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Unmanned Spaceflight.com _ Dawn _ Dawn Survey Orbit Phase

Posted by: Paolo Jul 17 2011, 09:09 AM

I think it's time we start a new thread

Posted by: dilo Jul 17 2011, 02:13 PM

Good idea, Paolo!
Dawn's ion engine have been OFF in the last hours (at least 9 hours from my checks) and, as expected, now spacecraft started to accelerate:


at current distance, I espect an acceleration toward Vesta of 1,0e-4 m/s2; considering current phase angle, close to 90°, this should cause an increase of total velocity close to 1 mph each 2 hours... until next engines power on!

Posted by: pablogm1024 Jul 17 2011, 02:28 PM

Would it be worth renaming the topic to Survey Orbit Phase, given that it is the name that the mission ops team uses for the first orbital phase?

Posted by: Bjorn Jonsson Jul 17 2011, 03:18 PM

QUOTE (pablogm1024 @ Jul 17 2011, 02:28 PM) *
Would it be worth renaming the topic to Survey Orbit Phase, given that it is the name that the mission ops team uses for the first orbital phase?

Done - and congratulations to the Dawn team!

Posted by: dilo Jul 17 2011, 06:53 PM

This is an answer to Greg question (from the old thread):
Your question wasn't so silly because helped me to find many answers! wink.gif
You had a nice idea about plotting escape velocity (which depends on distance from Vesta) toghether with speed... this my updated distance/speed plot, zoomed on last weeks:


You can clearly see the "capture event", when red curve goes below yellow one (speed axis on the right).
Well, as told in the press release nobody knows the exact moment of such event because Vesta mass is only roughly known for the moment (I used 2.69e20Kg value, reported also in Wikypedia; uncertain should be around 2%, which means 1% uncertain in escape velocity).

EDIT: meanwhile, Dawn is using again propulsion and speed seems stabilized now...

Posted by: dilo Jul 18 2011, 05:13 PM

With engines on, Dawn still decelerating, even though at a very slow rate (only 1m/s in last 20 hours) due to Vesta gravity... this is an update of previous plot with a new one (always suggested by Greg) showing speed as a function of distance from Vesta instead of time; I also added a curve showing speed required for circular orbit (pay attention, this is true only if velocity vector is perpendicular to distance vector and this is not the case of Dawn, at this moment!):

 

Posted by: elakdawalla Jul 18 2011, 07:21 PM

OK this is making me absolutely crazy. http://www.nasa.gov/mission_pages/dawn/multimedia/pia14313.html (yay!) but as with all the previous image releases the reported scale is wrong. They keep reporting the pixel scale for the original, unenlarged image, and then they post an image that has been enlarged (badly) by some non-integer factor and fail to divide the pixel scale by whatever their enlargement factor was.

Posted by: Stu Jul 18 2011, 07:37 PM

Hands up, I don't understand all the tech stuff, but I sense your frustration Emily. sad.gif

Pretty cool view, tho... more and more Mirandan...



Posted by: Phil Stooke Jul 18 2011, 07:47 PM

Another version of this beautiful new picture.

Phil


Posted by: bagelverse Jul 18 2011, 08:26 PM

Wow, stunning image.

While the south polar peak is either impact derived or tectonic, it certainly
reminds me of Ayers rock in central Australia. Nice hard hard of
rock that says "I am not going anywhere, no matter what you throw at me".

Also the ripples around the south polar peak really look like ripples in a pond
or maybe just wrinkles from shinkage.

Posted by: Juramike Jul 18 2011, 08:31 PM

Straight to Planetary Photojournal:
http://photojournal.jpl.nasa.gov/catalog/PIA14313
http://photojournal.jpl.nasa.gov/catalog/PIA14314 (anaglyph!)
http://photojournal.jpl.nasa.gov/catalog/PIA14315
http://photojournal.jpl.nasa.gov/catalog/PIA14316 (asteroid size comparison poster)

Posted by: Stu Jul 18 2011, 09:03 PM

Thanks for posting those links. Used the tiff file to creare a cleaner view...

http://twitpic.com/5s9axu

Posted by: Juramike Jul 18 2011, 09:49 PM

That's really nice, Stu!

Posted by: volcanopele Jul 18 2011, 10:09 PM

I think I shrunk the original image to something approaching the original resolution. I've also applied a light unsharp mask here:


 

Posted by: punkboi Jul 18 2011, 10:14 PM

Congrats to the Dawn team for a successful orbit insertion! Now looking forward to a color image of Vesta... smile.gif

Posted by: belleraphon1 Jul 18 2011, 10:36 PM


Thanks DAWN team for releasing these.

A lot to look forward to in the coming 12 months!

Mirandian indeed.

Craig

Posted by: Drkskywxlt Jul 18 2011, 10:59 PM

Is that picture facing the south pole?

For somewhat not geologically-minded, what is reminding all of you about Miranda? I don't see the similarities really...

Posted by: ugordan Jul 18 2011, 11:09 PM

A faux-color version based on color derived from Hubble WFPC2 F673N and F439W filters:


Posted by: belleraphon1 Jul 18 2011, 11:19 PM

Drkskywxlt:

Call it exhuberance.

Mirandian was perhaps more prominant in the lower resolution view from July 9th. Go to NASA photojournal and explore
Miranda.

Miranda has what I would call sectional terrain (not a geologist either nor do I pretend to be). Odd blocks of internal resurfacing surrounded by cratered terrain.
As we get closer the comparisons do seem to break down a bit. Is this a demonstration of how small bodies go through an early stage of internal processing?

But is it not wild that we can even make subjective comparisons of bodies so far apart in space and time!
That is what some 50 years of solar system exploration has given us.

Glad I was born to see it from the start.

Craig

Posted by: kap Jul 18 2011, 11:54 PM

QUOTE (ugordan @ Jul 18 2011, 03:09 PM) *
A faux-color version based on color derived from Hubble WFPC2 F673N and F439W filters:
]


Nice work. What does everyone think of that big scarp on the upper right area of the image. Could that be the edge of the southern hemisphere impact crater?

-kap

Posted by: Juramike Jul 19 2011, 12:03 AM

QUOTE (kap @ Jul 18 2011, 06:54 PM) *
What does everyone think of that big scarp on the upper right area of the image.


That's a neat cuspate scarp, and another just beside it. I'm looking at the small wavy pile of stuff right in front and wondering if material slumped to reveal an abrupt scarp.

Posted by: MarkG Jul 19 2011, 12:07 AM

Boys and girls, it's "Rampant Speculation Time...."
The patterns on the South Pole crater floor do resemble both Miranda, and Earthly sea-floor spreading. Perhaps a shock-melted mantle zone convected for a while, rafting surface debris and local volcanics into linear rows from spreading crack centers. Fun to speculate.
Vesta had it's "bell rung" pretty good with the impact, maybe there was a surface wave interference pattern that distributed things in the pattern seen.
Relaxation after impact, with the core wanting to re-center, and perhaps migration of the rotation axis, could cause some of the features we see. Also the floor striations could be caused by compressional wrinkling from this relaxation, plus landslides and collapse blocks from the crater rim.
Is the central mountain a volcano, an intrusive diapir, an infall debris pile, a garden-variety crater central mound, or a combination?
Stay tuned!


Posted by: belleraphon1 Jul 19 2011, 12:25 AM

"But is it not wild that we can even make subjective comparisons of bodies so far apart in space and time!"

My quote from my last post here.

Miranda and Vesta...far away in space but perhaps not in time. The period of resurfacing may have been in the same period of time. Early in solar system history.
Once again are we seeing how smaller bodies go through an early period of furious internal resurfacing that is restricted to segregated internal blocks of activity.
A herterageneous stew that cooks in spots but stays stone cold in others.

Shaken... not stirred?

Craig

Posted by: MarkG Jul 19 2011, 01:35 AM

There is a big difference between Miranda and Vesta, however. The difference is the presence of ice and tidal forces on Miranda, both largely absent on Vesta.
Ice is quite ductile, and small gravity can cause it to flow, but plain rock, like on Vesta, don't flow unless it is pretty much hot enough to melt, and the interior pressures in Vesta, with it's light gravity, are not going to contribute that strongly.
One of the big questions is how warm was the interior of Vesta at impact? We already know (pretty much) that Vesta got hot enough early to differentiate its core/mantle/crust, and then we can ask how much of this heat was left at impact. Since the planet as a whole did not re-spherize itself, it must have been largely cooled to a solid at impact time. Perhaps some of the core was still liquid -- radioactive decay might have kept it going a while.
On the other hand, Quite some time might have passed since the planetary system formed and cleared out the nebula and most debris before the impact. We know that a significant amount of asteroidal objects are dynamically related to Vesta and are shards of the great impact. The surface of Vesta also does not appear to be crater-saturated. (With further imaging, crater counts should be able to give a rough age estimate -- looking forward to that.)
So it seems (arms waving wildly) that the energy for reshaping parts of Vesta had to be delivered by the energy of impact. How much shock melting could accomplish is unclear, and a better answer is in the hands of the planetary modelers and the mega-computers.
An interesting idea is the possibility that accumulated surface volatiles were stirred up by the impact and ablated by solar and impact heating, and Vesta was a giant comet for a while...
Well, I think I've embarrassed myself enough for now. Its a free country, gotta love it.

Posted by: Steve G Jul 19 2011, 01:36 AM

Sometimes it's easier just to rotate and crop, and just look at a single feature at its best orientation. I just love these cliffs!

 

Posted by: nprev Jul 19 2011, 01:36 AM

I think we'll definitely need a true global view before we'll be able to understand what we're seeing now, but my working hypothesis is that Vesta was damn near remelted globally after this tremendous impact. However, it probably cooled quite quickly as well; we may well be seeing a landscape frozen in time after a catastrophe, perhaps like the ancient Earth (sans atmosphere & oceans) after the big whack that formed the Moon.

Posted by: Explorer1 Jul 19 2011, 01:44 AM

How far will coverage of the northern hemisphere go; will it stay mostly in shadow for the full duration of Dawn's visit?

Posted by: belleraphon1 Jul 19 2011, 02:06 AM

Shaken or stirred?

That is the question.

Posted by: Gladstoner Jul 19 2011, 03:13 AM

On second thought (or third), it looks like material from the original crater 'wall' has slumped toward the center -- basically the same as what occurs in craters on the moon and Mercury. In this case, though, the slumps have slid all the way to the central peak/uplift, and continued to flow as they were displaced by more material sliding down from above. After eons, a jumbled flow was the result.

Posted by: MarkG Jul 19 2011, 04:02 AM

Replies...
My understanding is that the North pole of Vesta will just begin to be illuminated at the end of the Vesta mission, so there will be eventual global photo coverage by Dawn.
Also, mass wasting from the crater sides does not seem to explain the 5-km-ish spaced parallel ridges on the crater floor. I'm wondering if they are ridges of olivine....

Posted by: tasp Jul 19 2011, 04:12 AM

Love the "asteroid size comparison poster", amazing to see all the suspects in a police lineup style poster, and LOL, I gets my 1 pixel Itakowa comparison!

Posted by: antipode Jul 19 2011, 04:34 AM

I can't wait to see...errrr...the antipode of that crater! Mega chaotic terrain?

P

Posted by: Gladstoner Jul 19 2011, 04:36 AM

QUOTE (MarkG @ Jul 18 2011, 11:02 PM) *
Also, mass wasting from the crater sides does not seem to explain the 5-km-ish spaced parallel ridges on the crater floor. I'm wondering if they are ridges of olivine....


They could be pressure ridges between adjacent debris flows.

Posted by: Gladstoner Jul 19 2011, 10:15 AM

A little bit of Vesta on Mars?:

[attachment=24854:MarsRA_sm.jpg]

And on Earth?:

[attachment=24855:eastspringcomp.png]

(Double Spring landslide complex, Oregon)

I had a heck of a time finding a decent example of a terrestrial landslide to compare to Vesta. If the grooved terrain is indeed a system of debris flows, they may turn out to be the finest example of the process anywhere in the Solar System.

Posted by: centsworth_II Jul 19 2011, 11:17 AM

I was intrigued by the quick look Cassini got at the conical craters of Saturn's Phoebe. Now it looks like we'll get a much better look at the same sort of crater on Vesta. The images below are very roughly to the same scale. Although Vesta is a little more than twice the diameter of phoebe, the craters in question seem to be about the same size on both bodies.


Posted by: centsworth_II Jul 19 2011, 11:35 AM

QUOTE (Drkskywxlt @ Jul 18 2011, 05:59 PM) *
For somewhat not geologically-minded, what is reminding all of you about Miranda? I don't see the similarities really...

From http://planetary.org/blog/article/00003103/
"The interior of that south polar basin sure looks weird. All around the central peak are chevron-shaped ridgy features that bring to mind Miranda -- which, by the way, is very similar in size to Vesta."

Posted by: Drkskywxlt Jul 19 2011, 12:37 PM

QUOTE (centsworth_II @ Jul 19 2011, 07:35 AM) *
From http://planetary.org/blog/article/00003103/
"The interior of that south polar basin sure looks weird. All around the central peak are chevron-shaped ridgy features that bring to mind Miranda -- which, by the way, is very similar in size to Vesta."


Yeah...I guess I can see that. To me (again, not a geologist), it just all looks like grooves similar to those on other small bodies like Phobos and Lutetia.

Posted by: Stefan Jul 19 2011, 01:22 PM

QUOTE (elakdawalla @ Jul 18 2011, 09:21 PM) *
OK this is making me absolutely crazy. http://www.nasa.gov/mission_pages/dawn/multimedia/pia14313.html (yay!) but as with all the previous image releases the reported scale is wrong. They keep reporting the pixel scale for the original, unenlarged image, and then they post an image that has been enlarged (badly) by some non-integer factor and fail to divide the pixel scale by whatever their enlargement factor was.


The last few images were enlarged by an integer factor. Did you find something wrong with how they were enlarged?

While the quoted pixel scale is indeed not valid for the enlarged image, it is the relevant number for knowing the smallest detail that can be resolved.

