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

[lpetrich]

I was wondering how you did that so fast.
Is that X-code?
Not only do I need to relearn maths, I need to relearn how to code.

My image measuring was fast, but not the coding of my Image Measurer. I'd written it some months back, though I'd recently improved it to add some more types of rescaling.

I had indeed written it with Xcode, Apple's IDE for Cocoa apps.

 

[OmCheeto]

My image measuring was fast, but not the coding of my Image Measurer. I'd written it some months back, though I'd recently improved it to add some more types of rescaling.

I had indeed written it with Xcode, Apple's IDE for Cocoa apps.

Ok. After about 14 hours, Xcode is now installed. Marcus's "original trajectory" problem looks like fun, but hand digitizing images is a pain in the b***!
I went to bed last night and thought about this for about an hour before I fell asleep.
This will give me something to do while waiting for the images to be published.

ps. I got tired of waiting, and photographed my log again.

This is not Ceres!
This is Om's log, sitting in the back of his truck, photographed from a distance of 17 feet.
This is only a predictive indicator of the resolution we are to see from the static images.

 

[mfb]

A beautiful log! Are those impact craters? :D

How do you adjust for the different camera quality?

 

[OmCheeto]

A beautiful log! Are those impact craters? :D

How do you adjust for the different camera quality?

Experimentally, of course.
Since I couldn't understand what:

Framing Camera (FC) Instrument
...at an angular resolution of 93.7 µrad px-1...

meant. (Fowla Deutschern! Immer mit der hoch-gesrpachen...)
From the previous "Ceres" thread:

Today I took my baseball out and photographed it at the appropriate distance: 83 feet
I blew it up, and it only had a resolution of about 13 pixels diameter. Since the Dawn team claims the resolution they will be taking should be 26 pixels, I replaced the baseball with a log.
...

Looking at the moon/Ceres/baseball from a certain distance, gives us a human perspective, but doesn't give you a resolution, if you had eagle eyes, or camera eyes.

 

[mfb]

Ah.
93.7 µrad/pixel are 10600 pixel per rad or 186 pixel per degree.

 

[OmCheeto]

Ah.
93.7 µrad/pixel are 10600 pixel per rad or 186 pixel per degree.

I suppose, I could have done the math...

Fowla Om!

ps. For those who don't speak Kraut, my mother, a native of Germany, used to call me and my siblings; "Faule affen!" Which sounds a lot like "Foul apes!". But, it really means, "Lazy apes".

Es stimmt. (= I agree)

pps. Wait a minute. Who's holding up these images?

JPL manages the Dawn mission for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. The University of California, Los Angeles (UCLA) is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Virginia, designed and built the spacecraft . The Dawn framing cameras were developed and built under the leadership of the Max Planck Institute for Solar System Research, Gottingen, Germany, with significant contributions by German Aerospace Center (DLR), Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL. The Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.

This appears to be, an international conspiracy!

Faule missgeburt*!

*This is what mom called us, when we were really, really bad.

Thank god, google translates this word, mildy, as "Freak".

 

[marcus]

Om, I'm reluctant to offer any rational excuse because your cussing out NASA helps make the delay bearable. However Monday is *Presidents Day* a federal holiday and there may be key technical personnel at JPL who go home for long weekends leaving facilities shut down that the scientists need for analyzing data.
Down at the end of comment thread #5 of http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/
Marc Rayman says:
==quote==
February 13, 2015 at 4:21 pm
Hi Andrew,

We will post pictures on this website and elsewhere as soon as all the necessary steps are complete. After receiving the data, the team has to process the images before making them public, following established processes. Monday is a federal holiday, so some of the steps will not be possible before Tuesday.
==endquote==

I was also interested by what he said here:
==quote==
February 13, 2015 at 3:15 pm
Hi Jorrie,

The time to transmit a picture depends on the details of the image, because the spacecraft compresses the data, but generally it is between one and two minutes. The full analysis of the pictures for scientific purposes, however, requires additional information from the spacecraft . In addition, to keep our distant robotic explorer healthy, we scrutinize myriad measurements of currents, voltages, temperatures, switch positions, pressures, valve positions, software states, instructions it has executed, decisions it has made, and much more. Following RC1, it took Dawn about 16 hours to download all of its Ceres observations plus this additional information.

