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

[mfb]

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

 

[marcus]

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

 

[OmCheeto]

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.

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.

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?

 

[OmCheeto]

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.

 

[mheslep]

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.

 

[marcus]

Today, 1 March, is another one of the planned optical navigation photoshoots.

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

 

[marcus]

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

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
v_escape is the escape velocity at that given distance
v_probe is the predicted velocity the probe will actually have that day. It must fall below v_esc to achieve capture.

 

[OmCheeto]

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.

 

[OmCheeto]

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.

 

[marcus]

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 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)

 

[OmCheeto]

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 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!

 

[marcus]

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

 

[OmCheeto]

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.

 

[mfb]

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.

 

[OmCheeto]

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.)

Pure speculation, of course. But at least, I know they're not headlights anymore. (They did go out in frame 6).

 

[Dotini]

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.

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."

 

[mheslep]

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.

 

[marcus]

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.

 

[Dotini]

The surface of Ceres is covered with craters of many shapes and sizes, as seen in this new mosaic of the dwarf planet comprised of images taken by NASA's Dawn mission on Feb. 19, 2015 from a distance of nearly 29,000 miles (46,000 kilometers)

IMAGE: NASA/JPL-CALTECH/UCLA/MPS/DLR/IDAhttp://mashable.com/2015/03/02/cere...er-All-Partial&utm_medium=feed&utm_source=rss

 

[OmCheeto]

The surface of Ceres is covered with craters of many shapes and sizes, as seen in this new mosaic of the dwarf planet comprised of images taken by NASA's Dawn mission on Feb. 19, 2015 from a distance of nearly 29,000 miles (46,000 kilometers)

IMAGE: NASA/JPL-CALTECH/UCLA/MPS/DLR/IDAhttp://mashable.com/2015/03/02/cere...er-All-Partial&utm_medium=feed&utm_source=rss

I found out where JPL.NASA hides their top-secret images this morning: Photojournal

 

[OmCheeto]

Shhh! I'm trying to listen!

In spite of my preparations, I think I only captured 20% of the "live feed".

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.

 

[OmCheeto]

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.

 

[Dotini]

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:

 

[mheslep]

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.

 

[marcus]

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.

 

[lpetrich]

I'm still lusting after the sourceXcode for the digitizer.

Here it is: my Image Measurer along with my most recent build of it. It's for MacOS X, so you won't be able to use it for Windows or Linux unless you can build it with GNUstep. It is not very well-documented, and it is incomplete in some ways. I haven't figured out how to display clicked-on points on the image in some easily hidable fashion.

 

[marcus]

Petrich! very glad to see you! We have been making a lot of use of your tabulation of numbers. As I recall you extrapolated them from trajectory images found in the November Dawn Journal. It has surprised me to see how well they have matched up with the daily progress we see in current status. The approach seems to be going fairly close to the way it was planned.

 

[wabbit]

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

Hello, just dropping by here - thanks for all the links and live thread. We can see Rigel in that pic (together with a good part of Orion, including Bellatrix and belt), but I don't see the Sun.

Quite a time for solar system astronomy - seeing both Rosetta and Dawn bring us all these pictures and data almost seems like too much at once !

 

[OmCheeto]

Here it is: my Image Measurer along with my most recent build of it. It's for MacOS X, so you won't be able to use it for Windows or Linux unless you can build it with GNUstep. It is not very well-documented, and it is incomplete in some ways. I haven't figured out how to display clicked-on points on the image in some easily hidable fashion.

OH MY GOD!

Houston, we have liftoff, of the lpetrich image measurer.

Above is the digitization of the stars and Ceres from the Mar.04.2015 01:00:06 UTC image.

I tried to find the sun yesterday by rotating and matching the star backgrounds of the "Sun" and "Ceres" images from Dawn, but was unsuccessful. But I decided that Mars was probably in the image also.

How can I ever repay you! This is priceless!
And a zoom feature! Ahhhhh!

 

[marcus]

Hello, just dropping by here - thanks for all the links and live thread. We can see Rigel in that pic (together with a good part of Orion, including Bellatrix and belt), but I don't see the Sun.

Quite a time for solar system astronomy - seeing both Rosetta and Dawn bring us all these pictures and data almost seems like too much at once !

Yes! Orion is getting more completely visible---three of the four corner stars and the belt.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
Considering the phase of Ceres and our looking approximately from Dawn's perspective, it seems to me that the sun ought to be in the picture---towards the upper left corner of the picture. Because the thin sliver of Ceres that is lit is on the upper left.
http://en.wikipedia.org/wiki/Orion_(constellation)

Another possibility is that the Ceres-Sun line makes a 20+ degrees angle with the Dawn Ceres line, which would put the Sun out of the box, to the upper left. The greater that angle the more of Ceres should be shown as lit. (If it is zero degrees the sun is directly behind the planet.)
The very thin edge phase doesn't quite make sense to me.