Posted by: centsworth_II Jul 19 2011, 01:31 PM

QUOTE (Drkskywxlt @ Jul 19 2011, 07:37 AM) *
...it just all looks like grooves...
All groves are not alike. There are straight grooves, sinuous groves, grooves with right angles.

Posted by: Stefan Jul 19 2011, 01:36 PM

QUOTE (punkboi @ Jul 19 2011, 12:14 AM) *
Congrats to the Dawn team for a successful orbit insertion! Now looking forward to a color image of Vesta... smile.gif


There is a false color image on the http://www.dawn.mps.mpg.de/index.php?id=21&L=1 (click the latest headline).

Posted by: MahFL Jul 19 2011, 02:00 PM

The focus is getting better.
The Clangers definetly live there.

Posted by: Steve G Jul 19 2011, 02:08 PM

The south polar crater is, by appearances, a flat slice right across the south pole. However, gravity is always pulling towards the center of the body. So on the outer limits of this flat massive basin, it is gravitationally speaking, an up hill slope. This would naturally draw the loose surface material towards the center of the crater, and perhaps create the cracks and rifts, would it not?

Posted by: algorimancer Jul 19 2011, 02:37 PM

Was arrival facing the south polar crater planned, or a coincidence of orbital mechanics and intent to enter a polar orbit? I understand that it is a target of interest, just wondering about the extent of the planning process in that regard.

Posted by: Juramike Jul 19 2011, 03:03 PM

Coordinated views of the normal and contrast-enhanced IR composite of 4 Vesta
(lineup is approximate) note the 4-pack of craters to the N in both images.


Posted by: Phil Stooke Jul 19 2011, 03:11 PM

Nice one, Mike.

The orange spot in the false color view coincides with the darker spot seen in distant views, including the 'crater with tails' as someone described it, on the edge of the smooth patch we saw a while ago.

Phil

Posted by: Phil Stooke Jul 19 2011, 04:33 PM

Here's a composite to illustrate that.

Phil


Posted by: elakdawalla Jul 19 2011, 04:51 PM

QUOTE (Stefan @ Jul 19 2011, 05:22 AM) *
The last few images were enlarged by an integer factor. Did you find something wrong with how they were enlarged?

The most recent one wasn't -- its enlargement factor was something around 2.2. And the resolutions stated (and widely requoted) in all the released captions are just wrong.

With spherical bodies it is very easy to back out an accurate image resolution from a global image -- measure any diameter and you're done. But for bodies with very different principal axis lengths, especially irregular ones like Vesta, it's hard to do this accurately, which prevents me from doing size comparisons. Size comparison posts are some of the most popular things that I do, which is why this is driving me so crazy.

As of yesterday I think the press person at JPL now understands what I am complaining about, so hopefully we'll see captions fixed soon. Of course what I really want is for them to quit enlarging the released images.

Posted by: MarkG Jul 19 2011, 04:52 PM

QUOTE (Phil Stooke @ Jul 19 2011, 08:11 AM) *
Nice one, Mike.

The orange spot in the false color view coincides with the darker spot seen in distant views, including the 'crater with tails' as someone described it, on the edge of the smooth patch we saw a while ago.

Phil


The orange area is around the sub-solar point, so I think it just represents daytime heating. Over time, a strong lead or lag behind nearby features with different times-of-day (Vesta Sols!) would be very interesting.

Posted by: Stefan Jul 19 2011, 07:14 PM

QUOTE (elakdawalla @ Jul 19 2011, 06:51 PM) *
The most recent one wasn't -- its enlargement factor was something around 2.2. And the resolutions stated (and widely requoted) in all the released captions are just wrong.


http://dawn.jpl.nasa.gov/multimedia/images/571329main_pia14313-full_full.jpg was enlarged by a factor 2 (I know because I enlarged it). The resolution of the image as shown http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_071711.asp is actually close to the quoted value. But what do you think of the caption http://www.bbc.co.uk/news/science-environment-14195373? The media will take that image and do with it whatever they like, and then quote the original numbers.

Yes, I understand your concern about the caption, and no, I didn't write it.

Posted by: elakdawalla Jul 19 2011, 09:18 PM

You did the enlargement? It's great to actually talk to someone who knows what's going on smile.gif So tell me where I'm wrong here. The diameter of Vesta in that released image is 860 pixels. At 700 m/pixel (1.4 / 2x enlargement) that gives you 600 km diameter, which I *think* is much too large.

If the pixel scale were rounded incorrectly and the original image scale were 1.3 km/pixel then it would correspond to 560 km diameter, which is within the accepted range of Vestian diameters...

You're right that reporting pixel scales will inevitably result in mainstream media screwing things up. For that reason I'd actually advocate abandoning pixel scales -- ONLY IF the images get released at their original resolution, or if they are enlarged by whole-number factors that are stated in released captions. Those of us who care about these things will get the numbers right.

Posted by: Juramike Jul 19 2011, 11:39 PM

Here's a mashup of the image on the DLR website with high-resolution image PIA14313. I took the enhanced-color IR composite and broke it up into little chunks, then took each chunk and warped it to try to align with surface features in the high res image. Reassembled the color composite, then used that to blend to the high-res layer underneath. Full details on flickr (http://www.flickr.com/photos/31678681@N07/5956204678/)

Neat how the scarp and some of the craters and ejecta are greenish in the IR composite.


Posted by: dilo Jul 20 2011, 07:26 AM

An update on Dawn trajectory:
in spite of engine running in last 20 hours, the probe is gently accelerating, progressively approaching a "circular orbit speed", as showed below:


The green triangles indicates definitive survey orbit; they are two because I'm not sure if 2700km nominal height is referred to the center or the surface of Vesta... can someone help me? unsure.gif
As additional info, now average acceleration toward Vesta is 3e-5 m/s2 while angle between trajectory and Vesta-to-Dawn vector is approaching 70°.

Addendum: I do not share Emily's bad feeling about image release policy... look to the bright side, last released image was captured only 3 days before and also contrast/gamma is a lot better than previous ones! smile.gif

Posted by: Greg Hullender Jul 20 2011, 02:13 PM

Another interesting stat might be energy/kilogram. Although kinetic energy is increasing, potential energy is decreasing.

--Greg

Posted by: Stefan Jul 20 2011, 03:20 PM

QUOTE (elakdawalla @ Jul 19 2011, 11:18 PM) *
You did the enlargement? It's great to actually talk to someone who knows what's going on smile.gif So tell me where I'm wrong here. The diameter of Vesta in that released image is 860 pixels. At 700 m/pixel (1.4 / 2x enlargement) that gives you 600 km diameter, which I *think* is much too large.


The distance for that image was (or should have been) 15222 km (center of Vesta). You already know the angular extent of one pixel. You tell me where you are wrong... rolleyes.gif

We are working to improve the caption.

Again, I ask you if you think the enlargement of the last image was done badly. Reading your blog, I am not sure. I used the Mitchell-Netravali algorithm, which I think is appropriate. Remember, it is a tradeoff between blurriness and jagged edge.

Posted by: djellison Jul 20 2011, 03:29 PM

QUOTE (Stefan @ Jul 20 2011, 07:20 AM) *
Again, I ask you if you think the enlargement of the last image was done badly.


Why is it being done at all? If (as we have been told) there is a constraint on the teams time in producing images for outreach...why waste some of that precious time in un-necessarily enlarging these images?

Posted by: ugordan Jul 20 2011, 03:49 PM

To be fair, that practice of magnifying otherwise poststamp-sized images is pretty much the norm for NASA image advisories, although they do tend to specify the magnification factor in most cases.

Posted by: machi Jul 20 2011, 06:09 PM

Enlarging images is standard procedure. NASA use that, almost every amateur processor use that. When one is working with mosaic from multiple images, then resizing is even necessary. When one have post-stamp size image, enlarged variant looks somewhat better, than original one.
"waste some of that precious time"
It's not, in IrfanView (my favorite software for resampling images) it's matter of seconds. smile.gif
"I used the Mitchell-Netravali algorithm, which I think is appropriate."
Mitchell is fine, it's my favorite one, but I think, that it isn't what Emily is complaining about.
She simply need information about actual size of pixels, that's all.

Posted by: machi Jul 20 2011, 09:41 PM

South pole of Vesta in stereo. Cross eye and anaglyph version. Resolution is approx. 1 km/pix.
Stereo images were made from one published hi-res image and synthetic image (made from both published hi-res images).


 

Posted by: Decepticon Jul 20 2011, 09:48 PM

machi Thank you for the 3D!

My kids appreciate it also!

Posted by: Phil Stooke Jul 20 2011, 10:11 PM

Fantastic! Thanks.

Phil

Posted by: ElkGroveDan Jul 20 2011, 10:56 PM

QUOTE (machi @ Jul 20 2011, 01:41 PM) *
South pole of Vesta in stereo.


Really nice Daniel.

Posted by: machi Jul 21 2011, 12:04 AM

Thank you all!

I prepared one more cross-eye/anaglyph stereo image, using second published hi-res image.

 

Posted by: peter59 Jul 21 2011, 09:07 AM

Today is Thursday, maybe we'll see images acquired on July 18 ?
http://dawn.jpl.nasa.gov/mission/status.asp
Dawn team usually publishes something on Thursday.

Posted by: belleraphon1 Jul 21 2011, 11:17 AM

Awesome!

Thanks machi

Posted by: Phil Stooke Jul 21 2011, 02:17 PM

Recent images would be of a narrow crescent, but in a few days we will be seeing the northern hemisphere... brand new territory again, and from closer range.

Phil

Posted by: Juramike Jul 21 2011, 02:25 PM

With such a lumpy surface, the high-phase images should be pretty dramatic.

Posted by: tfisher Jul 21 2011, 04:05 PM

QUOTE (Stefan @ Jul 20 2011, 11:20 AM) *
The distance for that image was (or should have been) 15222 km (center of Vesta). You already know the angular extent of one pixel. You tell me where you are wrong...


I'm curious about the answer as well. I get a diameter of 615km trying to replicate the calculation, and I don't see anything wrong with how Emily is doing it. But that is well outside the biggest dimension of the oblate spheroid model. Is it just that the oblate spheroid is that lousy of a fit for vesta's true shape?

Posted by: Phil Stooke Jul 21 2011, 04:46 PM

Hopefully this will be out of date very soon, but here's a composite view of all the closer images we have seen so far. Please let me know if I am missing any.

Phil



(EGD points out - I should have scaled the first to match the long axis dimension, not the polar axis!)

Posted by: kap Jul 21 2011, 05:35 PM

QUOTE (Phil Stooke @ Jul 21 2011, 06:17 AM) *
Recent images would be of a narrow crescent, but in a few days we will be seeing the northern hemisphere... brand new territory again, and from closer range.

Phil


It was my understanding that a good portion of the northern hemisphere will be in darkness (winter) for the first months of the mission, am I mistaken in believing that?

-kap

Posted by: Phil Stooke Jul 21 2011, 05:44 PM

Only the north polar area itself will be hidden - most of the northern hemisphere will be visible now.

Phil

Posted by: elakdawalla Jul 21 2011, 05:56 PM

QUOTE (tfisher @ Jul 21 2011, 08:05 AM) *
I'm curious about the answer as well. I get a diameter of 615km trying to replicate the calculation, and I don't see anything wrong with how Emily is doing it. But that is well outside the biggest dimension of the oblate spheroid model. Is it just that the oblate spheroid is that lousy of a fit for vesta's true shape?

Thanks for checking my math, and now I feel a little more confident in questioning the factor-of-2 enlargement. Here's the http://adsabs.harvard.edu/abs/2007DPS....39.3003M on Vesta's dimensions from Hubble data (289, 280, 229 km semi-major axes, or 578, 560, 468 for diameter), which refers to a previous http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1989BAAS...21Q1247M&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf with a diameter based on an occultation (561 +/- 3 km). In no way are any of these consistent with any principal axis diameter above 600 kilometers. So either the enlargement factor or the range to the target has not been reported correctly.

I know I'm beating a dead horse here and I think the Dawn team now regards me as kind of a pest and really I am very excited about seeing a new world. But it's hard to do outreach when I know that some of the information that I'm getting must be wrong.

Posted by: elakdawalla Jul 21 2011, 06:04 PM

Regarding the enlargement, I like neither the blurriness nor the jaggedness of the limb. Both, I think, do a disservice to the FC which I think is supposed to be a very fine instrument. Now that details can be resolved, it's much better just to post images that are not enlarged. Consider http://photojournal.jpl.nasa.gov/jpeg/PIA14313.jpg. Now consider http://photojournal.jpl.nasa.gov/jpeg/PIA06064.jpg. The Cassini image looks so much crisper, and a comparison between the blurry-looking FC image and really any other deep-space camera image makes FC look like a crappy instrument, when we know it's not. it's not a fair comparison, because the Cassini image started out with 800 pixels, while the Dawn one started out with only 400. But most people don't know that; they just see a blurry, pixelated image.

Posted by: Stefan Jul 21 2011, 07:54 PM

QUOTE (elakdawalla @ Jul 21 2011, 07:56 PM) *
I know I'm beating a dead horse here and I think the Dawn team now regards me as kind of a pest and really I am very excited about seeing a new world. But it's hard to do outreach when I know that some of the information that I'm getting must be wrong.


Please realise that at this stage, we face similar uncertainties. There is one thing about which I am 100% sure: the enlargement factor is 2. But then, there are so many possibilities:

1. I calculated the distance wrong, and my colleague made the same mistake
2. The SPICE kernel we used is wrong
3. We used the wrong SPICE kernel
4. The camera FOV has shrunk
5. Your measurement is correct
...

We are using trajectory *predictions*! Would it make a difference if I say that we (the FC team) are going through an extremely busy period, in which our main priority is to ensure the FC is in good health and taking images as planned?

Posted by: Stu Jul 21 2011, 09:00 PM

QUOTE (elakdawalla @ Jul 21 2011, 06:56 PM) *
... I think the Dawn team now regards me as kind of a pest ...


