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Unmanned Spaceflight.com _ New Horizons _ New Horizons Parallax Program
Posted by: dtolman Feb 3 2020, 06:48 PM
New Horizons is going to be launching a http://pluto.jhuapl.edu/Learn/Get-Involved.php#Parallax-Program this year - with planned simultaneous observations from Earth and New Horizons of Proxima Centauri and Wolf 359 on April 22nd and April 23rd.
At New Horizons distance the change in position for those two will be very noticeable - over an arcsecond - and the combined 3-d image should have some noticeable "pop" for those two stars versus other background ones.
As always this decade, the latest photo ever taken by New Horizons will be the Farthest Ever Taken.
Posted by: Mark Gurwell Feb 3 2020, 07:00 PM
At New Horizons distance the change in position for those two will be very noticeable - over an arcsecond - and the combined 3-d image should have some noticeable "pop" for those two stars versus other background ones.
As always this decade, the latest photo ever taken by New Horizons will be the Farthest Ever Taken.
I think the parallax is much higher than that...New Horizons is at ~47 AU, and the projected distance perpendicular to Proxima Centauri is around 41-42 AU. Thus the apparent parallax must be > 30" which would be spectacular that's true.
Posted by: Tod R. Lauer Feb 5 2020, 04:48 PM
Proxima Cen will have a parallax of 32'', Wolf 359 16".
Posted by: fredk Feb 29 2020, 05:52 PM
This is a very cool demonstration project. If anyone's curious how the increased parallax precision due to the long baseline compares with state of the art measurements, here's a rough estimate. One LORRI pixel corresponds to about 1" (1 second of arc). The Proxima Centauri effective baseline of 40+AU is around 20 times the usual 2 AU baseline for Earth-based parallax measurements. So a 1" LORRI precision would correspond to roughly 50 millisec precision from Earth. (Of course the star's position could be determined to better than a pixel, although how much better will depend on the S/N.)
Gaia is supposed to measure parallaxes of stars down to 15th magnitude with something like 20 microsec precision. So LORRI won't come close to telling us anything new about the distances to these stars. But of course, as I mentioned, that isn't the point - this is meant as a demonstration and as a way of getting amateurs involved. I can't wait to see the anaglyphs!
Posted by: john_s Mar 2 2020, 03:25 PM
FWIW, during the navigation campaign on the approach to Arrokoth in late 2018, we were achieving an astrometric precision of about 0.1 arcseconds, even though (like the upcoming parallax demo) we were using LORRI in 4x4 binned mode, with effectively 4 arcsecond pixels. So we could do better than your estimate, though Gaia still won't have to worry about the competition.
John
Posted by: Alan Stern Jun 11 2020, 11:55 PM
Our parallax program succeeded!
The feature stories on the New Horizons parallax images are live on the NASA and New Horizons mission websites:
https://www.nasa.gov/feature/nasa-s-new-horizons-conducts-the-first-interstellar-parallax-experiment
http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20200611
NASA has also tweeted a note about tomorrow’s Reddit “Ask Me Anything” session on the images and the mission latest, 1 pm ET:
https://twitter.com/NASA/status/1271133599253827590
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Posted by: nprev Jun 12 2020, 01:47 AM
What an achievement. Congratulations to you and the team, Alan! 
Posted by: tanjent Jun 13 2020, 08:35 AM
The term “parallax second of arc” refers to the observable angular shift in the position of a object seen from opposite sides of the earth’s orbit around the sun, an offset distance of some 2 AU at the base of the triangle. This is much less than the distance to New Horizons at the present time. So can we conclude that the reason why this shift was not observed from Cassini or Juno or other distant spacecraft is simply because they did not look for it? But for navigational observations, surely they would have to take it into account...
Longer baseline, probably coupled with a higher resolution camera, will allow more precise distance measurements than previously possible. But what Is scientifically new here?
Posted by: nprev Jun 13 2020, 08:54 AM
Alan, has any consideration been given to applying this technique to search for undiscovered nearby faint stars or brown dwarfs? Might also work for large objects far out in the Oort Cloud.
Posted by: Alan Stern Jun 13 2020, 11:14 AM
Longer baseline, probably coupled with a higher resolution camera, will allow more precise distance measurements than previously possible. But what Is scientifically new here?
We can't think of any case of a known object that NH can do better on than ESA's Gaia did.
Posted by: Alan Stern Jun 13 2020, 11:15 AM
Not following. Say more.
Posted by: Xcalibrator Jun 13 2020, 02:13 PM
> But what Is scientifically new here?
As Alan has said elsewhere, not really anything, but it could be used as a nice illustration of parallax in textbooks.
> Alan, has any consideration been given to applying this technique to search for undiscovered nearby faint stars or brown dwarfs? Might also work for large objects far out in the Oort Cloud.
There are much better/faster methods for doing this. One example is the http://www.recons.org/ project, which is focused on finding new close objects. Gaia measures the distance of anything it can see, and it can see deeper than NH. Infrared is also a good band to look for such (optically) faint objects, and https://neowise.ipac.caltech.edu/ did/is doing that very successfully.
Posted by: nprev Jun 13 2020, 08:02 PM
What I meant is ask amateurs to image given patches of sky as NH does the same, then do blink comparisons ...a pure fishing expedition. Low probability of success, but this might uncover nearby objects like small red & brown dwarfs with very low proper motion relative to the Solar System as well as extremely long-period TNOs.
Again, super long-shot stuff.
Posted by: Alan Stern Jun 13 2020, 10:01 PM
Again, super long-shot stuff.
Thanks for the explanation. Not a good use of New Horizons because of our low bit rates asnd small telescope (8 inch diameter). Better done from Earth with really large telescopes.
Posted by: nprev Jun 13 2020, 10:17 PM
Fair enough. Thanks!
Posted by: JohnVV Jun 14 2020, 03:08 AM
now if only they can update the SPICE files
https://naif.jpl.nasa.gov/pub/naif/pds/data/nh-j_p_ss-spice-6-v1.0/nhsp_1000/data/spk/?C=M;O=D
this would be very nice to have
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