New Horizons: Pre-launch, launch and main cruise, Pluto and the Kuiper belt Options

[john_s]

With its 20cm scope NH will be able to perform a population survey of the Kuiper belt by direct imaging and by measuring dust debris, what search strategy will be used?

282 more days and nights before launch

We don't plan to use New Horizons for Kuiper belt population studies by searching for individual KBOs. Even though it will be much closer to its little piece of the Kuiper Belt than ground-based telescopes, that won't make up for its lack of aperture compared to the 10-meter class telescopes back on Earth, and the narrow data pipeline back to Earth will also limit the area that we could cover. We'll be directly sampling the dust in the Kuiper Belt with the Student Dust Counter, which has no particular strategy- it simply records the dust particles as we run into them. It's also possible that we'll be able to image the sunlight scattered by Kuiper Belt dust, as you suggest, though I don't think we've studied this possibility in detail yet- the likely faintness of the "zodiacal light" at such large distances from the sun will be a challenge. The dust is particularly interesting because it can be directly compared to the dust we see in the "Kuiper Belts" around other stars, where we have no hope of seeing individual asteroid-sized bodies.

New Horizon's biggest contribution to our understanding of the Kuiper Belt will of course come from its close-up studies of Pluto, Charon, and the other one or two KBOs that we fly past- an area where ground-based facilities can't hope to compete.

[hendric]

John,
I never saw an answer to a previous question about using NH's position to take astrometry. Would it be a worthwhile thing to do?

[cIclops]

We don't plan to use New Horizons for Kuiper belt population studies by searching for individual KBOs.  Even though it will be much closer to its little piece of the Kuiper Belt than ground-based telescopes, that won't make up for its lack of aperture compared to the 10-meter class telescopes back on Earth, and the narrow data pipeline back to Earth will also limit the area that we could cover.  We'll be directly sampling the dust in the Kuiper Belt with the Student Dust Counter, which has no particular strategy- it simply records the dust particles as we run into them.  It's also possible that we'll be able to image the sunlight scattered by Kuiper Belt dust, as you suggest, though I don't think we've studied this possibility in detail yet- the likely faintness of the "zodiacal light" at such large distances from the sun will be a challenge.  The dust is particularly interesting because it can be directly compared to the dust we see in the "Kuiper Belts" around other stars, where we have no hope of seeing individual asteroid-sized bodies.

Yes NH has only 20/1000 of the resolving power of Keck but Keck has to peer through the atmosphere and NH will be right inside the Kuiper belt. What is the smallest KBO resolvable by Keck at 60AU - 100 kms? NH will have better resolving power than Keck for at least an AU in all directions *continuously* for several years. An automated onboard survey would greatly reduce the load on that narrow data pipe. Imaging the Kuiper dust should yield information about the object density assuming that it is generated by collision processes.

A survey of smaller KBOs should be possible with NH that is beyond Keck's capability to compete. In any case NH needs something to keep it busy once it has finished its KBO flyby

[Alan Stern]

The major contribution NH will make to understanding the size distribution of KBOs
will be documenting the crater size-frequency distributions on Pluto and Charon (and
KBOs--if we get that far--as we hope we will).

Our 1 km-resolution maps will allow us to count craters due to impactors
as small as 100 m-- something one can't detect from Earth, even at 40 AU.
The hi-res LORRI images near C/A will get craters as small as perhaps
50 m, thus due to impactors of scale 5 m size!

Most interestingly to me, Pluto's rapid atmospheric escape should have generated
one to several km in surface loss over 4 Gyr. This is thought to have, "wiped
the slate clean" over time, so that Pluto's surface should show only craters
from the "present-day" KB. Charon, with no atmospheric loss, should however show
the time-integrated history of impacts stretching back almost to its formation, when
the KB is thought to have been much more massive. Comparison of the two should
be fascinating.

-Alan

[john_s]

John,
  I never saw an answer to a previous question about using NH's position to take astrometry.  Would it be a worthwhile thing to do?

You mean astrometry of stars for parallax determination? It's possible we could do something useful in that area. Our highest-resolution imager, LORRI, has pixels about 1 arcsecond in size, and we can measure star positions to an accuracy of a few tenths of a pixel. This is pretty good, though we can't compete for precision with specialized satellites like Hipparcos in Earth orbit, which though it only had a 2 AU baseline to work with, compared to the 30 or 40 AU we'll get from New Horizons, could measure star positions to 0.001 arcsec or better. We do have one advantage over Hipparcos, though- we can look at much fainter stars, magnitude 16 or fainter compared to Hipparcos' limit of about magnitude 12. So maybe we could get some useful parallax measurements of a few high-priority targets that were too faint for other techniques (if technology at 1 AU hasn't caught up with us by 2015!). But we couldn't do a wide survey- it would take too much bandwidth and maneuvering fuel that we need for our prime mission.

Good questions- keep 'em coming!

[hendric]

Yes NH has only 20/1000 of the resolving power of Keck but Keck has to peer through the atmosphere and NH will be right inside the Kuiper belt. What is the smallest KBO resolvable by Keck at 60AU - 100 kms? NH will have better resolving power than Keck for at least an AU in all directions *continuously* for several years.  An automated onboard survey would greatly reduce the load on that narrow data pipe.  Imaging the Kuiper dust should yield information about the object density assuming that it is generated by collision processes.