I'm sure that's not the case.

...but if any of them do think like that, then I really think they should be grateful that a respected and accomplished science journalist like yourself is so excited by, and passionate about, the mission, wants to ensure its success by writing about it for a public audience, and is trying hard to get the facts straight in order to write accurate reports.

Posted by: elakdawalla Jul 21 2011, 09:06 PM

I apologize for being such a pest. I think I don't properly appreciate or understand the differences in navigational certainty between an ion-powered mission -- and one that's approaching a small body with relatively poorly constrained mass -- and the kind of orbital or flyby missions I'm accustomed to writing about. I'm glad to have a definitive answer about the enlargement factor, and now at least I think I understand which bits of information are the sources of the uncertainty. I had assumed wrongly that the range to the target was one of the more precisely known bits of information. So, sorry! I hope you'll take my pestiferousness as a sign of my real interest in and excitement about the mission!

Posted by: tfisher Jul 21 2011, 09:45 PM

another thing to question is the size of the error bars on the Hubble measurements of Vesta's size. The Thomas et al 1997 paper is online at http://www2.keck.hawaii.edu/inst/people/conrad/research/ccre-wg/icarus97.pdf. Skimming through that, they use images with a resolution of 52km per pixel. They estimate errors in the semi-major axes of +/- 5km, or 1/10 of a pixel. I don't know details of their fitting, but it doesnt seem crazy to me that they might have missed by a bigger fraction of a pixel than that. Getting sub-pixel info from images is hard.

Posted by: elakdawalla Jul 21 2011, 09:52 PM

What surprised me about that paper was that their definitive reference for Vesta's size based on occultation data was from 1989. My 5 minutes of trawling in ADS didn't turn up anything obviously better. Given Vesta's huge size and interesting shape I'm surprised there haven't been more, better-quality occultation studies since then.

EDIT: Looking at fig 2 of that paper, I think it can be stated pretty strongly that no semi-axis of Vesta is at all likely to be longer than 290 km.

Posted by: Juramike Jul 21 2011, 10:12 PM

New image! http://www.nasa.gov/mission_pages/dawn/multimedia/dawn20110721-image.html

Posted by: elakdawalla Jul 21 2011, 10:17 PM

OK, now it looks like Hyperion. Vesta's an asteroid of many guises smile.gif

Posted by: ugordan Jul 21 2011, 10:18 PM

So *that's* what it was reminding me of!

Posted by: tfisher Jul 21 2011, 10:21 PM

QUOTE (elakdawalla @ Jul 21 2011, 04:52 PM) *
Looking at fig 2 of that paper, I think it can be stated pretty strongly that no semi-axis of Vesta is at all likely to be longer than 290 km.

I'm not so convinced. My understanding is those numbers are for best fit ellipses. But Vesta has a big chunk missing on one side. Fitting an ellipse to a shape which isn't an ellipse could give a systematic bias. The missing chunk would make all the best fit ellipses underestimate the true maximum dimension.

Posted by: Mongo Jul 21 2011, 10:23 PM

Has anybody looked at the effects of geometric perspective? Dawn is now close enough to Vesta that it should show a somewhat greater angular diameter as seen from Dawn than you would expect by simply dividing Vesta's diameter by its distance from Dawn. Vesta's edge, as seen by Dawn, is actually slightly closer to Dawn than the "great circle" perpendicular to the line connecting the centre of Vesta with Dawn, which would be slightly smaller as seen by Dawn (if it could be seen through solid rock). Therefore the number of pixels from one side of Vesta to the other would be slightly more than calculated using Vesta's diameter, and its distance from Dawn.

I do not know if the difference would be enough to account for the discrepancy described earlier, but somebody could check?

Posted by: jsheff Jul 21 2011, 10:53 PM

I have a question about Vesta's reference grid. A few days ago an image release specified as "The original image was map-projected, centered at 55 degrees southern latitude and 210 degrees eastern longitude." OK, the latitude is determined by Vesta's spin axis, of course, but how is the system of longitude determined? What feature on Vesta defines 0° (or some other standard) longitude?

Posted by: elakdawalla Jul 21 2011, 11:37 PM

The answer to that question is in the paper that tfisher linked to: http://www2.keck.hawaii.edu/inst/people/conrad/research/ccre-wg/icarus97.pdf

QUOTE
We propose a prime meridian centered on the most prominent visible feature. This is a nearly circular area, about 200 km across, with a lower albedo than its surroundings. Its origin is unknown at this time. Because it is the largest visible feature on Vesta, the name Olbers Regio has been proposed in honor of the asteroid’s discoverer; the name is not yet official. We have adjusted the longitude system to put 08 longitude at the center of this feature....

Posted by: jsheff Jul 22 2011, 12:43 AM

QUOTE (elakdawalla @ Jul 21 2011, 07:37 PM) *
The answer to that question is in the paper that tfisher linked to: http://www2.keck.hawaii.edu/inst/people/conrad/research/ccre-wg/icarus97.pdf


Thanks, Emily ...

Posted by: Greg Hullender Jul 22 2011, 01:49 AM

QUOTE (Mongo @ Jul 21 2011, 03:23 PM) *
Dawn is now close enough to Vesta that it should show a somewhat greater angular diameter as seen from Dawn than you would expect by simply dividing Vesta's diameter by its distance from Dawn.


Well, it's the difference between 2*r/d vs 2*arcsin(r/d), right? So if I take 10,500 km as the distance and 289 km as the radius, then I get an angular diameter of 3 degrees, 9 minutes, 16 seconds. As I figure it, your approximation is 2 seconds smaller.

In survey orbit, at 2700 km, the difference will amount to about a minute and a half. (Someone should double check me, though.)

--Greg

Posted by: Mariner9 Jul 22 2011, 03:44 AM

I think we have a new image just posted at JPL website. Taken on July 18th.

Not sure how to embed a thumbnail, so I'll just have to put in a link.

http://www.nasa.gov/mission_pages/dawn/multimedia/dawn20110721-image.html


Posted by: djellison Jul 22 2011, 04:11 AM

QUOTE (Mariner9 @ Jul 21 2011, 07:44 PM) *
I think we have a new image just posted at JPL website. Taken on July 18th.


Already being discussed for a page of this thread - first cited here

http://www.unmannedspaceflight.com/index.php?showtopic=7011&st=60&p=175945&#entry175945



Posted by: dilo Jul 22 2011, 07:16 AM

QUOTE (Greg Hullender @ Jul 20 2011, 02:13 PM) *
Another interesting stat might be energy/kilogram. Although kinetic energy is increasing, potential energy is decreasing.

Nice idea, Greg; this is the output in terms of energy per mass unit (on the left), with a zoom around the insertion time:

On the right, a plot of ratio between the two energies vs distance (obviously, I considered absolute vaue of potential energy, which is increasing while approaching Vesta); target is a 2700 km distance with a 0.5 ratio (a circular survey orbit).

Posted by: Phil Stooke Jul 22 2011, 02:09 PM

I have been playing with a very rough map of Vesta from the released images. Please bear in mind this is VERY approximate and not controlled by any shape model or pointing information. It is intended just to show approximate image coverage and locations of major features. The tie to more distant images is very rough. Zero longitude in the Hubble map/shape model coordinates would be at the left end (and the right, I guess). A much earlier version of this, posted here earlier, used a different (arbitrary) zero longitude.

Phil


Posted by: Phil Stooke Jul 22 2011, 07:53 PM

Dawn's looping round the north side now, so the 'where is Dawn' page is showing an illuminated crescent:

http://neo.jpl.nasa.gov/orbits/fullview4.jpg

(presumably that links to the current image, when you link to it, not the version I am looking at now)

Enough of the surface is visible to see that the texture map currently in use is really from Tethys! Penelope and the chain of craters to its west are visible right now.

Phil

Posted by: elakdawalla Jul 22 2011, 08:04 PM

biggrin.gif Funny, and well spotted! I've attached the current screenshot, since it will have changed by the time some people here look at it.


 

Posted by: Phil Stooke Jul 23 2011, 12:28 PM

Here's a crater - middle of this view - with dark markings inside and outside its rim. Other distant images show at least one other dark spot like this as well.

Phil


Posted by: ElkGroveDan Jul 23 2011, 02:31 PM

It looks like maybe a fresh impact inside an older crater.

Posted by: Phil Stooke Jul 23 2011, 02:34 PM

I'd say excavation of dark subsurface material.

Phil

Posted by: peter59 Jul 23 2011, 10:13 PM

I'm curious if MYSTIC simulator use real data to create the image of Vesta ? Is this a true picture of Vesta? If it corresponds to reality, it is very interesting.


Ion engine is not operating from a few hours, I hope that the framing camera just works.

Posted by: Gsnorgathon Jul 23 2011, 11:09 PM

http://www.unmannedspaceflight.com/index.php?showtopic=7011&view=findpost&p=176019, that's Tethys.

Posted by: elakdawalla Jul 24 2011, 02:38 AM

If our images of Vesta were already that good, we'd have no need of a Dawn mission...

Posted by: Juramike Jul 24 2011, 02:50 AM

QUOTE (Phil Stooke @ Jul 23 2011, 07:28 AM) *
Here's a crater - middle of this view - with dark markings inside and outside its rim. Other distant images show at least one other dark spot like this as well.


Tried to line up the IR image with this view. If I got it right, that crater is right in the middle of a "greenish" splatty zone. This is the same tint as the sharp scarp face. There are two other greenish splatty zones below the central peak in the image, but I'm almost positive this area is misregistered. I'm going to run with the idea that the green tint indicates fresher material.



Posted by: Juramike Jul 24 2011, 02:56 AM

BTW, here's the blink animation between the original black and white image, and the manually warped IR image:



[animated GIF: Click to animate]

Posted by: TritonAntares Jul 24 2011, 10:21 AM

QUOTE
I have been playing with a very rough map of Vesta from the released images. Please bear in mind this is VERY approximate and not controlled by any shape model or pointing information. It is intended just to show approximate image coverage and locations of major features. The tie to more distant images is very rough. Zero longitude in the Hubble map/shape model coordinates would be at the left end (and the right, I guess). A much earlier version of this, posted here earlier, used a different (arbitrary) zero longitude.

Phil


As your rough map is rather disorted it would be interesting to see a south polar view, probably with a grid.
For sure that is only a approximate but a nice overview showing locations of major features

Posted by: dilo Jul 25 2011, 06:59 AM

In the last hours, Dawn turned off it's engines and distance/speed are quite stable; this could means he reached a circular orbit but, looking to the plots below, actual speed/energy are below such a level, suggesting that probe is near the apoapsis of an elongated orbit:


Indeed, current orbit should be almost circular (5500x5200 km, e=0,028) with a 161 hours period. Obviously, this is true until next (imminent) engine burn, which should be in direction roughly opposite to orbital motion in order to have a progressive distance reduction, spiraling toward survey orbit...

Note: In all my figures, I am assuming that distance declared in the simulator is measured from Vesta's centre...

Posted by: Phil Stooke Jul 25 2011, 01:45 PM

"it would be interesting to see a south polar view, probably with a grid."

For the time being I will not do this. Better to leave it to the Dawn team to do a proper one. Think of my map as just a guide to image coverage at the moment. For one thing, the latitude scaling is very uncertain.


Meanwhile Dawn has looped over the north pole, and then the equator over the weekend, and it's now back over the south pole.

Phil


Posted by: alan Jul 25 2011, 04:37 PM

Next Monday on NASA TV:

QUOTE
August 1, Monday

2 p.m. - NASA Science News Conference - Dawn Images of the Vesta Asteroid - JPL (Public, HD and Media Channels)

Posted by: elakdawalla Jul 25 2011, 06:29 PM

Goody goody smile.gif

Posted by: stewjack Jul 25 2011, 07:08 PM

RE: August 1, Monday 2 p.m. - NASA Science News Conference - Dawn Images of the Vesta Asteroid - JPL (Public, HD and Media Channels)

I think that is 2:00 PM Eastern Time Zone or 18:00 GMT for those unfamiliar with NASA TV's broadcast schedule.

Posted by: Explorer1 Jul 25 2011, 08:24 PM

Yes, they're always on eastern time. I sincerely hope for movies of the first orbit (has it even been completed yet)?

Posted by: Phil Stooke Jul 25 2011, 08:33 PM

Very close to completed, at the least. We're over the south pole again (approximately).

A Vesta rotation movie is more likely that an orbital movie because of the frequent times when no images are taken.

Phil

Posted by: elakdawalla Jul 25 2011, 08:55 PM

I agree with Phil -- I think (or at least hope) we'll be seeing one of the "rotation characterizations" in movie format, and I would hope also another nice image release from closer in, or maybe more of their reprojected mosaics.

Posted by: pablogm1024 Jul 26 2011, 02:23 AM

QUOTE (Explorer1 @ Jul 25 2011, 09:24 PM) *
Yes, they're always on eastern time. I sincerely hope for movies of the first orbit (has it even been completed yet)?

Although strictly the spacecraft is about to complete the first orbit around Vesta, the mission is still are officially on Approach. Science activities will not start until the first week of August.
In the meantime, back to the lit side of Vesta, the camera continues to do optical navigation. I am sure the media team will soon have new images published.

Posted by: elakdawalla Jul 27 2011, 04:01 PM

QUOTE
MEDIA ADVISORY: M11-157

NASA TO UNVEIL FULL-FRAME IMAGE OF VESTA AT NEWS CONFERENCE

WASHINGTON -- NASA will host a news conference on Monday, Aug. 1, at 2 p.m. EDT, to discuss the Dawn spacecraft's successful orbit insertion around Vesta on July 15 and unveil the first full-frame images from Dawn's framing camera. The news conference will be held in the Von Karman auditorium at NASA's Jet Propulsion Laboratory (JPL), 4800 Oak Grove Dr., Pasadena, Calif. Journalists also may ask questions from participating NASA locations or join by phone. To obtain dial-in information, journalists must contact JPL's Media Relations Office at 818-354-5011 by 9 a.m. PDT on Aug. 1.