As you know, no one antenna can point at Dawn for 16 hours, just as you cannot point at the sun, moon or a star for that long. Earth rotates too quickly. To return the data yesterday and today, we used the three largest antennas of the Deep Space Network, each 230 feet (70 meters) in diameter. We started with the one in Canberra, Australia, then moved over to the one in Madrid, Spain, and concluded in Goldstone, California.

Thank you for your interest!

Marc

- See more at: http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/#comment-8599
=endquote==

So there is the unspoken rule that in-house professionals get "first crack" at new data (given which understanding I think JPL is pretty generous) and there is the thing of "established procedures" for releasing photos, which I guess makes sense if you don't want variants to flood the media ahead of more reliable copy. And the more interesting observation, I thought, was that sending pix takes only a couple of minutes! But the whole communication session took 16 HOURS! It's intriguing to think of all that other stuff going on. Reminds me of going into the doctor's for a complete medical exam with all the blood tests and the poking and tapping on the knees and listening to the lungs etc etc.

Classic comment on excessive use of technical jargon:
Fowla Deutschern! Immer mit der hoch-gesprachen...
Behind every really funny humorist there is a Mom

 

[OmCheeto]

Om, I'm reluctant to offer any rational excuse because your cussing out NASA helps make the delay bearable...

As Red Green once said; "If you can't figure out why the the 4th power polynomial interpolation of a radian graph fits so well, you may as well attempt, to make a funny"

Feb 16 thru Mar 3, radian vs pixel distance.
Upper JPL image.​

...
Behind every really funny humorist there is a Mom

And sometimes, a dad.

 

[OmCheeto]

Om, I'm reluctant to offer any rational excuse because your cussing out NASA helps make the delay bearable. However Monday is *Presidents Day* a federal holiday and there may be key technical personnel at JPL who go home for long weekends leaving facilities shut down that the scientists need for analyzing data.

Not sure if you're aware of this, but I retired last May, so I no longer know what day of the week it is, nor worry about long weekends.
My bad.

...

I was also interested by what he said here:
==quote==
February 13, 2015 at 3:15 pm
Hi Jorrie,

The time to transmit a picture depends on the details of the image, because the spacecraft compresses the data, but generally it is between one and two minutes. The full analysis of the pictures for scientific purposes, however, requires additional information from the spacecraft . In addition, to keep our distant robotic explorer healthy, we scrutinize myriad measurements of currents, voltages, temperatures, switch positions, pressures, valve positions, software states, instructions it has executed, decisions it has made, and much more. Following RC1, it took Dawn about 16 hours to download all of its Ceres observations plus this additional information.

As you know, no one antenna can point at Dawn for 16 hours, just as you cannot point at the sun, moon or a star for that long. Earth rotates too quickly. To return the data yesterday and today, we used the three largest antennas of the Deep Space Network, each 230 feet (70 meters) in diameter. We started with the one in Canberra, Australia, then moved over to the one in Madrid, Spain, and concluded in Goldstone, California.

Thank you for your interest!

Marc

- See more at: http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/#comment-8599
=endquote==

So there is the unspoken rule that in-house professionals get "first crack" at new data (given which understanding I think JPL is pretty generous) and there is the thing of "established procedures" for releasing photos, which I guess makes sense if you don't want variants to flood the media ahead of more reliable copy. And the more interesting observation, I thought, was that sending pix takes only a couple of minutes! But the whole communication session took 16 HOURS! It's intriguing to think of all that other stuff going on. Reminds me of going into the doctor's for a complete medical exam with all the blood tests and the poking and tapping on the knees and listening to the lungs etc etc.

...

I understand all that. But, "I'm a TAXPAYER"! They should know what I want, and give it to me, when I want it.

Anyways, I digitized the alternate original flight path, tried to figure it out, and have decided that I am brain dead.
Switching between Cartesian and Polar coordinates is making me crazy.
It's no wonder Newton went mad.

Wait!

​

He wasn't mad. I've done spectral experiments, also. And I'm not mad.
I'm sure it's just a mild case, of ADD.


