Dawn dead in Ceres orbit, ran out of fuel Oct 2018

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In summary, the Dawn spacecraft observed Ceres for an hour on Jan. 13, from a distance of 238,000 miles (383,000 kilometres). A little more than half of its surface was observed at a resolution of 27 pixels. This video shows bright and dark features.
  • #141
marcus said:
This just posted, is it RC2? Is this from the recent shoot, 19 Feb, or the earlier RC1? It doesn't say AFAICS.
View attachment 79561

I guess it is from the earlier shoot on 12 or 13 Feb, but sharper print for some reason. In any case the RC2 pictures should be online soon.
I spent half an hour comparing the original RC1 image to this one. The only thing I could conclude was that I had low definition eyes. But I think you are right. I also think it's from RC1.

OMG! OMG! The new Journal is out! The new Journal is out!​

Dawn Journal | February 25
by Marc Rayman

Dear Fine and Dawndy Readers,
CeresBig_LR.jpg

Feb 19th 2015, RC2​
 
Astronomy news on Phys.org
  • #142
Ceres seems to have no shortage of polygonal craters.
 
  • #143
Personally, I like the pictographic message the Cerians have sent us:

Cerians.regarding.Einstein.god.and.dice.jpg

"Einstein was wrong.
God does play dice, and he rolled a 5.
Though, his dice appear to be round.
We haven't yet figured out how that's possible.
But welcome, Earthlings!
Perhaps, together, we can figure this out."​
 
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  • #146
Om, who is shooting a death ray at whom? btw humor aside do you like the term "dwarf planet"?
As I understand the definitions, if something is massive enough to pull itself into a roundish ball shape (rather than an irregular chunk shape like asteroids and comets) then it is officially either a PLANET or a DWARF-PLANET
and what makes the difference is whether it has been massive enough to sweep clear and control its orbit pathway.

I don't like the terminology. It sounds unkind. It lacks a feeling of affection. Here are some alternatives that don't give the unfortunate impression that there is something wrong about a planet that hasn't cleared the debris out of its path.

1. Miniplanet
2. Planette
3. Planikin
4. Orblet
5. Planetino

Which of these would you like best? What alternative name SHOULD they have given the category.
 
  • #147
For the next ten days the critical thing to watch is the meters-per-second speed of the probe. In order to achieve capture by 6 March it has to get its speed down to around 46 m/s ---then it will actually be bound in orbit rather than just a "fly-by" visitor.
From today (26 Feb) to 6 March, as its distance increases from 41 to 61 kkm, the speed should decrease roughly as Petrich calculated. I've adapted his numbers

X Y Z are coordinates relative to Ceres, which is (0,0,0), measured in kkm---thousands of km.
X is directed out from sun, in Ceres orbit plane
Y is directed perpendicularly up off the orbit plane, approximately in Ceres' north pole direction
Z is directed forwards in Ceres orbit plane, the direction Ceres is moving, a negative shows the probe trailing behind.
distance from Ceres continues increasing for a while because the probe has some excess momentum
vescape is the escape velocity at that given distance
vprobe is the predicted velocity the probe will actually have that day. It must fall below vesc to achieve capture.
Code: 
date      X          Y          Z        distance  v_esc  v_probe
F17   -45.9972    6.4086    -27.2882    53.86           
F18   -38.555    9.71627    -28.2185    48.75
F19   -32.3324    12.4392    -29.202    45.30           
F20   -26.169    14.8491    -29.9728    42.46
F21   -19.6171    17.2648    -30.4689    40.14
F22   -13.2794    19.4975    -30.6993    38.71
F23   -6.73346    21.6416    -30.593    38.07
F24   -0.502056    23.4431    -30.212    38.24
F25     5.62894    25.0851    -29.7158    39.29    56.67    71.36
F26     11.407    26.4613    -29.1488    40.98    55.48      69.67
F27     17.2899    27.6663    -28.1919    43.11    54.10     68.44
F28     22.8583    28.5286    -27.0313    45.46    52.68    64.25
M1      27.9985    29.1842    -25.6846    47.90    51.32     60.73
M2      32.8862    29.7513    -24.1873    50.51    49.98     58.67
M3      37.6439    30.1647    -22.7166    53.31    48.65     55.28
M4      41.9734    30.4246    -21.3167    56.05    47.44     50.18
M5      45.8274    30.5605    -19.8726    58.55    46.42     46.96
M6      49.5028    30.6491    -18.2955    61.02    45.47     44.35
M7      52.8252    30.4896    -16.7451    63.24    44.66     40.49
M8      55.7681    30.3242    -15.1946    65.27    43.97     37.71
M9      58.5427    30.0761    -13.6441    67.21
M10     58.5427    30.0761    -13.6441    67.21
M11     63.2886    29.4796    -10.5963    70.61
M12     65.1256    29.1961    -9.32939    71.97
The table starts 17 Feb and it shows the probe overshooting Ceres in the X direction (it has not had time to slow its X motion and will need Ceres gravity to pull it back in line)
likewise it shows the probe overshooting in the upwards Y direction.
Ceres' orbit inclination is 10 degrees and it just recently passed its descending node, so it is sloping down relative to the ecliptic (solar system plane) and to Dawn's prior orbit.
This gives Dawn some unwanted Speed in the "up" or Y direction. Again Ceres gravity will help draw the probe in.
 
