Raumfahrt+Astronomie-Blog von CENAP - Blog: Raumfahrt - NASA-Raumsonde Dawn auf Kurs zu Zwergplaneten Ceres

Dienstag, 17. Februar 2015 - 19:15

Raumfahrt - NASA-Raumsonde Dawn auf Kurs zu Zwergplaneten Ceres - Update-1

4.12.2013

This artist's concept shows NASA's Dawn spacecraft heading toward the dwarf planet Ceres. Dawn spent nearly 14 months orbiting Vesta, the second most massive object in the main asteroid belt between Mars and Jupiter, from 2011 to 2012.

Image Credit: NASA/JPL-Caltech

It's going to be a ball when NASA's Dawn spacecraft finally arrives at the dwarf planet Ceres, and mission managers have now inked in the schedule on Dawn's dance card.

Dawn has been cruising toward Ceres, the largest object in the main asteroid belt between Mars and Jupiter, since September 2012. That's when it departed from its first dance partner, Vesta.

Ceres presents an icy -- possibly watery -- counterpoint to the dry Vesta, where Dawn spent almost 14 months. Vesta and Ceres are two of the largest surviving protoplanets -- bodies that almost became planets -- and will give scientists clues about the planet-forming conditions at the dawn of our solar system.

When Dawn enters orbit around Ceres, it will be the first spacecraft to see a dwarf planet up-close and the first spacecraft to orbit two solar system destinations beyond Earth.

"Our flight plan around Ceres will be choreographed to be very similar to the strategy that we successfully used around Vesta," said Bob Mase, Dawn's project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This approach will build on that and enable scientists to make direct comparisons between these two giants of the asteroid belt."

As a prelude, the team will begin approach operations in late January 2015. The next month, Ceres will be big enough in Dawn's view to be imaged and used for navigation purposes. Dawn will arrive at Ceres -- or, more accurately, it will be captured by Ceres' gravity -- in late March or the beginning of April 2015.

Dawn will make its first full characterization of Ceres later in April, at an altitude of about 8,400 miles (13,500 kilometers) above the icy surface. Then, it will spiral down to an altitude of about 2,750 miles (4,430 kilometers), and obtain more science data in its survey science orbit. This phase will last for 22 days, and is designed to obtain a global view of Ceres with Dawn's framing camera, and global maps with the visible and infrared mapping spectrometer (VIR).

Dawn will then continue to spiral its way down to an altitude of about 920 miles (1,480 kilometers), and in August 2015 will begin a two-month phase known as the high-altitude mapping orbit. During this phase, the spacecraft will continue to acquire near-global maps with the VIR and framing camera at higher resolution than in the survey phase. The spacecraft will also image in “stereo” to resolve the surface in 3-D.

Then, after spiraling down for two months, Dawn will begin its closest orbit around Ceres in late November, at a distance of about 233 miles (375 kilometers). The dance at low-altitude mapping orbit will be a long waltz -- three months -- and is specifically designed to acquire data with Dawn's gamma ray and neutron detector (GRaND) and gravity investigation. GRaND will reveal the signatures of the elements on and near the surface. The gravity experiment will measure the tug of the dwarf planet, as monitored by changes in the high-precision radio link to NASA's Deep Space Network on Earth.

At this low-altitude mapping orbit, Dawn will begin using a method of pointing control that engineers have dubbed "hybrid" mode because it utilizes a combination of reaction wheels and thrusters to point the spacecraft. Up until this final mission phase, Dawn will have used just the small thruster jets, which use a fuel called hydrazine, to control its orientation and pointing. While it is possible to explore Ceres completely using only these jets, mission managers want to conserve precious fuel. At this lowest orbit, using two of the reaction wheels to help with pointing will provide the biggest hydrazine savings. So Dawn will be spinning up two of the gyroscope-like devices to aid the thrusters.

In 2011, the Dawn team prepared the capability to operate in a hybrid mode, but it wasn't needed during the Vesta mission. It was only when a second (of four) reaction wheels developed excessive friction while Dawn was leaving Vesta in 2012 that mission managers decided to use the hybrid mode at Ceres. To prove the technique works, Dawn engineers completed a 27-hour in-flight test of the hybrid mode, ending on Nov. 13. It operated just as expected.

"The successful test of this new way to control our orientation gives us great confidence that we'll have a steady hand at Ceres, which will enable us to get really close to a world that we only know now as a fuzzy dot amidst the stars," said Marc Rayman, Dawn's chief engineer and mission director, based at JPL.

Of course, mission planners have built some extra days into the schedule to account for the small uncertainty in the efficiency of the solar arrays at such a large distance from the sun, where sunlight will be very faint. The solar arrays provide power to the ion propulsion system, in addition to operating power for the spacecraft and instruments. Mission planners also account for potential variations in the gravity field of Ceres, which will not be known precisely until Dawn measures them.

"We are expecting changes when we get to Ceres and, fortunately, we built a very capable spacecraft and developed flexible plans to accommodate the unknowns," said Rayman. "There's great excitement in the unexpected -- that's part of the thrill of exploration."

Starting on Dec. 27, Dawn will be closer to Ceres than it will be to Vesta.

"This transition makes us eager to see what secrets Ceres will reveal to us when we get up close to this ancient, giant, icy body," said Christopher Russell, Dawn's principal investigator, based at UCLA. "While Ceres is a lot bigger than the candidate asteroids that NASA is working on sending humans to, many of these smaller bodies are produced by collisions with larger asteroids such as Ceres and Vesta. It is of much interest to determine the nature of small asteroids produced in collisions with Ceres. These might be quite different from the small rocky asteroids associated with Vesta collisions."

Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team. The California Institute of Technology in Pasadena manages JPL for NASA.

NASA's Dawn spacecraft will be getting an up-close look at the dwarf planet Ceres starting in late March or the beginning of April 2015.

Image Credit: NASA/JPL-Caltech

This graphic shows the planned trek of NASA's Dawn spacecraft from its launch in 2007 through its arrival at the dwarf planet Ceres in early 2015.

Image Credit: NASA/JPL-Caltech

Quelle: NASA

Update: 5.12.2013

Ice on Ceres: 'An Interesting Paradox'

Hubble Space Telescope imaged the asteroid Vesta and the dwarf planet Ceres in 2007, both targets of NASA's Dawn mission. Credit: NASA, ESA, J. Parker (SwRI), L. McFadden (U Maryland)

As NASA's Dawn mission draws closer to its encounter with the dwarf planet Ceres in early 2015, excitement continues to mount for scientists looking forward to what the satellite might observe. Britney Schmidt, of the George Institute of Technology, and Nicole Gugliucci of CosmoQuest, recently hosted a Google+ Hangout titled 'Ceres: Great Expectations' to discuss the upcoming visit to the nearest dwarf planet in the solar system.

Orbiting in the asteroid belt, a little more than three times as far from the Sun as Earth, Ceres is thought to contain an icy mantle that makes up approximately a third of its mass.

"Ceres is very different and very exciting in a lot of ways, totally different from any place that we've been," Schmidt said in the broadcast. "It may be the only primarily icy planet that's out there, at least within reach."

Scratching the surface

Seen through a telescope, Ceres may not appear very exciting. Scientists can use the light reflected off of a body to find out information about its composition.

"Ceres, to the eye, would appear basically pretty black because it's reflecting most colors more or less the same, and reflecting very little light at all," said Andy Rivkin of the Johns Hopkins University Applied Physics Lab.

Even the infrared spectrum, which tends to reveal more information about asteroids such as Vesta — Dawn's first stop — provided very little information about its composition. By utilizing instruments such as the SpeX instrument on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea in Hawaii, scientists were able to catch hints about the dwarf planet's surface.

These observations revealed suggestions of brucite, hydroxyls, and two other features Rivkin says are thought to be due to carbonate minerals.

"[This] makes Ceres one of only a few places where we've found carbonates," Rivkin said. "I think other than Earth and Mars, it's Ceres."

He went on to explain that scientists think water interacting with the minerals formed the brucite and the carbonates.

"For Ceres, we think it is much more consistent with a body that had a lot of water available to interact with."

But water, considered a potential habitat for life to start, can't exist on the surface of the dwarf planet in either solid or liquid form.

"We see no real evidence for ice at the surface of Ceres," Rivkin said, noting that the dwarf planet is too warm. "However, conditions beneath Ceres’ surface should allow buried ice to remain there."

At the same time, observations from the Hubble Space Telescope, as well as theoretical data such as the planet's density, suggest that a large amount of ice exists.

"That creates this interesting paradox. We think there's a lot of ice there, (but) we don't see any at the surface," Rivkin said. "How that's going to translate into what we find when we show up there is still very much an open question."

The layers of Ceres. Scientists think that the dwarf planet contains a rocky inner core surrounded by a thick mantle of water-ice. A thin outer crust covers the surface, with carbonates and other signs that water lay on the planet's skin at some point. Credit: NASA, ESA, and A. Feild (STScI)

Samples sent to Earth

When Dawn arrived at Vesta in mid-2011, scientists already had a head start on what the spacecraft might find. That's because debris from the asteroid had split off and fallen to Earth in the form of meteorites some time ago.

Katie Dyl, of Curtin University in Australia, studies different types of meteorites in an effort to understand what the solar system was like in its earliest stages.

By comparing the composition of the meteorites in laboratories with asteroids in space, scientists are able to locate their sources.

"That's how we learned we have meteorites from Vesta," Dyl said. "People like Andy [Rivkin] measured spectra in space, and people like me took meteorites from the lab and measured their spectra, and they're exactly the same."

But scientists have yet to locate any samples that come from Ceres.

"We can't quite do that with Ceres yet," Dyl said. "That's why it's really interesting to actually go there and get a better look."

Rivkin agreed.

"We're pretty sure we don't have meteorites from Ceres itself, so we're missing that link that we had for Vesta to be able to put it all together," he said. "Dawn is really going into new territory in that sense."

But the spacecraft isn't flying completely blind. Although scientists don't have samples from Ceres, they are using other meteorites to garner insight into what the dwarf planet might contain.

Two competing theories suggest why carbonates lay on the dwarf planet's surface.

The first has to do with the early days of Ceres. Like full-sized planets, Ceres was once a collection of dust and gas orbiting the young Sun in a pancake-like disk. Gravity drew the different components together, and the collection grew into the dwarf planet. (Were it not for the disrupting presence of Jupiter, Ceres might have continued growing into a full-scale planet.)

During its formation, the ice and rock separated, with the rocky crust sinking down through the ice and water. But Ceres lies too close to the Sun for ice to remain at its surface, especially near the equator, though it may continue to exist at the poles.

"That ice would then start to sublime away, and leave whatever was collected in the ice behind," Rivkin said — including the brucites and carbonates now seen on the surface.

The other option involves punctures in Ceres’ rocky crust due to impacts or natural stresses. Icy lava welling up to the surface would drag brucites and carbonates with it. When the ice sublimated, the materials themselves would be left behind.

