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Unmanned Spaceflight.com _ Dawn _ Dawn's last mission extensions at Ceres

Posted by: Holder of the Two Leashes Feb 1 2017, 02:37 PM

This thread will cover all final phases of the Dawn mission, the end of which is not certain at this point.

XMO3 was suppose to be the final orbit, but now plans have changed and it will move into a new higher altitude and higher phase orbit soon. This will be XMO4.

An interesting monthly journal for January details the plan:

http://dawn.jpl.nasa.gov/mission/journal_01_31_17.html

Posted by: TheAnt Feb 4 2017, 06:09 PM

Ahuna mons have turned out to be what is called one "ice volcano"
(Used in lack of a better word in american English I guess, my native language got a word for underground water that instantly freeze as it enter the surface in the wnter which would have been very suitable here.)
Now why only a single such feature?
The http://news.agu.org/press-release/new-research-shows-ceres-may-have-vanishing-ice-volcanoes/ put some thought on that matter and suspect there's other ones that have flattened out and started a search for potential other sites.

Posted by: ngunn Feb 4 2017, 07:10 PM

QUOTE (TheAnt @ Feb 4 2017, 06:09 PM) *
Now why only a single such feature?


Another possible answer might be that the whole of Ceres is acting like a single pressure vessel with relatively fluid contents. This would require only a single relief valve (at any given time).

Posted by: Gladstoner Feb 4 2017, 08:16 PM

QUOTE (TheAnt @ Feb 4 2017, 12:09 PM) *
Now why only a single such feature?
The http://news.agu.org/press-release/new-research-shows-ceres-may-have-vanishing-ice-volcanoes/ put some thought on that matter and suspect there's other ones that have flattened out and started a search for potential other sites.


Perhaps the raised area adjacent to Ahuna is such a feature:



The elevation of this area seems to be anomalous compared to the surrounding topography. It does not appear to be associated with any crater/ basin rims or central peaks. Its association with Ahuna seems to imply a relationship of some kind. The surface of this feature is heavily cratered, which means it has been around much longer than Ahuna. Either this feature is an area of general uplift associated with the formation of Ahuna, or it is an older volcanic edifice of the upwelling that produced Ahuna (i.e. 'ancestral Ahuna') that has subsequently suffered subsidence and erosion. Or perhaps both processes were in play. Finally, it is possible it presence there could be purely coincidental.

Posted by: TheAnt Feb 6 2017, 12:39 AM

@Gladstoner: You might indeed have pointed out Ahuna mons predecessor there.
But yes, it cannot be ruled out that it's associated with the current formation. We just have to wait for the verdict by the professionals.
Regardless of which two it turn out to be, I don't think it's coincidental.

What is interesting is the comparatively short timeframe for a feature like this to relax and get near invisible.
If it is lets say 10 MY, that would mean that there's some ongoing activity inside Ceres to create a feature like Ahuna mons.
The big question then will be if it's continuous or periodical.

Well this higher altitude orbit might perhaps get us a chance to catch an image of the possible fog over Occator. Backlit by the Sun would be the best way to catch it just as on Enceladus.

Posted by: Gladstoner Feb 6 2017, 06:12 AM

QUOTE (TheAnt @ Feb 5 2017, 06:39 PM) *
What is interesting is the comparatively short timeframe for a feature like this to relax and get near invisible.
If it is lets say 10 MY, that would mean that there's some ongoing activity inside Ceres to create a feature like Ahuna mons.
The big question then will be if it's continuous or periodical.


Based on the features' appearances and on the (apparent) lack of extensive activity on Ceres, I'd think any volcanic processes would be episodic.