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  • #148
marcus said:
Om, who is shooting a death ray at whom? btw humor aside do you like the term "dwarf planet"?
No!
As I understand the definitions, if something is massive enough to pull itself into a roundish ball shape (rather than an irregular chunk shape like asteroids and comets) then it is officially either a PLANET or a DWARF-PLANET
and what makes the difference is whether it has been massive enough to sweep clear and control its orbit pathway.

I don't like the terminology. It sounds unkind. It lacks a feeling of affection. Here are some alternatives that don't give the unfortunate impression that there is something wrong about a planet that hasn't cleared the debris out of its path.

1. Miniplanet
2. Planette
3. Planikin
4. Orblet
5. Planetino

Which of these would you like best? What alternative name SHOULD they have given the category.
Hadn't really thought about it before.
From your list, Planetino is the best, IMHO.

Though, I would have probably come up with "Hobbit planet", myself.
 
  • #149
  • #150
How about planetino versus planetello?

I'm thinking of 200 or 300 years hence when some DNA-engineering has enabled people to live healthy lives in soft gravity, like the planetello Ceres gravity of 3% Earth normal gee. And somebody says "My sister and her husband got jobs on that icy planetello just beyond Mars."
"They like living in the planetello's caverns, they're learning springboard ballet and muscle-powered flight."

I suspect it's not unlikely they'd just wind up calling it a "planet" (even though astronomer's conventions limit the use of that term) or calling it a "world". If people live on a solar system orb why not use the general term and call it a world?

Om, there's the old question "how high could you jump?" Using the radius 475 km and the mass 943 billion billion kg, I calculated the surface gravity as 1/35 of our 9.8 ms-2. Around 0.28 m/s2.

Is it as simple as saying that you could jump 35 times as high?

BTW just checked current status and it said speed relative to Ceres (as of 22h UT, or 2pm pacific on 26 Feb) is 70 m/s. Which fits fairly well with Pterich's timetable. He gives 69.67 m/s for 26 Feb.
 
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  • #151
marcus said:
Is it as simple as saying that you could jump 35 times as high?
It is not, but it gives a good lower estimate if you take the change in center of mass after leaving ground, and a good upper estimate if you take the total shift in center of mass.

The acceleration distance will be the same, but you don't have to fight against so much gravity so your final velocity is larger, giving you more than 35 times the height after leaving the ground.
The acceleration time will be lower for the same reason, which means you can at most put the same energy into the jump, giving you at most 35 times the total height difference in your center of mass.

With ~50cm and 1m for those two values on Earth (note: don't include pulling your legs up, that does not change the center of mass and will have a negligible effect on the height on Ceres), you could jump somewhere between 20-35 meters high.
Related discussion
 
  • #152
Thanks! makes very good sense explained like that.

