In 2006, New Horizons shipped into space to investigate celestial bodies in the Kuiper Belt near Pluto. Unfortunately, now it turns out that this mission of several years can end in total failure because there are problems with choosing the right object.
Astronomers have the biggest problem with the choice of the KBO (Kuiper Belt Object), or, in short, the proper object to investigate for the instruments of the New Horizons unit. Once the ship has reached Pluto, it must know the trajectory of the object that it should investigate in order to approach it safely. Unfortunately, finding a good KBO is not easy because terrestrial telescopes are too weak to accurately view an object and calculate its trajectory, so the chance of choosing the right celestial body is at most 40 percent.
However, the astronomers do not intend to give up so easily, so they hope to be able to use the Hubble Space Telescope for this purpose, which should increase the chances of successful missions by as much as 90 percent.
It would seem that setting up a KBO for New Horizons should be a priority, so you can ask why the issue was left at the last moment. This is not easy, as it has to wait until it can be determined exactly which ships the ship will be able to reach. This wait can be revenged, because until the last phase of the mission was only a few months before the ship will have to fire their engines and eventually pick up some trajectory.