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Forum:Satellites - Robotic Probes
Topic:NASA's Dawn mission to asteroids Vesta and Ceres
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In addition to the framing camera, Dawn's instruments include the gamma ray and neutron detector and the visible and infrared mapping spectrometer. The gamma ray and neutron detector uses 21 sensors with a very wide field of view to measure the energy of subatomic particles emitted by the elements in the upper yard (meter) of the asteroid's surface. The visible and infrared mapping spectrometer will measure the surface mineralogy of both Vesta and Dawn's next target, the dwarf planet Ceres. The spectrometer is a modification of a similar one flying on the European Space Agency's Rosetta and Venus Express missions.

Dawn also will make another set of scientific measurements at Vesta and Ceres using the spacecraft's radio transmitter in tandem with sensitive antennas on Earth. Scientists will monitor signals from Dawn and later Ceres to detect subtle variations in the objects' gravity fields. These variations will provide clues about the interior structure of these bodies by studying the mass distributed in each gravity field.

"The new observations of Vesta are an inspirational reminder of the wonders unveiled through ongoing exploration of our solar system," said Jim Green, planetary division director at NASA Headquarters in Washington.

Dawn launched in September 2007. Following a year at Vesta, the spacecraft will depart in July 2012 for Ceres, where it will arrive in 2015. Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. 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.

Robert PearlmanNASA release
NASA's Asteroid Photographer Beams Back Science Data

NASA's Dawn spacecraft has completed a graceful spiral into the first of four planned science orbits during the spacecraft's yearlong visit to Vesta. The spacecraft started taking detailed observations on Aug. 11 at 9:13 a.m. PDT (12:13 a.m. EDT), which marks the official start of the first science-collecting orbit phase at Vesta, also known as the survey orbit.


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

Above: This anaglyph image of Vesta's equator was put together from two clear filter images, taken on July 24, 2011 by the framing camera instrument aboard NASA's Dawn spacecraft.

Survey orbit is the initial and highest orbit, at roughly 1700 miles (2700 kilometers) above the surface, which will provide an overview or "big picture" perspective of the giant asteroid.

The primary objective of survey orbit is to image the surface with near-global coverage in visible and infrared wavelengths with the mapping spectrometer, also known as VIR. Dawn also will be using its framing camera to collect image mosaics that complement the VIR spectral data to produce geologic and compositional maps of Vesta's surface. Ultrasensitive measurements of the spacecraft's motion using radio signals will allow improved understanding of the giant asteroid's gravity field. Dawn's gamma ray and neutron detector will continue to collect background data.

The survey phase is planned to last 20 days. Each orbit takes almost three days, which will provide the spacecraft seven trips around Vesta. After survey orbit, Dawn will resume thrusting, taking about a month to spiral down gently to its next science orbit for an even closer view. That orbit, known as High Altitude Mapping Orbit, or HAMO, begins in late September. Dawn will spend about a month in HAMO, circling around Vesta in half a day, rather than three. Dawn will orbit more than 60 times during HAMO, allowing the camera to fully map the illuminated portion of Vesta at even higher resolution, and enable the science team to generate stereo images.

SpaceAholicNASA release
Dawn Gets Extra Time to Explore Vesta

NASA's Dawn mission has received official confirmation that 40 extra days have been added to its exploration of the giant asteroid Vesta, the second most massive object in the main asteroid belt. The mission extension allows Dawn to continue its scientific observations at Vesta until Aug. 26, while still arriving at the dwarf planet Ceres at the same originally scheduled target date in February 2015.

"We are leveraging our smooth and successful operations at Vesta to provide for even more scientific discoveries for NASA and the world." said Robert Mase, Dawn project manager based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This extra time will allow us to extend our scientific investigation and learn more about this mysterious world."

The extension will not require any new funding, and will draw on financial reserves that have been carefully managed by the Dawn project. The flexibility provided by the spacecraft's use of efficient ion propulsion system allows it to maintain its originally planned Ceres arrival.

The extension allows for extra observations at Dawn's current low-altitude mapping orbit (average altitude 130 miles or 210 kilometers), which will now last until May 1. The additional time enables the gamma ray and neutron detector to build the best possible maps of the elemental composition of Vesta's surface and improve data for the gravity experiment, the two primary scientific investigations at the low-altitude orbit. The spacecraft's camera and spectrometer are also obtaining additional high-resolution images.

Additional time will also be spent in the planned second high-altitude mapping orbit later this summer. When Dawn arrived at Vesta in July 2011, much of the northern hemisphere was in shadow. But with the passage of time, more of that area will bask in sunshine.

"Dawn has beamed back to us such dazzling Vestan vistas that we are happy to stay a little longer and learn more about this special world," said Christopher Russell, Dawn's principal investigator at UCLA. "While we have this one-of-a-kind opportunity to orbit Vesta, we want to make the best and most complete datasets that we can."