A survey of smaller KBOs should be possible with NH that is beyond Keck's capability to compete. In any case NH needs something to keep it busy once it has finished its KBO flyby

I did some thinking and here's what I came up with:

1. Being closer to the KB makes the KBOs brighter by a factor of (40/1)^2.
2. NH light collecting area is only (20/1000)^2 of Keck

So overall, for KBs at 1AU from NH and 40 AU from Keck, you get a .64 factor.

3. Differences in size/technology of CCDs at Keck and on NH. I have to give this one to Keck since they can continuously update their tech, and go with enormous CCD arrays.
4. Cosmic ray hits would go way up that far away, I assume.
5. Time sharing. Keck isn't 100% searching for KBOs. NH could be, though. This would help mitigate 2 and 4.
6. Velocity while searching. The high speed needed to get to the KB would tend to smear any pointlike KBO into something resembling a cosmic ray. My best guess is that at 13km/s your typical KBO at 1AU is going to be a streak about 15 arc seconds long on your CCD in a 5 minute shot. This is bad because you split up the KBOs light across several pixels, and that streak now resembles a cosmic ray hit.
7. You'll have lots of power (cpu and RTG) with nothing to do, so you could take lots of pictures, offset them by what you would expect for a KBO streak at various distances and directions, and see what pops out when you add them up. I remember reading about a paper where they did a KBO search like this, by creating an "orbit space" and moving around a series of pictures and summing them to see what popped out of the noise. You could do this with a fairly large number of images. As amateur astronomers know, you get a sqrt(#of images) improvement to the picture.
8. The area near the spacecraft is probably going to be well-searched from the ground by the time it gets to the KB. By that time, 30m telescopes should be operational, I think.

But if you're going to spend the time to look for dust anyways...

[Jeff7]

Kind of OT here, but I'd love to see them strap some solar sails onto the NH probe. Either that, or else do another probe for it. A solar sail craft might be going fairly fast by the time it'd make a pass by Pluto. Or maybe not, I don't know much about their actual acceleration rates, and max speeds. If there were enough light for it, deploy the sails after the Pluto flyby, and race out of the solar system in style.

[Chmee]

I do too.  I would like to see a Galileo-2 type mission.  It could probably be developed more quickly than a Europa orbiter.  With a high data rate and a very large data recorder, it could really send back some incredible shots

Just make sure though that the High Gain Antenna on a Galileo-2 works...

[tedstryk]

That is definitely true. When one looks at the coverage of the moon Galileo obtained during its Earth flyby, one can only dream of what it could have returned from Jupiter with a working antenna. What would be really cool is to send a Cassini class mission a la Voyager - with two cloned spacecraft, and a much larger data recorder than Cassini has. The two orbiters would flyby the four galileans (and perhaps encouter Amalthea and or Thebe during Jupiter orbit insertion) for four to six years. Then one of the spacecraft would use gravity assists to insert itself into Europa orbit. The other would conduct repeat Io flybies until the damage became so severe from the radiation that it would be crashed into Io.

[Guest_BruceMoomaw_*]

Well, then, you'll be pleased to know that the second-decade set of candidates for New Frontiers-class missions includes an "Io Observer" and a "Ganymede Observer", each of which would observe those moons during multiple close flybys in Jupiter orbit. The latter could easily be expanded to include Callisto. Indeed, it might be possible to design a mission that made repeated flyby observations of all 3 moons -- except that, to greatly reduce its radiation exposure and maximize the number of working Io flybys, you want the Io orbiter to be in a polar Jupiter orbit, which makes flybys of Ganymede and Callisto far harder to achieve with the same spacecraft. (Since it proved impossible to design a New Frontiers-cost mission that would include both a Jupiter polar orbiter and multiple entry probes, a Jupiter flyby with 3 entry probes is another candidate for a second-decade NF mission.)

[tedstryk]

Well, then, you'll be pleased to know that the second-decade set of candidates for New Frontiers-class missions includes an "Io Observer" and a "Ganymede Observer", each of which would observe those moons during multiple close flybys in Jupiter orbit.  The latter could easily be expanded to include Callisto.  Indeed, it might be possible to design a mission that made repeated flyby observations of all 3 moons -- except that, to greatly reduce its radiation exposure and maximize the number of working Io flybys, you want the Io orbiter to be in a polar Jupiter orbit, which makes flybys of Ganymede and Callisto far harder to achieve with the same spacecraft.  (Since it proved impossible to design a New Frontiers-cost mission that would include both a Jupiter polar orbiter and multiple entry probes, a Jupiter flyby with 3 entry probes is another candidate for a second-decade NF mission.)

That is great to hear. Another possibility is to include proper instruments to study Io from afar on the Ganymede and Callisto mission. Then, a la Galileo, if it lasts a long time, bring it in to Io for as many flybys as it can stomach.

[Guest_Sunspot_*]

.....second decade? lol

My vote goes to the Io observor.

[cIclops]

As usual good news travels slower than the speed of bad news but it's finally arrived in this new update from Alan Stern, PI for NH.

115 Days to launch (in Hex)

[odave]

115 Days to launch (in Hex)

...and after that, 72 months to Pluto-Charon encounter (in Hex)

[Alan Stern]

Just for fun, see attached.

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