NASA Television and the agency's website will broadcast the event. It also will be carried live on Ustream, with a live chat box available, at:
http://www.ustream.tv/nasajpl2

Goody goody goody smile.gif

I'm moving the Asimov discussion to http://www.unmannedspaceflight.com/index.php?showtopic=7023 now...

Posted by: bagelverse Jul 27 2011, 04:49 PM

Does full frame mean full lighted view of Vesta, or full frame of the field of view of the camera?

Posted by: alphasam Jul 28 2011, 02:20 AM

Hi, long-term lurker

Anyway I hadn't seen this discussed so far, I hope we'll get to see for ourselves soon, but this piece from the Beeb sounds interesting.

http://www.bbc.co.uk/news/science-environment-14249515

QUOTE
And in a tantalising trailer of pictures yet to be released, Professor Chris Russell, from the University of California Los Angeles told the BBC this week: "The surface is much more colourful; the colours are deeper than they are on the [Earth's] Moon." "The Moon is rather bland compared to the surface [of Vesta]." "That was my first surprise when we started taking some colour images. There are orange regions, and bluish regions. The colours are deeper than I've seen before on asteroidal and lunar-type bodies."

Posted by: dilo Jul 28 2011, 07:43 AM

First complete orbit is now almost accomplished (Dawn hasn't been using engines in the last 5 days).
During orbit, the speed and distance were constant; such a circular orbit is possible only if we assume that "distance from Vesta" declared in the simulator is measured from asteroid's surface (otherwise, speed should be significantly higher). I updated plots, using an average Vesta radius of 266km and assuming that also final survey orbit height will be 2700 km from surface:


Meanwhile, look to last spectacular "family portrait" from simulator:

Posted by: kap Jul 28 2011, 06:25 PM

QUOTE (dilo @ Jul 28 2011, 12:43 AM) *



I'm still a newb at this, is r on the left hand chart the orbital radius?

Thanks,
-kap

Posted by: pablogm1024 Jul 29 2011, 12:10 AM

QUOTE (bagelverse @ Jul 27 2011, 05:49 PM) *
Does full frame mean full lighted view of Vesta, or full frame of the field of view of the camera?

By now Vesta is filling the field of view of the Framing Camera, so you will see very nice image of Vesta even without having to zoom in wildly. Indeed, the FC has a 1024x1024 CCD, so the full frame view would fill most of your screen essentially on any laptop.

Posted by: Greg Hullender Jul 29 2011, 02:19 AM

QUOTE (kap @ Jul 28 2011, 10:25 AM) *
I'm still a newb at this, is r on the left hand chart the orbital radius?

It's the distance from Dawn to the center of Vesta. When Dawn is in a circular orbit, it'll be the orbital radius. Part of the point is trying to determine when that happens.

--Greg

Posted by: Gladstoner Jul 29 2011, 04:28 AM

New image!

http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_072311.asp

Hmmm.... Is that a dead spider near the bottom? smile.gif

Posted by: ElkGroveDan Jul 29 2011, 04:38 AM

I was looking at that. Unusual dark splat on the inside of the crater.

Here it is rotated 180, enlarged 5.5x , sharpened a bit, etc.

 

Posted by: mchan Jul 29 2011, 05:27 AM

If I have been following this correctly, the July 23 view is of the north on the night side, yes?

Posted by: Explorer1 Jul 29 2011, 05:48 AM

Iapetus, eat your heart out; we have a new snowman!

Vesta is the rock of a thousand faces, indeed (though this doesn't look like a very 'dark' side like the caption says, IMO).

Posted by: volcanopele Jul 29 2011, 05:58 AM

QUOTE (ElkGroveDan @ Jul 28 2011, 09:38 PM) *
Unusual dark splat on the inside of the crater.

Remembering my crater dynamics, that would mean that it JUST touched a darker, mafic layer (remember boys and girls, basalt is at the surface (or was at least when it formed, gabbro is below your feet, so not knowing where this stuff was formed, let's just say mafic)

By the way, I am definitely printing that picture for my wall in my office.... Where is the swear jar? ***** **** ***** *****!!!

Posted by: pablogm1024 Jul 29 2011, 06:33 AM

QUOTE (mchan @ Jul 29 2011, 06:27 AM) *
If I have been following this correctly, the July 23 view is of the north on the night side, yes?

Indeed, this is a view over the dark north pole and part of the northern hemisphere. And, btw, the surroundings of the snowman craters ARE indeed visibly darker, I promise.

Posted by: Hungry4info Jul 29 2011, 07:03 AM

That's one huge groove. blink.gif

Posted by: Explorer1 Jul 29 2011, 07:19 AM

I thought the caption meant dark in the same way there's a colloquial 'dark side' of the moon.
If the north actually is darker than the south (and not just shadow), then I stand corrected!

Posted by: belleraphon1 Jul 29 2011, 10:53 AM

New Event Time NASA To Unveil Vesta Images At News Conference
Monday Aug 1 at noon EDT (changed from 2:00pm)

Update -- New Event Time NASA To Unveil Vesta Images At News Conference WASHINGTON -- NASA will host a news conference on Monday, Aug. 1, at noon EDT, to discuss the Dawn spacecraft's successful orbit insertion around Vesta on July 15 and unveil the first full-frame images from Dawn's framing camera. The news conference will be held in the Von Karman auditorium at NASA's Jet Propulsion Laboratory (JPL), 4800 Oak Grove Dr., Pasadena, Calif. Journalists also may ask questions from participating NASA locations or join by phone.

To obtain dial-in information, journalists must contact JPL's Media Relations Office at 818-354-5011 by 8 a.m. PDT
on Aug. 1.

NASA Television and the agency's website will broadcast the event. It also will be carried live on Ustream, with a live chat box available, at:


http://www.ustream.tv/nasajpl2



Posted by: Phil Stooke Jul 29 2011, 01:30 PM

To clarify the 'dark' description... and see the camera facebook page for more of those comments! - Vesta has a large low albedo feature on its equator in one hemisphere, first seen using speckle interferometry by Jack Drummond and colleagues in the 90s, and confirmed by Hubble. It is referred to as Olbers and is used as the zero longitude in the Hubble-derived shape model. This image includes the darker longitudes at low latitudes. It is the low-albedo side.

Phil

EDIT - now the caption suggests it referred to passing over the dark (= unilluminated) side prior to taking this image...

Posted by: Bjorn Jonsson Jul 29 2011, 01:36 PM

The latest image is interesting. The dark area to the right of and a bit below center is interesting. I get the impression that is is at least partially caused by topography. But there is another dark area left of center and its right edge is rather sharply defined. It even seems that some craters may have been partially erased there - this is going to be interesting to see at higher resolution:



If these dark/brighter areas are mostly albedo variations Vesta has remarkably big albedo variations.

It's going to be interesting to create DEMs of Vesta using stereo imagery once the raw image data appears at the PDS. Doing so should distinguish between topography and albedo variations (anaglyphs, more images or even false color images might do so as well).

Vesta now looks like a weird mix of Miranda, Mimas, grooved asteroids/satellites and possibly Hyperion to me. But mostly it's just uniquely Vesta.

Posted by: Phil Stooke Jul 29 2011, 02:13 PM

A comparison view to show where we are...

Phil


Posted by: Phil Stooke Jul 29 2011, 03:52 PM

... and a map. Very approximate and uncontrolled still.

Phil


Posted by: dilo Jul 29 2011, 03:52 PM

Engines on again!

 

Posted by: Steve G Jul 29 2011, 05:07 PM

I can't help but get a sense of familiarity with those two large craters. Ritter and Sabine from Ranger has a close resemblance. In any case, the flat floored nature of the craters seem out of place on such a small body.

 

Posted by: elakdawalla Jul 29 2011, 05:47 PM

Aha, Steve G, that's what made them so strange-looking -- most of the craters on Vesta seem to be simple bowl shapes, but these do have flat floors.

Here's a cartoon of what I think I see. (Warning: this is more arm-wavey and speculative than my usual -- so it's probably wrong but I couldn't help but try to interpret this.) I'm not sure if the "head" of the snowman formed at the same time as the other two craters -- it looks more rounded so I think it predated the other two. But I think the other two formed at the same time (outlined in pink). You can see an area immediately surrounding the two craters that is almost devoid of impact craters -- that's the continuous ejecta blanket. Beyond that is the dark area that Bjorn noted -- that, I'm going to argue, is the discontinuous or secondary ejecta. I was puzzled about the lumpy looking deposit within both craters, which partially fills their floors -- I think that's where the two ejecta curtains of the simultaneously forming craters collided and piled up against each other so that all the ejecta wound up falling on the region where the two craters touch.

YMMV. smile.gif


 

Posted by: kap Jul 29 2011, 06:25 PM

QUOTE (Explorer1 @ Jul 28 2011, 11:19 PM) *
I thought the caption meant dark in the same way there's a colloquial 'dark side' of the moon.


I don't think that could be correct, Vesta is not tidaly locked to anything. It rotates on it's axis every 5 hours or so. I think that part of the northern hemisphere is dark right now because it's "winter" there and the pole is currently tilted away from the sun. Anyone know what the figure on Vesta's polar tilt is relative to the ecliptic?

-kap

Edit: looks like we are still looking at the south pole, but the large impact crater is dark and we are seeing some of the surrounding features.

Posted by: Explorer1 Jul 29 2011, 07:12 PM

Wikipedia says 7 degrees to the ecliptic.
Phil's map implies that we should get some pretty good coverage of the north, I was worried about a Uranus-style scenario where we'd have nothing, that's not the case.

Posted by: Hungry4info Jul 29 2011, 09:22 PM

We'll be at the asteroid long enough for its 'seasons' to reveal the rest of it anyway.

Posted by: pablogm1024 Jul 29 2011, 10:11 PM

QUOTE (kap @ Jul 29 2011, 06:25 PM) *
Edit: looks like we are still looking at the south pole, but the large impact crater is dark and we are seeing some of the surrounding features.

Sorry to correct you, kap, but see http://maps.grida.no/go/graphic/extreme-days-and-nights-daylight-variation-in-the-arctic-reykjavik-murmansk-and-alert for an example. With tilted axis, each pole stays dark for half an orbit and then in the light for another half.

Taking into account that a couple of weeks ago we imaged the south pole, it is impossible that it is now in the dark. What you (don't) see here is the north pole in the dark and part of the northern equatorial region.

Regards

Posted by: kap Jul 29 2011, 10:21 PM

QUOTE (pablogm1024 @ Jul 29 2011, 02:11 PM) *
Sorry to correct you, kap, but see http://maps.grida.no/go/graphic/extreme-days-and-nights-daylight-variation-in-the-arctic-reykjavik-murmansk-and-alert for an example. With tilted axis, each pole stays dark for half an orbit and then in the light for another half.

Taking into account that a couple of weeks ago we imaged the south pole, it is impossible that it is now in the dark. What you (don't) see here is the north pole in the dark and part of the northern equatorial region.

Regards


Ah I see, I just wrote a whole post about how I thought the dark area in this image: http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_072311.asp was the south pole and the image was upside down, but I just looked at it some more and I was incorrect, I just don't think I had the correct perspective in my head.

-kap

Posted by: volcanopele Jul 29 2011, 10:49 PM

Thankfully, Vesta has a nice, clearly visible marker for where the south pole is smile.gif

Posted by: elakdawalla Jul 29 2011, 10:55 PM

Yeah, I think the only big body in the solar system that does a nicer job of providing a visual marker of its coordinate system is Iapetus!

Posted by: mchan Jul 30 2011, 01:30 AM

QUOTE (Explorer1 @ Jul 29 2011, 11:12 AM) *
Wikipedia says 7 degrees to the ecliptic.

Ah, that is the inclination of the orbit to the ecliptic. The same article states an axial tilt of 29 degrees. Axial tilt is usually stated relative to the orbital plane of the object and not the ecliptic.

Posted by: tanjent Jul 30 2011, 06:30 AM

QUOTE (Hungry4info @ Jul 29 2011, 03:03 PM) *
That's one huge groove. blink.gif

Almost like the thread on a lightbulb. Where in the solar system do you suppose it was screwed in?

Posted by: antipode Jul 30 2011, 07:42 AM

Yeah, are we seeing some of Jutzi & Asphaug's (2011) "Mega Ejecta" here?

P

Posted by: Paolo Jul 30 2011, 10:14 AM

QUOTE (Phil Stooke @ Jul 29 2011, 05:52 PM) *
... and a map.


how things change! this was the first map of Vesta ever, compiled in 1983 from monitoring its spectrum over one rotation

 

Posted by: Phil Stooke Jul 30 2011, 12:31 PM

Nice one! This map was made by Michael Gaffey by studying how the reflection spectrum changed as Vesta rotates. As he used an incorrect rotation period (twice the true period) it can't be easily compared with new maps, his features must be distributed differently. This specific map is a redrawing for Sky and Telescope. The original is in his abstract for LPSC in 1983, and it shows something not seen here... the south pole was tilted away from Earth at the time of observation, so here the map says 'no data' but Gaffey's original map labelled it "Here there be dragons". So now you know what lives in the south pole... sounds like the mountain should be called The Lonely Mountain.

Phil


Posted by: Paolo Jul 30 2011, 12:41 PM

the "here be dragons" map is here http://cdsads.u-strasbg.fr/abs/1983LPICo.497...14G

Posted by: kwp Jul 30 2011, 02:31 PM

QUOTE (elakdawalla @ Jul 29 2011, 03:55 PM) *
Yeah, I think the only big body in the solar system that does a nicer job of providing a visual marker of its coordinate system is Iapetus!

Don't forget Saturn's thoughtful provision of a marker denoting both its equator and the orbital plane of its family of moons.

Posted by: Steve G Jul 30 2011, 05:35 PM

Here is a magnified and sharpened look at the far right rim, giving a good cross section of the large trough. Another deep crater and a mountain which promises to be spectacular when we have a closer look. I added some sky to the picture so there is a less cramped feeling to the image.

