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LAMO, aka Low Altitude Mapping Orbit
Phil Stooke
post Nov 30 2011, 04:18 AM
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This link...

http://pds-smallbodies.astro.umd.edu/data_...ase_sched.shtml


... suggests a later date.

Phil



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dilo
post Dec 1 2011, 07:02 AM
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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! rolleyes.gif


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SFJCody
post Dec 1 2011, 07:06 AM
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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! rolleyes.gif


I believe that's the PDS data release date, not the spacecraft event date.
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angel1801
post Dec 1 2011, 12:03 PM
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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.


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Greg Hullender
post Dec 1 2011, 03:21 PM
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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
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algorimancer
post Dec 1 2011, 03:49 PM
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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 :/
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Explorer1
post Dec 1 2011, 09:01 PM
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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).
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stevesliva
post Dec 1 2011, 09:52 PM
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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
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stevesliva
post Dec 2 2011, 12:47 AM
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New Dawn Journal:

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.
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Greg Hullender
post Dec 2 2011, 06:06 PM
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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
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PDP8E
post Dec 2 2011, 06:50 PM
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The Dawn Journal and Dr. Marc Rayman should get some sort of award for 'modern science literature'. It is always a fascinating read.


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dilo
post Dec 3 2011, 06:10 AM
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I agree, PDP8E.


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dilo
post Dec 3 2011, 07:22 PM
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After last burns, nominal LAMO height (200km above average radius) was just reached:
Attached Image

However, now orbit needs to become circular...


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dilo
post Dec 4 2011, 09:40 PM
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No burns in last hours, orbits is now around 185x245km:
Attached Image

Curiously, most of last burns occurred around apoastron and this reduced periastrum distance only, increasing eccentricity...


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machi
post Dec 6 2011, 05:53 PM
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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)"


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