must
henceforth determine whether or not the giant impact
hypothesis is correct.
The third topic is the lunar mantle overturn model.
This model postulates that as the magma ocean
cooled, the magma became heavier than the rock
below it, leading to a reversal in position at some point
and the formation of the present-day lunar crust and
internal structure. We may also postulate that such a
mantle overturn created the differences between the
near and far sides of the moon.


While researchers currently work to gather evidence
that will prove which of these hypotheses are
correct, as the calibration accuracy of SELENE observation
data increases, new research results are
constantly being announced. For example, a research
paper—of which I am a co-author—led by Makiko
Ohtake of JAXA’s Institute of Space and Astronautical
Science (ISAS) uses spectral profi ler*1 data from
SELENE to report on the relative ratio of iron to magnesium
contained in rocks over the entire lunar surface.
Based on the results of this analysis, we are able
to build a scenario under which the lunar farside crust
began to crystallize earlier than its nearside counterpart
(please refer to the fi gure on page 18). I believe
that this research represents one of the most important
achievements to date from the SELENE project.
Candidate Landing Spots for the Next Lunar
Explorer
I would also like to briefl y discuss the candidate landing
spots for SELENE-2, JAXA’s proposed successor
to KAGUYA. Thanks to the emergence of research
results stemming from the SELENE project, I have
been able to co-author research articles with experts
from fi elds with which I previously had no contact.
Hence, I believe SELENE has spurred a broadening of
communication opportunities among scientists. I have
been interested in utilizing such dialogue to discuss
with a variety of scientifi c bodies what type of research
scientists are hoping to do through the SELENE-2 project
and fi nd out preferred locations for such research

on the moon’s surface. Consequently, approximately
70 candidate landing spots were put forward for
SELENE-2. Over a period of two years, this initial total
was reduced to 10 candidate spots. From among
these, I would like to introduce the main candidates.
The fi rst candidate region encompasses the
Copernicus, Tycho and Zucchius craters, whose investigation
includes such objectives as elucidating the
history of the formation of the lunar crust and differences
between the near and far sides of the moon—
or what may be termed the dichotomous nature of
the lunar geology. The Copernicus and Tycho craters
contain central peaks*2. Since it is thought that this
area includes material that has risen up from deep
underground, investigation of rocks here may provide
valuable information on the moon’s deep geology.
Zucchius Crater is believed to contain remnants of the
lunar crust from its earliest period.
Another candidate landing area is the Marius Hills, a
set of small volcanic domes. Similar to such terrestrial
volcanoes as Japan’s Izu Oshima, they are thought to
have formed where magma burst up through the surface.
SELENE’s Terrain Camera (TC)*3 found evidence
of a skylight in a large underground lava tube, which
may have signifi cant value for future lunar exploration.
This lava tube is believed to have formed during
underground lava fl ows, and the tube’s opening to
the surface was probably created by a meteorite impact.
The lava tube’s walls are likely coated in glass,
thereby providing an airtight enclosure. Since such an


underground lava tube interior would also be shielded
from cosmic radiation, it may be a candidate location
for a future lunar base.
Revealing the Earth’s History through Lunar
Exploration
In the past, it was thought that the moon was a simple
astronomical object and that its internal structure conformed
to the concentric model. However, it is now
known that the moon’s structure is, in fact, very heterogeneous.
The question of what happened on the
moon is of very great scientifi c interest, and I believe
that if we can answer this question satisfactorily it will
be very useful for understanding the Earth’s formative
period. On the other hand, when I look back at my
own reasons for pursuing research in this fi eld, since
childhood my dream has been to expand the boundaries
of human activity. Although I was too young to have
much memory of the Apollo program, which brought
back to Earth rocks from the moon, I was fascinated
by the images sent back by the Pioneer 10 and 11
space probes revealing many secrets of the outer
planets. Such achievements convinced me that by the
time I grew up, humans would be living on the moon. I
am still keen to see the early construction of a colony
on the moon, and hope that this will be the forerunner
of more distant space endeavor by humanity.