"Hopefully we'll be able to determine which of those two is going on at Ceres," Rivkin said.

Dyl echoed his enthusiasm at Dawn's impending arrival.

"I can't wait to be astounded, because it's just kind of how every single step we take in space seems to go," she said. "We see something that we couldn't have predicted."

Meteorites from the asteroid Vesta have been found on the Earth's surface, but no such samples have been discovered from Ceres. Credit: University of Tennessee

Quelle: Astrobiology-Magazine

Update: 18.03.2014

Where is Dawn Now?

Ceres rotates about once every nine hours. Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), and L. McFadden (University of Maryland, College Park)

Ceres' round shape indicates that it formed early in the life of the solar system. Ceres lies in the center. Clockwise from the lower left: 2 Pallas, 4 Vesta, 243 Ida, 433 Eros, 25143 Itokawa, 951 Gaspra, 5535 Annefrank. Credit: Composite image of NASA mission and HST images: Schmidt, Britney Elyce, Characterizing the protoplanets : observations and geophysics of Pallas, Vesta and Ceres, PhD Dissertation, University of California at Los Angeles, June 2010.

Quelle: NASA

Update: 21.09.2014

Als Folge von Schubriss , wird Dawn in eine geplante Umlaufbahn um Zwergplaneten Ceres im April 2015, erst einen Monat später eintreffen.

The Dawn spacecraft has resumed normal ion thrusting after the thrusting unexpectedly stopped and the spacecraft entered safe mode on September 11. That anomaly occurred shortly before a planned communication with NASA's Deep Space Network that morning. The spacecraft was not performing any special activities at the time.

Engineers immediately began working to restore the spacecraft to its normal operational state. The team determined the source of the problems, corrected them, and then resumed normal ion thrusting on Monday night, Sept. 15.

"This anomaly presented the team with an intricate and elaborate puzzle to solve," said Robert Mase, Dawn project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

After investigating what caused the spacecraft to enter safe mode, the Dawn team determined that it was likely triggered by the same phenomenon that affected Dawn three years ago on approach to the protoplanet Vesta: An electrical component in the ion propulsion system was disabled by a high-energy particle of radiation.

"We followed the same strategy that we implemented three years ago to recover from a similar radiation strike -- to swap to one of the other ion engines and a different electronic controller so we could resume thrusting quickly," said Dawn Mission Director and Chief Engineer Marc Rayman of JPL. "We have a plan in place to revive this disabled component later this year."

Complicating the issue, the team discovered that the spacecraft had experienced not just one anomaly, but also a second one that affected the ability to point the main antenna at Earth to communicate. Because the spacecraft could not communicate using its main antenna, the team had to utilize the weaker signals of another antenna, slowing their progress. In addition, Dawn is so far from Earth that radio signals take 53 minutes to make the round trip. Although they have not yet specifically pinpointed the cause of this issue, it could also be explained by a high-energy particle corrupting the software running in the main computer. Ultimately the team reset the computer, which restored the pointing performance to normal.

As a result of the change in the thrust plan, Dawn will enter into orbit around dwarf planet Ceres in April 2015, about a month later than previously planned. The plans for exploring Ceres once the spacecraft is in orbit, however, are not affected.

Dawn orbited Vesta, the second most massive object in the main asteroid belt, from July 2011 until September 2012. The spacecraft's ion propulsion system enabled it to spiral away from Vesta and head toward Ceres, the most massive object in that region. Thanks to the power of ion propulsion, Dawn is the only mission ever targeted to orbit two deep-space destinations.

JPL manages the Dawn mission for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. The University of California at Los Angeles (UCLA) is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.

Quelle: NASA

Update: 7.12.2014

Dawn Snaps Its Best-Yet Image of Dwarf Planet Ceres

From about three times the distance from Earth to the moon, NASA's Dawn spacecraft spies its final destination -- the dwarf planet Ceres. This uncropped, unmagnified view of Ceres was taken by Dawn on Dec. 1, 2014.

Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The Dawn spacecraft has delivered a glimpse of Ceres, the largest body in the main asteroid belt, in a new image taken 740,000 miles (1.2 million kilometers) from the dwarf planet. This is Dawn's best image yet of Ceres as the spacecraft makes its way toward this unexplored world.

"Now, finally, we have a spacecraft on the verge of unveiling this mysterious, alien world. Soon it will reveal myriad secrets Ceres has held since the dawn of the solar system," said Marc Rayman, of NASA's Jet Propulsion Laboratory in Pasadena, California, chief engineer and mission director of the Dawn mission.

Dawn will be captured into Ceres' orbit in March, marking the first visit to a dwarf planet by a spacecraft. To date, the best images of Ceres come from the Hubble Space Telescope. In early 2015, however, Dawn will begin delivering images at much higher resolution.

Since launching in 2007, Dawn has already visited Vesta, a giant protoplanet currently located 104 million miles (168 million kilometers) away from Ceres. The distance between Vesta and Ceres is greater than the distance between the Earth and the sun. During its 14 months in orbit around Vesta, the spacecraft delivered unprecedented scientific insights, including images of its cratered surface and important clues about its geological history. Vesta and Ceres are the two most massive bodies in the main asteroid belt.

The nine-pixel-wide image of Ceres released today serves as a final calibration of the science camera that is necessary before Dawn gets to Ceres. The dwarf planet appears approximately as bright as Venus sometimes appears from Earth. Ceres has an average diameter of about 590 miles (950 kilometers).

