Ceres High Altitude Mapping Orbit (HAMO), Late summer through fall 2015 |
Ceres High Altitude Mapping Orbit (HAMO), Late summer through fall 2015 |
Aug 17 2015, 01:42 AM
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Member Group: Members Posts: 541 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
DAWN arrived in its new lower mapping orbit on August 13th. The DAWN team is preparing to resume science observation tomorrow on the 17th.
From the Current Mission Status page at the DAWN website: QUOTE August 13, 2015 - Dawn Arrives in Third Mapping Orbit
Dawn completed the maneuvering to reach its third mapping orbit and stopped ion-thrusting this afternoon. This was a little ahead of schedule because the spiral descent went so well that some of the allocated thrusting time was not needed. Since July 14, the spacecraft has reduced its orbital altitude from 2,700 miles (4,400 kilometers) to approximately 915 miles (1,470 kilometers). The orbit period has correspondingly decreased from 3.1 days to 19 hours. Dawn is scheduled to begin its new observations on the evening of Aug. 17 (PDT) and continue for more than two months. First, however, the mission control team will measure the actual orbit parameters accurately and transmit them to the spacecraft. |
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Aug 30 2015, 02:42 PM
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Senior Member Group: Members Posts: 3002 Joined: 30-October 04 Member No.: 105 |
Even the crustal morphology of Ceres will prove to be engimatic.
By the Survey Orbit, Elevation maps were developed and they told a strange story. Ceres has a significant elevation relief of +/-- 7.5 Km around a zero datum. And it seems to be more relief than can be accounted for with a warm-ish icy crust without sagging down or up, back to the datum. But look at the distribution of elevations-- the highland areas are several discrete continents with the abyssal plains in between. Intuitively it would seem that the continental highlands are a low density, thick icy material floating isostatically on the higher density silicates of the upper mantle with the abyssal plains created by relict large impact craters. This is just arm-waving, and we'll learn more from upcoming gravity surveys and determination of the composition of the crust. By terrestrial analogy, these are granitic crustal blocks bobbing about in basaltic ocean basins. Illustrations: A geomorphology map of Ceres showing surface features and continents and abysses: https://univ.smugmug.com/Dawn-Mission/Ceres...geomorph-v1.jpg Elevation map, cylindrical projection: http://photojournal.jpl.nasa.gov/catalog/PIA19606 Elevation map, hemispherical projection: http://photojournal.jpl.nasa.gov/catalog/PIA19607 Global animation: http://photojournal.jpl.nasa.gov/catalog/PIA19605 Be thinking about the distribution of surface features on these two crustal provinces. --Bill -------------------- |
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