Quelle: JAXA

 


3410 Views

Freitag, 18. Januar 2013 - 23:17 Uhr

Raumfahrt - Boeing´s SLS-Mars-Lander-Studien

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Currently, Boeing estimates that the MTV, SEP, and CTH systems could be capable of achieving a 12 year lifetime. If this comes to pass, the MTV would be used for multiple missions to Mars – thus significantly reducing programmatic costs compared to architectures calling for non-reusable MTVs and crew habitats.

Uncrewed Mars surface cargo mission:

Under this proposed mission, an evolved SLS rocket would be used to launch a Mars Cargo Lander (MCaL) with attached In-Space Stage into LEO – with the MCaL then ferried by the In-Space Stage to the EMLP platform and the MTV.

Under this configuration, the MTV’s CTH would be removed and the MCaL attached instead.

With this plan, the MCaLs would serve not only as stock pile locations for crew supplies and storage but would also serve as the primary habitats for Mars crew surface operations.

Departing from the EMLP, the MTV would use the In-Space Stage to transfer itself into a TMI trajectory. After fuel exhaustion, the In-Space Stage would be jettisoned and the MTV’s SEP would carry the uncrewed vehicle to Mars.

After attaining Mars orbit, the MCaL would separate from the MTV and descend to the Martian surface.

Once safely on the surface, the MCaL’s cylindrical surface would be raised and its habitatable volume inflated – again capitalizing off Bigelow’s inflatable habitat technology.

The MTV would then return to the EMLP platform for refurbishment and reuse.

Crewed mission to Martian surface:

The coup de grace.

Launching aboard an evolved SLS rocket, the Martian surface crew would carry to LEO with them an In-Space Stage. A Mars Crew Lander (MCL) would be launched beforehand and transferred to the MTV at the EMLP platform.

After propelling themselves to the MTV, the crew would transfer SEP xenon or krypton resupplies to the MTV, check out the craft’s systems, attach the MPCV, MCL, and In-Space Stage to the MTV, and prepare for their journey to the Red Planet.

After using the In-Space Stage for the TMI burn, the In-Space Stage would be jettisoned, and the MTV would use its own SEP to sail to Mars.

After achieving Mars orbit, the crew would board the MCL and descend to the Martian surface near the already-present MCaL.

During landing, Boeing states that the crew would “land on Mars with accent and decent stages with CH4 engines, tankage, and other lander systems that demonstrate heritage” from the Boeing-proposed lunar architecture missions.

After safely landing on Mars, the crew would transfer to the MCaL, where they would live and work for the duration of Mars surface operations.

After completing their mission, the crew would transfer back the MCL and ascend to Mars orbit, where they would rendezvous with the MTV.

The MTV’s SEP would then take the craft out of Mars orbit and place it on a return trajectory to the EMLP platform.

Once back at the EMLP platform, the crew would board the MPCV and return to Earth.

Quelle: Boeing


5225 Views

Freitag, 18. Januar 2013 - 22:52 Uhr

Astronomie - Meteoriten-Einschlag am 7.Oktober 1862 von Kleinmenow

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Meteorit von Menow weltweit gefragt

 

Kleinmenow ((mat)) Neben der 725-Jahrfeier von Fürstenberg gab es im vergangenen Jahr im Bereich der Wasserstadt ein weiteres Jubiläum, das jedoch weitgehend unbeachtet blieb: Am 7.Oktober jährte sich zum 150.Mal der Meteoriten-Einschlag von Kleinmenow.

Es muss nicht immer im Desaster enden: Laut einer weit verbreiteten wissenschaftlichen Theorie soll ein Meteorit für das Aussterben der Dinosaurier und zahlreicher anderer Arten vor rund 65Millionen Jahren verantwortlich sein. Bei Menow indes, westlich von Fürstenberg unweit des Ziernsees an der Havel gelegen, wurde lediglich ein Schäfer bei seiner Arbeit erschreckt, als der Brocken 1862 an einem Dienstag zwischen 12 und 13 Uhr auf einem Feld des damaligen Erbpachtgutes niederging. Dass dies ein nicht alltägliches Ereignis war, zeigen die Zahlen: So sind nach Auskunft des Museums für Naturkunde in Berlin nur 46Meteorite erhalten, die auf dem heutigen Gebiet der Bundesrepublik gefunden wurden. Heute sind Teile des Menow-Meteoriten in der ganzen Welt verstreut. Sie befinden sich unter anderem in Indien, den USA und der Sammlung des Vatikans.

