On Tuesday (two days from now, for visitors from the future), the first optical navigation image will be taken... hopefully we'll have it in our hands soon after that. So it's time for a new topic. Over the next few months we'll have progressively closer images and full orbit characterization sequences, no doubt including multispectral image sets.

A new world...

This is a bit of reprocessing I have been doing with the Hubble images from a few years ago.

Click to view attachment


Phil

I very excited to see this little world better. Nice processing on those Hubble images though!

WOW, Phil : you are still the best !
Thanks to this VERY NICE processing of yours, I just realize how bright some craters are (very bright indeed)... and why the astronomers community is just drooling over the underlying layer of ice (and a possible ocean) on this small world.
Thanks so much again !

Beautiful! I've fooled with this dataset a little and not gotten anything worth showing out of it.

This is a cylindrical map made from those images. Longitudes start at 0 at the left edge, following the mapping by Li et al. in Icarus in 2006. My registration is not very good, and the dark southern polar region must be an artifact, but it's something to play with as we start to get the early images.

Phil

Click to view attachment

Very Nice!
can i post it on my blog later today?

Great map!
Besides the lighter patches I see one or two interesting dark ones.

Hi Paul - by all means post it. It's not as nice as you suggest but it's a start! I look forward to its very rapid replacement with something better.

Phil

I am most intrigued by the apparent 'bluing' near the poles. will be interested to see if that is real.

In the single images, it's bluer near the limb and terminator, and the composite leaves that blue near the poles but loses it where images overlap near the equator. I expect it's an artifact or a photometric effect, but there is a possibility of higher albedo (looking blue) near the poles as we see at Ganymede.

Phil

true. but some of the images seem to show stronger 'blue' near the poles. wont know till we get there!

Dawn is supposed to take another Ceres image today -- release will most likely be .....? (soonish)

can't comment on pronunciation as my latin is rusty, but i do have a blog about the approach posted . . .

http://stereomoons.blogspot.com/2015/01/ye...-pluto-get.html

It's now the evening of the 13th. Is it safe to say that the Dawn team is looking at the 25 pixel image of Ceres as we speak?

The image that was taken Dec 1,2014 took 7 or 8 days to release.


We just have to wait.

"Is it safe to say that the Dawn team is looking at the 25 pixel image of Ceres as we speak?"

You might very well think that. But I couldn't possibly comment.

Phil

Is every image during approach going to be delayed several days? If so, is there a reason for that? Not to sound too impatient -- I don't recall that being the case for past missions so I'm just curious. And I may or may not have marked Jan 13, Jan 26, Feb 4, etc in my calendar...

Pretty sure it was like that for Vesta too; thrusting takes a priority, since it can't point at Ceres and keep on trajectory at the same time. Dawn isn't Voyager, so no scan platform.

It was very much the case for Vesta approach. Dawn doesn't operate an image policy like MER, MSL and Cassini.

Ah, I guess my memory from the Vesta encounter is fuzzy -- thanks for the clarification.

During Vesta approach Dawn did the following:

http://dawn.jpl.nasa.gov/mission/journal_05_27_11.asp



It was this image:

http://3.bp.blogspot.com/-d3pKJNvHCGg/Te2F...Sad%20Vesta.jpg

An image of Vesta from 1.3 or so million km away was taken on May 3 and released a week later. The next one was released on June 18th at a distance of 218,000 km, this one:

http://3.bp.blogspot.com/-XLZukRt5LlY/Tfw4...s1600/Vesta.jpg

Later on (though I don't remember where exactly I read it) the team said they didn't release the images in between because they were small, boring, untouched, etc.

Because of the severe limitations imposed on the mission by the loss of the use of the reaction wheels, Dawn will be taking fewer approach images of Ceres than it did of Vesta -- I think there are only 8 opnav sessions planned before arrival (compared to 24 for Vesta), so it's far from every day. These limitations also mean fewer comm sessions. On the other hand, op nav images are by definition important for navigation, so I expect they are planned in such a way that they can be returned to Earth very soon after being taken. But it took them forever to release approach images for Vesta, and I don't expect Ceres to be any different.

Thats correct. The cadence of observations is that a set is taken for a hour or so on approach every 1 to 2 weeks, depending on the distance. >95% of mission time is spent ion thrusting and it can't point at ceres. There are a variety of exposures and filters and such during each sequence and it takes a few days to select the optimal exposure, remove camera artifacts, etc to release to the public. No worries, the team is eager to show the world what the target looks like! Once they settle into mapping phase, there will likely be a photo of the day release just as there was for Vesta.

I wonder. Because on the other hand Ceres is already at a distance where it has a similar resolution to the second Vesta photo, the one where the team thought it had become interesting enough to release.

I wouldn't. Images will show up when they show up. There's really very little point in try to guess when it'll happen.

Wonder no more: I have a strange sense that an image will be released on the 20th.

https://twitter.com/NASA_Dawn/status/555511503369940992

It pays to check the most obvious source sometimes...

Nice! I was looking at that Twitter feed earlier in the day before they wrote that, glad to see they've given us a date.

nice to see these dates are being posted!

Close but not quite, due to the flywheel problem Dawn will have to use thruster power to reorient to send back to Earth.
To conserve fuel Dawn will be spending longer time taking images and do measurements, therefore we will be getting new images every second day at best.

yes, but by then there will be lots more archived to chose from to post on the Pic-o-the-Day site. Each orbit returns dozens of frames. The number will vary depending on altitude and which mapping phase we are in, of course, but I don't have those numbers.