BTW the speed relative to Ceres is declining steadily, which is good news. Current status puts it at 69.3 m/s at 42.5 kkm , That is as of 8 pm pacific on 26 Feb.

EDIT: As an update as of 8pm pacific on 28 Feb, current speed rel. Ceres is 63.9 m/s at a distance of 46.0 kkm
 
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  • #153
marcus said:
How about planetino versus planetello?

I'm thinking of 200 or 300 years hence when some DNA-engineering has enabled people to live healthy lives in soft gravity, like the planetello Ceres gravity of 3% Earth normal gee. And somebody says "My sister and her husband got jobs on that icy planetello just beyond Mars."
"They like living in the planetello's caverns, they're learning springboard ballet and muscle-powered flight."

I suspect it's not unlikely they'd just wind up calling it a "planet" (even though astronomer's conventions limit the use of that term) or calling it a "world". If people live on a solar system orb why not use the general term and call it a world?
Planetello sounds a bit like Portabella, which is a mushroom, which is how our descendants would have to live on Ceres.
So that sounds appropriate.
Om, there's the old question "how high could you jump?" Using the radius 475 km and the mass 943 billion billion kg, I calculated the surface gravity as 1/35 of our 9.8 ms-2. Around 0.28 m/s2.

Is it as simple as saying that you could jump 35 times as high?
According to my calculations, that number is accurate to 32 decimal places. :oldwink:

Code: 
Om can jump     8    inches              on Earth
g on Earth    9.8    m/s^2  
in/m        39.37      
h           0.203    m  
u = gh       1.99    specific pe  
g on Ceres   0.28    m/s^2  
h on Ceres    7.1    m                   that Om could jump (I'm fat)
multiple     35.000000000000000000000000000000

And yes, I did extend my legs, as mfb recommended. :oldbiggrin:

BTW just checked current status and it said speed relative to Ceres (as of 22h UT, or 2pm pacific on 26 Feb) is 70 m/s. Which fits fairly well with Pterich's timetable. He gives 69.67 m/s for 26 Feb.

Where is he?
 
  • #154
Just got tweeted, that Leonard Nimoy narrated a piece for the Dawn mission.
I thought that was kind of cool.


​

The ESA just tweeted about another one, but my bandwidth forced me to download it.
It appears to be an earlier, abbreviated version.
But watching the Delta II liftoff scene, made it worth the wait.

:smile:
 
  • #155
As it happens, Nimoy died this morning from a long term illness. I'm happy to see he narrated the like of these Dawn videos before his end.
 
  • #156
Today, 1 March, is another one of the planned optical navigation photoshoots.
Code: 
Jan 13  (383,000) 27  (36) 0.83 95% OpNav 1
Jan 25  (237,000) 43  (22) 1.3 96% OpNav 2
Feb 3   (146,000) 70  (14) 2.2 97% OpNav 3
Feb 12  (83,000) 121  (7.8) 3.8 98% RC1
Feb 19  (46,000) 221  (4.3) 7.0 87% RC2
Feb 25  (40,000) 253  (3.7) 8.0 44% OpNav 4
Mar 1   (49,000) 207  (4.6) 6.5 22% OpNav 5
Apr 10  (33,000) 304  (3.1) 9.6 18% OpNav 6
Apr 15  (22,000) 455  (2.1) 14 50% OpNav 7

I just checked the current status view and it showed the probe still thrusting, not yet flipped around for picture-taking:
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
Picture taking session should be brief, just to get a shot of the known stars in the background, to determine the probe's angle on Ceres to help locate the probe relative to the planit. I don't think I missed it, though the shoot might have been so brief I didn't notice it on current status.
Whenever todays picture is ready for transmission we should see an antenna receiving data from Dawn here. Canberra most likely
https://eyes.nasa.gov/dsn/dsn.html

