[X] My Assistant

[xtruel]

Hi,

I’m regular follower of NH and I’m also interested in the 2nd leg of the mission, i.e the 2016+ KBOs encounters. Does anyone know when operations about this leg (starting with searching objects of interest with HST or some other earth-based means, I suppose) are expected to begin ?

[Vultur]

The first post in this thread says the search would start in 2010 - has it started yet, or will it be later this year?

[Alan Stern]

The first post in this thread says the search would start in 2010 - has it started yet, or will it be later this year?

Our best imager, LORRI, can resolve the size of an object from roughly 10^5 object diameters away. So for a 100 km object, for example, we have to be w/i 10^7 km just to resolved it; if you want crude shape information, cut that to 10^6 diameters, and if you want "geology," well, better come to approx 30,000 diameters or better. The point here is Crantor and other distant flybys don't yield much of use, so we have not expended effort on them.

As to our KBO search, John Spencer is leading the organizational effort to recruit search teams; Andrew Steffl is helping John. Our plan is to conduct the search in 2011 and 2012, though Scott Shepard at least has already begun.

-Alan

[illexsquid]

Our best imager, LORRI, can resolve the size of an object from roughly 10^5 object diameters away. So for a 100 km object, for example, we have to be w/i 10^7 km just to resolved it; if you want crude shape information, cut that to 10^6 diameters, and if you want "geology," well, better come to approx 30,000 diameters or better.

Alan, thanks for the info, but I'm a little confused... I assume that for crude shape information, you mean cut the maximum distance to 10⁶ kilometers, since 10⁶ diameters would be 10⁸ kilometers. But which do you mean for the "geology" figure? 30,000 diameters would be 3 million kilometers for our theoretical 100 km object, which is tough enough, but 30,000 kilometers is more or less a bullseye: better targeting than even Apophis will manage . It seems to me you could get at least some worthwhile surface-feature resolution at a greater distance than that. The famous LORRI images of Tvashtar's plume resolved fine details at 2.5 million km. On the other hand, I know that spacecraft (and ground) resources are limited, and you have to be sure you're getting enough meaningful data for any expenditure. Could you give any hints as to when you think it might be worthwhile to observe during one of these flybys?

[Gsnorgathon]

The Tvashtar plume images were taken a lot closer to the sun than any KBO images will be. I imagine blurring due to longer exposure times would reduce resolution at comparable distances.

[john_s]

I'll chip in here. Alan was talking about science at Centaurs that we might fly past on our way to Pluto- none of those will get close enough to be resolved. For the KBO target(s) beyond Pluto, we will deliberately target to get within a few tens of thousands of kilometers or closer- from 20,000 km, for instance, we would get 500 pixels across a 50 km KBO- sufficient to do some serious geology. LORRI can get well-exposed, unsmeared, images at Pluto's distance from the sun (it was designed to do that, of course), and while illumination conditions will be more challenging further out in the Kuiper Belt, there's enough performance margin that we expect to be able to do the same there.

At Crantor's distance, a LORRI pixel is 2000 km across, much bigger than Crantor itself. So there's no hope of getting any shape information.

And to make sure no-one is still confused on this point, we will not be searching for KBOs with NH itself- huge ground-based telescopes with wide-field imagers can do that much better, even though they're stuck at 1 AU.

John

[MahFL]

The Search for KBO's to begin.