Posted by: Daniele_bianchino_Italy Feb 8 2017, 09:46 AM

" Asteroid Dust Cloaks True Composition Of Dwarf Planet Ceres "

" Observations of Ceres indicate that asteroids might be camouflaged "
http://www.seti.org/seti-institute/press-release/observations-ceres-indicate-asteroids-might-be-camouflaged

" Dwarf planet Ceres camouflage by asteroid dust ":
http://www.space.com/35451-dwarf-planet-ceres-camouflage-asteroid-dust.html

Posted by: Daniele_bianchino_Italy Feb 8 2017, 09:53 AM

?
Is expected to map temperatures of Ceres? I expected Already for long time :-/

Posted by: Paolo Feb 17 2017, 06:03 AM

on today's Science (and behind the paywall... mad.gif )

http://science.sciencemag.org/content/355/6326/719

QUOTE
Organic compounds occur in some chondritic meteorites, and their signatures on solar system bodies have been sought for decades. Spectral signatures of organics have not been unambiguously identified on the surfaces of asteroids, whereas they have been detected on cometary nuclei. Data returned by the Visible and InfraRed Mapping Spectrometer on board the Dawn spacecraft show a clear detection of an organic absorption feature at 3.4 micrometers on dwarf planet Ceres. This signature is characteristic of aliphatic organic matter and is mainly localized on a broad region of ~1000 square kilometers close to the ~50-kilometer Ernutet crater. The combined presence on Ceres of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and organic material indicates a very complex chemical environment, suggesting favorable environments to prebiotic chemistry.


see also the Science perspective article: http://science.sciencemag.org/content/355/6326/692
and the JPL press release: http://www.jpl.nasa.gov/news/news.php?feature=6751

Posted by: TheAnt Feb 18 2017, 04:46 PM

This is the kind of news that could have me literally jumping up and down.
Water, ammonia, salts, cabonates and now this!
It might be quite premature to speculate if any space agency will jump at this opportunity.
But it's a fact that Ceres would provide an easy target for a lander mission.
With the very low gravity it would even be possible to have a 'jumping' lander visiting several sites for sampling.
Even the idea of returning samples might be considered.
Aliphatic organic matter - it's not any of the lighter ones, they would be long gone, from a single spectral line it's hard to say how complex those molecules are.
But I'd give an arm and a leg to have closer look at a sample here on Earth.


Posted by: Explorer1 Feb 19 2017, 05:30 AM

There's probably already samples of Ceres on Earth, just not yet identified as such. All those craters must have made sprayed ejecta everywhere and some meteorites must be here now, just by probability.
Otherwise a sample return mission might in fact be easier than Mars; lack of atmosphere and low gravity making up for the greater difference in orbits...

Posted by: fredk Feb 19 2017, 03:50 PM

QUOTE (Explorer1 @ Feb 19 2017, 06:30 AM) *
lack of atmosphere

Doesn't atmosphere help you at Mars? You'd need a heck of a lot of fuel to brake from orbit and land without atmospheric drag. The drag would affect a launch from the surface, but with low launch speeds and thin atmosphere I'm guessing that's not a big effect.

Of course lower gravity at Ceres means lack of atmosphere won't be as important as it would've been at Mars.

Posted by: Explorer1 Feb 19 2017, 06:48 PM

Yes, I was talking about launching from the surface. I vaguely recall reading an article a few years ago about someone working on an engine for an ascent stage to get straight to Earth, no need for rendezvous; can't find it now. Anyway, this is a discussion for another thread, another time.

Posted by: Daniele_bianchino_Italy Feb 22 2017, 10:15 AM

QUOTE (Daniele_bianchino_Italy @ Feb 8 2017, 09:53 AM) *
?
Is expected to map temperatures of Ceres? I expected Already for long time :-/


Repropose my UP question... ?

I know that Ceres has no seasons like earth. However, we can say that it is entering its warm period. Dawn was arrived to Ceres in the beginning of the cold season. Too bad the mission will end before the maximun warm season of Ceres.


Posted by: PhilipTerryGraham Feb 25 2017, 11:02 AM

They're starting to publish XMO3 images on the NASA Photojournal! The first is http://photojournal.jpl.nasa.gov/catalog/PIA11240, taken on 11 February.

EDIT: https://commons.wikimedia.org/wiki/File:PIA11240_-_Occator_and_Ahuna.jpg, with annotations labelling all the discernible features in the image, per the https://planetarynames.wr.usgs.gov/images/ceres.pdf.

