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Old 06-05-2012, 10:36 AM   #106
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The Planetary Society Blog: Dawn Journal: Riding gravitational currents to HAMO2
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Old 06-06-2012, 08:22 PM   #107
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NASA / NASA JPL:
Dawn Mission Video Shows Vesta's Coat of Many Colors

June 06, 2012

PASADENA, Calif. - A new video from NASA's Dawn mission reveals the dappled, variegated surface of the giant asteroid Vesta. The animation drapes high-resolution false color images over a 3-D model of the Vesta terrain constructed from Dawn's observations. This visualization enables a detailed view of the variation in the material properties of Vesta in the context of its topography.


The video is available online at: http://www.jpl.nasa.gov/video/index.cfm?id=1085.

The colors were chosen to highlight differences in surface composition that are too subtle for the human eye to see. Scientists are still analyzing what some of the colors mean for the composition of the surface. But it is clear that the orange material thrown out from some impact craters is different from the surrounding surface material. Green shows the relative abundance of iron. Parts of the huge impact basin known as Rheasilvia in Vesta's southern hemisphere, for instance, have areas with less iron than nearby areas.

Click on image for details
Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI


Dawn has imaged the majority of the surface of Vesta with the framing camera to provide this 3-D map. While some areas in the north were in shadow at the time the images were obtained by the camera, Dawn expects to improve its coverage of Vesta's northern hemisphere with additional observations. Dawn's viewing geometry also prevented mapping of a portion of the mountain of the south pole.

The spacecraft is currently spiraling up from its lowest-altitude orbit into its final science orbit, where its average altitude will be about 420 miles (680 kilometers). Dawn is scheduled to leave Vesta around Aug. 26.

{...}




Universe Today: Vesta’s Amazing Technicolor Surface

SPACE.com: NASA Video Reveals Huge Asteroid Vesta's Complex Surface

Discovery News: Protoplanet Vesta's Coat of Many Colors: Big Pic
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Old 06-14-2012, 06:52 PM   #108
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NASA / NASA JPL:
Dawn Easing into its Final Science Orbit

June 14, 2012

After successfully completing nearly five months scrutinizing the giant asteroid Vesta at its lowest orbit altitude, NASA's Dawn spacecraft will begin its final major science data-gathering phase at Vesta on June 15, at an average altitude of 420 miles (680 kilometers) above the surface.

Over the past six weeks, Dawn has been gently spiraling up from its lowest orbit - 130 miles, or 210 kilometers, above the surface - to the final planned science orbit, known as high-altitude mapping orbit 2. Observations obtained from this orbit will provide a companion set of data and images to those obtained during the first high-altitude mapping orbit phase, completed in October 2011. A key difference will be that the angle of sunlight hitting Vesta has changed, illuminating more of its northern region. The principal science observations planned in this new orbit will be obtained with the framing camera and the visible and infrared mapping spectrometer.

Following this final science data gathering phase, Dawn will then spend almost five weeks spiraling out from the giant asteroid to the point at which Vesta will lose its gravitational hold on the spacecraft. That departure day is expected to be around Aug. 26. Dawn will turn to view Vesta as it leaves and acquire more data. Then, Dawn will set its sights on the dwarf planet Ceres, and begin a two-and-a-half year journey to investigate the largest body in the main asteroid belt. Dawn will enter orbit around Ceres in 2015.

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Old 07-07-2012, 10:21 AM   #109
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The Planetary Society Blog: Dawn journal: seeing Vesta in a new light
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Old 07-12-2012, 09:20 AM   #110
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Universe Today: Dawn’s Vestan Endeavour Exceptionally Exciting near End of Year Long Super Science Survey


Location of Dawn in 23 minutes from this post's creation time.
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Old 08-13-2012, 08:13 PM   #111
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The Planetary Society Blog: Pretty picture: Vesta's crater Aelia in high resolution

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Old 08-14-2012, 10:22 AM   #112
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NASA / NASA JPL:
Dawn Engineers Assess Reaction Wheel

August 13, 2012

Dawn Mission Status Report

PASADENA, Calif. -- Engineers working on NASA's Dawn spacecraft are assessing the status of a reaction wheel -- part of a system that helps the spacecraft point precisely -- after onboard software powered it off on Aug. 8. Dawn's mission is to study the geology and geochemistry of the giant asteroid Vesta and dwarf planet Ceres, the two most massive objects in the main asteroid belt. Dawn is now using its thrusters to point at Earth for communications. The rest of the spacecraft is otherwise healthy.

During a planned communications pass on Aug. 9, the team learned that the reaction wheel had been powered off. Telemetry data from the spacecraft suggest the wheel developed excessive friction, similar to the experience with another Dawn reaction wheel in June 2010. The Dawn team demonstrated during the cruise to Vesta in 2011 that, if necessary, they could complete the cruise to Ceres without the use of reaction wheels.

