New Horizons, Pluto and the Kuiper belt Options

[Alan Stern]

Alan, can you explain a bit more about that "target area searches". What will that search be done with? HST, Pan-STARRS , LSST or some other telescope? LORRI???

Toma B-- Groundbased, but TBD telescope. We will negotiate who will partner w/NH in 2009-2010 as the groundbased search engine.


-Alan

[elakdawalla]

Alan -- just want to chime in with my thanks to you for taking the time to answer all these questions! A lot of these are questions I get asked a lot -- it saves a lot of effort and repetition to be able to point people to this forum, and gives people a chance to get answers to questions they didn't even think to ask.

--Emily

[jasedm]

Hi all - I seem to recall reading (can't remember where - could have been here...) that NH will pass through the area of Neptune's trailing (L5) Lagrange point en-route to Pluto, a year or so prior to the prime mission.No L5 Neptune Trojans are yet known (although I think a handful have been discovered at the L4 point) I wonder if there will be a concerted effort from the ground to discover an asteroid at L5 which may fortuitously come within range of NH in this area?

EDIT Sigh!! my apologies this topic has been covered extensively earlier this thread - been away on holiday, left my brain in "something to declare"

[tedstryk]

Will any of the observations of Uranus and Neptune be disk resolved? Also, am I correct in thinking that the phase curve studies would end up including Triton too, by virtue of proximity to Neptune? If any of the mid to high phase views are at all resolved, it would be neat to have a series of images to stack - I realize data-gathering constraint, but it would be neat to see what could be pulled out with the noise reduction this would allow.

[ugordan]

Will any of the observations of Uranus and Neptune be disk resolved?

Neptune will subtend around 3 arc seconds maximum: SSS view
Uranus is already at the maximum apparent diameter at cca. 3.3 arc sec and will only be shrinking: SSS view

If my math isn't failing me, 3 arcsec is around 3 LORRI pixels across. Add in PSF and that's something like a 4-5 pixel smudge. Not resolved very much.

[tedstryk]

Neptune will subtend around 3 arc seconds maximum: SSS view
Uranus is already at the maximum apparent diameter at cca. 3.3 arc sec and will only be shrinking: SSS view

If my math isn't failing me, 3 arcsec is around 3 LORRI pixels across. Add in PSF and that's something like a 4-5 pixel smudge. Not resolved very much.

Still, a half phase Neptune and unresolved Triton (with Voyager or HST colorization) would be a neat shot. Voyager got some low phase views like that a year or two before the flyby, and got some beautiful high phase views while leaving. I realize this image would be tiny, but it would be a perspective that we haven't seen. With deconvolution and stacking, a neat little shot might be pulled out.

[Greg Hullender]

You guys DO realize that the L5 point, Neptune, and the Sun form an equilateral triangle, and that this means New Horizons will be about the same distance from Neptune as Neptune is from the Sun, right? Yes, it'll be at a different phase angle, but it'll be way too far away to see much of anything.

--Greg

[tedstryk]

It isn't quite that bad (closest approach is long before it reaches the orbit of Neptune), but it is nearly so. Still, Neptune does produce a small disk from earth. What I am interested in is the phase angle, not resolution, which will be extremely low. In running the simulator, it does look as though it will be too late before the more extreme phase angles are achieved.

[Greg Hullender]

Interesting. What can you learn from high phase angle observations at a resolution of just a handful of pixels?

--Greg

[tedstryk]

The reason they are being taken is for photometry. Measurements of the overall brightness of the planet at different illumination angles can be useful scientifically. Since Uranus and Neptune are always at extremely high phase angles when seen from Earth, this will be a rare opportunity.

[Greg Hullender]

Do you have something specific in mind? Voyager should have already found anything obvious. Are you thinking there might be something that varies over time, or is there some measurement NH can make that Voyager could not?

Terminology point: Uranus and Neptune are always nearly 0 phase angle as seen from Earth -- not "extremely high" phase angle, correct? It's the sun-object-observer angle, with the object at the vertex, and from (say) Neptune, the Earth and Sun are never more than 2 = atan(1/30) degrees apart.

--Greg

[tedstryk]

Extremely low phase was what I meant. Oops.
New Horizons is taking the images because we only have Voyager's data set for other phase angles. Another data set would be handy to have. No, there probably won't be some huge discovery from these images, but they are certainly worth taking.

[GregM]

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[mchan]

They found a good PAO person.

[nprev]

I wouldn't read too much into a single adjective, here. NH's Jupiter system imagery was undeniably stunning, though...