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KBO encounters
stevesliva
post Jun 16 2017, 08:14 PM
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There is an update about a July 10 occultation over the Pacific that SOFIA will observe.
And a July 17 occultation that crosses Patagonia.
https://www.nasa.gov/feature/new-horizons-t...xt-flyby-target

That said, info on the June 3 occultation is "stay tuned."
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Paolo
post Jul 5 2017, 05:25 PM
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early results: no occultation detected, MU69 may be smaller than expected
https://www.nasa.gov/feature/new-mysteries-...xt-flyby-target
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Paolo
post Jul 6 2017, 05:39 AM
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I re-read this and maybe I was wrong. what does it mean
QUOTE
While MU69 itself eluded direct detection
?

I interpreted this as meaning that no occultation was detected, but I am not so sure now.

also:

QUOTE
he fact that we accomplished the occultation observations from every planned observing site but didn’t detect the object itself
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Explorer1
post Jul 6 2017, 05:53 AM
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They observed the star, but not the occultation, is my interpretation. Future observations like SOFIA next week should tell us more about what's going on here (it can't have vanished!)
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Holder of the Tw...
post Jul 6 2017, 02:13 PM
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Among the possibilities I've read mentioned are that it might have a much brighter surface than everyone has been thinking, and therefore it is smaller. Or it might be a binary object (or triple, or multiple). Maybe both.

Being smaller and/or an orbiting pair would make it more likely to "slip through the cracks". That is, the shadow(s) could pass unseen through the spaces between the observing telescopes with higher probability.
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bkellysky
post Jul 7 2017, 03:23 AM
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My interpretation is that they did not see the object (not surprising), and I can't tell from the article if they recorded an occultation. Can we get some clarification?
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Explorer1
post Jul 7 2017, 05:57 AM
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There was no occultation observed, it's pretty unambiguous. Alan can correct me if I'm wrong, of course!
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HSchirmer
post Jul 7 2017, 11:19 AM
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QUOTE (Holder of the Two Leashes @ Jul 6 2017, 03:13 PM) *
Among the possibilities I've read mentioned are that it might have a much brighter surface than everyone has been thinking, and therefore it is smaller. Or it might be a binary object (or triple, or multiple). Maybe both.

Being smaller and/or an orbiting pair would make it more likely to "slip through the cracks". That is, the shadow(s) could pass unseen through the spaces between the observing telescopes with higher probability.


Were there any backup observations outside of the calculated 100 mile wide path?

Now that I think about the 5 hour time delay for light from Pluto, and 7 hour time delay for MU69
it's rather amazing that the occultation "starts" and then it takes 7 hours for the shadow to reach us.
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Paolo
post Jul 7 2017, 11:35 AM
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the orbit of MU69 appears to be well established, with residuals of 0.02 arcseconds, according to the IAUC. I have no idea of how much that would mean for the occultation path width.
http://www.minorplanetcenter.net/db_search...ct_id=2014+MU69
also, I didn't know that all the observations of MU69 available have been made by the HST
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HSchirmer
post Jul 7 2017, 12:22 PM
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QUOTE (Paolo @ Jul 7 2017, 12:35 PM) *
the orbit of MU69 appears to be well established, with residuals of 0.02 arcseconds, according to the IAUC. I have no idea of how much that would mean for the occultation path width.
http://www.minorplanetcenter.net/db_search...ct_id=2014+MU69
also, I didn't know that all the observations of MU69 available have been made by the HST


Um, apologies, (engineer brain and significant figures kicking in) but my quick trigonometry calculation
    1 arc second = 1 AU / 206,265 AU, 1 AU =93,000,000 miles,
    at 44 AU 1 arc second = 18k miles, and .02 arcsecond = 360 miles.

shows that the location of MU69 is only accurate to within ~360 miles.
Admittedly, that is amazing precision when you think about it.

If the location of the object is accurate to .02 arcseconds
then the location of the object's shadow cannot be known more accurately.
The error bars are the same ~360 miles.

-edit-

Ok the prime eclipse path was not the only place where telescopes were deployed http://www.boulder.swri.edu/MU69_occ/june3.html



-edit-
Ah, found it. Yes, the eclipse path is calculated out to 3 sigma, so it's just under 900 miles wide.

Ok, so it's really a picket fence problem, looking for a 30 mile wide shadow somewhere in a 900 mile wide swath.

Estimates of Shadow Track-
https://www.google.com/maps/d/viewer?mid=1z...0000046&z=2
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tasp
post Jul 7 2017, 03:12 PM
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Would a successful observation in the second or third occultation help ascertain where the first track actually was, and could they verify it was a 'picket fence' problem with the first one ?
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HSchirmer
post Jul 7 2017, 05:57 PM
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QUOTE (tasp @ Jul 7 2017, 03:12 PM) *
Would a successful observation in the second or third occultation help ascertain where the first track actually was, and could they verify it was a 'picket fence' problem with the first one ?


It should.
If you can confirm seeing the 2 second occulation you'd nail down a location within the 100 mile occultation band;
but if you only get 1 observation site, you still have 200 mile wide uncertainty, because you won't know whether
you're in the top, center or bottom of that 100 mile band.

Next comes a critical decision:

A ) space the telescopes further apart because the shadow of MU69 might be north or south of what was calculated.
B ) space the telescopes closer together because the shadow of MU69 might be narrower than projected.
C ) keep things the same, because you're uncertain about your uncertainties.

Tough call.
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Floyd
post Jul 7 2017, 06:35 PM
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D) enlist more telescopes and place them closer together in a much wider track cool.gif


--------------------
Floyd
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Ron Hobbs
post Jul 10 2017, 03:58 PM
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All planetesimals born near the Kuiper Belt formed as binaries

https://arxiv.org/abs/1705.00683

Could it be that we are going visit a couple (or more) of primordial planetesimals?

Go SOFIA!
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stevesliva
post Jul 10 2017, 07:29 PM
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QUOTE (Ron Hobbs @ Jul 10 2017, 10:58 AM) *
Go SOFIA!


Already went wink.gif
https://twitter.com/SOFIAtelescope

(I have to admit I was thinking "night" of July 10 was a few hours hence... but good to see it got its observations)
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