Dokumentiert ist der Einschlag in dem 1862 erschienen Band der Annalen der Physik und Chemie, herausgegeben von Johann Christian Poggendorf: "Vor den Augen des Schäfermeisters fiel plötzlich bei völlig heiterem Himmel ein großer feuriger Klumpen mit solcher Gewalt aus der Luft hernieder, dass der Sand ringsum hoch aufspritzte, und die Masse anderthalb Fuß tief in die Erde fuhr", zitiert Poggendorf einen Bericht der Allgemeinen Zeitung vom 3. Dezember 1862. Laut der Neustrelitzer Zeitung vom 16. November des Jahres erfolgte das Erscheinen des Himmelskörpers laut Ohren- und Augenzeugen mit einem Zischen und Sausen in der Luft, unterbrochen von heftigen Detonationen, vergleichbar einer fernen Kanonade. Der andere Bericht verschweigt dies, macht jedoch Angaben zum Aussehen des Fundes: "Sein Äußeres zeigt eine unregelmäßige Pyramidalform mit ziemlich ebener, aber etwas nach innen gebogener Fläche - eine Form, welche sich erzeugen würde, wenn zum Beispiel ein Klumpen weichen Tons mit Gewalt aus beträchtlicher Höhe niedergeworfen wäre".

Die Oberfläche sei mit einer glatten schwarzen Kruste umgeben, das Innere dunkelaschgrau, mit zahllosen silberglänzenden Metallteilchen. Seine Bruchflächen färben sich, wenn sie mit Wasser in Kontakt kommen, braunrot. Das Gewicht des Meteoriten wird mit 21 Pfund und sein Volumen mit 134 Kubikzoll angegeben. Metallurgische Gutachten im 20. Jahrhundert ergaben einen Eisenanteil von 27,41 Prozent. Die Färbung stammt von dem sich bildenden Eisenoxid. Die schwarze Schmelzkruste liegt in den hohen Temperaturen begründet, denen der Stein beim Eintritt in die Erdatmosphäre ausgesetzt war.

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Quelle; Märkische Oderzeitung


3075 Views

Freitag, 18. Januar 2013 - 19:19 Uhr

UFO-Forschung - Die eigenartige Geschichte von Robert Bigelow, der gerade NASA aufblasbare Space Station Module verkauft

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The Strange History of Robert Bigelow, Who Just Sold NASA Inflatable Space Station Modules

NORTH LAS VEGAS—An inflatable space pod to be attached to the International Space Station in a couple of years will be like no other piece of the station. NASA is contracting a private company to build an inflatable space pod for the International Space Station. Instead of metal, its walls will be made of floppy cloth, making it easier to launch (and then inflate). NASA said Wednesday that it had signed a $17.8 million contract with Bigelow Aerospace to build the module, which could reach the space station as soon as 2015.

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We were driving to Lake Tahoe, my wife and I, headed north on one of the most breathtaking highways in the world, U.S. 395 along the eastern spine of the Sierra Nevada. The winter sun had dropped behind the jagged mountains and we had already been on the road a couple of hours since leaving Los Angeles. It was time to find a motel and dinner and especially wine.

She said something like, "What's that light? Is that the next town?" It was very big and very bright, and I had also been wondering if it announced the next strip of traveler services. Or maybe it was a radio tower. But then the light would be blinking, and red, like radio tower lights. And while we were looking at this light, it became a very large black triangular-shaped airship of some kind, hovering nearly motionless over the desert. There were single round lights on each corner, and a huge spotlight beam out of the center—we could see it traveling over the sagebrush on the valley floor about a hundred yards off the road. I pulled over to get a better look at this tremendous shape, but it zoomed past us and became a speck of light in the southern sky before vanishing altogether. When we got to Lone Pine and checked into a motel—the Dow Villa, highly recommended and right under Mt. Whitney—I got online and looked for someone to call. It was the week after Christmas 2001, and at that time an organization run by Robert Bigelow took reports of "black triangles," supposedly under contract with the FAA. Then, as now, the massive low-flying silent ships were regularly spotted by drivers on the open road.

