Vesta departure and journey to Ceres, A new phase of Dawn adventure |
Vesta departure and journey to Ceres, A new phase of Dawn adventure |
Aug 26 2012, 05:45 AM
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
As suggested by "TheAnt", is time to start a new thread!
Due to lack of updates from "Mystic simulator", I asked directly to Marc Rayman for an update and he kindly sent me the following "unofficial" plots, showing evolution of distance, radial velocity and sub-spacecraft latitude (radius trend is splitted in two plots with different scales due to huge variation of the distance): I did not publish them immediately because I wanted to integrate them with my previous plots but, due to the lack of time in last week, I decided to post them directly with only minimal changes. As you can see, third engine stop occurred on Aug 8-18 at almost 2300km above Vesta while next (final) one is just started and, as reported by Marc in his latest journal, will be used to map North polar regions from 6000km distance. Thereafter thrust will resume and, based on plots, on Sept 5 total speed will overcome escape velocity (almost 45 m/s), so total energy balance will be zero; definitive exit from Vesta Hill sphere should occur after 20 days but consider that the times could slighty change due to orbit refinement and thrust plan changes. -------------------- I always think before posting! - Marco -
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Sep 21 2012, 04:03 PM
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Solar System Cartographer Group: Members Posts: 10183 Joined: 5-April 05 From: Canada Member No.: 227 |
"Phil . . . ? "
OK Chuck - here I have taken those two polar maps of topography and reprojected them into simple cylindrical. There are a few very minor errors in this composite but nothing to worry you in your work. It should be easy to match this with published gridded maps to get crater names, lat and long etc. (a grid is faintly visible on this, from the originals). But this gives you the topography to locate your ridge lines etc. PS - apparent mismatch along the equator is caused by different illumination of the rendered shaded relief between the two halves. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Sep 24 2012, 10:55 PM
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#3
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
This is my final update plot of Vesta departure:
Dawn is definitively out of Vesta sphere of influence, exact time depends on which Hill sphere radius you assume. In fact, while classic formula is based on average distance of the body from Sun, others reccomend to use pericenter distance, which gives a smaller radius; moreover, I calculated also the present Hill radius based on current heliocentric distance. Here below my results, based on interpolation of Mystic simulator distances (sorry for improper use of "code" format but table format appears problematic otherwise!): CODE Method (Sun distance) Distance from Vesta date/time UTC I tend to prephere last one, which occurrred few hours ago, probably during the weekly engine shutdown...
Periastron 113180 km Sep, 22 12:40 Average 124180 km Sep, 23 18:52 Current 134750 km Sep, 24 22:30 -------------------- I always think before posting! - Marco -
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