Dawn begins its approach phase toward Ceres on December 26.

The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington D.C. UCLA is responsible for overall Dawn mission science. The Dawn framing cameras were developed and built under the leadership of the Max Planck Institute for Solar System Research, Gottingen, Germany, with significant contributions by German Aerospace Center (DLR), Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL.

Dawn's Gateway View of Ceres

From about three times the distance from Earth to the moon, NASA's Dawn spacecraft spies its final destination -- the dwarf planet Ceres.

The resolution of this image does not yet exceed the best views of Ceres, which were obtained by the Hubble Space Telescope (see PIA10235). Nonetheless, Ceres' spherical shape is clearly revealed here. Sunlight illuminates the dwarf planet from the right, leaving a sliver of the surface in shadow at left.

A zoomed-in view is provided here, along with the original unmagnified, uncropped view.

The image was taken on Dec. 1, 2014 with the Dawn spacecraft's framing camera, using a clear spectral filter. Dawn was about 740,000 miles (1.2 million kilometers) from Ceres at the time. Ceres is 590 miles (950 kilometers) across and was discovered in 1801.

The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington D.C. UCLA is responsible for overall Dawn mission science. The Dawn framing cameras were developed and built under the leadership of the Max Planck Institute for Solar System Research, Göttingen, Germany, with significant contributions by DLR German Aerospace Center, Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL.

Enhanced Early View of Ceres from Dawn

As the Dawn spacecraft flies through space toward the dwarf planet Ceres, the unexplored world appears to its camera as a bright light in the distance, full of possibility for scientific discovery.

This view was acquired as part of a final calibration of the science camera before Dawn's arrival at Ceres. To accomplish this, the camera needed to take pictures of a target that appears just a few pixels across. On Dec. 1, 2014, Ceres was about nine pixels in diameter, nearly perfect for this calibration. The images provide data on very subtle optical properties of the camera that scientists will use when they analyze and interpret the details of some of the pictures returned from orbit.

Ceres is the bright spot in the center of the image. Because the dwarf planet is much brighter than the stars in the background, the camera team selected a long exposure time to make the stars visible. The long exposure made Ceres appear overexposed, and exaggerated its size; this was corrected by superimposing a shorter exposure of the dwarf planet in the center of the image.

A cropped, magnified view of Ceres appears in the inset image at lower left.

The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington D.C. UCLA is responsible for overall Dawn mission science. The Dawn framing cameras were developed and built under the leadership of the Max Planck Institute for Solar System Research, Göttingen, Germany, with significant contributions by DLR German Aerospace Center, Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL.

Quelle: NASA

Update: 30.12.2014

Dawn Spacecraft Begins Approach to Dwarf Planet Ceres

Dawn has entered its approach phase toward Ceres

The spacecraft will arrive at Ceres on March 6, 2015

NASA's Dawn spacecraft has entered an approach phase in which it will continue to close in on Ceres, a Texas-sized dwarf planet never before visited by a spacecraft. Dawn launched in 2007 and is scheduled to enter Ceres orbit in March 2015.

Dawn recently emerged from solar conjunction, in which the spacecraft is on the opposite side of the sun, limiting communication with antennas on Earth. Now that Dawn can reliably communicate with Earth again, mission controllers have programmed the maneuvers necessary for the next stage of the rendezvous, which they label the Ceres approach phase. Dawn is currently 400,000 miles (640,000 kilometers) from Ceres, approaching it at around 450 miles per hour (725 kilometers per hour).

The spacecraft's arrival at Ceres will mark the first time that a spacecraft has ever orbited two solar system targets. Dawn previously explored the protoplanet Vesta for 14 months, from 2011 to 2012, capturing detailed images and data about that body.

"Ceres is almost a complete mystery to us," said Christopher Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. "Ceres, unlike Vesta, has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised."

The two planetary bodies are thought to be different in a few important ways. Ceres may have formed later than Vesta, and with a cooler interior. Current evidence suggests that Vesta only retained a small amount of water because it formed earlier, when radioactive material was more abundant, which would have produced more heat. Ceres, in contrast, has a thick ice mantle and may even have an ocean beneath its icy crust.

Ceres, with an average diameter of 590 miles (950 kilometers), is also the largest body in the asteroid belt, the strip of solar system real estate between Mars and Jupiter. By comparison, Vesta has an average diameter of 326 miles (525 kilometers), and is the second most massive body in the belt.

The spacecraft uses ion propulsion to traverse space far more efficiently than if it used chemical propulsion. In an ion propulsion engine, an electrical charge is applied to xenon gas, and charged metal grids accelerate the xenon particles out of the thruster. These particles push back on the thruster as they exit, creating a reaction force that propels the spacecraft. Dawn has now completed five years of accumulated thrust time, far more than any other spacecraft.

"Orbiting both Vesta and Ceres would be truly impossible with conventional propulsion. Thanks to ion propulsion, we're about to make history as the first spaceship ever to orbit two unexplored alien worlds," said Marc Rayman, Dawn's chief engineer and mission director, based at NASA's Jet Propulsion Laboratory in Pasadena, California.

The next couple of months promise continually improving views of Ceres, prior to Dawn's arrival. By the end of January, the spacecraft's images and other data will be the best ever taken of the dwarf planet.

The Dawn mission to Vesta and Ceres is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. UCLA is responsible for overall Dawn mission science.

