Dawn approaches Ceres, From opnav images to first orbit Options

[dvandorn]

Hey, guys -- as with Sherbert, I was just giving my impression of what we're seeing from the distant images. Ceres does look lumpier than I expected from this distance, and I'm not the first here who has made that observation. Obviously, as distance decreases, we will know more and more of the truth of the matter. And also, as has been stated here, if we couldn't speculate at this point, it wouldn't be any fun...

As for Enceladus, I was looking with tired eyes, I guess -- and relying on Wikipedia being consistent in how it presents information, which is always dangerous. Before I wrote that, last night, I checked and Wikipedia said that each was about 500 km wide -- except that, upon a further look this morning, it was giving a diameter of Enceladus and a radius of Ceres. And, stupid me, I read them as being the same measurement. But, ultimately, my bad.

-the other Doug

[Hungry4info]

I thought Vesta looked oddly lumpy before we got closer, so I'm definitely reserving judgement on that for later.

[FOV]

Even poor lumpy Vesta is described as a proto-planet by the Dawn mission. Compared to asteroids seen up close by s/c, Ceres does not look like them. Can't wait for the next 2 sets of images, the added detail will help us see past the mirage created by lighting effects on not enough pixels.

[alk3997]

Hey, guys -- as with Sherbert, I was just giving my impression of what we're seeing from the distant images. Ceres does look lumpier than I expected from this distance, and I'm not the first here who has made that observation. Obviously, as distance decreases, we will know more and more of the truth of the matter. And also, as has been stated here, if we couldn't speculate at this point, it wouldn't be any fun...

...

Yes, the danger of speculating. For instance in the attached 2/04/15 photo, Ceres looks much like a hot air balloon where the bottom portion has had a small amount of air let out. The crater at the southern pole helps with the visual. It just *seems* that the southern hemisphere of Ceres is less round than the northern hemisphere. Whether that is real will be answered in the next few weeks.

I've also noticed that a lot of the enhancements are making the brightness of Ceres appear more uniform than the original non-enhanced images. That difference in brightness may be due to the viewing angle or may be because of surface differences. It may not even be real. But, again, a few more weeks and that question should be answered and a whole lot more questions will need to be answered.

The fun of arm-chair exploration...

Andy

Attached thumbnail(s)

 

[Gerald]

Here a first, very tentative version of a map towards (east-west) inclination data:


It's based on a map of estimators E[X] of the expected frame number of the light curve (as function of the frame number) for each 0.25°x0.25° longitude/latitude square, the light curve interpreted as a probability density function.
The goal is to find out the phase shift of the light curve for each lon/lat position, since the phase shift should be correlated to the east/west inclination.
There are still several issues. I've applied a hipass filter and a stretch to the raw estimator map to compensate for systematic errors in the model.
Be carefull with interpretations, since processing artifacts are likely.

Taking the issues into account, there appears to remain a diagonal chain of at least four craters from center north, eastward.
This may indicate, that the northern hemisphere is also heavily cratered. But thus far I don't see features similar to the pair of huge craters south of the equator.

I think I'm now near the limits of what I can squeeze out of the OpNav3 sequence with reasonable effort.
Next processing attempts with the new sequence.

[illexsquid]

Statistically, if other cratered bodies are anything to go by, there should not be a dichotomy in terms of what portions of Ceres were hit by large impactors and what portions were not.

I don't think either that such a dichotomy would make much sense

I hope it doesn't come across as patronizing to point out that what we have thought should be true has, so many times in this golden age of planetary exploration, been completely invalidated by what is actually out there. Little Miranda, for instance, has no business being anything other than a cratered lump, yet there those amazing coronae are. In a few weeks we'll doubtless have a clearer idea of what to argue about, but in the meantime I'm just going to enjoy the front-row seats to unfolding history.

[Explorer1]

Here's what I'm expecting: a unique body with some similarities to other objects of the same size, but also many important differences!
Maybe that's vague enough?
We'll go through the same speculation roulette wheel with Pluto soon enough; might as well get some practice in.

[Steve G]

Am I missing something or are we not waiting for the RC1 images? Or can I stop checking this site every four and a half minutes. The waiting is tortuous!

[Explorer1]

Yep; all waiting. Open tab on the Dawn twitter page.....

[Habukaz]

The previous release (as well as at least one more) was at around 14-15 UTC. That's more than two hours ago now. I don't think there has been given any guarantee that the images will be released today, but the day is still young in the right time zones. *crosses fingers*

[alk3997]

The previous release (as well as at least one more) was at around 14-15 UTC. That's more than two hours ago now. I don't think there has been given any guarantee that the images will be released today, but the day is still young in the right time zones. *crosses fingers*

Federal holiday in the U.S. today. I wouldn't expect any release today.

Andy

[Habukaz]

Federal holiday in the U.S. today. I wouldn't expect any release today.

Andy

Ouch. I actually have the public holidays and the like of many countries on my calender, but I never bother reading them.

[vikingmars]

Am I missing something or are we not waiting for the RC1 images? Or can I stop checking this site every four and a half minutes. The waiting is tortuous!

I've waited for 45 years to see Ceres up-close... I can wait a few days more...

[DrShank]

I've waited for 45 years to see Ceres up-close... I can wait a few days more...

Plan is for a tuesday release but that might be held up a day or two. the process is rather involved, at multiple levels of the project and NASA HQ to make sure that the images released are properly processed annotated and described. all rather complex, but the folks who help us do our job need to do theirs!

[jamescanvin]

I split the posts about airbrushed maps into a dedicated thread to save them getting lost here.

http://www.unmannedspaceflight.com/index.php?showtopic=7974