I think is time to start this new topic, now that Dawn is more than half-way in the transition from HAMO to LAMO (as showed in the plot below).
Full Version: LAMO
Good thing we aren't calling it a "Low Mapping Altitude Orbit." 
I get the feeling that many more surprises await us in finer detail as the surface resolution improves.
I get the feeling that many more surprises await us in finer detail as the surface resolution improves.
Another way to show the progress from HAMO to LAMO is the following updated plot where points colors reflects engine status:
Click to view attachment
I tried to interpolate average height with a blue line. Time gaps are due in part to me (not continuous monitor) and in part to Mystic simulator black-outs.
EDIT: plot updated to Nov,15
Click to view attachment
I tried to interpolate average height with a blue line. Time gaps are due in part to me (not continuous monitor) and in part to Mystic simulator black-outs.
EDIT: plot updated to Nov,15
Hopefully the daily image releases will resume shortly!
Phil
Phil
QUOTE (Phil Stooke @ Nov 16 2011, 04:59 PM) 
Hopefully the daily image releases will resume shortly!
You mean images rather than other data products? Or images specifically from LAMO?
Pace hasn't slackened... now here:
http://dawn.jpl.nasa.gov/multimedia/imageo...h=2011-November
Last two were HAMO images, though.
Images from Nov. 10-13 don't currently show up on the Dawn Image of the Day page (November), but they do show up on Photojournal.
The latest four images were posted on the same day... I check every day, believe me. We had a minibreak. But these are spectacular!
Phil
Phil
Updated situation, all plots:
Click to view attachment Click to view attachment
Engines are now silent and average height is around 270 km...
Click to view attachment Click to view attachment
Engines are now silent and average height is around 270 km...
Now that we have an improved simulator (better Vesta digital model and, especially, more frequent screen updates) I am frequently monitoring the simulated height of the probe; in the last 24 hours, engines were off but orbit isn't completely stable:
Click to view attachment
The interpolated sinusoidal curve correspond to a 5.1 hours average period between 235 and 285 km height. The reason of slight phase/amplitude variations sould be the irregular gravity field of Vesta. In fact, as explained in the last Mission Status, the purpose of these thrust stops is a natural or passive orbit adjustment (especially the orientation).
Edit: slightly modified previous text and updated plot (no orbit decay)
Click to view attachment
The interpolated sinusoidal curve correspond to a 5.1 hours average period between 235 and 285 km height. The reason of slight phase/amplitude variations sould be the irregular gravity field of Vesta. In fact, as explained in the last Mission Status, the purpose of these thrust stops is a natural or passive orbit adjustment (especially the orientation).
Edit: slightly modified previous text and updated plot (no orbit decay)
New update after two long simulator black-outs:
Click to view attachment
Based on today's status report, "The spacecraft thrusts occasionally with its ion propulsion system, but most of the time it coasts, letting Vesta's gravity reorient its orbit."
Note also that last two published images were taken 15 days ago from an intermediate distance of 480km:
http://dawn.jpl.nasa.gov/multimedia/imageo...p?date=20111123 http://dawn.jpl.nasa.gov/multimedia/imageo...p?date=20111122
Click to view attachment
Based on today's status report, "The spacecraft thrusts occasionally with its ion propulsion system, but most of the time it coasts, letting Vesta's gravity reorient its orbit."
Note also that last two published images were taken 15 days ago from an intermediate distance of 480km:
http://dawn.jpl.nasa.gov/multimedia/imageo...p?date=20111123 http://dawn.jpl.nasa.gov/multimedia/imageo...p?date=20111122
Now short engine burns are frequent:
Click to view attachment
Click to view attachment
"Dawn image EDR data will be publicly released to the science community by the PDS within 90 days after each acquisition phase. Therefore, raw Vesta approach images will be available in November 2011. Raw images for other acquisition phases including survey, high altitude (HAMO) and low altitude (LAMO) mapping orbits will be delivered throughout 2012"
"However, radiometrically calibrated PDS images (RDRs) will be publicly released six months after Vesta departure"
... from Jeffery Anderson's AGU poster abstract.