 

Posted by: dilo Jul 30 2011, 08:41 PM

The progressive orbit reduction through engine-controlled spiraling is clearly ongoing:

 

Posted by: Explorer1 Aug 1 2011, 04:01 PM

Press conference starting...

Posted by: Phil Stooke Aug 1 2011, 04:04 PM

http://www.nasa.gov/mission_pages/dawn/news/dawn20110801.html

Phil

Posted by: elakdawalla Aug 1 2011, 04:07 PM

Cool rotation movie!! What a cool mini-planet!
http://www.nasa.gov/multimedia/videogallery/index.html?collection_id=65362&media_id=104094441
I am at JPL now so ironically I can't do my usual quick image processing magic. I will plan to decompose this movie into separate frames and also make an animates GIF later today -- but would be very happy if someone else beat me to it!

Posted by: Phil Stooke Aug 1 2011, 04:15 PM

The map is at the Photojournal now.

Phil


Posted by: ugordan Aug 1 2011, 04:25 PM

Whoa, groovy!

Posted by: Explorer1 Aug 1 2011, 04:27 PM

False color... interesting splashes.

Posted by: Juramike Aug 1 2011, 04:57 PM

Well, now we know what the image release policy is going to be in the future...like MESSENGER with a selected processed image of the day.
(But no raw images like MER or Cassini). Ah well.

Posted by: Explorer1 Aug 1 2011, 04:58 PM

There will still be PDS releases, right?

Posted by: ugordan Aug 1 2011, 04:58 PM

http://www.nasa.gov/images/content/576344main_pia14322-full_full.jpg nicely showcases the equatorial grooves as well as curious dark spots in the dark hemisphere. I wonder what they're all about. Almost look like ejecta spray, but clumpy and more sporadic.

Posted by: Juramike Aug 1 2011, 04:58 PM

Press release on images presented: hhttp://www.nasa.gov/mission_pages/dawn/news/dawn20110801.html

Posted by: ugordan Aug 1 2011, 04:59 PM

QUOTE (Explorer1 @ Aug 1 2011, 06:58 PM) *
There will still be PDS releases, right?

Yes. I think that's pretty much mandatory for a U.S. mission. Not sure how it will play out with foreign instruments, but I wouldn't expect problems in this case.

Posted by: MarkG Aug 1 2011, 05:12 PM

Anyone know where/when the recording of the press conference will be available?

Posted by: hendric Aug 1 2011, 05:27 PM

Missed the press conference. Is this a close-up of a potential lava flow? (the darker area in the top right)

http://www.nasa.gov/mission_pages/dawn/multimedia/pia14324.html

Posted by: volcanopele Aug 1 2011, 05:30 PM

One major thought I had coming out of the presser was on the comments regarding the formation of the grooves. Now, Chris Russell stated that one idea is that the grooves formed shortly after the SP impact when Vesta was initially compressed in the N-S direction and then rebounded, forming grooves at the equator. But I think there is another possibility: Upspinning. It is possible that the impact sped up Vesta's rotation. Upspinning would cause the equatorial radius to expand and the polar radius to contract, resulting in extension at the equator and compression at the mid- to high-latitudes. Similar upspin/despin/re-orientation scenarios have been discussed for Iapetus (despinning to explain equatorial ridge) and Enceladus (upspinning and polar wander to explain south polar boundary, equatorial fractures, etc.)

Posted by: john_s Aug 1 2011, 05:36 PM

Complicating the picture is the possibility that the impact also changed the pole orientation, which may be quite likely as the missing mass associated with the impact crater is now aligned with the spin axis (shades of Enceladus again). A changed spin axis would produce stresses comparable to a spin-up or spin-down about the existing axis.

Excuse me if this was discussed at the press conference, which I missed...

John

Posted by: siravan Aug 1 2011, 06:03 PM

In the Enceladus case, change of the axis of rotation can be explained based on polhode phenomenon. But that needs an energy dissipation mechanism, which for Enceladus is based on the tidal lock (as also the possible 'ocean'). But for a free solid body like Vesta, what is the dissipation mechanism?

Posted by: tasp Aug 1 2011, 06:46 PM

My first thought about the cracks was we are seeing crustal sloughing into the crater hole. (it's big, for sure, but technically, the missing segment of Vesta is a hole) The tensile strength of the materials surrounding the crater would need to be checked for consistency this idea. Also, the segments between the cracks would be subject to compressive effects as the assemblage creeped (oozed? shifted?) downslope. Not sure I see anything that might be like that at this resolution in the images.

Posted by: john_s Aug 1 2011, 07:34 PM

QUOTE (siravan @ Aug 1 2011, 12:03 PM) *
In the Enceladus case, change of the axis of rotation can be explained based on polhode phenomenon. But that needs an energy dissipation mechanism, which for Enceladus is based on the tidal lock (as also the possible 'ocean'). But for a free solid body like Vesta, what is the dissipation mechanism?


Large Vesta-sized bodies will settle fairly quickly into stable rotation about the minimum moment of inertia after their rotation is perturbed, due to internal frictional dissipation - tumbling will produce internal stresses that will cause motion along fractures, etc., that will dissipate energy and damp out the tumbling (Burns and Safronov 1973).

John

Posted by: Tayfun Öner Aug 1 2011, 07:54 PM

Here is a quick smoothing of the rotation clip. I had to compress a lot it due to 1 MB limit.

 vesta_smooth_rotation.avi ( 1008.84K ) : 1010
 

Posted by: machi Aug 1 2011, 08:30 PM

Excellent!
Beautiful rotation wheel.gif rolleyes.gif

Posted by: Phil Stooke Aug 1 2011, 08:36 PM

The color image is up on the photojournal now.

Phil

http://photojournal.jpl.nasa.gov/catalog/PIA14325


PS before getting too carried away with explanations of grooves, let's consider the other grooved bodies - will the explanation work more generally?

Posted by: jasedm Aug 1 2011, 08:49 PM

Composed of completely different stuff I know, but it looks remarkably Miranda-esque to me

Posted by: antipode Aug 1 2011, 09:18 PM

The crater count looks low over the impact area - I guess that makes sense, what is it - a billion years old?
Seems to be several sites of mass wasting/downslope movement. And those dark areas are fascinating!

Very very rugged, very very cool. Might be a good place for a lightweight instrumented penetrator (if we ever visit again!)!
Although Ceres is the main course, this is a fantastic entree...

P

Posted by: ugordan Aug 1 2011, 09:22 PM

QUOTE (Tayfun Öner @ Aug 1 2011, 09:54 PM) *
Here is a quick smoothing of the rotation clip.

Very nice!

Posted by: nprev Aug 1 2011, 11:23 PM

Fantastic, Tayfun!!!

Man...there's a LOT of interesting features on this little world!

Posted by: elakdawalla Aug 1 2011, 11:30 PM

QUOTE (Explorer1 @ Aug 1 2011, 09:58 AM) *
There will still be PDS releases, right?

It may be a long wait. I asked about this after the press briefing, and Marc thought that the PDS timeline was 6 months....AFTER they leave Vesta. sad.gif

In the meantime, I have now decomposed the high-resolution version of the animation into its component frames. Here you go, guys; have fun.
http://planetary.s3.amazonaws.com/misc/Vesta_rotating.zip

 

Posted by: volcanopele Aug 1 2011, 11:39 PM

Lol, I got to about frame28 before I noticed your message. Oh well. I will work up a few anaglyphs if and when I find my red-blue glasses. I know it is here somewhere.

Posted by: nprev Aug 2 2011, 12:40 AM

Mrs. nprev's comment on the movie:

"Huh. Looks like biscuit. Even has lines around the middle like biscuit!"

laugh.gif, but insightful. The grooves sure look like compressional features to me from the south polar impact.

Posted by: MarkG Aug 2 2011, 01:04 AM

What can make a series of long, straight grooves along the equator of an isolated self-gravitating body?
Debris collapse into extension cracks is one possibility. But what would cause straight cracks at the thickest part of the body?
In the South Pole impact, as the debris was blasting away, the center of mass of Vesta became shifted towards its North Pole, and the area around the crater rim became very high ground. The result static force on the equatorial region would have been compressive.
However, the dynamic situation would have been different. In solids, compression waves travel faster than shear waves, and the bulk (2/3) of the momentum transfer (apart from vaporization heating) from the impact would be transferred by the shear waves, especially an angular momentum change.
With Vesta getting its bell rung so hard, the equator could have been the mega null/shear zone between torsional resonance modes. With debris falling on/in/around the cracks and partially filling them, we could end up with the current distribution.
With limited information coming from Dawn, they'll just have to put up with theories from the bleachers (cheap seats for the Brits).

Posted by: Phil Stooke Aug 2 2011, 01:45 AM

Despite the Dawn team wanting this to be a very primitive body dating back to the Dawn of the solar system, there's no particular reason why it could not have been larger at a very early date and to have lost a lot of mass though large impacts to become what we see today. I only suggest this to say that the grooves may be explained by events whose records are no longer visible to us. It's like Phobos - everybody wanted the grooves to be the result of Stickney despite the fact they have no geometric relationship to it at all. At least we can lay the old story of Mars ejecta to rest at last!

Phil

Posted by: Gladstoner Aug 2 2011, 01:58 AM

Wow. It looks like baling wire is holding the asteroid together.... smile.gif

It never ceases to amaze me how new types of features keep showing up on these newly explored worlds.

Speaking of new features, this little image artifact

[attachment=25052:Vesta_blemish.JPG]

looks a lot like Tsiolkovskiy on the moon:

[attachment=25053:R3440097...vsky_SPL.jpg]

Posted by: Juramike Aug 2 2011, 03:12 AM

Mashup of 3 images: full frame image coordinated to global mosaic, overlain by a warped false color view of IR data (?) PIA14325:



Full resolution on flickr: http://www.flickr.com/photos/31678681@N07/6000679166/

Posted by: Decepticon Aug 2 2011, 03:17 AM

Gladstoner you read my mind. blink.gif


I can't wait to see close ups of that crater.

Posted by: elakdawalla Aug 2 2011, 03:27 AM

I was excited when I first saw that too until I decomposed the animation and realized that it is in fact an artifact -- a bit of dust somewhere or something. Here's a teeny window on that little "Tsiolkovskiy" -- it doesn't move as Vesta rotates beneath it. There's a few other black specks that don't move from frame to frame.

 

Posted by: Gladstoner Aug 2 2011, 04:37 AM

Heh, I suppose the group of blemishes can be used to calibrate the cropped and blown-up images that are released to the media.

Posted by: pablogm1024 Aug 2 2011, 06:11 AM

QUOTE (Gladstoner @ Aug 2 2011, 05:37 AM) *
Heh, I suppose the group of blemishes can be used to calibrate the cropped and blown-up images that are released to the media.

Man, you are really crafty!!!

Posted by: Lewis007 Aug 2 2011, 06:36 AM

A recording of the Vesta press conference can be seen here http://www.youtube.com/watch?v=DJBcxfxNo-M&feature=channel_video_title

and here
http://www.space-multimedia.nl.eu.org/index.php?option=com_content&view=article&id=7033:nasa-science-news-conference-dawn-images-of-the-vesta-asteroid&catid=1:latest

Posted by: Decepticon Aug 2 2011, 06:44 AM

I shall call it the "Tsiolkovskiy Artifact" tongue.gif

Posted by: Gladstoner Aug 2 2011, 08:06 AM

And the next two largest specks can be "Grimaldi" and "Plato".

Posted by: Stefan Aug 2 2011, 09:32 AM

QUOTE (elakdawalla @ Aug 2 2011, 05:27 AM) *
I was excited when I first saw that too until I decomposed the animation and realized that it is in fact an artifact -- a bit of dust somewhere or something. Here's a teeny window on that little "Tsiolkovskiy" -- it doesn't move as Vesta rotates beneath it. There's a few other black specks that don't move from frame to frame.


These are indeed artifacts present in the raw image. We can correct for most of them by using a flat field.

Posted by: bk_2 Aug 2 2011, 09:44 AM

QUOTE (Phil Stooke @ Aug 1 2011, 09:36 PM) *
PS before getting too carried away with explanations of grooves, let's consider the other grooved bodies - will the explanation work more generally?


It won't work on Phobos, since the grooves on that body tail off on the trailing hemisphere.

It will be interesting to see the extent of these grooves on Vesta.

Posted by: PDP8E Aug 2 2011, 01:26 PM


Here is a little article from the AP about Vesta

http://news.yahoo.com/scientists-stunned-surface-asteroid-vesta-204550456.html

the last line has a 20th century kinda of feel to it:

....The team does not plan to post raw images online as other NASA missions have done. Instead, there will be just one picture released daily ....

Posted by: elakdawalla Aug 2 2011, 01:27 PM

QUOTE (pablogm1024 @ Aug 1 2011, 10:11 PM) *
Man, you are really crafty!!!

Pablo, this community is nothing if not crafty.

QUOTE (PDP8E @ Aug 2 2011, 05:26 AM) *
the last line has a 20th century kinda of feel to it:

....The team does not plan to post raw images online as other NASA missions have done. Instead, there will be just one picture released daily ....

I was very happy when Alicia (who has, several times, been nearly the only reporter besides me present onsite at Von Karman for a press briefing) asked that question, because I figured I'd worn out my welcome with such questions.

Posted by: Stu Aug 2 2011, 03:01 PM

QUOTE (elakdawalla @ Aug 2 2011, 02:27 PM) *
I was very happy when Alicia (who has, several times, been nearly the only reporter besides me present onsite at Von Karman for a press briefing) asked that question, because I figured I'd worn out my welcome with such questions.


Don't worry about it Emily, I think we're just going to have to accept that we're not going to make the mission's Powers That Be change their minds. It's a great shame, but it seems that, unlike the MER team for example, some of them just don't get how much they're going to miss out on having a hugely-enthusiastic community of space enthusiasts and image manipulators on their side, working with their raw images to create exciting new products that would benefit them. I think it's a huge, huge mistake, I really do, and jaw-droppingly short-sighted in this modern age of data sharing and "citizen science" when we're all encouraged to be part of the space missions we follow so devoutly. I don't "feel a part of" DAWN, I feel like I've been told I can watch what's going on but only if I go stand over there, out of the way, and don't make a nuisance of myself.