We filled out an online report at the National Institute for Discovery Science website. Once we were back in L.A., a NIDS investigator called, claiming to be a former FBI agent. And that's what he sounded like, if you'd ever seen "The X-Files."

The National Institute for Discovery Science, or NIDS, spent a lot of time and money collecting reports of "Big Black Deltas." In 2004, it published its inconclusive findings, which made it to Space.com and MSNBC:

A key NIDS conclusion is that the actions of these triangular craft do not conform to previous patterns of covert deployment of unacknowledged aircraft. Furthermore, "neither the agenda nor the origin of the Flying Triangles are currently known." The years 1990-2004 have seen an intense wave of Flying Triangle aircraft, the study observes. Sifting through reports by hundreds of eyewitnesses, the NIDS assessment states that the behavior of the vehicles "does not appear consistent with the covert deployment of an advanced DoD [U.S. Department of the Defense] aircraft."

Rather, it is consistent with (a) the routine and open deployment of an unacknowledged advanced Defense Department aircraft or (b) the routine and open deployment of an aircraft owned and operated by personnel outside the Defense Department, suggests the NIDS study.

"The implications of the latter possibility are disturbing, especially during the post-9/11 era when the United States airspace is extremely heavily guarded and monitored," the NIDS study explains. "In support of option (a), there is much greater need for surveillance in the United States in the post-9/11 era, and it is certainly conceivable that deployment of low-altitude surveillance platforms is routine and open."

[...] In wrapping up its look at the burgeoning number of Flying Triangle sightings in the United States, NIDS also took into account the work of writers and researchers delving into the topic both in the United States and abroad. Those analyses fall into two camps: One says the Triangles are human-made, while the other says they are not.

Robert Bigelow then shut down his Las Vegas-based Institute For Discovery Science and announced a new company, Bigelow Aerospace. An earlier NIDS study suggested that the triangles were "lighter-than-air, blimp-style craft of the U.S. military’s making" powered by new "electrokinetic/field drives, or airborne nuclear power units." The silent deltas reported around America in the 1990s and early 2000s may well have been prototypes of the massive airships that have just gone into official production in Southern California. Or maybe these monster blimps that will carry tanks and helicopters to Afghanistan are something altogether different—the black triangles have been seen worldwide for half a century now, with some sightings dating to World War II.

The idea of NIDS fascinated me, both then and now. This was an actual paranormal investigations organization, and the more I looked into it, the more fascinating it became. Bigelow, who made a fortune from the extended-stay motel chain Budget Suites of America, had for years been pouring money into paranormal studies at the University of Nevada at Las Vegas. The physics lab at UNLV is named for Bigelow, who also gave $3.7 million to "for the creation and continuation of a program that would attract to the university renowned experts on aspects of human consciousness." A parapsychologist named Charles Tart was the Bigelow Chair of the program, which dealt with "altered states of consciousness, near-death experiences and extrasensory perception."

NIDS assembled a team that would go into the field, investigating weird places and strange events. It even purchased a Utah ranch with a history of UFO sightings and "skinwalkers," a kind of ancient monster which apparently travels through dimensional portals on the property. These things would routinely turn into werewolves and terrorize the ranch's caretakers and animals. The house itself was a paranoid nightmare, with a long hallway lined with closets that locked from the inside.

The top man at NIDS is a familiar name to anyone who ever waded into these esoteric topics: Retired U.S. Army Col. John B. Alexander, the real-life psychic Jedi warrior in Jon Ronson's book The Men Who Stare At Goats. Alexander is called "Col. Harold E. Phillips" in longtime Vanity Fair reporter Howard Blum's book about Reagan-era UFO hunting by the Pentagon, Out There The Government's Secret Quest for Extraterrestrials. The rest of the NIDS crew had similarly spooky backgrounds.