Quelle: NASA

Update: 19.01.2015

Dawn Delivers New Image of Ceres

The Dawn spacecraft observed Ceres for an hour on Jan. 13, 2015, from a distance of 238,000 miles (383,000 kilometers). A little more than half of its surface was observed at a resolution of 27 pixels. This animated GIF shows bright and dark features.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Dawn mission for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. The University of California at Los Angeles (UCLA) is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Virginia, designed and built the spacecraft. UCLA is responsible for overall Dawn mission science. The Dawn framing cameras were developed and built under the leadership of the Max Planck Institute for Solar System Research, Gottingen, Germany, with significant contributions by German Aerospace Center (DLR), Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL. The Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.

This raw image, taken Jan. 13, 2015, shows dwarf planet Ceres as seen from the Dawn spacecraft on its approach. Dawn's framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres.

As NASA's Dawn spacecraft closes in on Ceres, new images show the dwarf planet at 27 pixels across, about three times better than the calibration images taken in early December. These are the first in a series of images that will be taken for navigation purposes during the approach to Ceres.

Over the next several weeks, Dawn will deliver increasingly better and better images of the dwarf planet, leading up to the spacecraft's capture into orbit around Ceres on March 6. The images will continue to improve as the spacecraft spirals closer to the surface during its 16-month study of the dwarf planet.

“We know so much about the solar system and yet so little about dwarf planet Ceres. Now, Dawn is ready to change that,” said Marc Rayman, Dawn’s chief engineer and mission director, based at NASA's Jet Propulsion Laboratory in Pasadena, California.

The best images of Ceres so far were taken by NASA's Hubble Space Telescope in 2003 and 2004. This most recent images from Dawn, taken January 13, 2015, at about 80 percent of Hubble resolution, are not quite as sharp. But Dawn's images will surpass Hubble's resolution at the next imaging opportunity, which will be at the end of January.

“Already, the [latest] images hint at first surface structures such as craters,” said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research, Gottingen, Germany.

Ceres is the largest body in the main asteroid belt, which lies between Mars and Jupiter. It has an average diameter of 590 miles (950 kilometers), and is thought to contain a large amount of ice. Some scientists think it’s possible that the surface conceals an ocean.

Dawn's arrival at Ceres will mark the first time a spacecraft has ever visited a dwarf planet.“The team is very excited to examine the surface of Ceres in never-before-seen detail,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. “We look forward to the surprises this mysterious world may bring.” The spacecraft has already delivered more than 30,000 images and many insights about Vesta, the second most massive body in the asteroid belt. Dawn orbited Vesta, which has an average diameter of 326 miles (525 kilometers), from 2011 to 2012. Thanks to its ion propulsion system, Dawn is the first spacecraft ever targeted to orbit two deep-space destinations. JPL manages the Dawn mission for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. The University of California at Los Angeles (UCLA) is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Virginia, designed and built the spacecraft. UCLA is responsible for overall Dawn mission science. The Dawn framing cameras were developed and built under the leadership of the Max Planck Institute for Solar System Research, Gottingen, Germany, with significant contributions by German Aerospace Center (DLR), Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL. The Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.

In this image, taken January 13, 2015, the Dawn spacecraft's visible and infrared mapping spectrometer (VIR) captures the dwarf planet Ceres from a distance of 238,000 miles (383,000 kilometers) in both visible and infrared light. The infrared image, right, serves as a temperature map of Ceres, where white is warmer and red is colder.

Quelle: NASA

Update: 21.01.2015

Dawn: Unterwegs zur eisigen Ceres

Eine dicke Eiskruste und darunter ein Ozean - das könnte die Planetenforscher des Deutschen Zentrums für Luft- und Raumfahrt erwarten, wenn die amerikanische Dawn-Sonde im März 2015 am Zwergplaneten Ceres ankommt. Bereits jetzt - aus 383 000 Kilometer Entfernung - sind erste Strukturen der Oberfläche zu erkennen: Auf der Aufnahme der deutschen Kamera an Bord vom 13. Januar 2015 sind deutlich hellere und dunklere Bereiche auf dem fast kugelförmigen Zwergplaneten zu erkennen. "Ceres ist immer noch ein unbekannter Himmelskörper, aber diese ersten Bilder lassen erahnen, dass die Oberfläche Strukturen wie Einschlagskrater und Brüche aufweist", sagt Prof. Ralf Jaumann vom Deutschen Zentrum für Luft- und Raumfahrt (DLR), Planetenforscher und Wissenschaftler im Team der Dawn-Mission. Bereits Ende Januar werden die Bilder der Kamera eine Auflösung erreichen, die besser als alle bisher mit dem Weltraumteleskop Hubble angefertigten Aufnahmen ist.

Erster Besuch bei einem Zwergplaneten

Weit hinter der Frostgrenze im Asteroidengürtel, dort, wo die Sonne kaum noch Wirkung zeigt und das Wasser zu Eis wird, liegt das Ziel der Sonde Dawn, das sie im März 2015 erreichen wird. Während sie 2011 mit dem Asteroiden Vesta einen "trockenen", felsigen Asteroiden untersuchte, steht nun das komplette Gegenteil als Untersuchungsobjekt an: Ceres ist ein "nasser" Asteroid, hat vermutlich einen Wasseranteil von 15 bis 25 Prozent und wurde 2006 von der Internationalen Astronomnischen Vereinigung zum Zwergplaneten hochgestuft. Sein Durchmesser von fast 1000 Kilometern und seine runde Form lassen vermuten, dass er es bei der Entstehung unserer Sonnensystems wohl nur knapp nicht zum regulären Planeten geschafft hat - und so bildet er ein Zwischenstadium ab, das für die Planetenforscher beim Blick in die Vergangenheit besonders interessant ist. "Wir untersuchen mit Dawn zum ersten Mal einen Zwergplaneten", betont DLR-Wissenschaftler Prof. Ralf Jaumann.