I'm hugely supportive of the mission, and very grateful for every image we have been shown, but oh, it could be so, so much better than this. Oh well. Roll on MSL! smile.gif

Posted by: Explorer1 Aug 2 2011, 04:18 PM

Don't give up; they may very well change their minds for Ceres.

Posted by: alan Aug 2 2011, 04:25 PM

I was hoping for some numbers (dimensions, mass, density) at the press conference to compare with the previous estimates based on very distant observations. Guess we'll have to wait awhile longer for those.

Posted by: dshaffer Aug 2 2011, 04:27 PM

QUOTE (elakdawalla @ Aug 2 2011, 09:27 AM) *
Pablo, this community is nothing if not crafty.
I was very happy when Alicia (who has, several times, been nearly the only reporter besides me present onsite at Von Karman for a press briefing) asked that question, because I figured I'd worn out my welcome with such questions.


IIRC, the question was whether all raw images will be made available as they were received (like MER), but was there a follow-up question as to why not?

Posted by: hendric Aug 2 2011, 05:03 PM

Any chance of showing Tayfun Oner's wonderful smoothing of the rotation movie to the Powers That Be? They could be getting stuff like this done *for free* by UMSF.

Posted by: algorimancer Aug 2 2011, 06:23 PM

QUOTE (dshaffer @ Aug 2 2011, 10:27 AM) *
...why not?

If these were politicians getting out of line then we, as citizens, would have the option of not re-electing them next time around (this happened in my county a few years ago). In the case of mission PI's, I suppose an equivalent option would be to advocate appropriately to our elected representatives when the next round of mission funding occurs. Not all missions are going to get funded, so we can at least see about ensuring that the ones that do have an immediate data-release policy in place. For that matter, this mission will presumably be seeking a post-Ceres extension....


Posted by: stevesliva Aug 2 2011, 06:40 PM

It's an orbital mission. Do the ones in orbit around the moon, mars, and mercury release everything immediately?

Posted by: climber Aug 2 2011, 06:42 PM

QUOTE (stevesliva @ Aug 2 2011, 08:40 PM) *
It's an orbital mission. Do the ones in orbit around the moon, mars, and mercury release everything immediately?

Cassini?

Posted by: hendric Aug 2 2011, 06:58 PM

That black material on the surface - could that be from carbonaceous chondrites? Those look like they could be dark enough.

Posted by: Mongo Aug 2 2011, 08:14 PM

QUOTE (stevesliva @ Aug 2 2011, 07:40 PM) *
It's an orbital mission. Do the ones in orbit around the moon, mars, and mercury release everything immediately?


These are the ones, currently in their science (imaging) missions, that I am aware of. I am not sure about the other Mars missions, the Lunar missions, etc.

CLASS 1 : Releases all imaging products immediately

MER
Cassini

CLASS 2 : Releases one image per day

Messenger
DAWN

CLASS 3 : Known to be taking images, but no regular releases

All the ESA missions?

Posted by: pablogm1024 Aug 2 2011, 08:33 PM

QUOTE (Mongo @ Aug 2 2011, 08:14 PM) *
These are the ones, currently in their science (imaging) missions, that I am aware of. I am not sure about the other Mars missions, the Lunar missions, etc.

How many of these are in their initial science phase vs. consolidated or extended science phases?

Posted by: Juramike Aug 2 2011, 09:19 PM

Cassini, MER, and Phoenix were releasing raw images to the public during their initial science phases.

Posted by: Stu Aug 2 2011, 09:51 PM

I fear we're going round in circles here. Heels have been dug in. If they were going to change policy they would have done so by now, but someone, somewhere, is simply determined not to release raw images out into the wild. Which is a great shame, and is wrong, and means the mission is losing out on a tremendous amount of interest, good will and public participation, but so be it. I think we'll just have to accept it now and make the best of what we're given. Which is going to be a lot, in the long run, but boy, what a wasted opportunity. sad.gif

Posted by: djellison Aug 2 2011, 10:21 PM

QUOTE (Mongo @ Aug 2 2011, 01:14 PM) *
CLASS 3 : Known to be taking images, but no regular releases

All the ESA missions?


Mars Express VMC - within minutes of hitting the ground
Envisat MIRAVI - on the web daily.


stevesliva - Using the argument that other missions fall short, therefore it's just fine for Dawn to fall short isn't valid. They should all be stepping up to the plate and delivering as Phoenix did, and as VMC, Cassini and MER continue to do.

Posted by: elakdawalla Aug 2 2011, 10:40 PM

Don't forget New Horizons which released raw images during cruise phase. I'm not sure anyone else can say that...?

Posted by: Floyd Aug 2 2011, 10:41 PM

I am a US government grant supported scientist studying microbial genomes. My NIH grants stipulate that I make all raw sequence data available to the scientific community within hours. Biomedical research is just as competitive as the space sciences and we do just fine publishing our results ahead of the competition.
Scientists on the Mer, Casini and Phonex missions seem to have been able to publish their papers in Science and Nature without UMSF or other scientists scooping them. As a scientist who is highly competitive in US government supported research and who makes raw data available freely, I don't understandwhat the Dawn PI could be thinking. He clearly is not trying to follow in the footsteps of Steve Squyres or Carl Sagan. He clearly is not interested in public outreach or public support for NASA at a time when public support is dearly needed. He is not interested in helping young scientists jump in and use his data.
How unbelievably disappointing.

Floyd Dewhirst, DDS, PhD
Senior Member of Staff
The Forsyth Institute
Professor, Department of Oral Medicine,
Infection and Immunity, Faculty of Medicine
Harvard University

Posted by: ElkGroveDan Aug 2 2011, 11:05 PM

ZING!

Posted by: machi Aug 2 2011, 11:06 PM

"My NIH grants stipulate that I make all raw sequence data available to the scientific community within hours."
Interesting, I always thought, that planetary research is most open to anyone (not only scientific community).
It's nice to hear, that this openness isn't specialty of planetary research.

"Don't forget New Horizons which released raw images during cruise phase. I'm not sure anyone else can say that..."
New Horizons isn't ordinary space mission! It's miracle! smile.gif

Posted by: ElkGroveDan Aug 2 2011, 11:14 PM

QUOTE (elakdawalla @ Aug 2 2011, 02:40 PM) *
Don't forget New Horizons which released raw images during cruise phase. I'm not sure anyone else can say that...?

unless you count Phoenix's image of its soil scoop taken during cruise rolleyes.gif

Posted by: Bart Aug 2 2011, 11:27 PM

QUOTE (Mongo @ Aug 2 2011, 12:14 PM) *
CLASS 2 : Releases one image per day

If it really is once per day, where is today's image?

Posted by: tedstryk Aug 2 2011, 11:34 PM

If they do as Messenger has done and have speedy PDS releases, I don't see a problem. I would like full raw releases as the images come in, but I can see the argument against it as well.

Posted by: volcanopele Aug 2 2011, 11:50 PM

How about one image per Vesta day? *ducks and runs*

Posted by: dilo Aug 2 2011, 11:58 PM

Science Survey Orbit is almost reached:


Now, Dawn is engine-off on almost circular orbit (taking navigation pictures?)... next engine burn could be the final one before "definitive" orbit insertion!

Posted by: Gladstoner Aug 3 2011, 12:04 AM

I too am a bit disappointed with the slow image releases, but because there is so much to take in with each new image, not to mention that the mission was almost cancelled -- twice, I'm happy that there is anything to see at all. After staring at the Hubble images for the past several years, I'm thrilled to see the smorgasbord of features and detail on this newly revealed, yet strangely familiar world.

(BTW, I'm not so sure I'll be the same if there is a similar policy with MSL. Having traveled to the American southwest 11 times in the last 20 years, I will probably have minor conniption fits if I have to stick to my imagination at Gale. For some of us travelers and hikers, its all about rolls and rolls of film -- and memory cards -- with thousands of photos....)

Posted by: Explorer1 Aug 3 2011, 12:05 AM

SOHO does pretty much constant releases, does it not count as a ESA mission (or because its not a planet mission)?

Posted by: Gladstoner Aug 3 2011, 12:14 AM

QUOTE (Explorer1 @ Aug 2 2011, 07:05 PM) *
SOHO does pretty much constant releases, does it not count as a ESA mission (or because its not a planet mission)?


SOHO images are probably released quickly because solar activity potentially has economic consequences across the world and needs to be disseminated in a timely manner.

Also, the armchair comet hunters would complain.... smile.gif

Posted by: djellison Aug 3 2011, 12:15 AM

QUOTE (dilo @ Aug 2 2011, 03:58 PM) *
Science Survey Orbit is almost reached:
Now, Dawn is engine-off on almost circular orbit (taking navigation pictures?)... next engine burn could be the final one before "definitive" orbit insertion!



http://dawn.jpl.nasa.gov/feature_stories/spacecraft_begins_science_orbits.asp
" That initial orbit of the rocky world Vesta begins Aug. 11, at an altitude of nearly 1,700 miles"

Posted by: machi Aug 3 2011, 12:27 AM

http://dawn.jpl.nasa.gov/mission/status.asp

"Dawn Completes Spiraling to Survey Orbit"

Posted by: elakdawalla Aug 3 2011, 04:00 AM

QUOTE (Gladstoner @ Aug 2 2011, 05:04 PM) *
I'm not so sure I'll be the same if there is a similar policy with MSL.

MSL is being held to the policy established by MER. You can start your drooling now smile.gif

I was thinking the other day that it would be interesting to try to actually quantitatively analyze the impact of releasing all raw images vs releasing one image a day vs releasing basically nothing except in occasional press releases. All three methods are being used. I've heard the argument before that releasing too many pictures blunts the impact of occasional releases. I know how we all feel about that argument; but I don't know of anyone who's tried to examine and quantify the amount of attention a mission receives and correlate that with their frequency of press releases and image releases. Scientists do (or at least should) respond to data. While I would like to believe that the data would show a greater impact correlating with greater openness with data, there's always the possibility that I'm wrong about that.

Posted by: Juramike Aug 3 2011, 04:34 AM

This might be easy to check.

Next time you give a talk (museum, library, schoolroom, general outreach):

"Show of hands, how many people have heard of the Mars Exploration Rovers?"
"How many have heard of the Cassini mission?" "How many know where it is?"
"How many have heard of the Dawn mission?" "How many know where it is?"

(As a control, see how many people know what planet the Mars Exploration Rovers are on).

Posted by: volcanopele Aug 3 2011, 04:38 AM

Well, one anecdotal piece of evidence is the activity level of the MESSENGER forum here. That project is also using a one image a day policy. The current thread for the project, has only 25 messages in the 4.5 months since the mission began.

Posted by: elakdawalla Aug 3 2011, 05:24 AM

That's not entirely a fair comparison -- orbital survey missions are just inherently not as sexy as the treks of the rovers or the Voyager-over-and-over-again tour of Cassini; so if I'd had to prioritize which two missions I'd want all the raws from, I'd've picked those two. Interestingly, most orbital survey missions appear to be following the image-a-day-ish model. MESSENGER - Odyssey - MOC did the same thing, in their day - Cassini's tried to have it both ways, raws plus captioned image a day (and how many of us actually pay any attention to those captioned images?) - HiRISE effectively does one-ish captioned per day, though their 3-month PDS release timeline appears to be close enough to immediate for just about everybody. LROC does 3 per week.

Ironically, it's now that Dawn's in survey orbit that I care less about getting all the images. I wanted them all when the images would have let me ride along with the adventure of navigating to a new, unexplored world. We've arrived, and we've just been given a trove of riches, a survey of all longitudes. And now we'll be fed postage stamps that we won't get to choose. I expect our communal attention to wane.

Posted by: hendric Aug 3 2011, 05:26 AM

In my opinion, there have only been one microscoop and one miniscoop.
The microscoop was the discussion we had here when the first Enceladus images were sent back with the geysers. Once they were confirmed there was some high-fives around here, but nothing "public" was ever really said.
The miniscoop was when a certain reporter asked a certain scientist about certain features returning to a certain planet during a lecture before the scientist got to see the images. Said scientist has made their feelings very well known about the incident, but beyond the immediate event the only public fallout that I know of was on here. The scientist's attitude in this specific case was very much of a gatekeeper to knowledge, vs the Steve Squyres' mentality of a co-explorer and companion on a wonderful journey. I don't go to the scientist's mission website precisely because of that attitude, and I'm probably not the only one. I'd much rather hang out with friends who are happy to point me in the right direction to do it myself or do it for me.

There are some real benefits to engaging with your fan base. Dawn could be getting continuous rotation movies like above, or 3d stereo images (red/blue, cross-eyed, parallel), Kodak moments, armchair analysis, comparison views, preliminary maps, etc, etc, done for free by a bunch of people who love space exploration, and love talking about it to their friends and families and schools (and congresspeople). We could be having discussions about the best image of the latest batch, discussing what causes A and B and C, and WTF is D?? Instead we'll get one image a day, sure it's showcasing something interesting, but I'm sure each of us have a different view of what is interesting, and even if we don't all necessarily talk, would like to hear the discussion among the rest of the UMSF crew.

That being said, I do want to thank the Imaging Team for their presence here at UMSF. Even though you'll probably get no credit for it, this is definitely outreach and it matters to me.

Posted by: stevesliva Aug 3 2011, 05:26 AM

QUOTE (djellison @ Aug 2 2011, 05:21 PM) *
stevesliva - Using the argument that other missions fall short, therefore it's just fine for Dawn to fall short isn't valid. They should all be stepping up to the plate and delivering as Phoenix did, and as VMC, Cassini and MER continue to do.

They're not falling short of what's ordinary, though. That was the point. When you ask them to do something that is extraordinary, you could at least do them the courtesy of admitting that it is. If the daily image release thing wasn't ordinary for HiRISE, for LROC, for MESSENGER, well then maybe I could understand the flogging here. It was, IMO, beginning to lack context. That's it. Not saying my heart's not in the same place.

