As http://www.unmannedspaceflight.com/index.php?s=&showtopic=7112&view=findpost&p=189713 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):
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.
Departure was not supposed to happen until the 26th.
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
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.
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...
A farewell animation:
http://www.youtube.com/watch?v=84vz6J8cnc8
Thank you for posting that one Explorer1.
Next stop Ceres in 2015, so lets find out what that bright spot is then.
It looks like a peak of a crater to me.
Looks like an informative Hasta La Vesta hangout:
"We’re celebrating this milestone with http://dawn.jpl.nasa.gov/news/hasta_la_vesta.asp.
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."
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 http://neo.jpl.nasa.gov/orbits/fullview4.jpg went back online...
A Last Look Back at Vesta ....bye Vesta...
http://dawn.jpl.nasa.gov/feature_stories/dawn_departs_vesta.asp
http://dawn.jpl.nasa.gov/multimedia/last_look_back.asp
From Protoplanet to Dwarf Planet.... Ceres here we come.
Craig
The pole at last! I'm assuming it's in the largest crater, right?
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 ?
According to the last SPICE kernel (but based on predicted trajectory), Dawn was at 20600 km from Vesta at 9:43 UTC 06 september.
For checking Dawn in real time, Mystic seems to be better than another simulator with extra information that SPICE haven't (like engine status).
I think that the administrators of "Eyes of Solar System" and others just didn't updated the new data.
Dilo, could you ask Marc if the remaining reaction wheels were turned off during the last observation of Vesta ?
Marc just updated his excellent blog:
http://blogs.jpl.nasa.gov/tag/marc-rayman/
So the reaction wheels are nominal and it was simply a programming error that was trying to deactivate them earlier? That is excellent news! C'mon Ceres... are we there yet? [:-p]
My reading of Marc's blog didn't indicate things were "nominal" with the reaction wheels--rather that one malfunctioned and all were turned off a week earlier than they were going to turn them off. I believe they started with 3 and 1 backup and have now lost 2. That is not good and will have to be worked around at Ceres when the space craft will need to do lots of turning for imaging and other science. Where did you hear it was an software/programming error rather than a hardware failure?
In a talk by Marc last week for the EPO folk on lab - he echoed what you describe Floyd. Marz - I think you have things wrong.
Update on departure progress:
I just received some informations from Dr Rayman which shed more light on the reaction wheel issue.
The wheels were all turned off on August 8, when the software detected the increase in friction, and were left off since then, including for the departure observations.
They restored spacecraft to normal operations, but one of "normal operational modes" is to fly with all wheels off (they flew that way from August 2010 to May 2011 and they intend to do so for the journey from Vesta to Ceres). So, "wheels off" is a normal operational mode and future Ceres exploration plan will be based on the use of the two reaction wheel + RCS "hybrid" control capability, installed on the spacecraft in April 2011. Marc highlighted that most of these information were available in previous Dawn journal articles and that he will write more about the reaction wheels, RCS control, hybrid control, and hydrazine in future Dawn Journals (although not the next one).
Herebelow an update on departure plots, showing also a brief engine stop occurred yesterday:
Marc confirmed there was a programmed engine stop on September,10 for communication with Earth (they do this each week but probably frequence will be relaxed during the journey to Ceres). Effect is clearly visible in velocity and orientation plots (right):
Update:
Update:
It's amazing how symmetrical Vesta's hemispheres are on the global scale, on this topographic map that includes the far north.
But the northern basin isn't from a giant impact, is it?
http://dawn.jpl.nasa.gov/multimedia/imageoftheday/image.asp?date=20120911
Explorer1, the northern basin isn't a crater and blue color is due to oblate spheroid shape of Vesta.
In fact, text underline that colors represent distance relative to Vesta's center (or height relative to a sphere with 500km diameter); most important, scale of the two maps isn't the same because lower (violet) points in Northern emisphere are only 22km below such sphere while South depressions reach -38km.
Anyway, the presence of spiral patterns in both polar regions (with opposite orientations) is very intriguing...
PS: I like very much the Giordano Bruno statement in your signature!
Yes, the spiral patterns resemble, more than anything else, the pattern of modification one sees at Mars' poles. But... Vesta couldn't possibly have ever had enough atmosphere to support ice caps, could it?
-the other Doug
It would be really helpful to have a 3D rendered globe of Vesta -- much would be come clear, I think.
Soon as Phil gives the okay, I'll get started on a fold-up map of the thing.
Phil . . . ?
Update:
Update:
"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
This is my final update plot of Vesta departure:
New blog post about Ceres cruise:
http://www.planetary.org/blogs/guest-blogs/marc-rayman/20131031-dawn-journal-thrusting-toward-ceres.html
New info about Ceres plan, with details on hybrid control mode for low-altitude mapping orbit:
http://dawn.jpl.nasa.gov/feature_stories/Dawn_Fills_Out_Ceres_Dance_Card.asp
According to the http://dawnblog.jpl.nasa.gov/2014/11/28/dawn-journal-november-28/, today is the day that Dawn takes its first resolved photos of Ceres, nine pixels across. These are being taken mainly to calibrate the camera. Still a couple of months to go before they start getting the really good stuff.