The spacecraft has been orbiting Vesta since July 15, 2011. Dawn concluded its primary science observations of Vesta on July 25, 2012, and has been spiraling slowly away from the giant asteroid using its ion propulsion system. Ion thrusting was halted to accommodate the reaction wheel investigation, which may briefly delay the escape from Vesta.

"The Vesta mission has been spectacularly successful, and we are looking forward to the exciting Ceres mission ahead of us," said Robert Mase, Dawn project manager, of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

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Old 08-17-2012, 09:41 AM   #113
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Aviation Week: NASA’s Dawn Mission Addresses Second Reaction Wheel Loss:
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HOUSTON — The Dawn mission team at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., have slowed the probe’s scheduled Aug. 25 gravitational escape from Vesta until early September while controllers checked out high friction readings from a second spacecraft reaction wheel.

The condition is not expected to affect the second leg of its eight-year main belt asteroid mission to Ceres, or data collection at the dwarf planet.

The difficulty, which triggered a software shutdown of the spacecraft pointing device on Aug. 8, should not interfere with Dawn’s scheduled arrival at Ceres in February 2015, according to Marc Rayman, NASA’s Dawn chief engineer and mission director.

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The spacecraft will slip from Dawn’s gravitational clutch on Sept. 5, 11 days later than originally scheduled, Rayman told Aviation Week Aug. 15 via e-mail.

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Old 08-17-2012, 10:03 AM   #114
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They can't know for sure that this won't effect the mission.
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Old 08-17-2012, 10:26 AM   #115
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Why not? They know the RCS prop levels, they already know the manevuers they want to perform and they know what they can cut/change to get the best out of the probe with the loss of the reaction wheels.
Yes, it's a bump in the road but it's not a major issue.
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Old 08-17-2012, 10:26 AM   #116
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Quote:
The spacecraft will slip from Dawn’s gravitational clutch
... from Vesta's?
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Old 08-17-2012, 10:36 AM   #117
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Quote:
Originally Posted by SiberianTiger View Post
 ... from Vesta's?
There's a section you can leave a comment on the article.

Anyway, I'll update the quote, if Aviation Week does it too.
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Old 08-30-2012, 03:57 PM   #118
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DLR: Parting ways with Vesta
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Old 08-30-2012, 06:40 PM   #119
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NASA / NASA JPL:
NASA's Dawn Prepares for Trek Toward Dwarf Planet

August 30, 2012

PASADENA, Calif. - NASA's Dawn spacecraft is on track to become the first probe to orbit and study two distant solar system destinations, to help scientists answer questions about the formation of our solar system. The spacecraft is scheduled to leave the giant asteroid Vesta on Sept. 4 PDT (Sept. 5 EDT) to start its two-and-a-half-year journey to the dwarf planet Ceres.

Dawn began its 3-billion-mile (5-billion kilometer) odyssey to explore the two most massive objects in the main asteroid belt in 2007. Dawn arrived at Vesta in July 2011 and will reach Ceres in early 2015. Dawn's targets represent two icons of the asteroid belt that have been witness to much of our solar system's history.

To make its escape from Vesta, the spacecraft will spiral away as gently as it arrived, using a special, hyper-efficient system called ion propulsion. Dawn's ion propulsion system uses electricity to ionize xenon to generate thrust. The 12-inch-wide ion thrusters provide less power than conventional engines, but can maintain thrust for months at a time.

"Thrust is engaged, and we are now climbing away from Vesta atop a blue-green pillar of xenon ions," said Marc Rayman, Dawn's chief engineer and mission director, at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are feeling somewhat wistful about concluding a fantastically productive and exciting exploration of Vesta, but now have our sights set on dwarf planet Ceres.

Dawn's orbit provided close-up views of Vesta, revealing unprecedented detail about the giant asteroid. The mission revealed that Vesta completely melted in the past, forming a layered body with an iron core. The spacecraft also revealed the scarring from titanic collisions Vesta suffered in its southern hemisphere, surviving not one but two colossal impacts in the last two billion years. Without Dawn, scientists would not have known about the dramatic troughs sculpted around Vesta, which are ripples from the two south polar impacts.

"We went to Vesta to fill in the blanks of our knowledge about the early history of our solar system," said Christopher Russell, Dawn's principal investigator, based at the University of California Los Angeles (UCLA). "Dawn has filled in those pages, and more, revealing to us how special Vesta is as a survivor from the earliest days of the solar system. We can now say with certainty that Vesta resembles a small planet more closely than a typical asteroid."

{...}




SPACE.com: Dawn Spacecraft Leaving Huge Asteroid Vesta Next Week
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