Author Topic: New Horizons updates  (Read 185213 times)

Offline cd-slam

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Re: New Horizons update
« Reply #60 on: 09/03/2011 01:30 AM »
The search area becomes narrower over time as New Horizons's (and Pluto's) orbits become better constrained.

Isn't it getting narrower because any target objects NH could fly by are slowly moving toward the viable trajectory cone (delta-v reserve-mandated) as time passes, not because Pluto and NH orbits are unconstrained?

I would have hoped they have a really good idea of NH's trajectory to be able to both get to Pluto aimpoint in the first place and also cancel the most recent TCM.
Surely the target objects would be limited by the gravity assist which could be achieved at Pluto and/or Charon? Hence I'm guessing what is meant that as time passes there is less ability to change the Pluto aimpoint and thus achieve the necessary gravity assist to reach the next object.

Offline MP99

Re: New Horizons update
« Reply #61 on: 09/03/2011 11:45 AM »
* Still no word on the post-Pluto target (searches under way), but they might go to up to two of them (depending on what the searches find). The search area becomes narrower over time as New Horizons's (and Pluto's) orbits become better constrained.

Interesting. Does that mean that there is work ongoing to improve knowledge of Pluto's orbit in order to finalise planning of the rendezvous?

cheers, Martin

Offline simonbp

Re: New Horizons update
« Reply #62 on: 09/03/2011 04:21 PM »
Interesting. Does that mean that there is work ongoing to improve knowledge of Pluto's orbit in order to finalise planning of the rendezvous?

Yes, of both Pluto's heliocentric orbit and (especially) Pluto and Charon's mutual orbit (it's mutual as Pluto is outside of the common center of mass). The latter is actually pretty poorly known for the amount of data we have because both Pluto and Charon have large albedo patterns (i.e. different colored terrains) which throw off the center-of-light, making precise orbital determination hard.

If we knew what the terrains were, it would be much easier, but one of the major thrusts of the workshop was that they change on decadal timescales due to the migration of different ices (mainly CH4). This is much like the migration of the Martian polar caps, but covering half the surface of Pluto at a time and occurring 10x slower.

So, it's not until we get "better than Hubble" images from New Horizons that we'll actually know, for instance, the eccentricity of the orbit. 10^-4 is an upper limit, but all the tidal models suggest it should be much lower (and if not, the interior structure people have some 'splaining to do...).

Offline Comga

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Re: New Horizons update
« Reply #63 on: 09/04/2011 04:51 AM »
Surely the target objects would be limited by the gravity assist which could be achieved at Pluto and/or Charon? Hence I'm guessing what is meant that as time passes there is less ability to change the Pluto aimpoint and thus achieve the necessary gravity assist to reach the next object.

There will be no targeting by "gravity assist" at Pluto.  The trajectory is determined by science goals, and survival issues as just mentioned, which will not be compromised to optimize the trajectory to a tiny Kuiper belt object. 
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline MP99

Re: New Horizons update
« Reply #64 on: 09/04/2011 08:55 AM »
Simon,

good info, many thanks.

cheers, Martin

Offline ugordan

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Re: New Horizons update
« Reply #65 on: 09/04/2011 09:53 AM »
There will be no targeting by "gravity assist" at Pluto.  The trajectory is determined by science goals, and survival issues as just mentioned, which will not be compromised to optimize the trajectory to a tiny Kuiper belt object. 

Precisely. Furthermore, any bending of the trajectory will be miniscule. Pluto system's mass is insignificant to significantly alter the trajectory of something flying by at 14 km/s.

John Spencer said a couple of years ago that the principal uncertainty in Pluto/Charon position remaining at c/a will be in the downtrack direction as that can't be determined by OPNAVs as precisely. As a result, some imaging observations have a big uncertainty buffer built in and we can expect a good deal of images of black space returned. This won't mean the s/c was aimed wrongly, just that we didn't know exactly where Pluto is at that time so a bigger imaging footprint was deliberately built in.

Offline racshot65

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Re: New Horizons update
« Reply #66 on: 11/08/2011 03:23 PM »
« Last Edit: 01/20/2012 05:49 PM by racshot65 »

Offline MP99

Re: New Horizons update
« Reply #67 on: 11/08/2011 09:33 PM »
The PI's Perspective
Is the Pluto System Dangerous?

http://pluto.jhuapl.edu/overview/piPerspective.php

Quote
More specifically, a good candidate SHBOT aim point would be near Charonís orbit, but about 180 degrees away from Charon on closest-approach day. Why this location? Because Charonís gravity clears out the region close to it of debris, creating a safe zone.