Current status (11am pacific on 4 March) gives the speed relative to Ceres as 51.4 m/s at 57 kkm.

 

[OmCheeto]

Yes! Orion is getting more completely visible---three of the four corner stars and the belt.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
Considering the phase of Ceres and our looking approximately from Dawn's perspective, it seems to me that the sun ought to be in the picture---towards the upper left corner of the picture. Because the thin sliver of Ceres that is lit is on the upper left.
http://en.wikipedia.org/wiki/Orion_(constellation)

Another possibility is that the Ceres-Sun line makes a 20+ degrees angle with the Dawn Ceres line, which would put the Sun out of the box, to the upper left. The greater that angle the more of Ceres should be shown as lit. (If it is zero degrees the sun is directly behind the planet.)
The very thin edge phase doesn't quite make sense to me.

Current status (11am pacific on 4 March) gives the speed relative to Ceres as 51.4 m/s at 57 kkm.

From my eyeball attempt, here's where I think the Earth, Sun, and Mars should be in the (lower) image. All based on relative positions to the stars in Orion from the upper image.
The sun is a bit off, as I placed Mars first, Earth 2nd, and I knew the Sun should fall in a straight line between them.
But close enough for me.

 

[wabbit]

I might be off but it looks to me like the illuminated part goes something like 10% of full diameter, if true that would be a phase angle of ~acos(0.8)~37° which would indeed place the Sun well outside the box to the upper left.

 

[marcus]

Om, it's a bold attempt! Wabbit, good thanks.
In the simulated view of the sun
http://neo.jpl.nasa.gov/orbits/fullview1.jpg
there are two bright stars down near where it gives the 17 km/s speed
I think they are Betelgeuse and Bellatrix. Over 20 degrees would then be right.

Pretty sure they are Betel and Bella because the horns of Taurus are up and to the right of them.

That frame is a 45 degree view. So half width would be a bit over 20 degrees.

 

[wabbit]

marcus:

Betelgeuse and Bellatrix

Agreed, that's right where they should be in relation to Taurus. This appears to confirm the "off, upper left Sun" relative to the previous picture unless I'm linking them together wrong.

 

[marcus]

Your figure of 37 degrees is now making very good sense. I put http://neo.jpl.nasa.gov/orbits/fullview1.jpg
and http://neo.jpl.nasa.gov/orbits/fullview2.jpg
together and see a straight line from the Sun through Bellatrix to Ceres (from Dawn's perspective).

Bellatrix is in both pictures, in http://neo.jpl.nasa.gov/orbits/fullview1.jpg it is the bright star near the "s" in "17 km/s" at the bottom edge of the frame.

Very roughly there is about a 20 degree angle between the Sun and Bellatrix in http://neo.jpl.nasa.gov/orbits/fullview1.jpg which is a 45 degree width view.

Then if you continue from Bellatrix to Ceres in http://neo.jpl.nasa.gov/orbits/fullview2.jpg there is about another 20 degrees (in that 30 degree width view). So it makes a roughly 40 or as you said 37 degrees, from the Dawn Ceres line. Beautiful, I'm glad to see some consistency in the simulated views!

 

[wabbit]

Wow thanks! I sure didn't expect such precision from eyeballing!

(Well not eyeballing exactly, I tried to measure it very roughly on the picture, but still)

 

[marcus]

I'm glad you set me straight on the phase angle. I wasn't thinking
Since we turned a page I'll bring forward the currently relevant part of the Petrich table shown in post#148, for easy reference.
The probe has been "retro" thrusting in an effort to slow itself down to around 46 m/s by 6 March
In current status view it looks to me like the thruster beam is pointed straight out ahead in the direction the probe is going.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
Current status says speed is now 50.5 m/s at distance of about 57.7 kkm (as of 5pm pacific on 4 March) so that actually agrees fairly well with what the table says for 4 March. The distance is a bit more than the table projected it would be. That makes escape speed lower and makes it harder for probe to get UNDER escape speed, and thus achieve capture, but things still look OK to me as nonexpert onlooker.

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

Some explanation:
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
v_escape is the escape velocity at that given distance
v_probe is the predicted velocity the probe will actually have that day. It must fall below v_esc to achieve capture.

 

[OmCheeto]

Om, it's a bold attempt!
...

