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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#1
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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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Aug 26 2012, 11:17 AM
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#2
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Junior Member Group: Members Posts: 22 Joined: 23-August 11 From: France Member No.: 6134 |
Thanks Dilo for the updating. I was little worried. Last spice spk file (25 august) shows that Dawn will not escape form Vesta indicating an another problem. But it seems now that this file was only a test.
My little contribution with this video created thanks to spice data from NAIF. http://www.youtube.com/watch?v=EL5nbFU3xl8 Since SPICE doesn't indicate the states of engines, the orbital parameters are only "guessed" assuming a Vesta like a point mass of 2.59^20 kg. |
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Aug 26 2012, 05:18 PM
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#3
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Departure was not supposed to happen until the 26th.
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Aug 26 2012, 11:41 PM
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#4
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Junior Member Group: Members Posts: 22 Joined: 23-August 11 From: France Member No.: 6134 |
Sorry, I meant the date of spk file releasing (25 august) not the date of depart which is scheduled on 5 september as dilo wrote.
The initial departure was planned on 26 august but after the problem with wheels reaction it was postponed as we know. But i remain concerned: the last spice ck file shows that the observation of Vesta to mapping north pole didn't occur |
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Aug 27 2012, 06:15 PM
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#5
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Junior Member Group: Members Posts: 22 Joined: 23-August 11 From: France Member No.: 6134 |
I must apologize for my previous post.
According to the spice files released today, there was an attempt to observe Vesta as planned. The ck file shows that the probe has problem to maintain her orientation but i don't know if this effect is due to the ck files (always under construction) or the problem of lack of one reaction wheels. From now, I will avoid any speculations useless alarmist and I will wait the official update of wonderfull Dawn journal and Dilo states plots (specially the states of engine propulsion ) (from Mystic or Marc). And of course hope of beautiful images of Vesta's north pole Again very sorry. |
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Aug 28 2012, 04:59 PM
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#6
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
I had a private comunication from Mark, he confirmed that they successfully imaged Vesta over the weekend.
Moreover, he said there wasn't any problem with the SPK file. As explained in several Dawn Journals (including November 29, 2011), they generate a reference trajectory that goes all the way to the next destination but then, as they fly along, they generate updated flight profiles to account for all the usual error sources (orbit determination accuracy, unmodeled perturbations from RCS, deviations in IPS thrust from the modeled value, etc.). Each time an updated thrust plan is sent to the spacecraft, they only send the next thrust segment, not the full reference trajectory; in this way, in case of failure, they don't have onboard ephemeris based on thrusting that didn't occur. So when they upload the new thrust segment, they upload a new ephemeris as well. Probably, SPK issue Sarunia found is for an isolated thrust segment which then is followed by a ballistic propagation... -------------------- I always think before posting! - Marco -
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Aug 31 2012, 07:48 AM
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#7
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Senior Member Group: Members Posts: 2106 Joined: 13-February 10 From: Ontario Member No.: 5221 |
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Aug 31 2012, 08:52 PM
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#8
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Member Group: Members Posts: 495 Joined: 12-February 12 Member No.: 6336 |
Thank you for posting that one Explorer1.
Next stop Ceres in 2015, so lets find out what that bright spot is then. |
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Sep 1 2012, 04:08 PM
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#9
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Senior Member Group: Members Posts: 1276 Joined: 25-November 04 Member No.: 114 |
It looks like a peak of a crater to me.
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Sep 2 2012, 02:39 AM
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#10
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Member Group: Members Posts: 311 Joined: 31-August 05 From: Florida & Texas, USA Member No.: 482 |
Looks like an informative Hasta La Vesta hangout:
"We’re celebrating this milestone with a live Google+ Hangout featuring the Dawn mission team September 8, 2012 at noon PDT. During the Hangout, moderated by Dawn’s education and public outreach (E/PO) liaison to the science team, Dr. Britney Schmidt, we’ll hear stories from Dawn scientists and engineers and get updates on latest mission findings. Pose the questions you’ve always wanted to ask. Submit your questions for the Dawn team by leaving them in the comments section below, on Dawn’s Facebook page, or by using the hashtag #HastaLaVesta on Twitter." |
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Sep 5 2012, 05:00 PM
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#11
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
Based on last Dr Rayman (unofficial) comunication, this morning at 6.45 UT, Dawn definitively leaved Vesta gravitational field when his speed exceeded escape speed (45 m/s at 18000 km height). Curiously, in the same hours MISTIC simulator went back online...
-------------------- I always think before posting! - Marco -
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Sep 6 2012, 01:17 AM
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#12
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Member Group: Members Posts: 813 Joined: 29-December 05 From: NE Oh, USA Member No.: 627 |
A Last Look Back at Vesta ....bye Vesta...
http://dawn.jpl.nasa.gov/feature_stories/d...parts_vesta.asp http://dawn.jpl.nasa.gov/multimedia/last_look_back.asp From Protoplanet to Dwarf Planet.... Ceres here we come. Craig |
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Sep 6 2012, 02:40 AM
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#13
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Senior Member Group: Members Posts: 2106 Joined: 13-February 10 From: Ontario Member No.: 5221 |
The pole at last! I'm assuming it's in the largest crater, right?
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Sep 6 2012, 08:42 AM
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#14
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Member Group: Members Posts: 102 Joined: 29-January 10 From: Poland Member No.: 5205 |
Hi
I see some difference in Dawn - Vesta position at Mystic Simulator and Eyes of the Solar System Date and time is 9:43 UTC - 06 Sep 2012 See screens below. What's wrong ? What distance are good ? --------- Added: In HORIZONS JPL is 64 540 km http://ssd.jpl.nasa.gov/horizons.cgi --------- Also in Solar System simulator is 64 549 km http://space.jpl.nasa.gov -------------------- Adam Hurcewicz from Poland
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Sep 6 2012, 10:27 AM
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#15
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
I see some difference in Dawn - Vesta position at Mystic Simulator and Eyes of the Solar System Adam, I can say Mystic is perfectly in line with Marc Rayman plots, as showed in these plots where I merged the two sources: (consider that Mystic hiatus ended yesterday and lasted 1 month; moreover, you will not see distance/velocity modulations due to elliptic orbit during third engine stop because I reported only average info in this period). Moreover, both Marc/Mystic data are in agreement with last Nasa updates about Vesta depart milestone (see links from bellarophon1); in my plots (left/bottom in particular) you can see that total energy becomes positive only on Sptember,5 while, if Dawn really lies at 64500 km from Vesta, this means he surpassed this point many days ago and is already half-way to Vesta Hill sphere margin! -------------------- I always think before posting! - Marco -
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