16 Monate wird Dawn aus unterschiedlichen Höhen auf die Oberfläche der eisigen Ceres blicken und mit der Kamera an Bord Aufnahmen erstellen. Aus diesen Daten wird am DLR-Institut für Planetenforschung dann ein dreidimensionales Höhenmodell berechnet, Ceres kartiert und die Topographie des Himmelskörpers untersucht. Mit der dreidimensionalen Vermessung können beispielsweise bei Kratern Rückschlüsse auf die Wucht des Einschlags gezogen werden. Unter der Eiskruste von Ceres vermuten die Wissenschaftler zudem eine hundert Meter dicke Schicht aus Wasser, in dem es sogar Spuren einfachen Lebens geben könnte. "Die Dawn-Sonde wird in den nächsten Monaten diesen Eiskörper genauer untersuchen und wir werden die eine oder andere wissenschaftliche Überraschung erleben", ist sich Planetenforscher Prof. Ralf Jaumann sicher.

Die Mission

Die Mission DAWN wird vom Jet Propulsion Laboratory (JPL) der amerikanischen Weltraumbehörde NASA geleitet. JPL ist eine Abteilung des California Institute of Technology in Pasadena. Die University of California in Los Angeles ist für den wissenschaftlichen Teil der Mission verantwortlich. Das Kamerasystem an Bord der Raumsonde wurde unter Leitung des Max-Planck-Instituts für Sonnensystemforschung in Göttingen in Zusammenarbeit mit dem Institut für Planetenforschung des Deutschen Zentrums für Luft- und Raumfahrt (DLR) in Berlin und dem Institut für Datentechnik und Kommunikationsnetze in Braunschweig entwickelt und gebaut. Das Kamera-Projekt wird finanziell von der Max-Planck-Gesellschaft, dem DLR und NASA/JPL unterstützt.

Spacecraft Dawn

With its wide solar arrays extended, Dawn is about as long as a tractor-trailer at 65 feet (19.7 meters).

The ion thruster is powered by large solar panels. The power ionizes the fuel (Xenon) and then accelerates it with an electric field between two grids. Electrons are injected into the beam after acceleration to maintain a neutral plasma.

Quelle: DLR

Update: 28.01.2015

NASA’s Dawn Spacecraft Captures Best-Ever View of Dwarf Planet

This animation of the dwarf planet Ceres was made by combining images taken by NASA's Dawn spacecraft on Jan. 25. The spacecraft's framing camera took these images, at a distance of about 147,000 miles (237,000 kilometers) from Ceres, and they represent the highest-resolution views to date of the dwarf planet.

Image Credit: NASA/JPL

NASA’s Dawn spacecraft has returned the sharpest images ever seen of the dwarf planet Ceres. The images were taken 147,000 miles (237,000 kilometers) from Ceres on Jan. 25, and represent a new milestone for a spacecraft that soon will become the first human-made probe to visit a dwarf planet.

"We know so little about our vast solar system, but thanks to economical missions like Dawn, those mysteries are being solved," said Jim Green, Planetary Science Division Director at NASA Headquarters in Washington.

At 43 pixels wide, the new images are more than 30 percent higher in resolution than those taken by NASA's Hubble Space Telescope in 2003 and 2004 at a distance of over 150 million miles. The resolution is higher because Dawn is traveling through the solar system to Ceres, while Hubble remains fixed in Earth orbit. The new Dawn images come on the heels of initial navigation images taken Jan. 13 that reveal a white spot on the dwarf planet and the suggestion of craters. Hubble images also had glimpsed a white spot on the dwarf planet, but its nature is still unknown.

"Ceres is a 'planet' that you've probably never heard of,” said Robert Mase, Dawn project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. “We're excited to learn all about it with Dawn and share our discoveries with the world."

As the spacecraft gets closer to Ceres, its camera will return even better images. On March 6, Dawn will enter into orbit around Ceres to capture detailed images and measure variations in light reflected from Ceres, which should reveal the planet’s surface composition.

"We are already seeing areas and details on Ceres popping out that had not been seen before. For instance, there are several dark features in the southern hemisphere that might be craters within a region that is darker overall," said Carol Raymond, deputy principal investigator of the Dawn mission at JPL. "Data from this mission will revolutionize our understanding of this unique body. Ceres is showing us tantalizing features that are whetting our appetite for the detailed exploration to come."

Ceres, the largest body between Mars and Jupiter in the main asteroid belt, has a diameter of about 590 miles (950 kilometers). Some scientists believe the dwarf planet harbored a subsurface ocean in the past and liquid water may still be lurking under its icy mantle.

Originally described as a planet, Ceres was later categorized as an asteroid, and then reclassified as a dwarf planet in 2006. The mysterious world was discovered in 1801 by astronomer Giuseppe Piazzi, who named the object for the Roman goddess of agriculture, grain crops, fertility and motherly relationships

“You may not realize that the word ‘cereal’ comes from the name Ceres. Perhaps you already connected with the dwarf planet at breakfast today," said JPL's Marc Rayman, Mission Director and Chief Engineer of the Dawn mission.

