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Why is the New Horizons Flyby of 2014 MU69 So Much Closer than its Pluto Flyby Distance?

-- | April 26, 2016

Question: There is talk of New Horizons travelling to another object in the Kuiper Belt. The fly by will be at about 1900 miles, much closer than the fly by of Pluto. How are the distances of observation of these type of objects arrived at and why would there be a difference between the two? — Robert

Answer: The closest approach of New Horizons to Pluto was about 7800 miles. Spacecraft trajectories and flyby distances are determined by a number of factors, including the measurement system used for determining the position and speed of a probe, the location from which these measurements are obtained, an accurate model of the solar system, and the availability of accurate models of the motion of a probe. There is a nice Scientific American article on this subject with more details. As for why the flyby of this new object, which is I believe a Kuiper Belt Object (KBO) called 2014 MU69, it is difficult to say. My guess is that the Pluto/Charon flyby imposed restrictions on how close New Horizons could get to Pluto based on the fact that it also had to get close to Charon, while the flyby of 2014 MU69 is a flyby of just one object, so they can get as close as they can.

Jeff Mangum

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