...but presumably avoiding anywhere within the region where objects can orbit around PCL3? If wiki is correct that Charon has ~1/8th the mass of Pluto, I would assume that PCL3 would be a relatively powerful attractor?

cheers, Martin

Offline simonbp

Re: New Horizons update
« Reply #68 on: 11/08/2011 11:19 PM »
No, L3 is a saddle point that's really hard to accidentally capture into. The "danger zone" is the regions around L4 and L5, as well as anything much interior of L1. So, at L3 you only really have to worry about horseshoe orbits (going between L4 and L5), and they are much easier to perturb than L4/5 halo orbits.

Also, Pluto-Charon is an extremely close system (a=17 Pluto radii, compared to the Moon at 60 Earth radii), so the gravity on objects at the L-points is not simply two point sources, thus making perturbations much easier.

Offline MP99

Re: New Horizons update
« Reply #69 on: 11/09/2011 08:39 PM »
No, L3 is a saddle point that's really hard to accidentally capture into. The "danger zone" is the regions around L4 and L5, as well as anything much interior of L1. So, at L3 you only really have to worry about horseshoe orbits (going between L4 and L5), and they are much easier to perturb than L4/5 halo orbits.

Also, Pluto-Charon is an extremely close system (a=17 Pluto radii, compared to the Moon at 60 Earth radii), so the gravity on objects at the L-points is not simply two point sources, thus making perturbations much easier.

Many thanks for that.

I had assumed that the tighter system would make purturbations harder. Obviously not.

cheers, Martin

Offline racshot65

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Re: New Horizons update
« Reply #70 on: 12/03/2011 09:49 AM »
New Horizons Becomes Closest Spacecraft to Approach Pluto

http://pluto.jhuapl.edu/news_center/news/20111202.php

Offline racshot65

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Re: New Horizons update
« Reply #71 on: 01/20/2012 05:48 PM »
The PI's Perspective - Late Cruise!

http://pluto.jhuapl.edu/overview/piPerspective.php

Offline Zed_Noir

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Re: New Horizons update
« Reply #72 on: 01/20/2012 06:21 PM »
A bit of news. The NASA New Horizon site announce the passing of Clyde Tombaugh's widow Patsy Tombaugh on Jan 12th.

http://pluto.jhuapl.edu/news_center/news/20120116.php

Offline racshot65

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Re: New Horizons update
« Reply #73 on: 01/28/2012 12:14 PM »
New Horizons Works through Winter Wakeup

http://pluto.jhuapl.edu/news_center/news/20120127.php

Offline racshot65

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Re: New Horizons update
« Reply #74 on: 02/01/2012 08:42 PM »
New Horizons Aims to Put Its Stamp on History

http://pluto.jhuapl.edu/news_center/news/20120201.php

Offline racshot65

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Re: New Horizons update
« Reply #75 on: 02/11/2012 10:02 AM »
New Horizons on Approach: 22 AU Down, Just 10 to Go

http://pluto.jhuapl.edu/news_center/news/20120210.php

Offline veblen

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Re: New Horizons update
« Reply #76 on: 03/13/2012 03:55 PM »
Today is the last day for the NH team to actively campaign for signatures in a petition to commemorate New Horizons spacecraft at Pluto on a U.S. postage stamp in 2015. They have over 12,000 lets help push it over the top (15,000). Anyone can sign the petition.  Show your support for the exploration of Pluto and the solar system by signing!

http://www.change.org/petitions/usps-honor-new-horizons-and-the-exploration-of-pluto-with-a-usps-stamp

Offline racshot65

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Re: New Horizons update
« Reply #77 on: 06/03/2012 09:18 AM »
Itís a Sim: Out in Deep Space, New Horizons Successfully Practices the 2015 Pluto Encounter

http://pluto.jhuapl.edu/news_center/news/20120601.php

Offline simonbp

Re: New Horizons update
« Reply #78 on: 07/11/2012 06:22 AM »
The IAUC telegram just went out to announce that they have found a fifth moon now, at 27th magnitude. That's a radius of 25 km, and it's close to the 1:3 mean motion resonance with Charon. All the other small moons are close to (but not at) MMRs with Charon, so that's not surprising.

Offline TheFallen

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Re: New Horizons update
« Reply #79 on: 07/11/2012 05:33 PM »
A 5th moon discovered... Wow. Looks like the New Horizons team has to go back to the drawing board and revise the Pluto encounter sequence (obviously) :)
« Last Edit: 07/11/2012 05:36 PM by TheFallen »

Tags: updates