Oh... Never mind.
The new pictures are up...

 

[marcus]

Heh heh, Newton (mad or not) would have been delighted by the new pictures, Om. Thanks for posting them! To me she's still looking like a ball of grimy ice, which is what I want her to be

 

[marcus]

Om, you remember the abbreviated table I made from Petrich's good XYZ trajectory numbers? I was playing around with that table to see if I could make it more readily intuitive. He is using a right-handed coordinate system: OUT--UP--Backwards (from Ceres orbital motion). So that Z becomes more positive as Dawn lags farther behind.
And RH is conventional orientation. But suppose we use a left-handed XYZ: OUT (from the sun) UP (off the orbital plane) and FORWARDS (with the planet motion)
All it means is changing the sign of his Z numbers.
When I hold up my left hand and think of the sun as far to my left (as in Rayman's diagrams) then thumb is X (pointing right, out from the sun) and indexfinger is Y (pointing up) and the third digit is Z (pointing forward or into the page of Rayman's upper diagram). So X and Z define the orbital plane. And Y is up off the plane in roughly the Ceres North pole direction. Actually the N pole is currently tilting slightly outwards (by about 3 degrees they estimate) away from sun, but basically it is up off the plane.

Petrich, I'm trusting that it is acceptable for us to play around with the numbers you posted. They're definitely helpful in understanding the approach trajectory. For looks I truncated some surplus precision in the rightmost column, and changed the sign of Z.

To review:
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.

date      X          Y          Z        distance from Ceres
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
F26     11.407    26.4613    -29.1488    40.98
F27     17.2899    27.6663    -28.1919    43.11
F28     22.8583    28.5286    -27.0313    45.46
M1      27.9985    29.1842    -25.6846    47.90
M2      32.8862    29.7513    -24.1873    50.51
M3      37.6439    30.1647    -22.7166    53.31
M4      41.9734    30.4246    -21.3167    56.05
M5      45.8274    30.5605    -19.8726    58.55
M6      49.5028    30.6491    -18.2955    61.02
M7      52.8252    30.4896    -16.7451    63.24
M8      55.7681    30.3242    -15.1946    65.27
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 today 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 inclination is 10 degrees and it just recently passed its descending node, so it is "plunging down" relative to the ecliptic and Dawns prior orbit, again Ceres gravity will help bring Dawn in)
meanwhile it shows the probe at first falling behind in the Z direction (to a minus 30.7 kkm!) but then beginning to catch up.
It shows the Z lag being reduced to a minus 9.3 kkm.
That's important. As I understand it, much of Dawn's thrust, since October, has been devoted to catching up with Ceres' 17 km/s orbit speed, and the probe is still coming in with a slight deficiency in that department. It has had to concentrate on getting its Z velocity right which is why it has not had time to kill more of the excess X and Y and is overshooting in those departments.

 

[marcus]

If I wanted to boil down the narrative of that 3 week table of Petrich numbers, from 17 Feb to 12 Mar, I could say
The X overshoot continues out to 65 kkm past Ceres
The Y distance up from Ceres maxes out at 30.6 kkm on 6 March, and begins to subside.
The Z lag behind Ceres maxes out at -30.7 kkm on 22 February, and shrinks to -9.3 kkm by the end of the period.

Maybe I should add a few more rows to the table to see if the trends continue. I'll start with 5 March which is sort of a nominal "capture" date when the probe velocity finally falls below the scape velocity at its then-distance from the planet. Y distance up off the Ceres orbital plane also peaks about that same time.

date      X          Y          Z        distance from Ceres
M5      45.8274    30.5605    -19.8726    58.55
M6      49.5028    30.6491    -18.2955    61.02
M7      52.8252    30.4896    -16.7451    63.24
M8      55.7681    30.3242    -15.1946    65.27
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
M13     66.8636    28.8417    -7.90296    73.24
M14     68.4790    28.2510    -6.38793    74.35
M15     69.7223    27.7726    -4.80202    75.20
M16     70.7383    27.1819    -3.57051    75.86
M17     71.5002    26.8275    -2.34785    76.40
M18     72.0023    26.5440    -1.37327    76.75
M19     72.3581    26.2900    -0.12403    76.98
M20     72.4098    25.8411     1.05432    76.88
M21     72.2873    25.4277     2.33013    76.66
M22     72.0303    25.0319     3.22497    76.32
M23     71.7734    24.5653     4.24385    75.97
M24     71.1281    23.9983     5.08554    75.23
M25     70.1580    23.3604     6.02468    74.18
M26     68.9840    22.7402     6.74232    72.94
M27     67.6521    22.1023     7.46883    71.56