The photo from the 25 Feb shoot has not yet been posted. That might happen tomorrow (Monday) and it will be the highest resolution so far. See the table for details. Distance 40 kkm, one pixel width = 3.7 kilometers. 44% of the planit's face illuminated.
When a 25 Feb photo is posted, one place to find it will be at the Dawn website
click on: multimedia > photos/images > Dawn science at Ceres
and you get: http://dawn.jpl.nasa.gov/multimedia/Ceres_science_gallery.asp
 
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  • #157
Here's the currently relevant part of the table shown in post#148
The probe has been "retro" thrusting in an effort to slow itself down to around 46 m/s by 6 March
Current status view shows the ion thruster beam pointed straight out ahead in the direction the probe is going.
The phase of Ceres indicates the direction to the sun
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
Current status now gives the speed relative to Ceres as 58.6 m/s (as of 8pm pacific, 1 March) and a distance of 49.9 kkm.
that is better than what we have listed in the table for 1 March.
It's rather more like what the table gives for 2 March.
So according to current status the slow-down is proceeding well
Code: 
date      X          Y          Z        distance  v_esc  v_probe
F25     5.62894    25.0851    -29.7158    39.29    56.67    71.36
F26     11.407    26.4613    -29.1488    40.98    55.48      69.67
F27     17.2899    27.6663    -28.1919    43.11    54.10     68.44
F28     22.8583    28.5286    -27.0313    45.46    52.68    64.25
M1      27.9985    29.1842    -25.6846    47.90    51.32     60.73
M2      32.8862    29.7513    -24.1873    50.51    49.98     58.67
M3      37.6439    30.1647    -22.7166    53.31    48.65     55.28
M4      41.9734    30.4246    -21.3167    56.05    47.44     50.18
M5      45.8274    30.5605    -19.8726    58.55    46.42     46.96
M6      49.5028    30.6491    -18.2955    61.02    45.47     44.35
M7      52.8252    30.4896    -16.7451    63.24    44.66     40.49
M8      55.7681    30.3242    -15.1946    65.27    43.97     37.71
X Y Z are coordinates relative to Ceres, which is (0,0,0), measured in kkm---thousands of km.
X is directed out from sun, in Ceres orbit plane
Y is directed perpendicularly up off the orbit plane, approximately in Ceres' north pole direction
Z is directed forwards in Ceres orbit plane, the direction Ceres is moving, a negative shows the probe trailing behind.
distance from Ceres continues increasing for a while because the probe has some excess momentum
vescape is the escape velocity at that given distance
vprobe is the predicted velocity the probe will actually have that day. It must fall below vesc to achieve capture.
 
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  • #158
I think we may have missed it. It's now just after midnight, March 2, UTC.
I think* I saw the thrusters off yesterday, checked the DSN, and no signal was being sent.
When I checked again later, the thrusters were back on.
We've missed our first OpNav.
So I think you're right, the picture taking session was very brief.

*I may be dreaming about this stinking Dawn mission now. :redface:
 
  • #159
ps. Is anyone else going to be watching the live telecast tomorrow morning?

http://dawn.jpl.nasa.gov/feature_stories/NASA%20Briefing_DAWN%20Arrival%20at%20a%20Dwarf%20Planet.asp
February 24, 2014- PASADENA, Calif. -- NASA's Jet Propulsion Laboratory will host a briefing at 9 a.m. PST (noon EST) Monday, March 2, to discuss the March 6 arrival of the agency's Dawn spacecraft at the dwarf planet Ceres. The news briefing, held at JPL's von Karman Auditorium at 4800 Oak Grove Dr., Pasadena, California, will be broadcast live on NASA Television and streamed on the agency's website.

I've been testing their feed today, in preparation.
 
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  • #160
Goldstone is talking with Dawn (as of 8 am pacific)
https://eyes.nasa.gov/dsn/dsn.html
And current status shows the spacecraft flipped around in photo+communication mode, thruster off.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
It looks like the navigation photo-shoot that was earlier scheduled for 1 March was postponed until 2 March, otherwise everything seems normal.