Exciting!
Phil
"However, radiometrically calibrated PDS images (RDRs) will be publicly released six months after Vesta departure"
... from Jeffery Anderson's AGU poster abstract.
Exciting!
Phil
Time for us to lurk on the Small Bodies Node website.....that is where they'll likely be hosted, right?
This link...
http://pds-smallbodies.astro.umd.edu/data_...ase_sched.shtml
... suggests a later date.
Phil
http://pds-smallbodies.astro.umd.edu/data_...ase_sched.shtml
... suggests a later date.
Phil
QUOTE (Phil Stooke @ Nov 30 2011, 04:18 AM)
This link... suggests a later date.
...and suggests also a new Vesta departure date (shifted from July 2012 to Jan 2013), probably in order to study also North Pole region!
QUOTE (dilo @ Dec 1 2011, 05:02 PM)
...and suggests also a new Vesta departure date (shifted from July 2012 to Jan 2013), probably in order to study also North Pole region!
I believe that's the PDS data release date, not the spacecraft event date.
I did a Solar System Simulator run for Vesta and I worked out that equinox for Vesta will be on or about July 27, 2012.
You can work this out by choosing the "from above" viewpoint for Vesta and finding the date when the phase angle is 90 degrees. This is when the sun's terminator is exactly over the North Pole.
I got this idea from doing this for Mercury where the phase angle as viewed directly from either pole is always 90 degrees.
You can work this out by choosing the "from above" viewpoint for Vesta and finding the date when the phase angle is 90 degrees. This is when the sun's terminator is exactly over the North Pole.
I got this idea from doing this for Mercury where the phase angle as viewed directly from either pole is always 90 degrees.
I think shifting the Vesta departure date would require a change to the laws of celestial mechanics--I don't think there's funding for that. :-)
--Greg
--Greg
QUOTE (Greg Hullender @ Dec 1 2011, 09:21 AM)
...require a change to the laws of celestial mechanics...
I think that with the ion drive, the laws of celestial mechanics allow a bit more leeway than otherwise. That said, I'd rather move on to Ceres sooner rather than later -- that's a much larger and more interesting world. Of course, I'd also like to see real-time data releases :/
Yeah, Dawn's launch was delayed three months, but the ion drive gives so much leeway it didn't matter in the end (compared with a conventional launch to Mars for example, that has a very specific window).
http://dawn.jpl.nasa.gov/multimedia/vesta_dawn_gallery.asp
Has this new 3D video goodness:
http://dawn.jpl.nasa.gov/feature_stories/d..._over_vesta.asp
Has this new 3D video goodness:
http://dawn.jpl.nasa.gov/feature_stories/d..._over_vesta.asp
New Dawn Journal:
Amazing.
QUOTE
There is always a tug downward, but because of Vesta's heterogeneous interior structure, the product of its complex geologic history, sometimes there is also a slight force to one side or another. With their knowledge of the gravity field, the team plotted a course that took advantage of these variations to get a free ride. This is akin to experienced sailors not only relying on their ships' engines but also following routes that use known currents to let nature do some of the work. Of course, sailors benefit from knowledge of currents measured by those who plied the waters before them. Dawn is the first, venturing boldly into mysterious seas never visited before. But the measurements of the gravity field in HAMO, even though it was at a higher altitude, gave navigators enough information about what lay ahead on the horizon that our vessel could safely and productively ride the gravitational currents. The flight plan from HAMO to LAMO then is a complex affair of carefully timed thrusting and equally carefully timed coasting. Under ion thrust, the spacecraft flies to a certain location in a certain orbit at a certain time, waits a certain interval as Vesta propels it to the next waypoint, and then it resumes thrusting.
Amazing.