Posted by: Habukaz Feb 26 2017, 01:25 PM

QUOTE (Daniele_bianchino_Italy @ Feb 8 2017, 10:53 AM) *
?
Is expected to map temperatures of Ceres? I expected Already for long time :-/


Some pictures showing temperature have been generated. http://www.hou.usra.edu/meetings/lpsc2016/pdf/1883.pdf a few that I am not sure if have been posted to the Photojournal, where you can find the others. Don't know about global or other larger maps, or time series of temperature.

Posted by: Daniele_bianchino_Italy Mar 6 2017, 06:24 PM

QUOTE (Habukaz @ Feb 26 2017, 01:25 PM) *
Some pictures showing temperature have been generated. http://www.hou.usra.edu/meetings/lpsc2016/pdf/1883.pdf a few that I am not sure if have been posted to the Photojournal, where you can find the others. Don't know about global or other larger maps, or time series of temperature.


Thanks!
235 K -38C
196 K -76C
However, the VIR images are of the last year.
Ceres from this year begins to warm. The mission will not arrive to the maximum hot season of Ceres, but it could show more high temperatures in the next months....

Posted by: nprev Mar 10 2017, 04:14 PM

ADMIN MODE: Moved four recent posts to the former "Water Vapor on Ceres" thread, which has been retitled "http://www.unmannedspaceflight.com/index.php?showtopic=7789". I think that discussion will continue long after the Dawn mission is completed. Thanks! smile.gif

Posted by: Gladstoner Apr 9 2017, 08:08 PM

Long-range image taken on March 28:

https://photojournal.jpl.nasa.gov/catalog/PIA21401



The brightness of the Occator faculae is pretty subdued at this lighting and viewing angle.

Posted by: Holder of the Two Leashes Apr 27 2017, 01:16 PM

Dawn has lost another (third) reaction wheel. But it looks like the opposition studies scheduled for Saturday the 29th will not be affected.

https://dawn.jpl.nasa.gov/news/news-detail.html?id=6830

Posted by: Explorer1 May 2 2017, 04:15 AM

Opposition observation data received! https://dawn.jpl.nasa.gov/mission/status.html

Posted by: hendric May 3 2017, 04:20 PM

Man, if I ever win the lottery I'm going to work on making longer-lasting reaction wheels for space missions. sad.gif

Posted by: djellison May 4 2017, 04:37 AM

There are many old spacecraft with great reaction wheels still working fine. But there must have been some batch - some particular hardware version rev that has hit Kepler and Dawn.

Posted by: Explorer1 May 18 2017, 10:08 PM

Movie from opposition observations released: https://www.jpl.nasa.gov/news/news.php?feature=6845
New journal soon, presumably.

Posted by: Holder of the Two Leashes Jun 18 2017, 09:31 PM

Dawn's fate to be decided soon. Sending it off to a new asteroid is one option back on the table.

https://spaceflightnow.com/2017/06/17/dawn-mission-managers-await-nasa-decision-on-spacecrafts-future/

Posted by: hendric Jun 19 2017, 05:36 PM

QUOTE (djellison @ May 3 2017, 10:37 PM) *
There are many old spacecraft with great reaction wheels still working fine. But there must have been some batch - some particular hardware version rev that has hit Kepler and Dawn.


Yep, here's a comment from this article ( https://spaceflightnow.com/2017/06/17/dawn-mission-managers-await-nasa-decision-on-spacecrafts-future/ )

Benjamin Hunt
Mass and size are always an issue on spacecraft, especially deep space probes. Remember, however, that Dawn is an exception in terms of reliability...while reaction wheels have failed on other missions, they all (I believe) failed *after* completing their primary missions, and usually their extended missions.

That said, the reaction wheels that have failed on Dawn and several other spacecraft that have made the news have been noted as coming from a bad batch made by Ithaco Space Systems. The decreased lifespans weren't understood until it was far too late to do anything about it, except for the Kepler mission; those wheels were sent back to Ithaco for preventative maintenance shortly before launch, but even that didn't fix the problem. Still, Kepler made it 4 years before failure compared to its planned 3.5 year mission, and it is still returning very useful science, even if at a reduced capacity.