We can see that the distance UP off the Ceres orbit plane continues to subside over this next period. More significantly the X overshoot finally maxes out at around 72.4 kkm by 20 March. Dawn gets as far past Ceres, away from sun, as it is ever going to get, and Ceres gravity begins to pull it in. Also by 20 March, Dawn has not only made up all its lag but has actually gotten out a little ahead of the planet.

These projected coordinates, with minor changes, are copied from some prepared by L. Petrich. I believe they were derived from figures shown in Marc Rayman's Journal. The dates/distances can differ fractionally from those in the journal, as if a different time zone or time-of-day sampling might have been used But by and large they seem to match up.

 

[OmCheeto]

Marcus, I'm pretty sure I've posted somewhere in the forum, that I'm both vertically and horizontally dyslexic. So no matter what convention you use, I'll be confused.

My Mac "Grapher" software doesn't let me delete data sets, but does let me hide the ones that are wrong.

Here's what it looks like with nothing unhidden:

​

Looks like the bags of Mardi Gras beads I have hanging in my closet.
hmm... google google google
Ah!
Mark this on your calendars! This is the first year, I've missed partying, on Fat Tuesday, in about 40 years.

ps. I think I'll add this to my list of proofs, that god exists.

 

[OmCheeto]

Latest tweet:

NASA's Dawn Mission ‏@NASA_Dawn 27m27 minutes ago
Happy Lunar New Year, #Earthings! No moons detected at #Ceres [so far] http://dawn.jpl.nasa.gov
​

I was worried about moons.

 

[marcus]

Today 19 Feb is another planned navigational photoshoot. This current status view refers to earlier today (around midnight pacific time or 8h UT) but I just checked more recently and current status for 10AM pacific (18h UT) gives the range as 45.83 kkm and speed relative to the planet 81.4 m/s. (Its velocity is not directly at Ceres so it isn't closing in that fast.)
Ceres seen from the probe is now 238% moon-size. 2 arcsin(475/45 830) = 1.1877 deg
http://neo.jpl.nasa.gov/orbits/fullview2.jpg

They take photos of Ceres against the background of known stars in order to help locate the probe for navigation purposes. These photos are not necessarily posted on line. They may be taken either with a lower-resolution "navigation camera" or with the larger higher resolution camera that will be used to study the planet. I think this time the shots will be with the "navcam".

 

[marcus]

As of 20h UT (noon pacific) the current status view shows Dawn taking pictures of Ceres.
this time the side of the cube with the large high-gain antenna is pointing at the planet.
if the simulated view is realistic down to that level of detail, it must mean the "navcam" they're using is located on that same side of the box.

Anyway it is a slightly different orientation from what I recall the last couple of times they took pictures.
the main distinction is the view shows the thruster off (no blue-green plasma trail) and the main axis with the solar panel "wings" vertical rather than nearly horizontal. When they finish picture-taking and communicating back with Earth the simulated view will presumably show the craft rotated back and the thrust back on.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg

 

[lpetrich]

I note the speed: 182 mph relative to Ceres -- nearly 300 km/h. The top speeds of many high-speed trains are typically 300 km/h, and sometimes a little bit more. These are the fastest land vehicles in regular service. Fast by familiar standards, but snail-paced by space-travel standards.

 

[marcus]

I note the speed: 182 mph relative to Ceres -- nearly 300 km/h. The top speeds of many high-speed trains are typically 300 km/h, and sometimes a little bit more. These are the fastest land vehicles in regular service. Fast by familiar standards, but snail-paced by space-travel standards.