Dear Dawn, thanks for the daily images. Some missions do more. Please follow their lead. The question of whether there can be too much released to the public was settled by pathfinder. There cannot be too much. It's be resettled by every mission that's turn on the firehose since.

Posted by: dshaffer Aug 3 2011, 11:57 AM

QUOTE (dshaffer @ Aug 2 2011, 12:27 PM) *
IIRC, the question was whether all raw images will be made available as they were received (like MER), but was there a follow-up question as to why not?


I've read with interest the follow-on traffic, but it seems to me that the answer is no - the simple and direct question as to why this policy has been adopted for dawn image release, has not been asked/answered. We can all reasonably speculate that it has to do with budget or PI's wanting to publish or who knows what else - just curious as to whether anyone in the Project has stepped forward to explain the rationale for this decision.

Posted by: Mr Valiant Aug 3 2011, 12:37 PM

Well, to change the tone of the conversation, I'm going to state what I'm looking forward to seeing,
namely - CAVES - or at least the observed openings. The presence or absence will tell us a lot about
Vesta's evolution and as early Mankind found out, caves are really useful things.

Posted by: dilo Aug 3 2011, 02:50 PM

A stereogram from still frames 50&51 of the movie (thanks to Emily for this!):

(crossed eyes)
(parallel)
A detail of sharpened snowman crates:

Posted by: pablogm1024 Aug 3 2011, 03:12 PM

QUOTE (Mr Valiant @ Aug 3 2011, 01:37 PM) *
Well, to change the tone of the conversation, I'm going to state what I'm looking forward to seeing,
namely - CAVES - or at least the observed openings. The presence or absence will tell us a lot about
Vesta's evolution and as early Mankind found out, caves are really useful things.

Talking about features, I think I would not step too much out of the line if I invite you to speculate about the feature in the red circle.

Sorry if the upload is in full size, someone please PM me to explain how to do the thumbnailing.


 

Posted by: Phil Stooke Aug 3 2011, 03:41 PM

I think all the dark spots are caused by impact excavation of a buried dark layer. Most large craters reach under the dark layer and also excavate deeper bright material. This particular spot looks to me like a smaller crater that is almost completely within the dark layer, not reaching under it. If you enlarge it and brighten it it looks like a typical small crater with a lot of dark material on its inner rim and slumping down its walls.

Phil

Posted by: algorimancer Aug 3 2011, 04:50 PM

The grooves/ridges are particularly interesting. Only one explanation makes sense to me, particularly after watching the rotation movie, and that is ring decay. Probably multiple impact-generated rings, at multiple orientations, over the course of Vesta's history. This is much as anticipated in the Small Body Grooves thread. We'll see more on Ceres smile.gif


Posted by: ElkGroveDan Aug 3 2011, 05:20 PM

My thought process is similar to Phil's. There exists darker material beneath the surface. The black streaks on the crater walls are caused by slumping and mass-wasting, possibly triggered or accelerated by regional impact shocks. The speckled area looks like it could have been caused by a spray of ejecta impacts. The other possibility is that a loose cluster of small debris impacted the region, perhaps a small Itokowa-like body was pulled apart in an encounter that set it on a trajectory toward Vesta.

Posted by: hendric Aug 3 2011, 06:36 PM

I call geysers! laugh.gif

Posted by: MarkG Aug 3 2011, 06:55 PM

Ring decay seems unlikely to explain most of the grooves, since many of them (especially the far-northern big ones) are not "great circles" and thus curve along the surface, and could not have underlain a ring system, even if the rotation axis had shifted. Better mapping of the Vesta surface and the gravity figure as the mission progresses will shed light on this. If the gravity field is "weird" enough, it would discourage ring formation.
When I look at the distribution of crater ejecta back onto a rapidly-rotating Vesta from the south pole impact (who did that simulation?), plus massive seismic forcing, and then extension cracking with debris collapse, I see a possible explanation. But extension cracking is a bit dirty, and doesn't usually result in such straight lines. So I am not satisfied yet with this picture.

Posted by: stevesliva Aug 3 2011, 07:26 PM

QUOTE (MarkG @ Aug 3 2011, 02:55 PM) *
When I look at the distribution of crater ejecta back onto a rapidly-rotating Vesta from the south pole impact (who did that simulation?)

http://www.planetary.org/blog/article/00002906

Jutzi/Asphaug... who incidentally just tried to explain the moon's farside/nearside dichotomy with impact sims.

Posted by: Gladstoner Aug 4 2011, 01:57 AM

Could the layer of dark stuff (assuming that's what it is) be remnants of (the hypothesized) basalt flows that have been protected with a mantle of ejecta from the South Pole crater (SPC)? If so, subsequent impacts would serve to expose the basalt under the ejecta, as appears to be the case.

Speaking of SPC itself, what was used to determine an age of 1 billion years? Was it the lack of craters in its interior? In that case, 1 BY would be the age of a resurfacing of the interior, not necessarily of the impact itself. Considering that the the interior is a churned mess, any previous, readily observable cratering record would have been at least partially disrupted by the slumping and flow of material.

Posted by: Reed Aug 4 2011, 05:57 AM

QUOTE (Gladstoner @ Aug 3 2011, 06:57 PM) *
Speaking of SPC itself, what was used to determine an age of 1 billion years? Was it the lack of craters in its interior?

That estimate didn't come from Dawn data, so definitely not crater counts. AFAIK it comes from characteristics of the family of asteroids believed to have been produced by the impact.

Posted by: Gladstoner Aug 4 2011, 06:45 AM

QUOTE (Reed @ Aug 4 2011, 12:57 AM) *
That estimate didn't come from Dawn data, so definitely not crater counts. AFAIK it comes from characteristics of the family of asteroids believed to have been produced by the impact.


Yeah. Now that I think of it, I barely remember reading something about that. I even have bits of one of those asteroids sitting on my desk.

Posted by: chuckclark Aug 4 2011, 01:16 PM

With all this incredible photography, Vesta is going to be an excellent specimen for a foldable map.
Tayfun -- are you out there with your CADCAM machine still operable? How long until we have enough data (a "shape model" do they call it?) for you to carve one for me of this beast, er, lady?
Chuck

Posted by: algorimancer Aug 4 2011, 02:38 PM

QUOTE (MarkG @ Aug 3 2011, 01:55 PM) *
Ring decay seems unlikely to explain most of the grooves, since many of them (especially the far-northern big ones) are not "great circles" and thus curve along the surface...

I agree, not all of the grooves are obviously due to ring decay. The most obvious candidates are the circum-equatorial grooves, though they seem to overlay grooves in different planes as well. The great-circle nature of the grooves will be easier to ascertain once a good 3D model of the surface is in hand. I suspect that a sufficiently "weird" gravity field may not necessarily prevent rings from forming, but would likely accelerate their decay.

I've been puzzled by the curving, non-great-circle grooves, and have had a difficult time explaining them. It occurs to me that if they are near the pole, and the ring decay is episodic, then they might be explainable in terms of a combination of the decay with rotation of Vesta. I can also envision a ring warped by interaction with a "weird" gravity field or satellite prior to impact as yielding these odd grooves. I really wish I had the resources to model this sort of thing :/

Posted by: Tayfun Öner Aug 4 2011, 04:38 PM

QUOTE (chuckclark @ Aug 4 2011, 04:16 PM) *
With all this incredible photography, Vesta is going to be an excellent specimen for a foldable map.
Tayfun -- are you out there with your CADCAM machine still operable? How long until we have enough data (a "shape model" do they call it?) for you to carve one for me of this beast, er, lady?
Chuck

A model seems a few years away, why don't you try to transfer your methods into software environment.

Posted by: chuckclark Aug 4 2011, 05:45 PM

QUOTE (Tayfun Öner @ Aug 4 2011, 11:38 AM) *
A model seems a few years away, why don't you try to transfer your methods into software environment.


No way I can see to extract the constant scale, not to say that I haven't been trying to transfer my Renaissance-era methods into the software environment.
Although to be fair, I'm not very skillful with PDS shape models, and perhaps someone else could do it.

I guess we may have to wait a few years, although the Itokawa team sent me a model a while back. You don't suppose the Dawn team has any plans to manufacture a small run of Vesta models?
Chuck

Posted by: charborob Aug 4 2011, 06:53 PM

A new image has been posted http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_073111.asp. Are we supposed to expect regular image releases from now on?

Posted by: Stu Aug 4 2011, 07:07 PM

QUOTE (chuckclark @ Aug 4 2011, 06:45 PM) *
You don't suppose the Dawn team has any plans to manufacture a small run of Vesta models?


Probably best not to hold your breath for that. wink.gif

Posted by: ugordan Aug 4 2011, 07:10 PM

QUOTE (charborob @ Aug 4 2011, 08:53 PM) *
A new image has been posted http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_073111.asp.

Nice. This one appears to lack the resize and unsharp/high pass filtering of some of the recent press release images.

Posted by: Stefan Aug 4 2011, 08:13 PM

QUOTE (ugordan @ Aug 4 2011, 09:10 PM) *
Nice. This one appears to lack the resize and unsharp/high pass filtering of some of the recent press release images.


Nice you noticed! The image was created from the calibrated data product, and I try to alter it as little as possible. After all, y'all need something to do in your spare time. laugh.gif

Posted by: Tayfun Öner Aug 4 2011, 08:18 PM

QUOTE (Stu @ Aug 4 2011, 10:07 PM) *
Probably best not to hold your breath for that. wink.gif

Here is a first try from the rotation movie.

 

Posted by: kap Aug 4 2011, 08:25 PM

QUOTE (charborob @ Aug 4 2011, 10:53 AM) *
A new image has been posted http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_073111.asp. Are we supposed to expect regular image releases from now on?


Anyone care to speculate on that long curved dark scar crossing a bunch of the left had side of the image? Re: regular images, Vesta is in survey orbit so it's probably taking way more pictures since the camera doesn't need to be turned away to thrust. Who knows if they will release more images just because they are capturing them.

-kap

Posted by: machi Aug 4 2011, 08:26 PM

Wow, that's very nice first try rolleyes.gif

Posted by: Hungry4info Aug 4 2011, 09:28 PM

Nice! I don't suppose that could be made available for download? smile.gif

Posted by: Paolo Aug 4 2011, 09:31 PM

QUOTE (charborob @ Aug 4 2011, 08:53 PM) *
A new image has been posted http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_073111.asp.


Any idea of what we are looking at? northern or southern hemisphere? it would be nice if the release had some context, not just the picture...

Posted by: Tayfun Öner Aug 4 2011, 09:38 PM

QUOTE (Hungry4info @ Aug 5 2011, 12:28 AM) *
Nice! I don't suppose that could be made available for download? smile.gif

First I will try some mapping, I don't know if it would be possible without image geometry data (maybe Phil could do it). I will upload it then.

Posted by: Hungry4info Aug 4 2011, 09:40 PM

QUOTE (Paolo @ Aug 4 2011, 04:31 PM) *
Any idea of what we are looking at?
Northern hemisphere. I recognise the shape of the scar at the top of the image. That darker curved mark is the same that was visible in one of the press release images.

Posted by: pablogm1024 Aug 4 2011, 11:06 PM

QUOTE (Hungry4info @ Aug 4 2011, 10:40 PM) *
Northern hemisphere. I recognise the shape of the scar at the top of the image. That darker curved mark is the same that was visible in one of the press release images.

Let me correct you quickly the shadowed part on the top left is in the northern hemisphere, but the equator basically runs in diagonal from top left to bottom right. See the annotated image. I will keep helping you with the orientation until someone prepares a map that can help you all. In the meantime, try not to guess. As soon as I have a chance I will give you the orientation of the images.
Tayfun, your shape model is outstanding!

 

Posted by: volcanopele Aug 4 2011, 11:37 PM

QUOTE (kap @ Aug 4 2011, 01:25 PM) *
Anyone care to speculate on that long curved dark scar crossing a bunch of the left had side of the image?

It looks like a flow of some sort to me. Post-impact volcanism? (by impact, I mean the little guy which seems to be the "source" of the digitate flows, or maybe that is the end of a flow....)

Posted by: machi Aug 4 2011, 11:39 PM

QUOTE (Paolo @ Aug 4 2011, 11:31 PM) *
Any idea of what we are looking at? northern or southern hemisphere? it would be nice if the release had some context, not just the picture...


Quick reprojection using one global image from HD animation (thanks Emily for images and Dawn team for animation!).

 

Posted by: Gladstoner Aug 4 2011, 11:53 PM

QUOTE (kap @ Aug 4 2011, 03:25 PM) *
Anyone care to speculate on that long curved dark scar crossing a bunch of the left had side of the image?


First, part of it seems to be draped over a crater, so it probably settled down from above.

Second, it seems to originate at that crater (or whatever) on the bottom.

Is the curviness of the dark streak real, or is it due to the viewing angle of an irregular surface?

Posted by: ElkGroveDan Aug 5 2011, 12:02 AM

There is something very unusual about that "flow" if that is what it is. If it were molten rock (or liquid of any kind) it would necessarily follow the contours of that last crater it crosses; either pool up in the bottom of it, or if the crater is on a slope then the flow would follow a circular path along the crater's wall. Instead it looks as though this dark feature was draped across the body from above like strands of hair or a veil. It has to have been deposited from above -- something like dust or fine particles continuously ejected downrange from it's source.

(enlarged and contrast enhanced crop)


 

Posted by: kap Aug 5 2011, 12:23 AM



Yeah I was thinking that too, otherwise it flowed "uphill" and out of some of those craters.

-kap

Posted by: Bjorn Jonsson Aug 5 2011, 12:39 AM

QUOTE (Tayfun Öner @ Aug 4 2011, 08:18 PM) *
Here is a first try from the rotation movie.

Wow, this looks extremely interesting and nice. I'm planning to do a 3D model of Vesta by running stereo imagery through my stereo processing software but doubt I'll be doing it until the data is released at the PDS so I was disappointed to see that apparently that's not going to happen until about 18 months from now.