What did Bigelow find out during his years as the benefactor of a well-funded Scooby Gang of paranormal researchers from the Pentagon? Maybe nothing—the mysteries of consciousness and reports of the bizarre have baffled even the most dedicated minds. Maybe thinking about extended-stay motels and reports of space-worthy stealth blimps just gave him a good idea for a cheap space station. In any case, if you have enough money, you can book an extended stay in one of Bigelow's planned private orbital motels right now: "$26.25 million for a 60-day stay, including the ride to orbit atop a Falcon 9 rocket built by Space Exploration Technologies, or SpaceX," according to The New York Times, which will always write about travel for the rich but very rarely about rich people investigating werewolves.

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Quelle:The AWL

 


3433 Views

Freitag, 18. Januar 2013 - 19:03 Uhr

Astronomie - Sieht so ein schwarzes Loch aus?

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This crescent-shape image is the best fit to observations of Sgr A*, the supermassive black hole at the center of our galaxy, according to a January 2013 study.
CREDIT: Kamruddin/Dexter

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A giant black hole is thought to lurk at the center of the Milky Way, but it has never been directly seen. Now astronomers have predicted what the first pictures of this black hole will look like when taken with technology soon to be available.

In particular, researchers have found that pictures of a black hole

―or, more precisely, the boundaries around them ― will take a crescent form, rather than the blobby shape that is often predicted.

By modeling what these pictures will look like, scientists say they are preparing to interpret the photos that will become available from telescopes currently under construction.


3184 Views

Freitag, 18. Januar 2013 - 12:00 Uhr

Raumfahrt - Saturn-Monde im Focus von Cassini

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This set of images from the radar instrument on NASA's Cassini spacecraft shows a relatively "fresh" crater called Sinlap (left) and an extremely degraded crater called Soi (right). Sinlap has a depth-to-diameter ratio close to what we see on Jupiter's moon Ganymede. Soi has a shallow depth compared to similar craters on Ganymede. These craters are both about 50 miles (80 kilometers) in diameter. Image credit: NASA/JPL-Caltech/ASI/GSFC