Yesterday it was 184 mph. They are obviously working to slow Dawn down between now and the beginning of March, when capture should occur.
So that is part of what the thrust should accomplish. Without that, probe would be accelerating as it gets closer to Ceres and capture would not happen.

So as we watch the speed change over the next couple of weeks, we are hoping/expecting it to slow down.

 

[marcus]

Of course from our usual solar system point of view, motion relative to the sun, the probe is going 17.32 kilometers per second
http://neo.jpl.nasa.gov/orbits/fullview1.jpg

It's only relative to Ceres that the approach must be gradual, and must slow down over the next couple of weeks.

You may remember that the earlier approach trajectory (before events in September necessitated redesigning it) would have had the probe coming in much more slowly, at this point. And there would have been no overshoot. It would have settled into circular orbit over a month earlier, because it would have slowed down more completely before now.

In either case the capture date is about the same, 5 or 6 March. Since we've turned a page, I'll bring forward the labeled diagram that Om made.

 

[marcus]

I just saw Canberra start talking with Dawn
https://eyes.nasa.gov/dsn/dsn.html
When I looked, it was quiet, as if standing by at ready (or during a pause) at 2:18 PM local time (20 Feb) and then at 2:19 PM it became active.

the antenna is one of the big ones, #43. It now seems to be on continuously.
It is in daylight, Madrid would seem to be the next one to take over, three or four hours from now, if it's a long session.

 

[OmCheeto]

I just saw Canberra start talking with Dawn
https://eyes.nasa.gov/dsn/dsn.html
When I looked, it was quiet, as if standing by at ready (or during a pause) at 2:18 PM local time (20 Feb) and then at 2:19 PM it became active.

the antenna is one of the big ones, #43. It now seems to be on continuously.
It is in daylight, Madrid would seem to be the next one to take over, three or four hours from now, if it's a long session.

A few minutes ago, I watched the Madrid dish #63 come online, switch on the carrier signal, receive some data, and then shut off. It all took about 20 minutes.
It was about 4:50 - 5:10 UTC, Feb 20.

I sure they post a picture from today. It's almost twice as close as the image posted two days ago. 46 kkm vs 83 kkm.

 

[marcus]

Thanks for the heads up, it is about time for them to switch. I went and looked and saw Canberra still engaged with Dawn, and Madrid was standing by (assigned to Dawn but quiet).
I hope you are right about them posting a picture. Here's that table of planned 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

http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/[/B

EDIT: just went back at 10:16 pacific and they had switched.
https://eyes.nasa.gov/dsn/dsn.html
it was 5:16 PM at Canberra and their antenna was off the job
It was 7:16 AM in Madrid and their antenna was working with Dawn.
I think you are right about a picture.

 

[marcus]

Goldstone antenna #14 is still receiving from Dawn. Transmission will presumably conclude sometime this afternoon (it is noon pacific time at the moment).
Then Dawn can get back to thrusting, to slow itself down wrt. Ceres
I see that the speed relative to Ceres has crept up from 182 to 185 just during this photoshoot session.
Prior to 19 Feb it had been coming down: 184...183...182... I'll switch to metric equivalents.
At the start of the shoot, on 19 Feb, when thrust was turned off, current status gave it equal to 81.4 m/s
and now at noon 20 Feb, with transmission not yet complete, it is equal to 82.7 m/s.
I'm noting that for the planned capture the speed re Ceres has to get down to around 45 m/s
and unless the craft is thrusting it will naturally tend to increase as approach continues.
So these long photo shoot sessions have a price.
https://eyes.nasa.gov/dsn/dsn.html
http://neo.jpl.nasa.gov/orbits/fullview2.jpg

 

[OmCheeto]

...
So these long photo shoot sessions have a price.
...

I wish you hadn't said that.

Marc Rayman says:
February 19, 2015 at 11:20 pm
Hi Matt,

Image releases will occur only on normal NASA/JPL work days, which do not include weekends.
...
Dawn is budgeted for single shift operations.
...

As a former 24/7 hospital worker, and 24/7 submariner, I found it somewhat depressing to find out that the Dawn mission is run on "banker's hours".

So I took a picture, of my log, again...