Oh yes you're absolutely right, and I don't believe anyone have the definite numbers of images but its obvious that there should be some who sits and make plans for the imagining campaign at Ceres now already. =)

I checked on the facts and this blog entry mentioned that I had in the back of my head when I posted:
"So over the course of 14 complete circuits around Ceres in 11 days, the spacecraft will turn only six or eight times. Ever the responsible conservationists, the team developed all the details of this plan to acquire as much data as possible with the minimum expenditure of hydrazine." Source

Moved a bunch of pronunciation posts to the Junk Drawer topic. Let's keep the signal-to-noise ratio high, folks.

Yes indeed. the team has done a fantastic job to make the adjustment to the hybrid form of orbital mapping and still meet the main objectives. It was also a very prudent decision to have a significant supply of hydrazine on board. without that it would be a bit more difficult to do the mapping of ceres without the wheels. Ceres has a lot more area to map as well (the ratio can be easily calculated of course from the radii), and also much darker than vesta. this will require longer exposures, but also a longer mapping phase to get the same coverage for stereo mapping. I'm impressed . . .

'Prudent' is nearly one understatement, considering the fact that space mission planning usually involves the task of hunting down every unnecessary gramme with even more diligence than a builder of a supercar. =)

And yes, Ceres is quite dark and comes with one albedo of 0,09 compared to the bright Vesta: albedo 0,423. This means there will most likely be a lot of dust that have been captured after various collisions of C type asteroids in the neighbourhood. I guess this asteroid 'pollution' might make it somewhat harder to determine some parts of the history of the asteroid, though I do rather think the idea of seeing Ceres as one surviving planetesimal in the end will be strengthened.

projectile contamination is also a question for ganymede and callisto. we have several members interested in that problem, and ill let them think about that when we get some spectra to work with. my main focus will be impact craters and what we can learn about the interior and icy shell.

Paul, you may know this right off the bat: Where does Ceres rate on the PPP scale? Is it on par with Mars, Europa & Titan, rated somewhat lower, or not even on the radar at this time?

Not directly applicable to Dawn, of course, save that it might be a factor in EOM planning.

http://www.jpl.nasa.gov/news/news.php?feature=4449


First pics - very nice.

Phil

Oh, boy; here we go!!!

Looks like the most obvious confirmed feature (since it's also in the Hubble imagery) is that big white spot in the northern hemisphere. Almost certainly a fresh impact crater, of course, but it'll be interesting to see if that high contrast persists at higher resolutions.

I see hints of 'wrinkles' or ridges on the rest of the surface as well as some older big craters. Might just be eroded crater rims from even older & bigger impacts.

Yeah, that spot seems like a crater; I can almost make out a dark edge at the top (shadows?).
Very nice!

Also VIRS first light (not in the link provided, strangely enough):

https://twitter.com/NASA_Dawn/status/557214894269800449

My layman-self is a bit confused.

This picture has several very obvious crater candidates (including the big one near the middle that makes Ceres look like Mimas looking like the Death Star), but the shiny contrast feature is nowhere to be seen; so how does it fit with the animation?

This picture, on the other hand, has no obvious crater candidates (except from the shiny feature, which is pretty unique), and it also has a big wavy low-albedo feature in the lower hemisphere (looks a bit like to massive craters on a leash).

So, to my untrained eyes, the first picture makes Ceres look a body with a very old surface, while the latter one makes Ceres look a place with a potentially youthful surface (although the image processing looks kind of different between the two images, so maybe that's a clue).

Comparing the new Dawn images to an HST image, I think it's clear that several surface features are visible in both.

replying to Habukaz - At this resolution you can't be making interpretations like that. It is not yet possible to tell the difference between albedo markings and topography, or noise and topography. The next set we get might make those things possible, or maybe the one after that.

Phil

Well, the lead investigator for the framing camera thinks we might be seing craters:

But I think the operative word there is "hint".

Yes, and that's why I labelled them as candidates. It will be interesting to see what's what as we get closer; I just felt like scribbling down what came to mind when I saw the pictures.

My main point was though that I don't get how the "cratery" picture without the bright spot fits the animation; is it included somewhere within it?

Chitchatting with other people here at the New Horizons science team meeting, I think it's true to say that many here would be surprised if some of the features we're looking at did not turn out to be craters. However, there are also a lot of spots that look weird that everybody's on the fence about whether they are craters or albedo markings, and we'll just have to wait and see. Jan 26 images will have resolution twice as good.

Spectacular pictures! Wild cheering from the bleachers...!

It's interesting that even though the resolution of these images is a bit lower than HST's, the higher phase angle apparently partially 'compensates' for that by making topography easier to see near the terminator thanks to what are probably shadows/topographic shading. I see hints of probable big craters. Also elongated features but I'm not sure whether they are ridges, depressions, albedo features or some combination of these. It will be very interesting to see the January 26 images; they should provide some answers.

Bjorn, what you said is pretty much what the New Horizons geology and geophysics team said about these images

These images, and especially the animation made from them, do give the impression of a cratered body. In much the same way that the early Mariner 10 images gave the impression of a cratered Mercury -- very suggestive, but not enough to say for sure.

Of course, we would most definitely expect Ceres to be cratered -- with no tidal "pumping" I can't conceive of a heat source (internal or external) that would result in ongoing re-surfacing, and every other airless body that lacks an internal heat source (i.e., pretty much all of them except Io, and to a lesser extent Europa and Enceladus) that we've looked at in our solar system has been heavily cratered. Even Enceladus has some heavily cratered terrain far away from its active plumes. It would be the scientific discovery of the decade were Ceres not heavily cratered.

The one nice thing we can say is that we don't have very long to wait, in the overall scheme of things, to get a much better look at this dwarf planet. The Hubble suggestions of an almost Mars-colored world have had me intrigued for quite some time. Now we are very near to knowing, if not the whole truth of the matter, then at least enough data to raise questions we don't even know enough to start asking yet.

-the other Doug