QUOTE (Explorer1 @ Dec 1 2011, 01:01 PM)
Yeah, Dawn's launch was delayed three months, but the ion drive gives so much leeway it didn't matter in the end (compared with a conventional launch to Mars for example, that has a very specific window).
Supposedly that delay was running up against the window from Vesta to Ceres, so I suspect there may not be much more leeway to stay at Vesta. Perhaps someone who knows for sure will chime in.
--Greg
The Dawn Journal and Dr. Marc Rayman should get some sort of award for 'modern science literature'. It is always a fascinating read.
I agree, PDP8E.
After last burns, nominal LAMO height (200km above average radius) was just reached:
Click to view attachment
However, now orbit needs to become circular...
Click to view attachment
However, now orbit needs to become circular...
No burns in last hours, orbits is now around 185x245km:
Click to view attachment
Curiously, most of last burns occurred around apoastron and this reduced periastrum distance only, increasing eccentricity...
Click to view attachment
Curiously, most of last burns occurred around apoastron and this reduced periastrum distance only, increasing eccentricity...
Interesting news via Emily's twitter:
"Russell: pole position for Vesta measured by Dawn differs from astronomically determined value. #AGU11 (1 hour ago)"
"Russrll: spring will return to dark north pole later than thought, so they will need to delay Vesta departure in order to image it. #AGU11 (1 hour ago)"
"Russell: pole position for Vesta measured by Dawn differs from astronomically determined value. #AGU11 (1 hour ago)"
"Russrll: spring will return to dark north pole later than thought, so they will need to delay Vesta departure in order to image it. #AGU11 (1 hour ago)"
Several updates here:
http://dawn.jpl.nasa.gov/multimedia/vesta_dawn_gallery.asp
Dated Dec. 5th, but I think they showed up more recently.
http://dawn.jpl.nasa.gov/multimedia/vesta_dawn_gallery.asp
Dated Dec. 5th, but I think they showed up more recently.
Now that Robert Gaskell's shape model of Vesta is available, I used it to create a movie comparing Vesta to two other Solar System bodies: Phoebe and Mimas. The movie contrasts the sizes, shapes and rotation states of the three objects. Though I'm familiar with the numbers, it's still impressive to see just how quickly Vesta spins (though I suppose contrasting it with a synchronously rotating moon isn't the fairest comparison.)
http://www.youtube.com/watch?v=dSGh_JHNFSI...eature=youtu.be
Enjoy!
--Chris
http://www.youtube.com/watch?v=dSGh_JHNFSI...eature=youtu.be
Enjoy!
--Chris
Beautiful. Thanks for sharing.
With the shape from Dr. Robert Gaskell (and providing by NAIF), I make this video, projecting some pictures from Survey Orbit to the shape.
And there's the bumpMap (simple cylindrical projection). It can be used with Celestia.
And there's the bumpMap (simple cylindrical projection). It can be used with Celestia.
Nice! This can be turned into a shaded relief map simply by using the 'emboss' filter in Photoshop, or its equivalent. Here's one version - varying the illumination direction makes drastic changes to the appearance of the map. The two distinct sets of troughs show up very well here.
Phil
Click to view attachment
Phil
Click to view attachment
And Nice! ^2, Phil. You can see a lot of history there.
--Bill
--Bill
Beautiful simulated views in this video, Sarunia! About the bumpMap, do you know which basic shape should I use with software other than Celestia?
(if is an ellipsoid, I would like to know axes lenghts...)
(if is an ellipsoid, I would like to know axes lenghts...)
Videos of numerous AGU talks on Vesta from this past week are available online here (three separate sessions). I saw just a few of them in person - mainly about the large south polar crater.
http://sites.agu.org/fallmeeting/scientifi...and-6-december/
http://sites.agu.org/fallmeeting/scientifi...and-6-december/
After long hiatus (related to safe mode event one week ago) the simulator is up again! Yesterday, several short engine burns put Dawn on a 209 km average height but, interestingly, now eccentricity is increasing due to Vesta gravitational field:
Click to view attachment
The yellow curve is my rough attempt to interpolate trend through a sinusoid with 4.3 hours period and increasing amplitude (8 km/day) - anyway, remember that simulator is based on a nominal orbit design, not real time data!