Sorry I didn't have time before shift end, to fix the image.

But check that out! In the upper left hand corner, is the track of a meteorite, streaking through the atmosphere.

 

[marcus]

Now Goldstone has stopped. 3 pm pacific, 23h UT, no antenna is working with Dawn.
It could be turned around and thrusting now, to slow down its arrival.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
But the current status update as of 23h UT on 20 Feb does not show as having resumed normal operation yet.

You may have discovered a creative use for old shredded magazines, newspapers, and computer manuals, namely to make asteroids out of them. My wife disagrees with me on this. She says it is not an asteroid but simply an ordinary log for the fireplace. The multicolored shredded debris around it just gives it a realistic look, she says. That is the natural lichen which often grows on logs in the woods.

 

[OmCheeto]

Now Goldstone has stopped. 3 pm pacific, 23h UT, no antenna is working with Dawn.
It could be turned around and thrusting now, to slow down its arrival.
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
But the current status update as of 23h UT on 20 Feb does not show as having resumed normal operation yet.

You may have discovered a creative use for old shredded magazines, newspapers, and computer manuals, namely to make asteroids out of them. My wife disagrees with me on this. She says it is not an asteroid but simply an ordinary log for the fireplace. The multicolored shredded debris around it just gives it a realistic look, she says. That is the natural lichen which often grows on logs in the woods.

I do believe that we are in some sort of cosmic synchronization period. I bought a shedder a couple of weeks ago and have been cursing myself for not listening to that "Dental Floss" guy, regarding saving old bank statements. I'm only finished back through 1999. My multicolored shredded debris has been joining the siblings of Ceres/Log in the fireplace, daily. Ugh. The only consolation is that kids, in the future, will have no clue what that reference is about. Thank god for "paperless".

Anyways, it's currently 4:02 UTC, the last image of Dawn was at 5:29 UTC, and the ion engine will be still off.

Never noticed before that they posted the images early.

Also, the minimum distance is only a couple of days away, according to lpetrich's numbers, so I wouldn't worry about too much speeding up.

Date      dist    speed    esc v
20-Feb    42.5    79.05    54.51
21-Feb    40.1    79.41    56.07
22-Feb    38.7    78.75    57.09
23-Feb    38.1    77.44    57.57
24-Feb    38.2    74.44    57.44
25-Feb    39.3    71.36    56.67
26-Feb    41.0    69.68    55.49
27-Feb    43.1    68.45    54.10
28-Feb    45.5    64.25    52.69
 1-Mar    47.9    60.73    51.32
 2-Mar    50.4    58.68    49.98
 3-Mar    53.4    55.29    48.65
 4-Mar    56.1    50.19    47.45
 5-Mar    58.5    46.97    46.42
 6-Mar    61.0    44.36    45.47
 7-Mar    63.4    40.50    44.67

 

[marcus]

Good point about closest approach on this pass coming up around 24 Feb. And anyway current status showed thrust was resumed an hour or so ago at 11PM pacific 20 Feb (or 7h UT 21 Feb) so all's apparently back to normal.

Now that Dawn is trailing Ceres somewhat, the planet is showing a phase. We can locate the sun and the orientation of the solar panels is making better sense in the simulated view.

 

[mfb]

Dawn is flying in a right angle relative to the Dawn/Ceres direction, so speed should not change much based on gravity (but velocity does - the acceleration from Ceres exceeds the acceleration from the ion engines if my calculations are not too far off). Still at 185 mph = 83m/s.

 

[marcus]

Good estimate! A little slower now that it is later in the day.
Current status as of 4 PM pacific on 21 Feb( that is 0h UT 22 Feb) says range 40.07 kkm and speed about 82 m/s (183 mph)
2 arcsin(475 / 40 070) = 1.36 deg
272% moon size. Appearing just a bit more gibbous than a half moon. Dawn passing nearly astern of the planet--give it a day or two more and Ceres should resemble a half moon.

Dawn's line of sight, trailing behind Ceres, should then make a right angle with the Sun-Ceres line.