Posted by: jasedm Jun 19 2017, 08:29 PM

It would be fantastic news if the budget allowed for another asteroid flyby - I'd be pretty surprised though if the idea was approved.

Just a fun thought, would it be possible for Dawn to make it back to Earth? The idea of it matching orbits with the ISS and being examined up close after ten years of spaceflight is strangely thrilling (well to me at least smile.gif )

Posted by: nprev Jun 19 2017, 11:09 PM

It'd be possible to make it back to the Earth's vicinity, but probably only as a flyby. I don't see any practical way to get it into near-Earth orbit, even if the attitude control suite was fully operational.

No value added there. An asteroid flyby would be a much, much better option.

Posted by: algorimancer Jun 20 2017, 05:25 PM

What about a Europa flyby, with some asteroid flybys en-route? Not sure about the gravity gradient, but it might be more efficient to head inward and get an orbital assist from Mars, or it might not. Given the current state of knowledge about Europa, we could probably learn a lot from a targeted flyby -- and probably 10 or more years before we have an orbiter in place.

Posted by: djellison Jun 20 2017, 05:45 PM

Europa? No way it'll survive that far from the Sun and that sort of radiation dose. It really is Adiona, or Ceres. That's honestly all the options.

Posted by: tedstryk Jun 21 2017, 01:28 AM

Another asteroid flyby would be cool, but I'd like to stay at Ceres to monitor it though perihelion to see if any changes/outgassing can be detected.

Posted by: nprev Jun 21 2017, 04:22 AM

Perihelion is next April, and it does seem as if most http://www.nature.com/nature/journal/v505/n7484/fig_tab/nature12918_F3.html by remote sensors have happened around then.

I concur with Ted.

Posted by: hendric Jun 21 2017, 06:40 AM

I agree, stay at Ceres, but in a long term parking orbit that would allow for long term observations, with possible dips to a close orbit for flybys of anything interesting. I doubt we'll see significant changes, but maybe we'll get lucky. Occator crater is such an enigma, with the youth of the central mound. It is fascinating that two icy bodies (Ceres and Enceladus) that span an order of magnitude of sizes have localized activity.


Posted by: algorimancer Jun 22 2017, 01:35 PM

QUOTE (djellison @ Jun 20 2017, 12:45 PM) *
Europa? No way it'll survive that far from the Sun and that sort of radiation dose...

True, only 28% as much solar energy at Jupiter (if I did the math right). Not sure if this is more a problem for propulsion or simply keeping the electronics running. And I have no expertise in judging the radiation problem, though (having been a software developer once upon a time), I do wonder whether radiation tolerant software could be developed -- perhaps using the RAM in a multiply redundant fashion -- but that's a broader problem.

Anyway, my vote would be to go elsewhere if possible, with the argument being that flyby observations of another -- never explored -- asteroid would be more valuable than spending a bit more time at Ceres.

Posted by: bobik Jun 23 2017, 06:29 AM

QUOTE (nprev @ Jun 21 2017, 04:22 AM) *
Perihelion is next April, and it does seem as if most http://www.nature.com/nature/journal/v505/n7484/fig_tab/nature12918_F3.html by remote sensors have happened around then.

"https://www.nasa.gov/feature/jpl/ceres-temporary-atmosphere-linked-to-solar-activity ... Villarreal and colleagues showed that past detections of the transient atmosphere coincided with higher concentrations of energetic protons from the sun. Non-detections coincided with lower concentrations of these particles. What's more, the best detections of Ceres' atmosphere did not occur at its closest approach to the sun. This suggests that solar activity, rather than Ceres' proximity to the sun, is a more important factor in generating an exosphere."

Posted by: Daniele_bianchino_Italy Jun 24 2017, 01:36 PM

I would like to stay up Ceres to the perihelion. However, it depends on which asteroid destination Dawn team proposing.


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