Robert PearlmanNASA release
NASA Dawn Mission Reveals Secrets of Large Asteroid

NASA's Dawn spacecraft has provided researchers with the first orbital analysis of the giant asteroid Vesta, yielding new insights into its creation and kinship with terrestrial planets and Earth's moon.

Vesta now has been revealed as a special fossil of the early solar system with a more varied, diverse surface than originally thought. Scientists have confirmed a variety of ways in which Vesta more closely resembles a small planet or Earth's moon than another asteroid. Results appear in today's edition of the journal Science.

"Dawn's visit to Vesta has confirmed our broad theories of this giant asteroid's history, while helping to fill in details it would have been impossible to know from afar," said Carol Raymond, deputy principal investigator at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Dawn's residence at Vesta of nearly a year has made the asteroid's planet-like qualities obvious and shown us our connection to that bright orb in our night sky."

Scientists now see Vesta as a layered, planetary building block with an iron core – the only one known to survive the earliest days of the solar system. The asteroid's geologic complexity can be attributed to a process that separated the asteroid into a crust, mantle and iron core with a radius of approximately 68 miles (110 kilometers) about 4.56 billion years ago. The terrestrial planets and Earth's moon formed in a similar way.

Dawn observed a pattern of minerals exposed by deep gashes created by space rock impacts, which may support the idea the asteroid once had a subsurface magma ocean. A magma ocean occurs when a body undergoes almost complete melting, leading to layered building blocks that can form planets. Other bodies with magma oceans ended up becoming parts of Earth and other planets.

Data also confirm a distinct group of meteorites found on Earth did, as theorized, originate from Vesta. The signatures of pyroxene, an iron- and magnesium-rich mineral, in those meteorites match those of rocks on Vesta's surface. These objects account for about 6 percent of all meteorites seen falling on Earth.

This makes the asteroid one of the largest single sources for Earth's meteorites. The finding also marks the first time a spacecraft has been able to visit the source of samples after they were identified on Earth.

Scientists now know Vesta's topography is quite steep and varied. Some craters on Vesta formed on very steep slopes and have nearly vertical sides, with landslides occurring more frequently than expected.

Another unexpected finding was that the asteroid's central peak in the Rheasilvia basin in the southern hemisphere is much higher and wider, relative to its crater size, than the central peaks of craters on bodies like our moon. Vesta also bears similarities to other low-gravity worlds like Saturn's small icy moons, and its surface has light and dark markings that don't match the predictable patterns on Earth's moon.

"We know a lot about the moon and we're only coming up to speed now on Vesta," said Vishnu Reddy, a framing camera team member at the Max Planck Institute for Solar System Research in Germany and the University of North Dakota in Grand Forks. "Comparing the two gives us two storylines for how these fraternal twins evolved in the early solar system."

Dawn has revealed details of ongoing collisions that battered Vesta throughout its history. Dawn scientists now can date the two giant impacts that pounded Vesta's southern hemisphere and created the basin Veneneia approximately 2 billion years ago and the Rheasilvia basin about 1 billion years ago. Rheasilvia is the largest impact basin on Vesta.

"The large impact basins on the moon are all quite old," said David O'Brien, a Dawn participating scientist from the Planetary Science Institute in Tucson, Ariz. "The fact that the largest impact on Vesta is so young was surprising."

Launched in 2007, Dawn began exploring Vesta in mid-2011. The spacecraft will depart Vesta on August 26 for its next study target, the dwarf planet Ceres, in 2015.

Robert PearlmanNASA release
Dawn departs the giant asteroid Vesta

Mission controllers received confirmation today (Sept. 5) that NASA's Dawn spacecraft has escaped from the gentle gravitational grip of the giant asteroid Vesta. Dawn is now officially on its way to its second destination, the dwarf planet Ceres.

Dawn departed from Vesta at about 11:26 p.m. PDT on Sept. 4 (2:26 a.m. EDT on Sept. 5). Communications from the spacecraft via NASA's Deep Space Network confirmed the departure and that the spacecraft is now traveling toward Ceres.

"As we respectfully say goodbye to Vesta and reflect on the amazing discoveries over the past year, we eagerly look forward to the next phase of our adventure at Ceres, where even more exciting discoveries await,” said Robert Mase, Dawn project manager, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Launched on Sept. 27, 2007, Dawn slipped into orbit around Vesta on July 15, 2011 PDT (July 16 EDT). Over the past year, Dawn has comprehensively mapped this previously uncharted world, revealing an exotic and diverse planetary building block. The findings are helping scientists unlock some of the secrets of how the solar system, including our own Earth, was formed.

Dawn spiraled away from Vesta as gently as it arrived. It is expected to pull into its next port of call, Ceres, in early 2015.

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