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2 Pallas
Paolo
post Oct 11 2009, 08:49 AM
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no one seems to have noticed this
http://www.sciencemag.org/cgi/content/abstract/326/5950/275
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nprev
post Oct 11 2009, 08:57 AM
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Well, well, well! Guess it's extremely premature to start lobbying for an XM for Dawn, but hopefully some wheels are turning in that regard already.


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Paolo
post Oct 11 2009, 10:55 AM
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I discussed about this with Mark Rayman a few weeks ago and he told me that

QUOTE
There has never been an investigation into a flyby of Pallas
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vjkane
post Oct 12 2009, 05:03 AM
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QUOTE (nprev @ Oct 11 2009, 09:57 AM) *
Well, well, well! Guess it's extremely premature to start lobbying for an XM for Dawn, but hopefully some wheels are turning in that regard already.

Ancient memory suggest that 2 Pallas orbits in an inclined orbit. If the memory chips are still functioning, this would make it hard...


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nprev
post Oct 12 2009, 05:11 AM
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I was thinking that it was maybe a few degrees off the ecliptic, but it's actually 35(!) freakin' degrees! Good trace memory, VJ.

Guess a flyby by Dawn might still be technically possible if Pallas is doing a plane crossing at the right time & place with respect to the spacecraft, but the whole thing sounds unlikely to the point of ain't-gonna-happen. Oh, well.


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Paolo
post Oct 12 2009, 05:38 AM
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From Wikipedia

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Pallas has not been visited by spacecraft, but if the Dawn probe is successful in studying 4 Vesta and 1 Ceres, it is possible its mission may be extended to include a flyby of Pallas as Pallas crosses the ecliptic. However, due to the high orbital inclination of Pallas, it will not be possible for Dawn to enter orbit.
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tedstryk
post Oct 12 2009, 02:54 PM
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There was a blurb about a Pallas encounter that briefly appeared on Astronomy Now's website back before DAWN launched, but it was pulled within a few hours of being posted.


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vjkane
post Oct 12 2009, 04:19 PM
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QUOTE (tedstryk @ Oct 12 2009, 03:54 PM) *
There was a blurb about a Pallas encounter that briefly appeared on Astronomy Now's website back before DAWN launched, but it was pulled within a few hours of being posted.

There has been talk from time to time about Dawn extended missions. The official blurb put out awhile ago is that any planning now is premature. The team will want to see how long they spend at Ceres, how much fuel is left, and what the efficiency of the engines will be at that distance from the sun. Very different than normal ballistic missions.


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PaulM
post Oct 12 2009, 07:34 PM
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I wonder if the Indians or Chinese have considered a flyby of 2 Pallas? Indian and Chinese missions to the Moon and Mars will never generate the public interest that would result from sending a spacecraft past a new Solar System body.

2 Pallas is one of the biggest objects in the Asteroid belt and so I am sure would have interesting and varied landscapes. For me the mission that really put the Japanese Space Agency on the map was Hayabusa because Itokawa was unlike any Solar System body visited before.
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Paolo
post Oct 14 2009, 06:17 PM
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Note also this LPSC paper http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2421.pdf
and its thanks to "STSCI and the Dawn mission for supporting this work."
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djellison
post Oct 15 2009, 07:01 AM
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A series of barely funny but fairly inappropriate posts have been culled.
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Paolo
post Dec 21 2009, 06:43 AM
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On ArXiv today: Physical Properties of (2) Pallas
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nprev
post Dec 21 2009, 06:55 AM
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Huh. Almost the same average density as Mars.

Hate to say it, but it's probably dry as a bone....metal-rich, though.


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elakdawalla
post Dec 22 2009, 06:05 PM
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Thanks very much for the pointer to that article, Paolo.

Of interest to some of the 3D modeling types here might be this website mentioned in the article, which has a database that currently includes 179 shape models for 112 asteroids.

http://astro.troja.mff.cuni.cz/projects/asteroids3D/web.php

--Emily


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HSchirmer
post Apr 24 2016, 12:06 AM
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Since there is already a 2 Pallas thread, so I'm putting thoughts about a Dawn extended mission to Pallas here.

If Dawn leaves Ceres, could it rendezvous with Pallas? Could it orbit it?
I'm beginning to suspect it could; if Dawn can catch Pallas as Pallas crosses Ceres' orbit then it would
appear that Dawn could use a gravity assist from Pallas to match the inclination of Pallas' orbit to the ecliptic.
Once Dawn is heading in the same general direction as Pallas, it could chase down Pallas the same way
it chased down Ceres.

I think this might work because I noticed a few very interesting things about the orbits of Ceres and Pallas-
They have an almost exact 1:1 orbit resonance. Not locked exactly, but the same orbital period
Ceres = 1680 days. Pallas = 1686 days They also have essentially identical mean motion (speed).
And, yes, Pallas is at 35 degrees inclination to the ecliptic, however, Ceres is at 10 degrees.
We were able to achieve a 10 degree inclination to rendezvous with Ceres without breaking the spacecraft,
so conceptually we can do 10 degrees again, and again, and then 5 degrees.

url="http://nssdc.gsfc.nasa.gov/planetary/factsheet/asteroidfact.html"]http://nssdc.gsfc.nasa.gov/planetary/facts...teroidfact.html[/url]
Asteroid Diameter ~Mass Rotation Orbital Spectral Semimajor Orbital Orbital Number
Name (km) 1015 kg Period Period Class Axis Eccentricity Inclination and Name
1 Ceres 965 x 961 x 891 939,300 9.074 hrs 4.60 yrs C 2.768 AU 0.0758 10.59 deg
2 Pallas 582 x 556 x 500 205,000 7.813 hrs 4.61 yrs U 2.772 AU 0.2310 34.84 deg

That makes this VERY interesting- Ceres and Pallas have essentially identical orbital period and semimajor axis.
The eccentricity and inclination are different, but if I recall my physics and mechanics correctly (not guaranteed)
then the energy of the two orbits is essentially the same, it is the direction and the shape of the orbits that is different.
Essentially, the total energy of the two orbits is the same, but the eccentric orbit exchanges
gravitational potential energy for kinetic energy as Pallas goes from perihelion to aphelion and back again.

So, remember Ulysses? No it's not Bloomsday...
Ulysses the spacecraft was redirected into an out-of-the-ecliptic orbit by using a gravitational slingshot around Jupiter.
That was able to redirect the spacecraft's orbit out of the ecliptic, not much of a change in delta-V IIRC, but change in direction.

Seems that when Pallas crosses [edit the ecliptic] the plane of ceres' orbit, Dawn could do a slingshot manoeuvre to
redirect it from a Ceres-like 1686 day 10 degree orbit into an inclined Pallas-like 1680 day 35 degree orbit.
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