Powered by a uniquely capable ion propulsion system, Dawn also orbited and explored Vesta, the second most massive body in the asteroid belt. From 2011 to 2012, Dawn returned more than 30,000 images, 18 million light measurements and other scientific data about the impressive large asteroid. Vesta has a diameter of about 326 miles (525 kilometers).

"With the help of Dawn and other missions, we are continually adding to our understanding of how the solar system began and how the planets were formed,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.

Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. of Dulles, Virginia, designed and built the spacecraft. JPL is managed for NASA by the California Institute of Technology in Pasadena.

The framing cameras were provided by the Max Planck Institute for Solar System Research in Gottingen, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research in Berlin, and in coordination with the Institute of Computer and Communication Network Engineering in Braunschweig.

The visible and infrared mapping spectrometer was provided by the Italian Space Agency and the Italian National Institute for Astrophysics, was built by Selex ES, and is managed by Italy’s National Institute for Astrophysics and Planetology in Rome. The gamma ray and neutron detector was built by Los Alamos National Laboratory in New Mexico, and is operated by the Planetary Science Institute of Tucson, Arizona.

Quelle: NASA

Update: 30.01.2015

Dem Zwergplaneten Ceres so nah

Noch nie zuvor konnten Planetenforscher den Zwergplaneten Ceres aus dieser Nähe sehen: In himmlischen Dimensionen lediglich noch 237 000 Kilometer entfernt, nahm die deutsche Kamera an Bord von Raumsonde Dawn den Zwergplaneten am 25. Januar 2015 auf. Stattliche 43 Pixel breit ist der kugelförmige, eisige Asteroid auf der Aufnahme, die erstmals Details zeigt, die selbst auf den bisherigen Aufnahmen des Weltraumteleskops Hubble nicht zu erkennen waren: "Wir sehen große, fast den gesamten Zwergplaneten umspannende Strukturen. Auch wenn man noch nicht genau sagen kann, um was es sich dabei handelt, ist doch klar, dass gewaltige Prozesse die Oberfläche von Ceres verändert haben", sagt Prof. Ralf Jaumann vom Deutschen Zentrum für Luft- und Raumfahrt (DLR), Planetenforscher und Mitglied im Dawn-Team. "Mit jeder neuen Aufnahme werden wir von nun an weitere Hinweise darauf erhalten, was uns bei unserer Ankunft am 6. März dieses Jahres bei Ceres erwartet." Selbst heute noch könnte der größte Himmelskörper zwischen Mars und Jupiter noch einen Ozean aus Wasser unter seiner Eiskruste verbergen.

Reihe von seltsam angeordneten Kratern

Bisher hielt das Weltraumteleskop Hubble den Rekord, wenn es um die beste Sicht auf den Zwergplaneten Ceres ging - es nahm den Himmelskörper zwischen Dezember 2003 und Januar 2004 auf und zeigte damals bereits unterschiedlich helle und dunkle Regionen sowie einen bisher noch nicht erklärten weißen Fleck auf Ceres. Doch nun hat die Kamera an Bord der Dawn-Sonde die Nase vorn: "Unsere Aufnahmen übertreffen die bisherigen Hubble-Bilder in der Auflösung um mehr als 30 Prozent", sagt DLR-Wissenschaftler Jaumann. In der südlichen Hemisphäre sind einige sehr dunkle Merkmale in einer insgesamt dunkleren Region zu sehen. "Zu erkennen ist eine globale Struktur, bei der es sich vermutlich um eine Reihe von großen, seltsam angeordneten Einschlagskratern handelt." Auch ist der bereits bekannte helle Fleck in etwa 90 Grad Entfernung von dieser Struktur zu erkennen.

Mit den Ergebnissen der Dawn-Mission könnte es den Planetenforschern gelingen, mehr über die Geburt der Planeten vor 4,5 Milliarden Jahren zu erfahren. "Asteroiden sind Bausteine eines Planeten, der nie fertiggestellt wurde." In der Nähe des Jupiters sorgten nämlich dessen Gravitationskräfte dafür, dass die einzelnen Fragmente immer wieder auseinbrachen und keine vollständigen Planeten entstehen konnten. Das Ergebnis ist der Asteroidengürtel zwischen Jupiter und Mars - mit seinen größten Körpern Vesta, Pallas und Ceres, drei der besterhaltenen embryonalen Planeten in unserem Sonnensystem.

Eisiges Untersuchungsobjekt Ceres

Über 30 000 Bilder, 18 Millionen spektrale Messungen und weitere wissenschaftliche Daten sind die Ausbeute, die die Dawn-Sonde 2011 bis 2012 von ihrem Besuch an Vesta zur Erde sendete. Der Körper mit einem mittleren Durchmesser von 525 Kilometern versetzte alle in Erstaunen mit zwei gigantischen Einschlagsbecken, tiefen Furchen und einem Berg, der mehr als doppelt so hoch wie der irdische Mount Everest ist. Im September 2012 verabschiedete sich die Sonde von Vesta und reist seitdem mit Ionenantrieb durchs All. Dabei hat sie im Asteroidengürtel bereits die Frostgrenze hinter sich gelassen - ihr nächstes Ziel Ceres wird daher auch ein besonders eisiges Untersuchungsobjekt, bei dem die Kräfte der 415 Millionen Kilometer entfernten Sonne nur wenig spürbar sind.