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Titan's siblings must be jealous. While most of Saturn's moons display their ancient faces pockmarked by thousands of craters, Titan - Saturn's largest moon - may look much younger than it really is because its craters are getting erased. Dunes of exotic, hydrocarbon sand are slowly but steadily filling in its craters, according to new research using observations from NASA's Cassini spacecraft. 
"Most of the Saturnian satellites - Titan's siblings - have thousands and thousands of craters on their surface. So far on Titan, of the 50 percent of the surface that we've seen in high resolution, we've only found about 60 craters," said Catherine Neish, a Cassini radar team associate based at NASA's Goddard Space Flight Center, Greenbelt, Md. "It's possible that there are many more craters on Titan, but they are not visible from space because they are so eroded. We typically estimate the age of a planet's surface by counting the number of craters on it (more craters means an older surface). But if processes like stream erosion or drifting sand dunes are filling them in, it's possible that the surface is much older that it appears. 
"This research is the first quantitative estimate of how much the weather on Titan has modified its surface," adds Neish. 
Titan is the only moon in the solar system with a thick atmosphere, and the only world besides Earth known to have lakes and seas on its surface. However, Titan has a frigid surface temperature of around minus 290 degrees Fahrenheit (94 kelvins). The rain that falls from Titan's skies is not water, but contains liquid methane and ethane, compounds that are gases at Earth's temperatures. 
Neish and her team compared craters on Titan to craters on Jupiter's moon Ganymede. Ganymede is a giant moon with a water ice crust, similar to Titan, so craters on the two moons should have similar shapes. However, Ganymede has almost no atmosphere and thus no wind or rain to erode its surface. 
"We found that craters on Titan were on average hundreds of yards [meters] shallower than similarly sized craters on Ganymede, suggesting that some process on Titan is filling its craters," says Neish, who is lead author of a paper about this research published online in the journal Icarus on Dec. 3, 2012. 
The team used the average depth-versus-diameter trend for craters on Ganymede derived from stereo images from NASA's Galileo spacecraft. The same trend for craters on Titan was calculated using estimates of the crater depth from images made by Cassini's radar instrument. 
Titan's atmosphere is mostly nitrogen with a trace of methane and other, more complex molecules made of hydrogen and carbon (hydrocarbons). The source of Titan's methane remains a mystery because methane in the atmosphere is broken down over relatively short time scales by sunlight. Fragments of methane molecules then recombine into more complex hydrocarbons in the upper atmosphere, forming a thick, orange smog that hides the surface from view. Some of the larger particles eventually rain out onto the surface, where they appear to get bound together to form the sand. 
"Since the sand appears to be produced from the atmospheric methane, Titan must have had methane in its atmosphere for at least several hundred million years in order to fill craters to the levels we are seeing," says Neish. However, researchers estimate Titan's current supply of methane should be broken down by sunlight within tens of millions of years, so Titan either had a lot more methane in the past, or it is being replenished somehow. 
Team members say it's possible that other processes could be filling the craters on Titan: erosion from the flow of liquid methane and ethane, for example. However, this type of weathering tends to fill a crater quickly at first, then more slowly as the crater rim gets worn down and less steep. If liquid erosion were primarily responsible for the infill, then the team would expect to see a lot of partially filled craters on Titan. "However, this is not the case," says Neish. "Instead we see craters at all stages; some just beginning to be filled in, some halfway, and some that are almost completely full. This suggests a process like windblown sand, which fills craters and other features at a steady rate." 
Solid materials under stress flow very slowly over time. This is called viscous flow, and it is like what happens when someone takes a scoop out of a fresh tub of whipped cream -- the material slowly flows in to fill the hole and flatten the surface. Craters on icy satellites tend to get shallower over time as the ice flows viscously, so it's possible that some of the shallow craters on Titan are simply much older or experienced a higher heat flow than the similarly sized, fresh craters on Ganymede studied in this work. 
However, Titan's crust is mostly water ice, and at the extremely low temperatures on Titan, ice shouldn't flow enough to account for such a large difference in depth compared to the Ganymede craters, according to the team. Also, just like stream erosion, deformation from viscous flow tends to happen rapidly at first, then more slowly as the material adjusts, so one would expect to see a lot of partially filled craters on Titan if its surface were deforming easily through viscous flow. 
As Cassini flies past Titan on its multi-year tour of Saturn and its moons, its radar instrument gradually builds up a map of the surface. To date, the instrument has provided data in strips covering approximately 50 percent of Titan's surface. The craters measured by the team are all within about 30 degrees of the equator, a relatively dry region on Titan. 
"However, the presence of liquids on the surface and in the near subsurface can also cause extensive modification to crater shape, as is observed on Earth," says Neish. "In the case of Titan, liquids consist of hydrocarbons, either as wet sediments (such as those observed at the Huygens landing site) or shallow marine environments (such as the lakes observed at the north and south poles). Craters formed in similar environments on Earth lack any significant surface topography, including the absence of a raised rim, as wet sediments slump into the crater. It is possible that the lack of topography associated with marine-target impacts may help to explain the relative scarcity of impact craters observed near the poles of Titan. If Titan's polar regions are saturated by liquid hydrocarbons, craters formed in those regions may lack any recognizable topographic expression." 
The team thinks these considerations are good areas for more research. Based on the data so far, the difference in depth between craters on Titan and Ganymede is best explained by filling from windblown sand. However, erosion from liquids and viscous flow might contribute to the modification of Titan's craters. 
NASA's Cassini mission, managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the NASA Postdoctoral Program, administered by Oak Ridge Associated Universities, funded the research. 
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries.
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Quelle: NASA

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Freitag, 18. Januar 2013 - 11:45 Uhr