DSS43 at Canberra DSN is tracking DAWN right now. Not far off sun-point as you can see.
the Max Planck Institute has a release (i n German) with the first, distant images of Ceres:
http://www.mps.mpg.de/3867888/PM_2014_12_05_Erster_Blick_auf_eine_neue_Welt
Here is a link to the picture on the Dawn web site: http://dawn.jpl.nasa.gov/feature_stories/Dawn_snaps_image_Ceres.asp
Without a doubt, Ceres is significantly larger than Vesta.
This is exciting! Can't wait to see Ceres close up. Almost looks like albedo differences in the photo, but could just be phase effects.
Exciting... but in a bittersweet way. This finishes the initial reconnaissance of the rocky terrestrial worlds in our local neighbourhood. If we want fresh terra incognita after this we have to go way, way out to the solar system's frigid fringes.
I'd like to see Pallas and Hygeia! I want to see how the biggies transition down to the small ones we've seen. Also, while I'm wishing for things, I want much better imaging of Deimos. And heck let's go visit some Trojans too.
Hektor especially would be a great destination: a contact binary an order of magnitude bigger than 67P and with a moon (always a bonus). We know practically nothing about that region...
Now to wait until the next round of Discovery proposals.
It would be interesting also to visit a large metallic asteroid.
Yep, the team proposing a Psyche mission agrees:
http://www.planetary.org/blogs/guest-blogs/van-kane/20140219-mission-to-a-metallic-world.html
I'm sure these are all fascinating in their own right. But there's something special about seeing the curving limb of a gravitationally relaxed body- Ganymede, Enceladus, Triton... these all seem like places to me in a way that Vesta never quite did.
Google Hangout about the Hubble/Dawn imagery comparison coming up:
http://dawn.jpl.nasa.gov/dawncommunity/google_hangout_12_11_2014.asp
It might also be time for a dedicated Ceres approach thread.
Less than 1 million km now!!! So close!
I'm wondering though, if the ion-thrusters would fail right now, how close would the flyby be? Or could it still limp into orbit by using all the remaining conventional fuel?
I'd say Callisto or Mimas, just keeping expectations low (i.e. completely saturated with craters). That way everything else can be a pleasant surprise.
There was a paper published last year, in Icarus I think, that suggested the warmer surface of Ceres compared to the outer moons might result in VERY subdued crater topography (really all but small and fresh craters slump over geological time until they become mere albedo features) except right near the colder poles. So, even if its geologically 'boring', (and I hope it isnt!), I doubt Ceres is going to look like Callisto or Mimas.
P
Huh, that's a tiny fraction of the tilt of Vesta and Ceres; its even smaller than Mars and Venus.
So many tempting targets out there for future missions (Dawn 2 anyone?).
I would love to see a series of smallsats sent to asteroids. If successful, the Procyon satellite launched with Hayabusa-2 might encourage such missions. Imagine using a large booster to put dozens of these into the asteroid belt at the same time...
While we wait for DAWN to snap more approach images of Ceres, I put the Dec 2014 Framing Camera image (PIA19049) through the deconvolution process. I hate going above 10x on an image, since we are pushing around noise, point spread functions of the camera, and other artifacts (such as working from a JPEG). But I ran this baby up to the max: 30x (!)
Don't try to see craters or such things other than a bright area on the right side (and a slightly darker 'depression' on the lower right --to be named the pdp8e abyss ). Most of the image is the deconvolver 'hallucinating' about what it thinks it sees... but it is fun!
The size difference (not resolution) is about what Ceres would appear at roughly 25,000 miles away
@PDP8E: Yes it is really to early to see anything on Ceres yet.
But keep it up and in a little over a month we might get to see the first detail.
Hubble images have hinted there is at least one surface feature that could be spotted even at the early approach.
Now craters, if our current thinking is correct Ceres got a dusting of material on top, so larger (and more recent) craters might have a bright bottom.
While I am at it, I am quite pessimistic on the outlook to find any satellite at Ceres for the same reason, any impact that might have sent material into orbit will be mostly be ice and might sublimate before it have time to coalescence, (which might be how the smaller satellites of Pluto came to be in that much colder environment.)
There could be a very small rock in orbit, as for example one component of a binary asteroid that been captured and the small size made it escape detection in telescopic searches.
"Very small rock" is a relative term - e.g. in http://www.helsinki.fi/acm2014/pdf-material/Day-5/Session-2/Room-1/SCHMIDT-91FC.pdf the detection limit mentioned for various searches of Ceres' inner Hill Sphere is somewhere around 1-2 km at 4000 km, possibly bigger further in. And since Ceres' Roche limit even for the most porous of rubble piles is well below 2000 km...
Yes "relative" is the word, I were aware of those searches mentioned in the paper and with a size of just one km or two it could be more suitable to name it 'rock' here than Moon which usually make people think of a more substantial object. =)
But yes it could be somewhat larger, especially if it is exceptionally dark.
Shouldn't this thread be closed now that Ceres finished its journey?
We are now talking about orbiting Ceres: http://www.unmannedspaceflight.com/index.php?showtopic=7981&st=0&#entry218672
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