As a matter of curiosity, how did you create this 3D model? It looks remarkably detailed keeping in mind limitations in the source data (no viewing geometry information etc.).

Posted by: Gladstoner Aug 5 2011, 01:27 AM

Another interpretation:

The "flow" could be a chance alignment of dark rays from two separate craters, and some topographic grooves.

In the image,

[attachment=25094:2_craters.PNG]

purple shows rays from the larger crater, green shows rays from the smaller crater, and orange is interpreted as part of a system of linear valleys, some of which can be seen extending beyond the "flow" zone. Pink shows what could be rays from either crater.

The dark stuff in the troughs could be exposed darker material, or the albedo effect of differing grain sizes, as could be the case with the features in the SP basin.

On the previously release full-frame image, the prominent dark crater also has some dark rays:

[attachment=25092:Dark_crater.PNG]

Posted by: Juramike Aug 5 2011, 01:38 AM

Whoo-hoo! The July 31 image almost perfectly matches up to the filtered false-color image released as PIA14325.

Here is a blink animation between the two (I had to warp PIA14325:


[Animated GIF: Click to animate]

The dark albedo area corresponds to the dark blue streak. It begins at a splat that is likely yellowish white like it's neighbors. And look at those other splatty features as well! The large flat-floored crater at the upper right ("Brachiopod Crater") that has a small indent from another impact is pretty distinctive in the global map mosaic and other images of Vesta. I've been using that as a identification feature. It is pretty average looking in the false-color spectra. But look at the detail around the large crater south of it. WOW! Lotsa different stuff.

Also note that the grooves do not show up in the false color image. They blend with the "average terrain" (constraining the ring hypotheses).

[Corrected based on comments from Pablo below]

Posted by: pablogm1024 Aug 5 2011, 02:03 AM

QUOTE (Juramike @ Aug 5 2011, 02:38 AM) *
Whoo-hoo! The July 31 image almost perfectly matches up to the VIR false-color image released as PIA14325.

Just a precision, the http://photojournal.jpl.nasa.gov/catalog/PIA14325 is a color composite of three filters of the Framing Camera. No offense for VIR, they are remarkable in many aspects, but this image is not a product of theirs.

Posted by: Juramike Aug 5 2011, 02:08 AM

Static image, detail enhanced in colorized region using multiple HiPass filters, also contrast regionally contrast-adjusted:


Posted by: Tayfun Öner Aug 5 2011, 05:20 AM

QUOTE (Bjorn Jonsson @ Aug 5 2011, 03:39 AM) *
As a matter of curiosity, how did you create this 3D model? It looks remarkably detailed keeping in mind limitations in the source data (no viewing geometry information etc.).

It was made from the rotation movie by first tracking the camera and creating the viewing geometry. Then a point cloud was generated and it was filtered and turned into a Poisson mesh. As you say there is not any viewing geometry data yet and this seems to be the only way to get a decent model. However mapping will be more tricky, I will try to fix the pole & equator from the published map.

Posted by: Stu Aug 5 2011, 06:21 AM

QUOTE (Tayfun Öner @ Aug 4 2011, 09:18 PM) *
Here is a first try from the rotation movie.


Wow, that's pretty amazing stuff! I have no idea whatsoever how you computer warlocks generate things like that, but I'm very glad you can! smile.gif

Posted by: stevelu Aug 5 2011, 06:22 AM

Just for fun, here's Vesta on a collision course with itself.

(It's my desktop for the moment rolleyes.gif )


Posted by: Fran Ontanaya Aug 5 2011, 09:24 AM

An edges map. It highlights a bit the age of the surface:



Posted by: Ian R Aug 5 2011, 09:29 AM

Here's my interpretation of the rotation movie. (Thanks Emily for the frames!) The frame rate interpolation isn't as smooth as Tayfun's, unfortunately:

http://youtu.be/eBHgcTxhG-Y?hd=1

Posted by: algorimancer Aug 5 2011, 12:37 PM

Any word yet on a detected magnetic field for Vesta? If present (and strong enough) it could have interesting effects on metallic or ionized ejecta as well as surface aging by solar ions, as seen on a few locations on the Moon.

Posted by: Adam Hurcewicz Aug 5 2011, 12:38 PM

Hi, I'm stich images into Spherical panorama. Only North is black.

Adam




and this funny version of stich smile.gif


Posted by: Phil Stooke Aug 5 2011, 01:00 PM

Very nice, Adam!

Algorimancer - there is no magnetometer on Dawn. It had to be removed due to mass limitations earlier in the design phase.

Phil

Posted by: Tayfun Öner Aug 5 2011, 02:29 PM

Adam wov! The funny version is really nice.

Posted by: alan Aug 5 2011, 03:21 PM

A question: is the central peak of the south polar basin at the south pole or offset from it?

Posted by: pablogm1024 Aug 5 2011, 03:24 PM

QUOTE (Ian R @ Aug 5 2011, 10:29 AM) *
Here's my interpretation of the rotation movie. (Thanks Emily for the frames!) The frame rate interpolation isn't as smooth as Tayfun's, unfortunately:

http://youtu.be/zig5pu3jb1U?hd=1

The de-rotation of the image to a constant north-up orientation is very nice. Perhaps you could give Tayfun the de-rotated frames for him to produce a super-dooper soft-rotating north-up movie!

Posted by: chuckclark Aug 5 2011, 10:24 PM

QUOTE (Tayfun Öner @ Aug 4 2011, 04:18 PM) *
Here is a first try from the rotation movie.


Tayfun -- is this something more than just pixels on the screen? That is, is it something you can make a physical object from?

Chuck

Posted by: belleraphon1 Aug 6 2011, 12:21 AM

QUOTE (algorimancer @ Aug 5 2011, 08:37 AM) *
Any word yet on a detected magnetic field for Vesta? If present (and strong enough) it could have interesting effects on metallic or ionized ejecta as well as surface aging by solar ions, as seen on a few locations on the Moon.


I believe the magnetometer was removed for budget reasons. A loss for science for reasons you noted.

Craig

Posted by: Tayfun Öner Aug 6 2011, 05:39 AM

QUOTE (chuckclark @ Aug 6 2011, 01:24 AM) *
Tayfun -- is this something more than just pixels on the screen? That is, is it something you can make a physical object from?

Chuck

It is a detailed 3D model, only a small area near the north pole (where there is no photographic data) is missing.

Posted by: Paolo Aug 6 2011, 07:14 AM

QUOTE (belleraphon1 @ Aug 6 2011, 02:21 AM) *
I believe the magnetometer was removed for budget reasons.


from a http://www.nature.com/news/2011/110713/full/475147a.html on the mission:

QUOTE
Before launch, budget issues caused the mission team to drop two instruments originally meant to fly aboard Dawn; one of them, a magnetometer, will be especially mourned once the craft reaches Ceres. The magnetometer could have looked for fluctuations in the strength of the asteroid's magnetic field that might have provided clues as to whether the body harbours a briny ocean. Losing the instrument "was a big blow",


Posted by: chuckclark Aug 6 2011, 11:09 AM

QUOTE (Tayfun Öner @ Aug 6 2011, 01:39 AM) *
It is a detailed 3D model, only a small area near the north pole (where there is no photographic data) is missing.


So presumably, if all systems continue moving along smoothly, that missing info will fill in pretty quickly?

And what is needed for you to locate poles, equator, and the rest of a lat-long grid?

Chuck

Posted by: Ian R Aug 6 2011, 12:09 PM

QUOTE (pablogm1024 @ Aug 5 2011, 04:24 PM) *
The de-rotation of the image to a constant north-up orientation is very nice. Perhaps you could give Tayfun the de-rotated frames for him to produce a super-dooper soft-rotating north-up movie!


I've had a second crack at smoothing the rotated movie, and it's looking much better:

http://youtu.be/eBHgcTxhG-Y?hd=1

Posted by: Gsnorgathon Aug 6 2011, 01:09 PM

QUOTE (chuckclark @ Aug 6 2011, 03:09 AM) *
So presumably, if all systems continue moving along smoothly, that missing info will fill in pretty quickly?
...

We'll have to wait for northern spring to fill in that missing data. (Anyone know when the Vestian equinox is?)

Posted by: Floyd Aug 6 2011, 02:27 PM

An orbit is 1325 days. So solstice to equinox is 331 days. I assume we are past solstice and going toward equinox--and therefore less than 331 days, but I'm only a microbiologist. rolleyes.gif

Posted by: ElkGroveDan Aug 6 2011, 02:52 PM

QUOTE
Before launch, budget issues caused the mission team to drop two instruments originally meant to fly aboard Dawn; one of them, a magnetometer, will be especially mourned once the craft reaches Ceres.

It's really too bad. I can't imagine how a magnetometer would represent a large cost component. It's not a complicated device. There's probably a magnetometer app available for my Droid.

Posted by: ZLD Aug 6 2011, 03:27 PM

As I recall, I don't think it was going to be a large cost component but somewhat intensive in man hours for testing since the type hadn't been flown before, and they were already behind schedule.

Posted by: Paolo Aug 6 2011, 03:55 PM

yes, magnetometers on spacecraft are simple devices but they need lots of testing because of the risk of interference from the metallic structure of the spacecraft itself...

Posted by: centsworth_II Aug 6 2011, 06:15 PM

There's already a paper Vesta model available! laugh.gif


http://www.koyalwholesale.com/pages-productinfo-product-6978/10_silver_round_paper_lanterns_6_pieces.html

Posted by: tanjent Aug 6 2011, 08:19 PM

I'm just wondering - if the mass in the pre-planetary solar system was concentrated into a disk, how is it possible for a body like Vesta to get smacked in the South Pole? If the impact site was at the south pole prior to the hit, then the impactor would have to have come from outside the ecliptic. If the impact site was not at the south pole before the impact, how could the impact have re-oriented things to put it there?

Posted by: nprev Aug 6 2011, 08:27 PM

Gotta remember that the 'disk' was undoubtedly millions of km thick at least, first of all. Also, I'm sure that the early Solar System was pretty chaotic indeed, with lots of stuff bumping into each other quite often, and frequently at oblique angles to boot. It's not beyond the pale at all to postulate a medium population of out-of-ecliptic bodies in the inner Solar System back in the day.

And, of course, it could have been a long-period comet. Those things often have quite funky orbits indeed.

Posted by: Hungry4info Aug 6 2011, 09:57 PM

Given two orbits that are inclined only by a degree or two of each other, if the two meet where the orbits intersect, from each body, the other will appear to be approaching from outside the ecliptic plane.

This quick drawing shows the orbits of two bodies with small inclinations, with a polar collision where the two meet.

 

Posted by: Paolo Aug 6 2011, 11:04 PM

QUOTE (tanjent @ Aug 6 2011, 10:19 PM) *
If the impact site was not at the south pole before the impact, how could the impact have re-oriented things to put it there?


the stable (minimum energy) rotation of an ellipsoid is with the spin axis passing through its shortest axis. so even if the impact was not at the south pole (and it probably wasn't) the stable rotation configuration required the crater to end up at one of the poles

Posted by: hendric Aug 7 2011, 10:00 PM

Also, during the early solar system most of your nearby objects would be orbiting in similar orbits with you, and collisions would be relatively low velocity. Two Vesta sized objects hitting each other, for example, would only hit at 2x escape velocity, or about .7 km/sec. Now, once Jupiter migrates inwards, it tends to scramble the orbits of the planetesimals, and so collisions could be between objects with vastly different semimajor axis, ie an object at Vesta could only be passing through due to eccentricity. As H4I shows above, an object with only a slight inclination difference results in essentially a polar hit. Also, it's difficult to tell the angle of the impact using debris except very roughly because of the energies involved, and might not even be possible with an impact of this size.

Posted by: algorimancer Aug 8 2011, 12:22 AM

Really disappointing to hear the magnetometer didn't make it onto the vehicle. Considering the nature of Vesta & Ceres, that's quite a loss.

Posted by: Tayfun Öner Aug 8 2011, 11:46 AM

Here is the simplified Vesta model. I fitted a sphere to the detailed model which even shows the grooves. As we don't yet have geometry information, the polygon lines do not necessarily pass through long/lat lines and poles of the model may not be at the real poles. It is also not to scale.

 vesta.zip ( 41.01K ) : 247
 

Posted by: chuckclark Aug 8 2011, 12:15 PM

QUOTE (Tayfun Öner @ Aug 8 2011, 07:46 AM) *
Here is the simplified Vesta model.


Hey -- I can import and open this file in my VectorWorks program!

Thank you, Tayfun.

Posted by: tedstryk Aug 8 2011, 04:33 PM

Hey Chuck, looks like you have a new place to apply your mapping technique!

Posted by: CosmicRocker Aug 9 2011, 03:37 AM

I took the frames posted by Emily, created anaglyphs from each sequential pair, and assembled them into an animated gif to show the rotating body in 3D. The full sized version is 17 megs. In order to reduce the file size to something that I can upload here I had to reduce the size to 25% and cut the range of colors in half.

The full sized version is much nicer than what I have to post here. I can't find a site that will host a large animated gif. Flickr won't take it and the animation doesn't work on Picasa. If anyone has any suggestions for a place to host the big file, please let me know.

************************************

Sorry. Apparently it was a few bytes larger than allowed. I'll go back to the drawing board to see if there is anything else I can do to shrink this file without totally destroying the imagery.

Posted by: nprev Aug 9 2011, 03:39 AM

Tom, can you link it to an external site? That would work. (MOST anxious to see this; it sounds great!!!)

Posted by: CosmicRocker Aug 9 2011, 04:02 AM

Nick: I tried Flickr and Picasa Web Albums without success. That's why I was asking if anyone knew of another site that accepted this kind of file. A few years ago I made one of these of Itokawa and a certain friend of umsf http://www.planetary.org/blog/article/00000965/. wink.gif Since Vesta is roughly spherical, it does not appear quite as exciting in 3D as Itokawa did, but it is still nice to see it in stereo.

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