Dawn approaches Ceres, From opnav images to first orbit Options

[fredk]

When you view an animated gif of the released set your brain can pull real structure out of the noise, and you end up seeing more structure than in any single frame. This makes me wonder about producing a super-res from this set. It would be a lot of work. You'd have to create a rotation model and transform each image into some fixed projection, before doing the stacking with each frame aligned in longitude. Of course you'd get maximal improvement near the central region of the central frame, and less improvement towards the edges. Still, it would be interesting to see what could be done.

Or you could wait for the next release...

[MarsInMyLifetime]

If only for a spare hole in the filter wheel that a parfocal 3x teleconverter could have been slipped into. ;-) But I suppose it would have been beyond budget and requirements.

[Bjorn Jonsson]

...This makes me wonder about producing a super-res from this set. It would be a lot of work. You'd have to create a rotation model and transform each image into some fixed projection...

I originally wasn't going to spend any time doing this since there isn't a long time until the next images arrive but I found that I simply couldn't resist checking if more details could be revealed, also this was an interesting image processing experiment. I used the last 9 images from the set, reprojected them to simple cylindrical projection and then aligned and stacked the maps. This was followed by rendering an ellipsoid using the map as a texture map. I was rather disappointed with the result and I'm not sure which 'new' details are real, maybe some but maybe none.

Below are two versions, the left one sharpened with an unsharp mask and the right one processed with a high pass filter followed by a contrast stretch:



I'm more happy with the version at left. The most interesting feature is the one below center that stretches from the left limb and more than half the way to the right limb. This looks like a possible 'depression' (reminds me a bit of Tethys' Ithaca Chasma!?) but an albedo feature (or something else) can't be ruled out. One important caveat is that the images in the rotation movie have been processed and enlarged - I'd me more confident in these results if I was using the original, raw images.

It should be mentioned that the original 20 images were obtained over a period of ~1 hour at a range of 383,000 km and the subspacecraft latitude is 28.2 degrees south.

[dvandorn]

Great work, Bjorn!

It seems obvious that the "head" of the dark horizontal feature you mention is surrounded by a brighter annulus -- at least, several brighter points appear in arcs around the place where the dark steak spreads out into a "handle" shape, the arcs defining what looks like a large encircling crater or basin. It certainly gives the impression of a large crater or small basin in the animation, though of course it's no more than an impression, at these resolutions.

However, if the center of the "handle" were some kind of eruptive feature, the bright annulus could be extent of the outer eruption ring. (Think in terms of Ionian volcanoes.)

It's quite exciting to know that we will have much better views within weeks!

-the other Doug

[fredk]

Very cool to see this, Bjorn. As important as any new features we can see this way are the fake features, due to noise, that go away. Nine frames should naively give us a 3-fold increase in S/N. This is probably the best image we have yet of Ceres.

[Bjorn Jonsson]

Looking at the movie and other versions of the image, I get the impression that the eastern end of the horizontal feature might be a big crater with a central peak and there might more craters and/or an elongated depresson to its west (probably both).

It will be very interesting to see the next set of images. It might have sufficient resolution to show what this feature is (and it will give me information on how well this image processing method works).

[Sherbert]

Very nicely done Bjorn.

I think there could be two deep craters to the North East of the elongated dark feature, similar but not as deep as the big white crater top left. One thing is for sure, to see features at this distance, the elevation changes could be quite dramatic on the surface, whatever their nature. We await with eager anticipation to see what the images planned for this week reveal.

[machi]

...The most interesting feature is the one below center that stretches from the left limb and more than half the way to the right limb. This looks like a possible 'depression' (reminds me a bit of Tethys' Ithaca Chasma!?) but an albedo feature (or something else) can't be ruled out...

Nice reprocessed images Bjorn!
I had similar thoughts about possible canyon on the Ceres after I've watched published animation.
My bet is that Ceres will be similar to the one of the middle size icy satellite of Saturn or Uranus.
Question is which one (Umbriel? Tethys?...).

[DrShank]

All very interesting speculations. I've wondered about that arcuate feature that looks like a possible depression, as well. But Im prepared for anything. Ive also been discussing Saturnian satellite analogs with colleagues, and thats a good starting point, but there are of course key differences, in composition, heat source, etc. be assured that the Saturnian moon maps will got some use when we start trying to figure Ceres out. Im posting a blog about it later tonite.
cheers
p

[Habukaz]

The first new Ceres images are coming down, and they 'look very impressive'. They may be released tomorrow already; although time will tell, I guess.

[Phil Stooke]

From Twitter:

Vishnu Reddy @moonyguy

We are getting the good stuff from OpNav2 from @NASA_Dawn of #dawn_ceres, first images look very impressive.

-------------------------------------------------------------
Let's hope we have them at the end of the week!

EDIT - Habukaz beat me to it!

Phil

[volcanopele]

I was playing around with Celestia this morning and I finally managed to get Dawn to work in that program. So without further ado, here are three animations for the first two opnav observations plus one for the next one which appears to include a satellite search observation...

Opnav1
Opnav2
Opnav3/(+satellite search?)

Now, my big concern now is making sure Ceres is right. I'm not sure I have the rotational model right. Right now it is just using a uniform rotation model. For one thing, the bright spot isn't the right bright spot...

[volcanopele]

To follow up, here are a new set of videos, which include the three rotational characterization observations (RC). For these videos, the left panel is a simulation of the Framing Camera field of view (give or take a few minutes of arc) while the panel on the right shows orientation of the Dawn spacecraft. Each video covers roughly 25 hours, running at 1000x speed.

OPNAV1 (January 13)
OPNAV2 (January 25)
OPNAV3/Satellite Search (February 4)
RC1 (February 12)
RC2 (February 19)
OPNAV4 (February 25)

EDIT: working on updated versions with Ceres working as it should this time. I'm using Phil's map now with a slight correction in longitudes (I think I shifted things 20 degrees to the right so that it better matches with other published maps). An issue I've run into though is that the Dawn team seems to be once again going there own way when it comes to Ceres longitudes, with the IAU using one prime meridian, and the Dawn team using another. I am going to just use the Dawn team's one, it seems to matches best with published maps.

EDIT2: I've uploaded new versions of these videos, now with the proper rotation model used for Ceres. I'm also using an updated version of Phil's map that now matches up, at least longitudinallly with various published albedo maps (specifically, I used the one posted here, a page about the first opnav image that I haven't seen posted here).

[DrShank]

The first new Ceres images are coming down, and they 'look very impressive'. They may be released tomorrow already; although time will tell, I guess.

as nice as it is to see a new planet the first time, remember we are still at only ~20 kilometers per pixel. Enough to see markings but interpretations are still going to be 'interesting'.

for fun, here is a tethys image at similar resolution, interpretable because we have the global high res map. the curvilinear markings are Ithaca Chasma and a large relaxed basin (Telamus).

Attached thumbnail(s)

 

[Bjorn Jonsson]

And images like this of Tethys are the exact reason I mentioned Ithaca Chasma in my post above containing the stacked image

I'm finding it remarkably difficult to wait for the higher-res images obtained today - they should be very interesting.