Well, for someone who's never even heard of Auriga before, I have to agree.

 

[mfb]

47.4 m/s (106mph) at 60350 km distance
45.7 m/s escape velocity

Nearly done.

 

[wabbit]

47.4 m/s (106mph) at 60350 km distance
44.5 m/s escape velocity

Nearly done.

Thanks for the update ! The peanut gallery was getting restless : )

 

[mfb]

Sorry, typo. 45.7 m/s escape velocity, even closer to the current speed.

 

[marcus]

This paper makes the case for further exploration of Ceres--after the Dawn mission.
http://www.lpi.usra.edu/decadal/sbag/topical_wp/AndrewSRivkin-ceres.pdf
Andrew Rivkin is the lead author. plus some 28 or so others. It's a report to a planning committee:
"We recommend Ceres be considered a candidate for a New Frontiers mission in the 2015-2022 timeframe, with mission architectures to be studied based on results from Dawn and other sources..."

And it gives some reasons.

 

[marcus]

Nearing CAPTURE! speed 46.5 m/s at 61 kkm (where escape is 45.4, so only 1 m/s left to scrub)

Current status as of 7am UT on 6 March (11pm pacific on 5 March) shows speed rel Ceres 46.5 m/s @ distance of 61.0 kkm. This is very close to what is required for capture into orbit.
Escape speed at that distance is
(2G*943e18 kg/(61000 km))^.5 = 45.4 m/s
So if the probe were going a mere 1 meter per second slower, at this point, it would already have achieved capture.

The constellation orion is fully visible in the background to the upper left of Ceres.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg

 

[OmCheeto]

Nearing CAPTURE!...

I'm holding my breath:

NASA's Dawn Mission ‏@NASA_Dawn 6 hours ago
Downlink to confirm arrival at #Ceres is expected to begin ~5:30am PT Friday. We will be posting updates.
​

It's currently 3:50 am PT Friday.
DSN Goldstone dish #14 is currently labeled "Dawn". No activity.

 

[mfb]

26 minutes ago:

Downlink has begun! We're analyzing the signal to confirm that the spacecraft is healthy and in orbit at #Ceres

Goldstone #14 has activity.

fullview2.jpg gives 45.6m/s which is slightly above the escape velocity estimate (now 45.2m/s extrapolating from marcus' post), but with the 3% mass uncertainty we had for the calculations the difference is meaningless. Also, the image is two hours old and still shows Dawn thrusting.

 

[marcus]

Good news! Thanks Om and Mfb for keeping track and signaling developments.

 

[marcus]

"Confirmed: I am in orbit around #Ceres"
https://twitter.com/NASA_Dawn

 

[marcus]

This NASA announcement
http://www.jpl.nasa.gov/news/news.php?feature=4503
says that capture occurred around 4:39am pacific time today.

It just took us a while to hear the news. Dawn had to communicate with the DSN antenna at Goldstone and so on.
See Mfb's post #196 of 6:15am pacific time. He was right on top of it.

 

[OmCheeto]

This NASA announcement
http://www.jpl.nasa.gov/news/news.php?feature=4503
says that capture occurred around 4:39am pacific time today.

It just took us a while to hear the news. Dawn had to communicate with the DSN antenna at Goldstone and so on.
See Mfb's post #196 of 6:15am pacific time. He was right on top of it.

Well, that'll teach me not to take a nap in the middle of the morning.
I was up doing calculations last night, and predicted it wouldn't take place until about 9 am.
http://en.wikipedia.org/wiki/Orbital_speed#Precise_orbital_speed

 

[OmCheeto]

This NASA announcement
http://www.jpl.nasa.gov/news/news.php?feature=4503
says that capture occurred around 4:39am pacific time today.

It just took us a while to hear the news. Dawn had to communicate with the DSN antenna at Goldstone and so on.
See Mfb's post #196 of 6:15am pacific time. He was right on top of it.

Well, that'll teach me not to take a nap in the middle of the morning.
I was up doing calculations, and predicted it wouldn't take place until about 10 am pacific time, based on our predicted numbers and an equation at wiki, Precise orbital speed, which I was able to manipulate to calculate the length of the semi-major axis of the elliptical orbit, a.
a = \frac {1} { \frac {2} { r} - \frac {v^2}{ \mu } }

Which switches from negative to positive at the moment of capture.

y axis = semi-major axis length in thousand of kilometers
​

I'm not sure why the graph gets kind of goofy from here on out.

March 10th thru April 23rd​

Probably has something to do with rocket science.
I'll have to document speed and distance, from here on out, to see if this is correct.