Exploring the Kuiper Belt

NASA's New Horizons is the only mission ever sent to Pluto, completing the Space Age reconnaissance of the classical nine planets that started 50 years earlier. Led by Principal Investigator Alan Stern, of the Southwest Research Institute, New Horizons is also the first mission to explore the solar system’s recently discovered “third zone,” the region beyond the giant planets called the Kuiper Belt.


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The motivation for New Horizons began long before launch, starting in 1989 when a small group of self-described “Plutophiles” started investigating the scientific potential of a Pluto flyby. This kicked off many years of work to design and propose the mission, build the spacecraft, and plan the operations and scientific observations that would bring these new worlds into focus for the first time.

The New Horizons spacecraft launched on Jan. 19, 2006, beginning its odyssey to Pluto and the Kuiper Belt.

Spacecraft and Instruments

Designed and integrated at APL — with contributions from companies and institutions in the United States and abroad — the New Horizons spacecraft is a robust, lightweight observatory that has withstood the long, difficult journey to the solar system's coldest, darkest frontiers.

The New Horizons science payload consists of seven instruments – three optical instruments, two plasma instruments, a dust sensor and a radio science receiver/radiometer. This payload was designed to investigate the global geology, surface composition and temperature, and the atmospheric pressure, temperature and escape rate of Pluto and its moons. It was also used to explore Arrokoth, the most distant object ever targeted for a flyby.

The instruments are incredibly power efficient – collectively drawing less than 28 watts – and were designed specifically to handle the cold conditions and low light levels in the Kuiper Belt.

Healthy and operating normally, New Horizons continues to make long-distance observations of Kuiper Belt objects more than 4 billion miles from Earth.

Rendering of the New Horizons Spacecraft, orbiting an asteroid
An interactive, 3D rendering of the New Horizons spacecraft. Click on the image and drag to see all angles of the spacecraft.

Results and Expectations

The flyby of Pluto and its moons on July 14, 2015, was a resounding success. New Horizons sent home data that resulted in profound new insights about Pluto and its largest moon, Charon, most surprisingly that Pluto is still geologically active after 4.5 billion years and likely has a liquid water ocean under its icy crust.

New Horizons broke its own record of farthest planetary exploration with its close flyby of a Kuiper Belt object called 2014 MU69 — officially named Arrokoth (Powhatan and Algonquian for “sky”) — on Jan. 1, 2019. Geologic evidence on Arrokoth showed that its two defining lobes merged at the dawn of the solar system in a gentle, mile-per-hour collision or “docking.”

The Kuiper Belt is a scientifically rich frontier. Its exploration has important implications for better understanding comets, small planets (some of which have or once had underground oceans), the solar system as a whole, the solar nebula and disks around other stars. It’s a natural laboratory for studying well-preserved, primitive material from the ancient era of planet formation.

The New Horizons Kuiper Belt Extended Mission, however, is much more than the close flyby of Arrokoth. The continuing mission also takes advantage of the unique capabilities of New Horizons as an observation platform in the Kuiper Belt to study dozens of other Kuiper Belt objects in multiple ways that can’t be done from Earth.

Hurtling toward the doorstep of interstellar space, New Horizons is also making groundbreaking measurements of dust and the heliospheric plasma environment far from the Sun.

Mission Facts

January 19, 2006

Jupiter Flyby
February 28, 2007

Pluto Flyby
July 14, 2015

Arrokoth Flyby
January 1, 2019

Principal Investigator
Alan Stern, Southwest Research Institute

Project Manager
Helene Winters, Johns Hopkins APL

Project Scientist
Hal Weaver, Johns Hopkins APL

Learn More About Instruments on this Mission