KBO encounters Options

[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 ?

[Gerald]

An essentially one-dimensional bright line in the backgound would result in a black mean background. Nevertheless, we could theoretically find all black foreground objects crossing this line with a probability of 1 with just one telescope. The telescope would need to be designed in a way, that it can observe the whole bright line more or less continuously. So, the question of how to distribute a set of telescopes the most efficient way for a known set of background stars and for an unknown number of dark foreground objects appears to be a little less trivial.

[AJAW]

An essentially one-dimensional bright line in the backgound would result in a black mean background. Nevertheless, we could theoretically find all black foreground objects crossing this line with a probability of 1 with just one telescope. The telescope would need to be designed in a way, that it can observe the whole bright line more or less continuously. So, the question of how to distribute a set of telescopes the most efficient way for a known set of background stars and for an unknown number of dark foreground objects appears to be a little less trivial.

If we had an elongated array of small telescopes (with the long axis at right angles to the most likely shadow paths) would we expect to get some detections with a good enough velocity accuracy (and fortunate orbit) that we could say, "we are in luck, this object may occult another detectable star from our array in about X weeks, so we will have the array look at that star at that time"? Obviously it would help if the array was very long....

Thinking about this a bit more, probably the best strategy would be to have two long 'picket lines' of telescopes, with the lines as far apart from each other as you could get whilst retaining a good chance that both would detect the same KBOs. That would maximise the time difference between your two position fixes and allow the greatest movement of the KBO between detections. (Which would be at what speed? 5 km/sec or so?) I assume that the greatest contributor to the shadow passage speed is actually the Earth's orbital velocity, not the KBO's speed.... but this will vary with the height above the horizon of the observation, I guess. I'm thinking that the times between position fixes could be of the order of 10s of seconds, which isn't much motion for the KBO. On the other hand, I was impressed by how well the now-known outline of Ultima Thule fitted the occultation data, so I'm hoping that position estimates can be pretty good.

[JRehling]

Great discussion. Little bit of astrophysics background (literally and figuratively): Unlike in the solar system, or looking out with naked-eye resolution into the night sky, galactic-scale empty space in the direction of Sagittarius is not optically null and void. The background does not consist of an idealized plane of pointlike sources of light but, in principle, a blotchy continuum of variable illumination. Individual stars co-align but also are hidden to varying degrees by dust and gas. A picture of this is here:

https://upload.wikimedia.org/wikipedia/comm...e_Milky_Way.jpg

In some cases, you almost have an inversion of the usual case: You're looking for a dark pixel moving across a known background.

A real quirk of the first KBO mission is that it is headed out into this small patch of sky with the brightest background possible. If the first Pluto mission had occurred when Pluto was basically anywhere else in its orbit, the circumstances of the KBO searches would have been quite different.