The object 2014 MU69 is much smaller and dimmer than Pluto. Even as New Horizons approaches, it will be much harder for its 8.2 inch aperture, cooled CCD long range imager LORRI to get a fix on it until it is quite close.
New Horizons made it's first sighting of Pluto nine years before it reached Pluto. MU69 is going to be about 100,000 times dimmer, which means it will make its first sighting more like nine days before it gets there (roughly) (actually it could be a few months, see this). Thus any navigation using the spacecraft's imaging system may have a narrow window of opportunity to be useful. This is why I think this question is particularly interesting - is there a plan to use the spacecraft's imaging data in any way to guide the flyby, or will it be done only with astrometry of MU69 from Earth's Neighborhood and radar range/rate of New Horizons plus data from its last known address, Pluto/Charon?
Pluto's orbit has been monitored for almost a century, while that of 2014 MU69 only about three years, although with three years of diffraction-limited precision astrometry from Hubble that can go a long way.
But going from spots on an image to a true three dimensional orbit and six dimensional state vectors is not straightforward. It seems there could be a larger envelope in distance/eccentricity that could generate the same apparent motion.
Question: How can 2014 MU69's orbit be know well enough for a close flyby by New Horizons?
I'm also wondering how well has 2014 MU69's actual orbit been plotted, and how close is the flyby expected to be to the target? Are they just aiming for zero impact parameter (straight-on) and letting the uncertainty determine the distance, or are they aiming a little to one side? But these are secondary and I will ask separately if needed.
Pluto 2014 MU69 ------- --------- Diameter 2380 km ~35 km Albedo ~0.58 ~0.04-0.14? distance to sun 5.0E+09 km 6.5E+09 km Vis mag from Earth ~15 ~ 27 Years of observation 87 yr ~ 3 yr
At the time of flyby:
- relative velocity ~ 50,000 kph
- distance to earth ~ 6,650,000,000 km
- round trip radio ~ 12.3 hours