 

[marcus]

Current status as of noon pacific 22 Feb ( 20h UT)
In the simulated view you see a "half moon" shape, almost. So Dawn is almost at right angles to the Ceres-Sun line
The blue-green ion tail is in the direction it is going, past Ceres and astern of it. It is thrusting to slow down.
Range is 39.02 kkm and speed is 80.5 m/s.

Simulated views in the online current status section are not always accurate. Sometimes the spacecraft attitude is wrong, sometimes the solar panels are not facing the sun when the thruster is on (and they would need full-face)
But right now it is beautifully accurate. You can see the tail goes in the right direction and the panels face the sun.

279% of moon-size right now. about as large as it will look for next month or so, since the distance to
Ceres will start growing in a day or two as Dawn overshoots and sails on past Ceres outwards (from sun)

 

[marcus]

To have it handy I'll bring forward a table derived from L. Petrich's numbers slightly modified so as to orient Z forwards in Ceres orbit plane.

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, 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.
Scroll the table down to get to the last row. It extends to 5 April and I may add some more days later.

date      X          Y          Z        distance from Ceres
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
F26     11.407    26.4613    -29.1488    40.98
F27     17.2899    27.6663    -28.1919    43.11
F28     22.8583    28.5286    -27.0313    45.46
M1      27.9985    29.1842    -25.6846    47.90
M2      32.8862    29.7513    -24.1873    50.51
M3      37.6439    30.1647    -22.7166    53.31
M4      41.9734    30.4246    -21.3167    56.05
M5      45.8274    30.5605    -19.8726    58.55
M6      49.5028    30.6491    -18.2955    61.02
M7      52.8252    30.4896    -16.7451    63.24
M8      55.7681    30.3242    -15.1946    65.27
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
M13     66.8636    28.8417    -7.90296    73.24
M14     68.4790    28.2510    -6.38793    74.35
M15     69.7223    27.7726    -4.80202    75.20
M16     70.7383    27.1819    -3.57051    75.86
M17     71.5002    26.8275    -2.34785    76.40
M18     72.0023    26.5440    -1.37327    76.75
M19     72.3581    26.2900    -0.12403    76.98
M20     72.4098    25.8411     1.05432    76.88
M21     72.2873    25.4277     2.33013    76.66
M22     72.0303    25.0319     3.22497    76.32
M23     71.7734    24.5653     4.24385    75.97
M24     71.1281    23.9983     5.08554    75.23
M25     70.1580    23.3604     6.02468    74.18
M26     68.9840    22.7402     6.74232    72.94
M27     67.6521    22.1023     7.46883    71.56
M28     66.0440    21.553       8.08901    69.94
M29     64.1702    20.9978     8.57630    68.06
M30     61.9597    20.5548     9.23193    65.92
M31     59.6842    20.2240     9.60404    63.74
A01      57.1311    20.0527     9.85212    61.34
A02      54.4022    19.8283    9.81668    58.72
A03      51.2408    19.6570    9.97616    55.78
A04      48.0025    19.6393    9.84326    52.79
A05      44.5782    19.8637    9.69264    49.75

 

[OmCheeto]

Has anyone else blown up the image of Ceres on the JPL "where is Dawn now" page

compared it to my log, and noticed

a weird similarity?

Disregarding the fact that they know how to use Photoshop, and I'm really bad with MacDoodlePaint.

Or should I not mention this, as it might get people thinking I'm in a conspiracy with the government, and this entire space mission was filmed from the back of my truck?

 

[OmCheeto]

On a somewhat "conspiracy" related side-note, Svetlana shows off the log from the back of her truck.

ESA Rosetta Mission ‏@ESA_Rosetta 11h11 hours ago
Happy birthday Svetlana Gerasimenko, co-discoverer of #67P! (Image: DLR (CC-BY 3.0), http://ow.ly/JupqF)

 

[marcus]

This just posted, is it RC2? Is this from the recent shoot, 19 Feb, or the earlier RC1? It doesn't say AFAICS.

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.

 

[marcus]

Today is 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

http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/[/B
I just checked the current status view and it showed the probe with thrust off, oriented for picture-taking:
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
Presumably we should see an antenna receiving data later today at DSN
https://eyes.nasa.gov/dsn/dsn.html