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

[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.

 

[lpetrich]

OmCheeto, you are better off calculating a's reciprocal, or else the total energy per unit mass, - μ/(2a). At the capture point, it will be zero instead of infinity.

 

[marcus]

Nice work Om! Petrich it is a credit to your table of numbers that Om could predict within a few hours. The difference between the projected and the actual seems to have been within reasonable uncertainty---not "statistically significant". that's great. I'm really happy with your and Om's numerical work which (albeit a small part) is, for me, a part of the accomplishment. Also Mfb's astute commentary. Cheers all round!

 

[marcus]

44.7 m/s at 62.23 kkm as of 10am pacific

Current status view has been updated

escape velocity (2G*943e18 kg/(62230 km))^.5 = 44.97 m/s
so probes actual speed is just a hair under what it would need to get away from Ceres. It has achieved orbit.

This view records the moment of capture. I uploaded it from desktop instead of inserting it as an image so that it would not get updated further and that particular moment lost.
If you want this image to share with friends and family just go to
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
and drag it to desktop. Ceres is a really interesting world and will IMHO become more so as we learn more about it. Also what you see in the picture is one of ourkind's first solar electric powered (ion drive) spacecraft .

 

[OmCheeto]

44.7 m/s at 62.23 kkm as of 10am pacific

Current status view has been updated

escape velocity (2G*943e18 kg/(62230 km))^.5 = 44.97 m/s
View attachment 80033

Now I'm suspicious, that they're not telling us something...

My 3 am predictions:

        UTC             r (meters)    v (m/s)    a(sma)(meters)          Pacific
3/6/2015 17:39:01       62791584.5      44.85    -8515192256.9     3/6/2015 09:39:01
3/6/2015 18:39:01       62953055.6      44.70    77452316883.5     3/6/2015 10:39:01
3/6/2015 19:39:01       63113990.3      44.56     6981228542.5     3/6/2015 11:39:01

ps. @lpetrich , I graphed your - μ/(2a).
It does look much better.
(It got rid of two "dreaded" infinities. )

 

[OmCheeto]

NASA's Dawn Mission ‏@NASA_Dawn 5m5 minutes ago
No more images of #Ceres until April because I am swinging around the dark side of Ceres at the moment - Deputy PI Carol Raymond​

Not a problem, Carol, as we know. Yes, we know...

We are nerds. And nerds, gohitr yjod djoy piy/

 

[OmCheeto]

ps. Let's not forget our forefathers, and mothers:

SpaceX ‏@SpaceX 16m16 minutes ago
Happy birthday to Valentina Tereshkova, 1st woman in space. We've got a conference rm for you http://en.wikipedia.org/wiki/Valentina_Tereshkova…
6 March 1937 (age 78)​

What a coincidence. I wonder if she's watching.

 

[wabbit]

*beep*...Dr marcus is requested at the triality thread... I repeat, Dr marcus at the triality thread...*beep*

Sorry for the interruption, please carry on.

 

[marcus]

Om, nice star map! It shows the sky from the Dawn probe's perspective, with Ceres in it AND the Sun in the position it would be against the background stars seen from the PoV of Ceres and Dawn. And there's Orion. I wish the NASA Dawn public outreach people had included a wide angle view like that which puts it all together.

Wabbit,
I will go and take a look at that thread.
https://www.physicsforums.com/threa...lities-to-trialities-deepens-dynamics.801408/
I thought it might interest people who had more understanding than I do about triality. I might learn something, but regret to say am not likely to be helpful.

I've been wondering about the possibility that Ceres might have some recoverable amounts of nitrogen. Moon doesn't seem to have nitrogen
but Mars atmosphere has 2.7% N₂.
https://books.google.com/books?id=YQ3rAQAAQBAJ&pg=PA324&lpg=PA324&dq=nitride+abundance&source=bl&ots=2hE3hrgoSG&sig=Uuo9HqhkYCuw5GwAXaSdacfGPao&hl=en&sa=X&ei=ikb6VNjREdKyogT2goLwBA&ved=0CC0Q6AEwBA#v=onepage&q=nitride abundance&f=false
Silicon Nitride (Si₂N₃) occurs as pre-solar dust particles in meteorites, apparently the result of supernova explosions.
It would have formed in surroundings that were carbon rich instead of oxygen rich. Oxygen would displace the nitrogen in the various nitride compounds.
So Si and N are abundant elements and you get a mineral dust under the right conditions. Then when a planet forms and heats up, nitrogen can OUT-GAS. and form part of the atmosphere. but if the atmosphere is hot (Venus) or the gravity is weak (Mars) most of the nitrogen can get escape velocity and blow off into space. You outgas it from bound mineral form (if the rocky material melts) and you keep the bulk of it in atmosphere if conditions are just right.

I suppose there is a chance that because some Ceres rock didn't get hot enough to outgas it may still contain MINERAL NITROGEN.
Could there be ammonia or ammonium salts dissolved in Ceres water?

 

[marcus]

Om it looks like your view (of the inner solar system from Ceres and Dawn standpoint) is a 50 degree by 40 degree frame (very rough, round numbers)
So that would make the spread between Sun and Mars a little over 1/3 of 50? Like a little over 17 degrees? 20 degrees?
So one half of the vertical height of the frame, which SAY is 40 degrees? Let's check that against the inner solar system diagram they give us. If you draw lines from the white dot labeled Ceres (down at the bottom) to the Sun and to Mars, would the angle between the lines be about 20 degrees? If so that sort of confirms the guess that the view you made is 50 degrees wide.
http://neo.jpl.nasa.gov/orbits/fulltraj.jpg

At the moment it looks about right to me. Of course in a few weeks the planets will have moved and they update these views so the angles will change, so it won't be 20 degrees any more. But that's irrelevant.

 

[mheslep]

The AP has a nice photo of the Dawn spacecraft pre-launch. Ion drive, panels, etc all shown closeup.