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Dawn Survey Orbit Phase, First orbital phase
Paolo
post Jul 17 2011, 09:09 AM
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I think it's time we start a new thread


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dilo
post Jul 17 2011, 02:13 PM
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Good idea, Paolo!
Dawn's ion engine have been OFF in the last hours (at least 9 hours from my checks) and, as expected, now spacecraft started to accelerate:
Attached Image
Attached Image

at current distance, I espect an acceleration toward Vesta of 1,0e-4 m/s2; considering current phase angle, close to 90, this should cause an increase of total velocity close to 1 mph each 2 hours... until next engines power on!


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pablogm1024
post Jul 17 2011, 02:28 PM
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Would it be worth renaming the topic to Survey Orbit Phase, given that it is the name that the mission ops team uses for the first orbital phase?


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Bjorn Jonsson
post Jul 17 2011, 03:18 PM
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QUOTE (pablogm1024 @ Jul 17 2011, 02:28 PM) *
Would it be worth renaming the topic to Survey Orbit Phase, given that it is the name that the mission ops team uses for the first orbital phase?

Done - and congratulations to the Dawn team!
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dilo
post Jul 17 2011, 06:53 PM
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This is an answer to Greg question (from the old thread):
Your question wasn't so silly because helped me to find many answers! wink.gif
You had a nice idea about plotting escape velocity (which depends on distance from Vesta) toghether with speed... this my updated distance/speed plot, zoomed on last weeks:
Attached Image

You can clearly see the "capture event", when red curve goes below yellow one (speed axis on the right).
Well, as told in the press release nobody knows the exact moment of such event because Vesta mass is only roughly known for the moment (I used 2.69e20Kg value, reported also in Wikypedia; uncertain should be around 2%, which means 1% uncertain in escape velocity).

EDIT: meanwhile, Dawn is using again propulsion and speed seems stabilized now...


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dilo
post Jul 18 2011, 05:13 PM
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With engines on, Dawn still decelerating, even though at a very slow rate (only 1m/s in last 20 hours) due to Vesta gravity... this is an update of previous plot with a new one (always suggested by Greg) showing speed as a function of distance from Vesta instead of time; I also added a curve showing speed required for circular orbit (pay attention, this is true only if velocity vector is perpendicular to distance vector and this is not the case of Dawn, at this moment!):
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Attached Image
 


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elakdawalla
post Jul 18 2011, 07:21 PM
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OK this is making me absolutely crazy. Another image release (yay!) but as with all the previous image releases the reported scale is wrong. They keep reporting the pixel scale for the original, unenlarged image, and then they post an image that has been enlarged (badly) by some non-integer factor and fail to divide the pixel scale by whatever their enlargement factor was.


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Stu
post Jul 18 2011, 07:37 PM
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Hands up, I don't understand all the tech stuff, but I sense your frustration Emily. sad.gif

Pretty cool view, tho... more and more Mirandan...

Attached Image



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Phil Stooke
post Jul 18 2011, 07:47 PM
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Another version of this beautiful new picture.

Phil

Attached Image


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bagelverse
post Jul 18 2011, 08:26 PM
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Wow, stunning image.

While the south polar peak is either impact derived or tectonic, it certainly
reminds me of Ayers rock in central Australia. Nice hard hard of
rock that says "I am not going anywhere, no matter what you throw at me".

Also the ripples around the south polar peak really look like ripples in a pond
or maybe just wrinkles from shinkage.
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Juramike
post Jul 18 2011, 08:31 PM
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Straight to Planetary Photojournal:
http://photojournal.jpl.nasa.gov/catalog/PIA14313
http://photojournal.jpl.nasa.gov/catalog/PIA14314 (anaglyph!)
http://photojournal.jpl.nasa.gov/catalog/PIA14315
http://photojournal.jpl.nasa.gov/catalog/PIA14316 (asteroid size comparison poster)


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Stu
post Jul 18 2011, 09:03 PM
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Thanks for posting those links. Used the tiff file to creare a cleaner view...

http://twitpic.com/5s9axu


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Juramike
post Jul 18 2011, 09:49 PM
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That's really nice, Stu!


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volcanopele
post Jul 18 2011, 10:09 PM
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I think I shrunk the original image to something approaching the original resolution. I've also applied a light unsharp mask here:

Attached thumbnail(s)
Attached Image
 


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punkboi
post Jul 18 2011, 10:14 PM
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Congrats to the Dawn team for a successful orbit insertion! Now looking forward to a color image of Vesta... smile.gif


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