[I would like to thank Dr Rayman for additional info through private communications!]
Click to view attachment
The yellow curve is my rough attempt to interpolate trend through a sinusoid with 4.3 hours period and increasing amplitude (8 km/day) - anyway, remember that simulator is based on a nominal orbit design, not real time data!
[I would like to thank Dr Rayman for additional info through private communications!]
Thanks, dilo.
For the bump projection, a tri-axial ellipsoid 289x280x229 km (recommended values by NAIF) is used. So a spheroid (289x229) works fine.
EDIT: correct wrong value: 229 instead of 219.
For the bump projection, a tri-axial ellipsoid 289x280x229 km (recommended values by NAIF) is used. So a spheroid (289x229) works fine.
EDIT: correct wrong value: 229 instead of 219.
Did my own conversion from the greyscale map into something a bit more funky 
QUOTE (scalbers @ Dec 11 2011, 12:47 PM)
Videos of numerous AGU talks ( on Vesta ) from this past week are available online here
As an interested amateur, the following AGU video appears to be a good summary of what has been discovered about Vesta so far. It is 2 hours long and I have only viewed 40% of it, but the quality has been very good up till now, and I understood most of it. It is HD and if you download it be prepared for a 900 MB file.
Here is the link: U21B Dawn Explores Vesta
http://vimeo.com/33317236
Note:This is not a link to the AGU page with the embedded player. It is a direct link to the hosting site VIMEO. Registered members can download file from here.
AGU page: Sessions on Demand (No downloads)
http://sites.agu.org/fallmeeting/scientifi...and-8-december/
Jack
QUOTE (claurel @ Dec 9 2011, 11:38 AM)
Now that Robert Gaskell's shape model of Vesta is available, I used it to create a movie comparing Vesta to two other Solar System bodies...
For Celestia users, here's an add-on that replaces Celestia's default low-resolution Vesta model with the Gaskell model:
http://www.shatters.net/~claurel/celestia/models/vesta.zip
The model contains less than 50,000 triangles, so it should display well on any system. It uses a normal map to supply the extra detail from the original high-resolution shape model.
--Chris
Thank you, I was just preparing a conversion for celestia but now i know that it's not necessary and it save my time
First (?) image from near LAMO?
http://dawn.jpl.nasa.gov/multimedia/dawn_o..._over_vesta.asp
Taken from 230km.
http://dawn.jpl.nasa.gov/multimedia/dawn_o..._over_vesta.asp
Taken from 230km.
QUOTE (stevesliva @ Dec 14 2011, 02:43 AM)
First (?) image from near LAMO?
Almost. Picture was taken before the two last main burns which reduced average height from 240 to 211 km, last week:
Click to view attachment
the purple arrow indicate the exact time/height when (I guess) the picture was snapped...
And now the image of the day is stalled again. Let's see some boulders!
QUOTE (stevesliva @ Dec 15 2011, 08:31 PM)
Let's see some boulders!
Steve, based on last Mission Status, The Dawn "image of the day" will take a break until Jan. 9.
We have to wait next year!
Doh. Thanks for pointing that out, it'll save some clicks on my part. That one photo is such a tease.
Is it just me, or does that sharp, young crater in the top right of the image below have gullies in its walls that look remarkably similar to those in craters on Mars? The debate has been raging for some years now whether Martian crater gullies are formed by dry flow or by the flow of brine. I'm not suggesting for one moment that there's liquid flowing on the surface of Vesta, but the similarity of gullies here might suggest that most, if not all, Martian gullies formed via a dry mechanism.
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