The current speed is nice and slow :smile: 57.2 m/s (as of 8am pacific) at a distance of 51.3 kkm

News briefing 9am pacific on 2 March
http://www.nasa.gov/multimedia/nasatv/index.html#.VPSWy0I-DVo (Om's link)
 
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  • #161
marcus said:
Goldstone is talking with Dawn (as of 8 am pacific)
https://eyes.nasa.gov/dsn/dsn.html
And current status shows the spacecraft flipped around in photo+communication mode, thruster off.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
It looks like the navigation photo-shoot that was earlier scheduled for 1 March was postponed until 2 March, otherwise everything seems normal.

The current speed is nice and slow :smile: 57.2 m/s (as of 8am pacific) at a distance of 51.3 kkm

News briefing 9am pacific on 2 March
http://www.nasa.gov/multimedia/nasatv/index.html#.VPSWy0I-DVo (Om's link)

Shhh! I'm trying to listen!
 
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  • #162
Here's an animation from the 25 Feb photoshoot. I don;t see how to embed it in this post, but I think if you click on the link you get the animation. Shows Ceres rotating, with highest resolution so far.
http://dawn.jpl.nasa.gov/multimedia/images/pia18920-rotating_lg.gif

One thing Carol Raymond at the press briefing mentioned several times as an explanation for the white spots was
salt residue left after salt laden water comes to the surface (after an impact) and the water evaporates.

As of 10am pacific, 2 March, Goldstone had stopped talking with Dawn, so the 2 March photoshoot is complete and the next update of current status should show the craft flipped back into normal thrusting mode, if I understand correctly. Current status is still as of 8am pacific, hasn't been updated yet, so it shows Dawn still oriented for a photoshoot.

I wonder if they will even bother to post today's pictures, since only a tiny sliver of the planeeto is sunlit---dawn is on the dark side now
 
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  • #163
marcus said:
Here's an animation from the 25 Feb photoshoot. I don;t see how to embed it in this post, but I think if you click on the link you get the animation. Shows Ceres rotating, with highest resolution so far.
http://dawn.jpl.nasa.gov/multimedia/images/pia18920-rotating_lg.gif

One thing Carol Raymond at the press briefing mentioned several times as an explanation for the white spots was
salt residue left after salt laden water comes to the surface (after an impact) and the water evaporates.

As of 10am pacific, 2 March, Goldstone had stopped talking with Dawn, so the 2 March photoshoot is complete and the next update of current status should show the craft flipped back into normal thrusting mode, if I understand correctly. Current status is still as of 8am pacific, hasn't been updated yet, so it shows Dawn still oriented for a photoshoot.

I wonder if they will even bother to post today's pictures, since only a tiny sliver of the planeeto is sunlit---dawn is on the dark side now
Ah! Did you notice, in the gif, that the "headlights" didn't go out, after they entered the shade?
Does this mean, that Ceres has an atmosphere?

I saw yesterday that Pluto's atmosphere extends further than Earth's atmosphere.
Pretty freakin' freaky.

But then, I suppose, everything is freaky, once you leave the crib.
:smile:
 
  • #164
The upper edge of atmospheres is arbitrary. The atmosphere at Pluto's surface would qualify as a good vacuum for Earth standards.

Individual frames of the rotation gif
The spots vanish as soon as they do not get sunlight any more. The spots are brighter than "fully white" in the usual images, so they stay very bright even with a lower level of sunlight. In addition, the surface could be tilted a bit.
 
  • #165
mfb said:
The upper edge of atmospheres is arbitrary. The atmosphere at Pluto's surface would qualify as a good vacuum for Earth standards.

Individual frames of the rotation gif
The spots vanish as soon as they do not get sunlight any more. The spots are brighter than "fully white" in the usual images, so they stay very bright even with a lower level of sunlight. In addition, the surface could be tilted a bit.

That website isn't working for me for some reason:

Error 522 Ray ID: 1c0f9fd88bd40d9d
Connection timed out​

But I googled, and found out that all I have to do is drag a moving gif to my desktop, and I can examine the individual images. (Yay Mr. Jobs!)