Raumfahrt - NASA beamt Mona Lisa zu Lunar Reconnaissance Orbiter auf dem Mond

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As part of the first demonstration of laser communication with a satellite at the moon, scientists with NASA's Lunar Reconnaissance Orbiter (LRO) beamed an image of the Mona Lisa to the spacecraft from Earth.
The iconic image traveled nearly 240,000 miles in digital form from the Next Generation Satellite Laser Ranging (NGSLR) station at NASA's Goddard Space Flight Center in Greenbelt, Md., to the Lunar Orbiter Laser Altimeter (LOLA) instrument on the spacecraft. By transmitting the image piggyback on laser pulses that are routinely sent to track LOLA's position, the team achieved simultaneous laser communication and tracking.
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"This is the first time anyone has achieved one-way laser communication at planetary distances," says LOLA's principal investigator, David Smith of the Massachusetts Institute of Technology. "In the near future, this type of simple laser communication might serve as a backup for the radio communication that satellites use. In the more distant future, it may allow communication at higher data rates than present radio links can provide."
Typically, satellites that go beyond Earth orbit use radio waves for tracking and communication. LRO is the only satellite in orbit around a body other than Earth to be tracked by laser as well.
"Because LRO is already set up to receive laser signals through the LOLA instrument, we had a unique opportunity to demonstrate one-way laser communication with a distant satellite," says Xiaoli Sun, a LOLA scientist at NASA Goddard and lead author of the Optics Express paper, posted online today, that describes the work.
Precise timing was the key to transmitting the image. Sun and colleagues divided the Mona Lisa image into an array of 152 pixels by 200 pixels. Every pixel was converted into a shade of gray, represented by a number between zero and 4,095. Each pixel was transmitted by a laser pulse, with the pulse being fired in one of 4,096 possible time slots during a brief time window allotted for laser tracking. The complete image was transmitted at a data rate of about 300 bits per second. 
The laser pulses were received by LRO's LOLA instrument, which reconstructed the image based on the arrival times of the laser pulses from Earth. This was accomplished without interfering with LOLA's primary task of mapping the moon's elevation and terrain and NGSLR's primary task of tracking LRO.
The success of the laser transmission was verified by returning the image to Earth using the spacecraft's radio telemetry system.
Turbulence in Earth's atmosphere introduced transmission errors even when the sky was clear. To overcome these effects, Sun and colleagues employed Reed-Solomon coding, which is the same type of error-correction code commonly used in CDs and DVDs. The experiments also provided statistics on the signal fluctuations due to Earth's atmosphere. 
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To clean up transmission errors introduced by Earth's atmosphere (left), Goddard scientists applied Reed-Solomon error correction (right), which is commonly used in CDs and DVDs. Typical errors include missing pixels (white) and false signals (black). The white stripe indicates a brief period when transmission was paused.
Image courtesy: Xiaoli Sun, NASA Goddard
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"This pathfinding achievement sets the stage for the Lunar Laser Communications Demonstration (LLCD), a high data rate laser-communication demonstrations that will be a central feature of NASA's next moon mission, the Lunar Atmosphere and Dust Environment Explorer (LADEE)," says Goddard's Richard Vondrak, the LRO deputy project scientist.
The next step after LLCD is the Laser Communications Relay Demonstration (LCRD), NASA's first long-duration optical communications mission. LCRD will help develop concepts and deliver technologies applicable to near-Earth and deep-space communication. 
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Laser light made records obsolete. NASA is on the verge of doing the same thing with space based communications. Before the end of the decade, the Laser Communication Relay Demonstration (LCRD) mission will revolutionize the way we move tons of data from orbit to ground and all around the solar system.
Credit: NASA's Goddard Space Flight Center
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NASA Goddard developed and manages the LRO mission and the LOLA instrument. The LRO mission is funded by NASA's Planetary Science Division in the Science Mission Directorate at NASA Headquarters in Washington. NGSLR is funded by the Earth Science Division at NASA Headquarters. LLCD is funded through a partnership with NASA's Space Communications and Navigation (SCaN) Program, and Science Mission Directorate. LCRD is funded through a partnership with SCaN and NASA's Office of the Chief Technologist.
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Quelle: NASA

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