NASA's Dawn spacecraft has maneuvered into low orbit around the giant asteroid Vesta. The altitude will average 130 miles. Missions plans call for this low orbit for 10 weeks. A new phase of scientific observations will be taking place to determine the characteristics of the solar system's second largest asteroid. NASA released the following composite of 3 images to illustrate the improvement in resolution and detail that will be seen in the low orbit phase. I added the yellow arrows to highlight the same feature in all three images. The survey orbit image was made soon after the spacecraft reached Vesta in July and started imaging from an average altitude of 1700 miles. The middle high-altitude mapping image viewed the same region at an altitude of 420 miles. The low-altitude mapping image is from Dawn's closest and current orbit of 130 miles.
For the best views of the improved resolution improvements in this and other images, click on the image for the full sized version. In some browsers, the image that opens can be clicked once more to view it at 100% scale. It is a remarkable improvement in quality. |
Below are more images taken at low-altitude revealing close details of Vesta. Two previous diaries about the Dawn mission are available. One covers an
overview of the mission just prior to reaching Vesta in July. The second covers the
science report by Dawn scientists in October.
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Dawn imaged this region Nov. 27 as it was spiraling down from its high altitude to low altitude mapping orbit. Dawn will not orbit closer to Vesta. The framing camera imaged this mid-northern latitudes from an altitude of about 140 miles.
Click on these images for a full scale view.
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This equatorial region shows many buried craters. The region shows evidence of the debris likely ejected by the impact that created the huge Rheasilvia basin in the asteroid's south polar region. Various linear features of different shapes and sizes are visible.
The image is centered around -15 degrees latitude and +50 degrees longitude on Dec. 13, 2011, altitude of 117 miles. It covers 11 miles by 11 miles.
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Part of one of the troughs at the equator of Vesta. The floor of one of the equatorial troughs has brighter deposits at the bottom and darker band at the edge. The image is centered -6 degrees latitude and +60 degrees longitude at 115 miles and covers 11x11 miles.
Equatorial troughs are a striking feature of Vesta. They are overlaid with craters and light and dark material.
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This image is calculated from a shape model of the topography of the south polar region. Vertical scale is 1.5 times that of the horizontal scale. It shows the topography without the curvature of Vesta. You would not have a view like this. Distant features would disappear over the curvature of the horizon. |
This is an area in Rheasilvia basin in the south polar area. Younger, darker ejecta material from an impact touches brighter, hilly deposits marked by craters. The brighter older material shows crisscrossing, linear features. The image is at +78 degrees latitude and +298 degrees longitude on Dec. 13 at 127 miles covering 12x12 miles. |
After this 10 week low altitude part of the mission, Dawn will begin firing its ion engine to start the slow ascent to higher altitude. The
ultimate goal is to leave orbit around Vesta in July 2012 and continue its journey toward the largest asteroid Ceres. It is scheduled to arrive there in 2015 and insert into orbit for a similar mapping and analysis mission.