Anyways, I grabbed images 4 & 5 and highlighted the headlights.
Either there is an atmosphere, or those are the peaks of ice volcanoes. (Or whatever these neoexoplanetary people call those things.)

pf.2015.03.02.1152.Ceres.frames.4.n.5.jpg


Pure speculation, of course. But at least, I know they're not headlights anymore. (They did go out in frame 6).
 
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  • #166
OmCheeto said:
Ah! Did you notice, in the gif, that the "headlights" didn't go out, after they entered the shade?
Does this mean, that Ceres has an atmosphere?

I saw yesterday that Pluto's atmosphere extends further than Earth's atmosphere.
Pretty freakin' freaky.

:smile:

Plumes have been noted before on Ceres. It would be astounding if Ceres turned out somehow to be an active body.
http://phys.org/news/2014-01-telescope-spies-plumes-dwarf-planet.html

The results are somewhat unexpected because comets, the icier cousins of asteroids, are known typically to sprout jets and plumes, while objects in the asteroid belt are not.

"The lines are becoming more and more blurred between comets and asteroids," said Seungwon Lee of JPL, who helped with the water vapor models along with Paul von Allmen, also of JPL. "We knew before about main belt asteroids that show comet-like activity, but this is the first detection of water vapor in an asteroid-like object."
 
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  • #167
It's not clear to me what water-ice would do in a Ceres atmosphere that is either not there or almost not there. Ice could be on Ceres in the dark, but if it is correct that any ice exposed to the sun would sublimate, then we should never be able to see any where the imagery depends on solar illumination.
 
  • #168
My two cents, about the bright spots:
I think they are salt residue as described in post #163.
I do not think they are mounds, just flat patches where impact brought salty water to the surface and the water sublimed in vacuum leaving the salt.

I don't think there is any mystery about them still showing as 100% bright white even under low angle dusk illumination. That is just an artifact of the contrast optimization. When you optimize the range for everything else, these spots are OFF SCALE so they read as 100% even though they are dull gray, just because they are still so much brighter than anything else. And as the sun goes down and the illumination gets less and less watts per square meter they are STILL off scale, and reading as 100% white, even though in reality they are duller and duller grey.

I don't think the spots involve volcanism, or geysers, or little mountains that catch the light of the setting sun or anything special---just high albedo salt "frosting" residue. Just a guess.
 
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  • #169
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  • #170
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  • #171
OmCheeto said:
Shhh! I'm trying to listen!
In spite of my preparations, I think I only captured 20% of the "live feed". :oldcry:

A more leisurely bandwidth of the briefing:


If anyone has a connection to the people NASA, please tell them that people on dial-up would appreciate an audio only, Om bandwidth friendly, live feed option. :oldgrumpy:
 
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  • #172
OmCheeto said:
Where is he? { @lpetrich }

Still on track:

55.29 m/s lpetrich
54.98 m/s = 123 mph (from current http://neo.jpl.nasa.gov/orbits/fullview2.jpg , 18:56:45 UTC)

I'm still lusting after the sourceXcode for the digitizer. :smile:
 
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  • #173
632397main_pia15491-full_full.jpg


This is a Dawn photo of a portion of Marcia crater on Vesta. In the press conference linked in the important above post (#172) it was announced, I think for the first time, Dawn had detected a gas emission from the center of this crater. One of the mission goals at Ceres is to determine if the body is in any way active, Director Green said in the press conference.

Unfortunately, it was also said they will not have new pix until April since Dawn will be on the dark side. ?:)

http://www.nasa.gov/mission_pages/dawn/multimedia/pia15491.html#.VPYAWUvoaX0

Another link to the JPL press Conference:
 
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  • #174
marcus said:
I do not think they are mounds, just flat patches

Yes that was confirmed in the press conference linked above - no mound / peak, which indicates something other than a volcanic release.
 
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  • #175
Could the sun be visible in the current status view, that large star over to the left?
http://neo.jpl.nasa.gov/orbits/fullview2.jpg

It's always possible that those responsible don't bother to get certain details right.
 
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