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KBO encounters
xtruel
post Aug 2 2008, 12:53 PM
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Hi,

I’m regular follower of NH and I’m also interested in the 2nd leg of the mission, i.e the 2016+ KBOs encounters. Does anyone know when operations about this leg (starting with searching objects of interest with HST or some other earth-based means, I suppose) are expected to begin ?
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nprev
post Aug 2 2008, 01:06 PM
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Hiya, X. If I remember correctly, the KBO search isn't really going to kick into gear until 2010 because Pluto (and the cone of possible follow-on destinations) is in Sagittarius from our viewpoint right now, which is the galactic core region...too much background optical 'noise' from all those stars to distinguish targets. Once it moves clear, the hunt will begin. Don't think that HST will participate (might be wrong), but several large ground-based observatories will certainly be involved.


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Alan Stern
post Aug 2 2008, 01:26 PM
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QUOTE (nprev @ Aug 2 2008, 01:06 PM) *
Hiya, X. If I remember correctly, the KBO search isn't really going to kick into gear until 2010 because Pluto (and the cone of possible follow-on destinations) is in Sagittarius from our viewpoint right now, which is the galactic core region...too much background optical 'noise' from all those stars to distinguish targets. Once it moves clear, the hunt will begin. Don't think that HST will participate (might be wrong), but several large ground-based observatories will certainly be involved.


KBO searches will be conducted in 2011-2012, when the relevant KB fields are out of Sag as Nprev described. Target characterization and prioritization will occur in 2013-2014. Target selection will be in 2015.

HST's FOVs are too small to use profitably for searches. We will use wide field imagers on groundbased, big guns like Keck, Subaru, etc.

-Alan
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Paolo
post Aug 2 2008, 03:32 PM
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QUOTE (nprev @ Aug 2 2008, 03:06 PM) *
Pluto (and the cone of possible follow-on destinations) is in Sagittarius from our viewpoint right now, which is the galactic core region...too much background optical 'noise' from all those stars to distinguish targets.


Remember when they called asteroids "the vermin of the sky"? smile.gif


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nprev
post Aug 2 2008, 04:48 PM
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smile.gif ...our definition of celestial vermin seems to be shifting, doesn't it? Bloody core stars...


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xtruel
post Aug 3 2008, 07:36 AM
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Thanks for these quick replies smile.gif

Given the tiny angular size of expected objects, It seems likely that science data about them to be collected by earth-based means, in order to perform target characterization & selection, will be limited, and may be already known in its headlines. Orbit characterization, absolute magnitude, color may be among these. Are there others ? In particular, will it be possible by earth-based means (or HST) to detect & characterize a binary object and is there a reasonable probability to find one ?


I also wonder if there is some hope that NH after its KBO mission may be aimed at an « inner Oort-Cloud object » (Sedna-like) as these objects raise currently deepest mysteries about how they formed, how they have been put in there, etc... . This would need some fuel left, and also long term NH survey and survival. Clearly this is not currently planned, but this may be the first realistic opportunity to have a close look at Oort cloud...
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Greg Hullender
post Aug 3 2008, 04:01 PM
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Trouble is, it'll take NH almost 10 years to go 40 AU, and the inner edge of the Oort Cloud is estimated to be about 2000 AU out. A 500-year extended mission is probably asking for too much. :-)

http://en.wikipedia.org/wiki/Oort_cloud

Since Sedna's the only thing like Sedna, I think it'll be hard to guess that we'll find another before 2015 AND that it'll be reachable by NH.

That does raise an interesting question, though. From the NH mission page: http://pluto.jhuapl.edu/mission/mission_timeline.php it's not clear how much time NH could have to reach a KBO. A ten-year extended mission could roughly reach the perihelion distance of Sedna from the Sun, but is anyone contemplating an XM that long? How long can we reasonably expect NH to work?

--Greg
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Alan Stern
post Aug 3 2008, 04:35 PM
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QUOTE (Greg Hullender @ Aug 3 2008, 04:01 PM) *
Trouble is, it'll take NH almost 10 years to go 40 AU, and the inner edge of the Oort Cloud is estimated to be about 2000 AU out. A 500-year extended mission is probably asking for too much. :-)

http://en.wikipedia.org/wiki/Oort_cloud

Since Sedna's the only thing like Sedna, I think it'll be hard to guess that we'll find another before 2015 AND that it'll be reachable by NH.