Wie eine Fliege im Bernstein

Ceres wird der erste Zwergplanet überhaupt sein, den eine Sonde aus dem Orbit untersucht. Mit einem Durchmesser von fast 1000 Kilometern ist der Himmelskörper der Rekordhalter im Asteroidengürtel und wurde 2006 von der Internationalen Astronomischen Vereinigung in die neue Kategorie der Zwergplaneten eingeordnet. Und er könnte unter einer Eiskruste ein Geheimnis verbergen - eine dicke Schicht aus Wasser, vermutet DLR-Planetenforscher Prof. Ralf Jaumann. "Wir sind bisher noch nie um solch einen Himmelskörper geflogen", betont er. "In Ceres ist vermutlich die Anfangsphase der Planetenentstehung konserviert - ähnlich wie uns eine Fliege im Bernstein die Geschichte urzeitlicher Insekten erzählt."

Die Mission

Die Dawn Mission wird vom Jet Propulsion Laboratory (JPL) der amerikanischen Weltraumbehörde NASA geleitet. JPL ist eine Abteilung des California Institute of Technology in Pasadena. Die University of California in Los Angeles ist für den wissenschaftlichen Teil der Mission verantwortlich. Das Kamerasystem an Bord der Raumsonde wurde unter Leitung des Max-Planck-Instituts für Sonnensystemforschung in Göttingen in Zusammenarbeit mit dem Institut für Planetenforschung des Deutschen Zentrums für Luft- und Raumfahrt (DLR) in Berlin und dem Institut für Datentechnik und Kommunikationsnetze in Braunschweig entwickelt und gebaut. Das Kamera-Projekt wird finanziell von der Max-Planck-Gesellschaft, dem DLR und NASA/JPL unterstützt.

Quelle: DLR

Update: 5.02.2015

Dawn Gets Closer Views of Ceres

This animation showcases a series of images NASA's Dawn spacecraft took on approach to Ceres on Feb. 4, 2015 at a distance of about 90,000 miles (145,000 kilometers) from the dwarf planet.

Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

NASA's Dawn spacecraft, on approach to dwarf planet Ceres, has acquired its latest and closest-yet snapshot of this mysterious world.

At a resolution of 8.5 miles (14 kilometers) per pixel, the pictures represent the sharpest images to date of Ceres.

After the spacecraft arrives and enters into orbit around the dwarf planet, it will study the intriguing world in great detail. Ceres, with a diameter of 590 miles (950 kilometers), is the largest object in the main asteroid belt, located between Mars and Jupiter.

Dawn's mission to Vesta and Ceres is managed by the Jet Propulsion Laboratory for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. of Dulles, Virginia, designed and built the spacecraft. JPL is managed for NASA by the California Institute of Technology in Pasadena. The framing cameras were provided by the Max Planck Institute for Solar System Research, Gottingen, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The visible and infrared mapping spectrometer was provided by the Italian Space Agency and the Italian National Institute for Astrophysics, built by Selex ES, and is managed and operated by the Italian Institute for Space Astrophysics and Planetology, Rome. The gamma ray and neutron detector was built by Los Alamos National Laboratory, New Mexico, and is operated by the Planetary Science Institute, Tucson, Arizona.

This image is one several images NASA's Dawn spacecraft took on approach to Ceres on Feb. 4, 2015 at a distance of about 90,000 miles (145,000 kilometers) from the dwarf planet.Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Quelle: NASA

Update: 6.02.2015

Dawn Probe's Views of Ceres Add to Mystery of the White Spots

NASA's Dawn spacecraft is snapping increasingly detailed pictures of the dwarf planet Ceres as it zooms in for next month's rendezvous, but so far the images have only heightened the mystery surrounding bright spots on the surface.

The pictures released Thursday show that Ceres — the largest asteroid as well as the closest and smallest known dwarf planet — is pockmarked by craters. The craters are to be expected: The 590-mile-wide (950-kilometer-wide) mini-world has been pummeled for billions of years by other objects in the asteroid belt. But the white spots? They're a real puzzle.

One spot in particular has shown up prominently in pictures from the Hubble Space Telescope and from Dawn, which was launched back in 2007 to study Ceres and its sister asteroid Vesta. The latest pictures, taken on Wednesday from a distance of about 90,000 miles (145,000 kilometers), appear to show still more bright blips on Ceres. Are they patches of light material or ice at the bottom of craters? Or frost on the top of prominences?

A picture of Ceres from the Dawn spacecraft shows craters with central peaks on the surface. The pictures will become clearer as Dawn comes closer over the next month.

"We are at a phase in the mission where the curtain is slowly being pulled back on the nature of the surface," UCLA planetary scientist Chris Russell, the principal investigator for the $466 million mission, told NBC News in an email. "But the surface is different from that of other planets, and at this stage the increasing resolution presents more mysteries rather than answers them."

Russell said the science team was particularly interested in the big bright spot and the region surrounding it.

"Naively we expect a bright region to be fresh and a dark region to be old. So the surface of Ceres seems to have a number of circular features of varying freshness on a predominantly dark, presumably old surface," Russell wrote. "The one type of feature that clearly came into view this time were examples of central peak craters with overall similarity to large lunar craters."

The mysteries will be cleared up by the time Dawn enters orbit around Ceres in March. OR WILL THEY?

Quelle: NBC-News

Update: 16.02.2015

Dawn Captures Sharper Images of Ceres

Dawn Approaches: Two Faces of Ceres

These two views of Ceres were acquired by NASA's Dawn spacecraft on Feb. 12, 2015, from a distance of about 52,000 miles (83,000 kilometers) as the dwarf planet rotated. The images have been magnified from their original size.

The Dawn spacecraft is due to arrive at Ceres on March 6, 2015.

« Zum vorherigen Eintrag Zum nächsten Eintrag »

5537 Views