NASA's Mission to Pluto and the Kuiper Belt
Following the flyby of Ultima Thule, New Horizons is scheduled to continue studying the Kuiper Belt through at least 2021, the limit of its currently funded extended mission.
It will take about 20 months, through late summer 2020, to return all the Ultima Thule flyby data to Earth. But even while doing that, the spacecraft will observe more Kuiper Belt objects (KBOs) with its telescopic, onboard Long Range Reconnaissance Imager (LORRI). These images will be used to study the rotation rates and surface properties of these KBOs, and to search for satellite systems around them. New Horizons will also continue to use its space plasma and dust sensors to map the charged-particle radiation and dust environment in the Kuiper Belt, out to a distance 50 times as far from the Sun as the Earth is, just past the outer limits of Pluto's orbit. At the same time, New Horizons will map the interplanetary hydrogen gas, from the solar wind, that fills the Kuiper Belt. These studies will improve on what the legendary Voyager spacecraft could do when they traversed this region, because the sensors on New Horizons are much more advanced over 1970s-era Voyager technology.
It is possible that another flyby target can be found and reached with New Horizons' remaining fuel supply. And after that? Another exciting possibility is that we can dramatically augment New Horizons' capabilities by uploading new observing and onboard data-reduction software once the spacecraft's flyby software is no longer needed. If NASA approves such a plan, New Horizons could survey the Kuiper Belt population in ways that no other mission or telescope on Earth or in Earth orbit can, and possibly even detect and hunt down its own next flyby target.
Future New Horizons extended missions, if funded by NASA, could explore even farther out. The spacecraft is on an escape trajectory from the Sun, traveling about three astronomical units per year. (An astronomical unit, or AU, is the average distance from Earth to the Sun, about 93 million miles or 149 million kilometers.) Moreover, New Horizons and its payload sensors are healthy and operating perfectly. The spacecraft has enough power and fuel to operate into the mid-2030s or longer, perhaps enough to reach the boundary of interstellar space.