That does raise an interesting question, though. From the NH mission page: http://pluto.jhuapl.edu/mission/mission_timeline.php it's not clear how much time NH could have to reach a KBO. A ten-year extended mission could roughly reach the perihelion distance of Sedna from the Sun, but is anyone contemplating an XM that long? How long can we reasonably expect NH to work?

--Greg



We're hoping for a 4-6 year extended mission (XM), taking us to perhaps 50 AU. The heart of the KBO population is at 42-43 AU, and after that it thins out. By 55 AU we're out of the Classical Belt and into the much more dilute Scattered Belt.

We expect to fly by 1 or perhaps 2 KBOs each ~40 km in diameter in the XM. Larger ones are too few and far between to reach with our fuel supply unless we are very lucky, but the statistics are against us.

My job as PI is not to fly as far as we can but to maximize the value of the KB exploration we can achieve. This translates to accomplishing one post-Pluto KBO flyby within 2 or 3 years if we possibly can (to ensure against later failures) and to pick up a second KBO for comparative purposes if possible thereafter.

-Alan
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surreyguy
post Aug 3 2008, 05:06 PM
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Is larger necessarily better? Planets (in the hydrostatic sense) are always interesting, of course, but geology has a way of erasing information. A 40km KB equivalent of a chondritic meteorite would be fascinating, if frustrating given only a few hours of remote sensing are possible.

I love the audacity of it, though, to go off to study something without having discovered it yet.
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Alan Stern
post Aug 3 2008, 05:09 PM
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QUOTE (surreyguy @ Aug 3 2008, 05:06 PM) *
Is larger necessarily better? Planets (in the hydrostatic sense) are always interesting, of course, but geology has a way of erasing information. A 40km KB equivalent of a chondritic meteorite would be fascinating, if frustrating given only a few hours of remote sensing are possible.

I love the audacity of it, though, to go off to study something without having discovered it yet.



We'll see it for days on the way in, possibly longer. And FYI, 40 km is Eros size.

Alan
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nprev
post Aug 3 2008, 05:49 PM
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Just out of curiosity, Alan, is encounter relative velocity for KBOs basically a constant? These things have very small heliocentric relative speeds if they are not in highly elliptical orbits, so NH's outbound velocity is presumably a criterion for deciding whether or not to select an object based on encounter timing & size (i.e., you'll get a lot more hang-time for a 500km diameter KBO then a 40km).


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Alan Stern
post Aug 4 2008, 10:59 AM
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QUOTE (nprev @ Aug 3 2008, 06:49 PM) *
Just out of curiosity, Alan, is encounter relative velocity for KBOs basically a constant? These things have very small heliocentric relative speeds if they are not in highly elliptical orbits, so NH's outbound velocity is presumably a criterion for deciding whether or not to select an object based on encounter timing & size (i.e., you'll get a lot more hang-time for a 500km diameter KBO then a 40km).


Nprev-- All KBO encounters are at approx the same relative speed, ~12-15 km/sec, independent of KBO size. Don't know whatyou mean about hang time...

Alan
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nprev
post Aug 4 2008, 11:10 AM
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Oh, sorry. What I meant is that presumably more data (esp. imagery) could be acquired when encountering a larger object then a smaller one; for example, a larger one would have resolvable features further out & also post fly-by.


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Alan Stern
post Aug 4 2008, 01:24 PM
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QUOTE (nprev @ Aug 4 2008, 11:10 AM) *
Oh, sorry. What I meant is that presumably more data (esp. imagery) could be acquired when encountering a larger object then a smaller one; for example, a larger one would have resolvable features further out & also post fly-by.



True, but the stats just make it unlikely--too few and far between. Best we can realistically hope for is 70 km diameter if I choose to go to just one instead of 2 KBOs. That's what the Monte Carlo models for detection statistics within our accessible region after Pluto tell us. Nontheless, the KBOs we will get will be 10^5 times the masses of km-scale comets and will teach us an enormous amount about KBO evolution, chemistry, geology, etc.

-Alan
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surreyguy
post Aug 4 2008, 06:42 PM
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Thanks for the correction, Alan. And yes, I should have said 'parent body of' somewhere in there.

Here's hoping that you get enough options to do some trading (red? grey? hot? cold? scattered?).
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